Recently, ride-sharing has become an essential service for daily use. Some popular mobile apps have been utilised to match up between a user and a rider. Mobile apps provide mutual location information and private information for checking security levels, such as their profile photos, the rider’s star level, and feedback records about the user. Despite providing such information, frequent mismatching between a user and a vehicle causes severe safety problems. Therefore, this paper proposes a secure coupling scheme between users and riders via fine-grained cyber-physical interaction to prevent getting into the wrong car. The proposed scheme relies on dynamic Bluetooth low energy (BLE) beaconing to provide precise mutual detection between passengers and riders. Smart mobile devices dynamically generate BLE beacon messages to recognise and authenticate each other, and such beaconing is also used to measure the highly accurate distance between them. For mutual beaconing, the scheme deals with frequent switching of the advertising and scanning modes of the Bluetooth channel and their interval. Since passengers and vehicles might continuously move, accurate distance detection is not trivial. So, this scheme considers edge servers to apply various machine learning techniques and filtering schemes to achieve precise detection. Performance evaluations rely on a proof-of-concept prototype, and various field test data are utilised to prove the proposed concept’s performance.

Along with the advent of COVID-19 epidemic, delivery services have become one of the most common services in our daily life. However, the current services merely assume that the contact for handing over delivery items is denied to avoid facing between carriers and receivers. This extreme concept might lead to the ruin of typical processes for delivery services, such as face-to-face authentication, item checking, and payment in person. So, it may cause insufficiency regarding both sides of the secure item delivery and customers’ personal security. Therefore, this paper comes up with a novel CONTACTFUL delivery service with the digital twin paradigm to resolve contactless problems. The proposed idea establishes two-tier digital twin architecture to arrange digital twins and physical twins of carriers and receivers. Then, inter-digital-twin interaction virtually supports on-site delivery service processes. The inter-twin interaction relies on highly accurate proximity detection for items, carriers, and receivers. So, the proposed scheme considers machine-learning technologies and filtering algorithms to achieve high precision based on mobile-based Bluetooth low energy (BLE) beaconing. This scheme is implemented as a proof-of-concept prototype, and various field data are exploited to build ML-filtering models including their ensemble one. On the steel door, the ensemble model shows an accuracy improvement of 65% compared to SVM, 14% to CNN, and 73% to MLP. On the wood door, the ensemble model shows an accuracy improvement of 21% compared to SVM, 9% to CNN, and 17% to MLP.

To provide information dissemination among distributed wireless networks, mobile devices can be utilized as a relay node. Communications between mobile nodes and gateways require paradigms to deal with the temporal availability whose link occurs at a certain time interval and lasts for a short period. In addition, it should guarantee the data delivery due to timeout before entering the next coverage. We propose an information dissemination scheme among gateways with mobile relays based on the temporal graph approach. The proposed scheme models the network topology connected between gateways as a temporal graph and applies a minimum spanning tree algorithm to construct the shortest paths. Gateways opportunistically select a forwarding mobile relay whenever it needs lower cost than the pre-constructed paths. Simulation results have shown significant improvement in reducing the cost of traversal weight.

In wireless sensor networks, sink mobility support is one of the essential functionalities in many applications. With continuous advancement, future applications will require not only sink mobility support but also high-performance data delivery service. Multipath routing is one of the promising technologies for improving data delivery performance by collaboratively using alternative or redundant multiple routing paths. However, existing multipath routing protocols had not dealt with sink mobility. As a result, they lead to bad performance in terms of energy efficiency due to the end-to-end path reconstruction. Consequently, a novel multipath management scheme is required thereby supporting sink mobility without performance degradation. In this paper, we propose a multipath management scheme for supporting sink mobility. The proposed scheme dynamically constructs multipath along the moving path of a sink. In addition, the proposed scheme provides the path shortening schemes according to the sink’s movement for reducing energy consumption. Our simulation results show that the proposed scheme is superior to existing path management schemes in terms of reliability and energy efficiency.

The maturing deployment of the Internet of Things is gradually realizing new smart applications that strongly leverage recent advances in proximity detection methods. To this end, Bluetooth low energy (BLE) beacons are one of the preferred candidates because of the widespread use of Bluetooth-enabled devices. However, traditional battery-powered BLE beacons suffer from a limited operation lifetime, inducing additional maintenance operations and costs. This paper addresses this issue by proposing design principles for an ambient light energy harvesting BLE beacon capable of perpetual operation in the indoor environment. The contributions made in this paper include: 1) investigation and modeling of related hardware components, namely the BLE beacon, photovoltaic panel, and capacitor; 2) design principles for selecting hardware components subject to varying environmental conditions and application requirements; and 3) prototyping and field-tests to prove its practicality. Through multiple experiments, this paper proves that the design can operate perpetually under 40 lux light intensity, and can last over 17 h once fully charged.

Large-scale phenomena monitoring such as fire or toxic gas monitoring is one of major applications in industrial wireless sensor networks. A multitude of sources stemming from a large-scale phenomenon brings heavy communication overhead to report data to a sink. Many researches have focused on monitoring a large-scale phenomenon and reporting to a static sink with an energy-efficient way. Recently, large-scale phenomena monitoring needs a mobile sink for real-time response. However, the sink mobility support in large-scale phenomenon monitoring brings challenging issues. Given the existing approaches to support sink mobility in individual object detection, a mobile sink should establish one-to-many communication with all sources of a large-scale phenomenon for location update. The one-to-many communication between a mobile sink and all sources triggers early energy depletion and thus reduces the network lifetime. In this paper, we propose the origin-mediated communication scheme exploiting a hierarchy-based architecture to resolve the one-to-many communication problem. The origin node builds the virtual backbone network to propagate a location update message on behalf of the mobile sink. Simulation results show that the proposed scheme outperforms all the other work and exhibits significant amounts of savings in terms of the entire network's energy consumption.

Nowadays, mobile applications are engaged with and depended on the physical world more and more. Interaction with a certain proximity and thing is bringing smarter services into our daily lives through cyber-physical world collaboration. Push notification of meaningful content associated with the proximity or thing is one of key technologies of the cyber-physical services. For example, empty parking spot recommendation in a parking lot or promotion coupon notification of a shop at a shopping cent er should be delivered accordingly. This paper explores reliable push notification of content for novel interactive mobile applications over Bluetooth Low Energy (BLE) beacon infrastructure. Since mobile users move around with different speeds, this paper deals with such difference to relay right content in a reliable manner, called Reliable Push Notification (RPN). RPN dynamically clusters contents and links them to a beacon to achieve reliability, and then adaptively pre-allocate contents for transmission.

In geographical network systems, face routing is the unique recovery solution for local minimum problem. A node in local minimum could not choose its neighbor node closer to the destination. Since the face routing is based on novel graph named planar graph, the nodes search a link between adjacent nodes in the graph and send their data via the link. During the planarization of the topology, many links become hidden although the links are available for communication. Due to the hidden links, the graph leads too many number of data transmission in the face routing. With this reason, face routing leads lots of node energy and shortens the lifetime of sensor networks. This paper proposes the novel face routing which is able to reduce the data transmission. The proposed scheme searches the hidden links which are able to select the farthest neighbors at first. When the proposed scheme finds those neighbor links, it stops the searching behavior and transmits the data packets to them directly in order to reduce the data transmission. The simulation compares the proposed scheme with the previous face routing and shows that the proposed scheme is more energy efficiency.

Internet of Things (IoT) has been prevailing to offer advanced connectivity of devices, systems, and services. As connected IoT devices have enhanced smart home, connected smart homes are expected to grow into smart community. However, several previous studies about smart community require a remote central server and do not consider local collaboration based on local direct communication networks. This paper proposes home-to-home (H2H) communication based on wireless communication between homes in a local community. Several types of local collaborations are described. Two plausible H2H communication architectures are presented such as centralized and distributed. Two architectures are evaluated using two metrics: traffic volume and communication reliability. Clustering is also adopted to reduce traffic volume. The evaluation results show that the centralized architecture is superior in traffic volume and it is more adequate for all-to-all type of local collaboration such as information sharing; that the distributed architecture is superior in communication reliability and it is more adequate for one-to-all type of local collaboration such as safety and security. Clustering greatly reduces traffic volumes. Therefore, the proposed H2H communications will provide more efficient communication and more reliable services under the circumstances of IoT-enabled smart homes.

In wireless sensor networks, the multipath has been attracted for reliable data transmission due to the limited feature of sensors. The disjoint feature of multipath is one of important issues because it maintains how to separate each path in order to prevent the node energy depletion or node failure. In this issue, void areas should be considered since it disturbs the disjoint path construction. Existing multipath studies proactively detect the voids in the entire network by void modeling and thus construct paths by detouring the voids. However, void modeling causes large overhead to energy-limited nodes and even it could lead to the energy exhaustion of nodes or the node failure. To deal with this, we propose an energy- efficient and disjointed multipath routing for void handling based on geographic void handling approach. The proposed scheme is able to construct disjoint multipath avoiding the overspend of node energy and detouring the void area without additional method like modeling. Simulation results show the proposed scheme is better than the previous works in terms of energy consumption, delivery delay time, and path length around void area.

Geographic greedy routing in Wireless Sensor Networks (WSNs) suffers from the local minimum problem, which cannot select the next forwarding node such as the void. Especially, the void, which encountered during data transmission, have a negative effect on the time-sensitive application by the time delay in order to detour the void. Further, it is caused the void diffusion problem to exploiting the same node repeatedly in order to detour the void. To solve these problems, we proposed a dynamic anchor based void avoidance scheme for real-time service in WSNs. The proposed scheme broadcast the information of the void in network initialization phase in order to reduce a disadvantage caused the shape and location of the void. Furthermore, the source node calculates the dynamic anchor points using the information in order to satisfy the requirement of the real-time application and transmits the data to the sink node. Simulation result shows the proposed scheme is suitable for time-sensitive application and alleviate the void diffusion problem.

The wireless sensor networks (WSNs) are special network which has purpose of gathering information in certain area. The reliability is an important factor in the WSNs for transferring the information to the destination. However, the reliability is decreased while multi-hop transmission of the information because a node which composes the WSNs has limited communication range. Also, the transmission process may suffer from the various factors including the faulty nodes and network congestion. To solve this, the multipath routing protocols, which transfer the information through a multipath to the destination at the same time, have been proposed for improving the reliability. In the existing multipath routing protocols, however, the network scale should be sufficient for constructing multipath to guarantee of the disjoint path and the energy is consumed for multipath construction/maintenance consistently. The energy consumption leads to the reduction of networks lifetime and the restricted network scale may not even ensure the enough reliability. Thus, we proposed Low-Cost Multipath Routing Protocol by Adapting Opportunistic Routing which can reduce consistent energy consumption and less affected by network scale. The proposed protocol exploits the opportunistic routing that improves the single-hop reliability in order to improve the reliability in each path. It reduces the number of paths, which constructed for ensuring the enough reliability. Also, a fewer path reduces the energy consumption and alleviates the restriction of network scale. Simulation results show that the proposed protocol provides the more reliable performance than the existing protocols in the network, which restricted scale, and consumes the less energy.

In wireless sensor networks, sink mobility support is one of the essential functionality in many applications. With continuous advancement, the future applications will require not only sink mobility but also high performance. Multipath routing is one of the promising technologies for improving network performance. However, existing multipath routing protocols have not dealt with the sink mobility. As a result, they lead to bad performance in terms of energy efficiency due to the end-to-end path reconstruction. Consequently, a novel path management scheme is required thereby supporting sink mobility without performance degradation. In this paper we propose a multipath management scheme for supporting sink mobility. The proposed scheme dynamically constructs multipath along the moving path of a sink. In addition, the proposed scheme provides the path shortening mechanism according to the sink's movement for reducing energy consumption. Our simulation results show that the proposed scheme is superior to existing path management schemes in terms of reliability and energy efficiency.

In wireless sensor networks, one of the most important application is tracking diffusive and large-scale phenomena, called continuous object. A number of sources from the large size of a continuous object bring huge communication overhead that former studies have to deal with. Meanwhile, recent application scenarios, such as forest fire suppression by firefighters, require sink mobility support. Most sink mobility support schemes have proposed for individual object tracking. They provide one-to-one connection between a mobile sink and a source. That is, too many connections resulting excess energy consumption are built if continuous object tracking directly adopts them. In this paper, we propose a solution to the problem with building a one-to-many connection between a sink and sources detecting a continuous object. The proposed scheme gradually extends the initial connection between a sink and the first source according to the spread of the continuous object. Our simulation results show that the proposed scheme is superior to existing schemes in terms of energy consumption.

The real-time data dissemination is based on a minimum delivery speed of each hop on the end-to-end shortest distance in order to ensure to reach the destination within the desired time deadline in hop-by-hop fashion. In other words, the schemes depend not only on single hop-delay, but also on the distance between the source and destination. However, the performance of the real-time data dissemination could suffered from some "Voids" in the irregular sensor network which blocks the data forwarding. Namely, the voids lengthen the delivery path and the time for detour the voids. These extended delivery path and time aggravate real-time data dissemination success ratio because the additional distance and time increment were not considered in the calculated minimum delivery speed at source node. To deal with this phenomenon, there are detouring methods of voids such as perimeter routing, back pressure. Although the methods enable a void detouring of data packets, the real-time data dissemination success ratio have not improved much because of a many control message to detour voids. To solve this problem, we propose void avoidance scheme for real-time data dissemination. In our scheme, nodes surrounding a void could detect. This void information are transmitted to whole sensors in the network by broadcasting. When a source transmits data to sink, the source uses the void information to find certain point for avoiding voids by the shortest distance. Thus, the source could set desired speed toward the destination via the point without facing a voids. Performance evaluation shows that our scheme provides better real-time dissemination success ratio in practical environments.

Quorum-based schemes have been receiving much attention since they can efficiently provide the Sink Location Service (SLS) with large-scale networks and lightweight sensor nodes. Recently, researchers try to adopt them to real irregular fields with voids as well as non-rectangular shapes. However, such schemes make quorums only on particular path such as boundary or selected circle, thus leading to rapid energy exhaustion of nodes on the path. In this paper, we propose an energy-balanced SLS scheme. By constructing a quadrangle quorum per each sink connected by four random points, the scheme costs a balanced energy consumption of nodes, thus can prolong the network lifetime.

With technology advancement, Vehicular Ad Hoc Networks (VANETs) have been requested to provide one-to-many group communications (i.e. multicasting) for business and entertainment applications such as video conferences and file sharings. For these group communication applications, the existing broadcasting-based and unicasting-based approaches designed for safety applications however cause high packet generations and redundant data transmissions, respectively. Although the well-known Shortest Path Tree (SPT) and Minimum Spanning Tree (MST) algorithms for multicasting have been proposed, they achieve only a specific goal such as the reduction of delay or tree cost. Thus, for reducing end-to-end delay, delay variation, and transmission number requested for delay-sensitive and cost-efficient group communications and supporting high mobility of vehicles, this paper proposes a multicast protocol which uses the Farthest destination Selection and Shortest path Connection (FSSC) strategy to form a multicast tree. FSSC relies on the road map information and the location information of vehicles and intersections. Simulation results are provided to verify the effectiveness of FSSC.

Communications for mobile sink groups such as rescue teams or platoons bring about a new challenging issue for handling mobility in wireless sensor networks. Recently, a group region-based approach has been proposed to send data to a mobile sink group. However, it uses flooding for discovering and notifying group region information and flooding or long distance forwarding for disseminating data. Thus, it causes high energy consumption and data delivery failure. Moreover, its per-sink mobility supporting scheme makes energy consumption and data delivery failure more serious. Thus, this letter proposes an Energy-efficient and Reliable Mobile Group communication protocol (ERMG) to support a mobile sink group, which exploits a virtual grid structure. For the group region discover and notification and the data dissemination, ERMG uses communications with only cell heads of grid cells that manages group sinks. ERMG also uses a per-grid based scheme to support sink mobility. Simulation results show that ERMG has better performance than the existing protocols.

Opportunistic routing (OR) has been emerged as a promising routing strategy to improve transmission reliability for wireless networks. By taking broadcast nature of wireless medium, a set of forwarding candidate nodes receive a data packet simultaneously, so one of them can relay it unless they all fail to receive. This strategy can dramatically improve one-hop reliability even in unreliable wireless links, however, it cannot be directly applied into large-scale wireless multi-hop networks since multi-hop communication significantly decreases end-to-end reliability. In this letter, we propose a novel opportunistic routing scheme for large-scale wireless multi-hop networks, which adopts multipath based routing in order to improve end-to-end reliability. While taking advantages of opportunistic routing, each intermediate node can determine whether it branches into multiple paths or not without any network topology information, so that a desired delivery ratio from a source to a destination given by application demands can be achieved in a fully localized manner.

The adoption of multi-hop wireless networks has received attention from industrial cyber-physical system. In industrial applications, real-time multicasting is widely used for controlling and monitoring machines. In multi-hop wireless networks, the end-to-end delay depends on the end-to-end distance. Existing real-time multicasting studies use a fixed distance limitation to achieving real-time transmission without complexity from time factor. However, when given time factor changes, existing protocols might lead to real-time fails and inefficient multicasting because of the difference between the fixed distance limitation and the maximum transmittable distance under the given time. To solve the problems, in this paper, we propose a flexible real-time multicasting protocol based on given time factor. We first introduce a scheme for obtaining a maximum transmittable distance under a given time. Then we provide a real-time multicasting protocol based on the maximum transmittable distance. Our simulation results show that the proposed protocol achieves higher real-time delivery success ratio and energy efficiency than existing protocols.

Real-time applications in wireless sensor networks require that packets should reach to a sink within the time deadline. To satisfy the requirements, existing studies exploit nodes whose speed is higher than the desired delivery speed decided by the spatiotemporal approach. However, they fail real-time transmission in the area where there is no neighbor nodes which meet the requirements toward a sink since the desired delivery speed is fixed. This paper proposes a scheme to pass the area using time gain which occurs by the nature of the existing real-time transmission scheme. Thus, in the area, a sending node could make full use of nodes which do not satisfy the requirements. In the end, the packet passes across the area with a lower speed than the desired delivery speed. The simulation results show that the proposed scheme is superior in terms of real-time transmission success ratio to the existing schemes.

The selective wakeup scheme is the energy saving mechanism that is used for an object detecting or tracking in wireless sensor networks. Recently, many protocols are proposed using the selective wakeup scheme for the continuous objects tracking such as forest fires, poison gas, and oil spills. They predict the future shape of the continuous objects and activate only sensors in the predicted boundary area of the objects. It works normally in a uniformly deployed wireless sensor networks. However, it cannot be directly applied to a randomly deployed practical sensor networks with void areas. When a void area is around the boundary area, the activation message cannot reach to the next activation area and the activation control will be fail. Moreover, if activation control is once foiled then the next activation control might be failed continuously. It leads to many detection errors for continuous object. The detection errors can be result in serious harm to people, because most of continuous objects are dangerous substances. In this paper, we propose a chaining selective wakeup scheme for robust continuous object tracking in wireless sensor networks. In our protocol, we collect the information of a void area during the network configuration time, if the next boundary area is in the void area, we activate the chained area surrounding the void area with activation control message. Simulation results show the better performance than the previous studies in terms of success ratio of continuous objects detection and tracking.

Geographic routing in Vehicular Sensor Networks (VSNs) has been considered as an efficient and scalable approach since it exploits location information instead of topology information to route data packets. Geographic routing requires sources to be aware of the location information of destinations. Many solutions have been proposed to provide the location information of destinations in ad hoc and sensor networks. However, they are not suitable and energy-efficient for VSNs because the field property of VSNs is very different from that of ad hoc and sensor networks. In VSNs, sensor nodes are deployed on roads and vehicles also moves on the roads. Thus, we propose a quorum-based location service scheme to provide source nodes with the location information of the vehicles in VSNs. The proposed scheme exploits the property of the road map in VSNs. For providing location service, a location query makes a quadrangular path quorum and a location update makes a line path quorum. Then, the proposed scheme guarantees a crossing point between the quadrangular path quorum and the line path quorum. A sensor node on the crossing point sends a location reply to source nodes. The source nodes deliver their data to the vehicle via geographic routing. For data delivery to the moving vehicles, we also propose a mobility supporting scheme. Simulation results shows that the proposed scheme has better performance than the existing scheme in terms of the number of transmitted and received packets and the location service delay.

In legacy networks, overlay multicast protocols are stateless multicast relying on unicast with IP addresses regarding multicast routing states on routers, and thus they offer cost-effectiveness and robustness. Wireless sensor networks (WSNs) consist of a large number of randomly deployed sensors with unattended batteries and constrained device capabilities. For non-uniform and resource-sensitive WSNs multicast protocols also have taken an overlay approach. The protocols establish a cost-optimal structure, a Steiner tree, among destinations as an overlay structure and exploit geographic routing for unicasting. However, such concentration on the Steiner tree structure may paradoxically burden the irregular and resource-constrained WSNs with heavy loads for heuristic structure construction and fault-tolerant maintenance. In addition, it leads to frequent tree reconstruction, thus it could harm data multicast transmission seriously. Regarding these problems, we consider a proxy district per a destination for overlay tree formation to prevent structural dynamic alteration and support local state management. This district-based overlay multicast might be able to keep the stateless advantages of traditional overlay multicast. By overhead analysis and various computational simulations, we prove that our proposal provides robust and efficient multicast transmission.

Disjoint multipath routing is an attractive approach for improving the reliability of data delivery in wireless sensor networks. Recently, the issue for maintaining the robustness and efficiency of the disjoint multipath routing against network failures such as network holes are being studied. Several protocols have been proposed to handle the network failures. However, they cause the large performance degradation on data delivery ratio and delay due to its centralized manner for detouring the network holes in irregular network environments. Thus, we propose a Localized Disjoint Multipath Routing protocol called LDMR which can achieve reliable data delivery ratio and stable data delivery delay while handling network failures. LDMR constructs the fully disjoint multipath and manages them by using a localized management method with a path priority rule. Simulation results show that our protocol provides the more stable and reliable performance than the previous protocols in terms of packet delivery ratio and packet delivery delay.

In wireless sensor networks, the existing real-time routing protocols for stationary sinks exploit a spatiotemporal approach, utilizing the delivery speed based on the end-to-end distance to fulfill the desired time deadline. This approach cannot be directly applied to a mobile sink since the distance can be varied depending on its movement. That is, the delivery speed cannot be determined without knowing the intermediate sensors to know the current location update of the mobile sink and control their transmission speeds. We focus on the real-time protocol for slowly varying mobile sink compared to transmission speed, which may be the most common case. By the slowly varying constraint, the movable area of a sink can be determined by the two factors: its moving distance and initial location. The movable area could provide the maximum transmission distance between a source and a mobile sink. This letter proposes a real-time data dissemination protocol for mobile sinks utilizing the movable area concept. Simulation results show the proposed protocol provides high success ratio of real-time requirement.

In wireless sensor networks (WSNs), real-time service is one of the important issues. Typically, existing studies for the service are relied on beacons. Recently, beaconless routing has been proposed to overcome control overhead for resource constrained environment of WSNs. Thus, real-time communication based on the beaconless scheme could give great advantages with less energy consumption. To do that, however, it brings new challenges. For the real-time communication, each node needs to be aware of single hop delay for data forwarding within desired time. In conventional approaches, it is based on delay in neighbor information through beacons. An appropriate next forwarder is selected by a sender. However, in the beaconless scheme, a sender could not select a next forwarder since that is determined by a receiver after transmitting data. Also, contention delay is included in single hop delay for beaconless routing. Thus, the delay estimation principle should be renovated. In this paper, we present a receiver-based beaconless routing for real-time services. We design a novel delay estimation strategy. The single hop delay from a sender to a receiver could be calculated by a receiver but not a sender. Therefore, the receiver itself makes a decision whether desired time requirement is satisfied. Simulation experiments show that the strategy achieves higher performance in terms of energy consumption.

The information of boundary area is important to track the continuous objects such as forest fires, radioactive matter, and oil spills. Recently, many of protocols are proposed for the continuous object tracking. They predict the future boundary shape of the continuous objects and activate only sensors in the predicted area of the objects. It is very efficient strategy in a uniformly deployed wireless sensor networks. However, it should be needed more advanced algorithm that is suitable for a randomly deployed practical sensor networks with voids. If the void area is in the predicted area, the activation message cannot reach and the predicted area cannot be activated at the right time. It is a major cause of many detection errors for the continuous object. Moreover, if activation control is once foiled then the next activation control might be continuously failed. The detection errors can be result in serious harm to people, because most of continuous objects are dangerous substances. In this paper, we propose a chaining selective wakeup scheme suitable for continuous object tracking in wireless sensor networks. In our protocol, we collect the information of a void area during the network configuration time; if the next boundary area is in the void area, we activate the chained area surrounding the void area with activation control message.

In this paper, we propose an opportunistic real-time data dissemination protocol in order to solve the transmission failure problem in error-prone WSNs. Retransmission is well-known for recovery of transmission failure, however, this may cause the severe time delay possibly to violate the real-time requirement. To solve the problem, our protocol exploits both broadcasting nature and temporal opportunity concept. In a radio-range of a sensor node, there may be multiple neighbor nodes to satisfy the real-time requirement. By broadcasting property, all neighbors can receive a data from a node, and only each satisfying neighbor decides its relay toward the destination by using temporal selection function. The temporal function is related to the tolerable time period to be able to satisfy the real-time requirement. By giving the priority to the node with smaller tolerable time, we have more opportunities to forward toward the destination. That is, even if a node with a long tolerable time waits for the longer period of time, it still has a chance to forward with the real-time requirement. In summary, the proposed protocol attains the high reliability and real-time requirement by removing data retransmission and multiple opportunities with temporal consideration. Simulation results show that the proposed protocol is superior to the existing real-time protocols in terms of real-time data dissemination and energy consumption.

Geographic multipath routing is one of the most appropriate approaches which can improve the end-to-end reliability via multiple paths for the wireless sensor networks that have frequent network dynamics such as both node and link failures. It has been focused on how to construct a node-disjoint multipath that an intermediate node should be belonged by only a single path. It is because that if two or more paths share one intermediate node, the node may be congested by multiple traffics. Even it might bring multiple path failures if the shared node fails. However, if the node-disjoint multipath schemes are used, there might be another significant problem such as transmission failure or corrupted packet reception due to collisions between adjacent paths. Therefore, we propose a radio-disjoint geographic multipath scheme to avoid the collisions, which allow multiple paths to keep a certain distance between each other. Unfortunately, this simple idea still remains inevitable interference regions, i.e., both source side and destination side. So we eliminate the interferences in these regions by using local scheduling algorithms. We demonstrate that the proposed protocol shows better performance than the previous studies via extensive simulation in terms of end-to-end packet delivery ratio and the end-to-end delay.

In wireless sensor networks (WSNs), the real-time data dissemination protocols exploit the spatiotemporal communication approach which forwards data at the delivery speed calculated with the desired time deadline and the end-to-end distance. However, the protocols do not focus on the reliable communication. Recently, MMSPEED is proposed for both reliable and real-time data delivery based on multipath. For construction of the multipath in MMSPEED, the relay nodes branch off by local decision. Namely, in order to improve the reliability, the protocol locally chooses branch nodes among neighbor nodes which fulfill the real-time constraints and have the better reach ability to the sink. However, since the paths are branched off blindly, the branched paths have no information of each other. So, the paths could be merged each other. The end-to-end reliability of multipath could decrease due to the failure of the merged path. Moreover, as the reach ability to the sink is not estimated but calculated, the value could not be applied for reliability in real world. In this paper, we propose a reliable and real-time service protocol with geographical parallel track concept. The parallel track concept provides the information of each path to all paths. In the proposed protocol, the branch of multipath occurs only by real-time constraint. Simulation results show that the proposed protocol is superior to the related studies in terms of successful data delivery in desired time deadline.

This paper studies on data dissemination for mobile sink groups in wireless sensor networks. A mobile sink group denotes a set of tightly coupled mobile sinks for team collaborations such as a team of firefighters and a group of soldiers. This mobile sink group has a collective movement feature. That is, even though sinks in a group randomly move in their own personal spaces, they collectively move together as a single entity. For mobile sink groups, previous studies provide flooding-based protocols that determine immediate areas of a group at moments, which are successive snapshots of a group continuously moving, and then propagate data within the areas by flooding. However, since a group is still moving during decision of each snapshot, they cause asynchrony between an immediate area and the actual area at a moment. Eventually, it harms reachability and energy-efficiency. This paper therefore proposes a novel data dissemination protocol that takes into account continuous motion properties of a mobile sink group: slowly varying and streamlike movement. Based on the slowly varying property, the protocol predictively and effectively deliver data to a mobile sink group through a band of sensor nodes located in front of the streamlike trajectory of the group. Numerical analysis and computational simulations prove that this band-based data dissemination show better performances than the previous schemes with respect to both reachability and communication costs including data forwarding as well as signaling in a variety of scenarios.

To support a group of mobile sinks in wireless sensor networks, region-based routing protocols by using a single entity nature have been proposed. They periodically register the region location information of the mobile sink group and exploit flooding for the data delivery within the region. However, they have a data delivery failure problem for some sinks due to the asynchrony between the registered region and the actual region of the mobile sink group due to its mobility. They also have an excessive energy consumption problem due to flooding data within the region. Thus, to solve the data delivery failure and the excessive energy consumption problems, we propose a routing protocol for a mobile sink group by utilizing its movement pattern which has a slow variance and continuous stream i.e. moving properties. In the proposed protocol, a source sends its data only to sensor nodes on a line that a mobile sink group potentially passes, and mobile sinks get the data from the line when they pass it. Simulation results show that the proposed protocol has better performance than the existing protocols.

For tracking a continuous object, mass communications are generated in the sensor field because of their huge scale and extensive diffusing property. Due to the severe resource constraints of sensor nodes, the redundant information and communications should be reduced in order to prolong the life time of WSNs. Although there have been numerous studies on continuous object tracking, most of the proposed schemes have focused on reducing the redundant boundary nodes and control messages through static/dynamic clustering in space domain. However, it is not enough to reduce the redundancy only with space domain. Redundantly sampled reporting packets could be a cause of generating redundant long range transmission, which is an important source of energy consumption. For reducing the redundancy, we need to consider not only the method to reduce the redundancy in space domain but also an adaptive sampling scheme in time domain. However, adaptive sampling is difficult to design in continuous object tracking because local sensor nodes hard to figure out how far the continuous object is diffused. To solve this problem, we suggest a new scheme which picturizes the diffusing object by dividing the sensor field into several cells like a pixel on TV and samples reporting time based on pixel image. In addition, we use pictured image of diffusing object for selecting the boundary information of diffusing object in space domain to reduce the redundant boundary information. To present the sensor field as an image, we adopt a virtual grid which divides the sensor field into several cells under the static clustering WSN architecture. The performance of proposed scheme is verified with simulation and the results show that the total number of control messages, reporting packets and boundary nodes can be reduced.

In order to find a completely disjointed multiple routes, traditional multipath strategies try to get global topology information by using frequent flooding or end-to-end signaling. It is very useful, but too much expensive to directly adapt to the resource constrained wireless sensor networks. Thus, recently there has been proposed an energy-efficient localized multipath scheme (EDM), which exploits geographic information for multipath discovery and routing. However, EDM has a significant limitation that it does not consider the case of simultaneous transmission between adjacent paths. Because of the path interferences, the transmission fails or corrupted packet receptions might be frequently occurred even if EDM has made completely disjointed multiple paths. Therefore we propose an interference-free geographic multipath protocol by allowing the paths to separate each other. To implement that, we utilize a logical multipath pipeline approach. Each pipeline has to keep a certain distance between each other, and a route can be allowed to be made within a pipeline.

In order to disseminate data to a mobile sink by location-based routing, it is important to provide location information of the sink altering continuously with a source in wireless sensor networks. Fundamentally, it could send directly location information message to a source whenever the sink moves. On the other hand, some schemes without additional cost for location update are proposed recently. The schemes could learn location information by utilizing overhearing of broadcasting nature in wireless transmission environments. Transmission path is turned steadily to the new location at an intermediate node hop by hop per packet along the reverse path. However, if the sink moves frequently while the path is being changed, new location information of the sink exists on the other previous paths rather than on the current path. Therefore, the information might not be propagated to a source securely. Namely, it could not guarantee reachability. In this paper, we propose a novel implicit location service scheme, which guarantees the reachability. With this scheme, we exploit location information of static sensor node as destination information instead of actual location of the dynamic sink. Then, packets are delivered toward one sensor node so the packets could be delivered to the destination. We provide the proof of its reachability and simulation result shows that the proposed scheme has improved than previous works in terms of reliability.

The real-time data dissemination schemes exploit the spatiotemporal communication approach which forwards data at the delivery speed calculated with the desired time deadline and the end-to-end distance in wireless sensor networks (WSNs). However, the schemes do not focus on the reliable communication. Recently, MMSPEED is a well-known scheme for both reliable and real-time data delivery based on multipath. For construction of the multipath in MMSPEED, the relay nodes branch off by local decision. Namely, in order to improve the reliability, MMSPEED locally chooses branch nodes among neighbor nodes which fulfill the real-time constraints and have the better reachability to the sink. However, since the paths are branched off blindly, the branched paths have no information of each other. So, the paths could be merged each other. The end-to-end reliability of multipath could decrease due to the failure of the merged path. Moreover, as the reachability to the sink is not estimated but calculated, the value could not be applied for reliability in real world. In this paper, we propose a reliable and real-time service protocol with geographical parallel track concept. The parallel track concept provides the information of each path to all paths. In the proposed protocol, the branch of multipath occurs only by real-time constraint. Simulation results show that the proposed protocol is superior to the related studies in terms of successful data delivery in desired time deadline.

A principal issue for wireless sensor networks is energy efficiency, which is necessary for prolonging applications to track continuous object, such as wild fire and poison gas. Selective wakeup approach is an effective way to save energy in such networks. However, most previous studies on selective wakeup schemes have concentrated on individual objects, such as intruders and tanks, and they cannot be applied for tracking continuous objects. This is because the continuous object is pretty flexible and dynamic due to its sensitiveness to surrounding natural effects so that movable area cannot be correctly estimated by the just spatiotemporal mechanism. Therefore, we propose a grid-based protocol for applying the efficient and accurate selective wakeup technique to tracking continuous objects. When an object is detected in some specific area which tightly surrounds the object, a pre-designated area where the target may move is activated to prepare the target without any complex calculations. Moreover, our protocol is simple and asynchronous, which makes it more suitable for wireless sensor networks.

ABSTRACT Nodes mobility brings flinty challenges to multicast in Mobilead hocNetworks (MANETs). To track nodes mobility, flooding messages are widely used for data delivery structure construction and maintenance in many multicast protocols. These periodic flooding messages significantly consume network resources, such as energy and bandwidth, and result in network collisions. To release data delivery structure maintenance onus, profited from GPS location service, a number of stateless location based multicast protocol were proposed, where a destination list is encapsulated into each data packet for data packet orientation. However, due to data packet capability limitation, the way of encapsulating a destination list in each data packet header restricts the protocol scalability. To solve the scalability issue of multicast protocols, we propose a Scalable Location Guide Overlay Multicast (SLGOM) for MANETs. Analysis and simulation results show that SLGOM achieves high performance in large multicast group and significantly improves the scalability of stateless multicast with respect to group size. Copyright © 2010 John Wiley & Sons, Ltd.

Recently, detection schemes of specific phenomena, called continuous objects, such as wild fire and bio-chemical material have been actively studied. A continuous object might cover a wide area and it could dynamically change its own shape according to physical environments, e.g. wind and geographical features. For continuous object detection, the schemes have focused on detection of the current boundary shape of a continuous object at a time period. However, the schemes merely aim at reducing communication costs for boundary information collection, but they do not take into account reliable information transport. Hence, we propose a Reliable Boundary Information Transport (RBIT) protocol for continuous object detection. The protocol is composed of three major mechanisms: 1) explicit Representative Boundary Node (RBN) election, 2) cluster-based boundary information loss recovery, and 3) cluster-by-cluster packet loss recovery. The explicit RBN is considered in order to estimate boundary information loss due to the dynamic property of continuous objects. The protocol then constructs coarse-grained grid clusters, and it allocates a header node per each cluster. The header node collects location information of RBNs in its own cluster and revises lost boundary information. By the clustering the protocol distributively manages all RBNs of the large-scale continuous object. Finally, cluster-by-cluster packet loss recovery is provided for end-to-end reliable transmission from a header node to a sink. The cluster-by-cluster loss recovery fills up lost packets by data packet retransmission between clusters.

In wireless sensor applications such as disaster recovery and military actions, the behavior of mobile sinks is characterized by group features. A number of mobile sinks move together in a group manner, and mobile sinks in the group stay closely and randomly move within a geographically restricted region. Recently, many communication schemes have been suggested to reflect the properties of the mobile sink group to effectively support the group communications. These schemes calculate the group region and disseminate the source's data to the calculated region in a certain discrete-time. However, as they ignore the continuous movement behavior of the group, they might have a serious reach ability problem that some mobile sinks cannot receive the source's data. Also, the periodic calculation of the region and propagation of data extrinsic to the movement of the group cause a waste of network resources. In this paper, we propose a novel data dissemination scheme for mobile sink group considering continuous movement of the group, which could resolve the problems of reach ability and inefficiency faced by the previous schemes. The proposed scheme allows the sink group to receive the source's data from virtual grid infrastructure when the group moves out from a local grid. Simulation results show that the proposed scheme is superior to previous ones in terms of transmission success ratio and node energy consumption.

In wireless sensor networks, many studies on data dissemination to individual mobile sinks traditionally rely on a strategy that consists of a virtual infrastructure to serve current location of the mobile sinks and a per-sink foot-print chaining mechanism to support local mobility after location update. To adapt the strategy for supporting mobile sink groups, it may be simply considered to exploit a representative per a mobile sink group in order to representatively register location of the mobile sink group and representatively make a foot-print chain of the sink group. However, the representative manner may lead to considerable problems with respect to efficiency and robustness of data dissemination: inefficient data collection problem, needless location update problem, and relay path loss problem. These problems could be caused from dependency between the group and the representative, i.e. a member sink. Therefore, we propose a novel protocol for data dissemination decoupled with any member sink of a mobile sink group. In order to independently deal with a mobile sink group, the protocol is composed of three major mechanisms: 1) representative location update, 2) distributed data collection, and 3) per-group foot-print chaining.

Geocasting has been known as the appropriate scheme for providing effective data dissemination from a source to all nodes in a geographically restricted region. However, since the geocasting typically assumes the restricted region is stationary, it is hard to directly adopt the traditional geocasting in order to offer effective data delivery to mobile sink groups that have geographically collective mobility. Hence, this paper proposes a novel geocasting, called M-Geocasting (Mobile Geocasting) to support mobile sink groups. M-Geocasting provides the representative location information of a sink group to sources. The location information contains information in terms of a restricted region in which all member sinks of the group exist. A source disseminates data to the closest node in the region; then, the node restrictedly floods the data only within the region. Also, to support local movement of member sinks toward out of scope of the region, some nodes on boundary of the region maintain the data and offer it to member sinks out of scope of the region. We have evaluated M-Geocasting performance through simulation experiments, and our results show that M-Geocasting effectively supports mobile sink groups that have geographically collective mobility.

In wireless sensor networks, reliable event detection is one of the most important research issues. For the reliable event detection, existing studies usually assume that events are individual objects such as tanks, people, and animals. The existing studies estimate detection reliability of an individual object by the ratio of the number of successfully received data packets at a sink to the number of data packets determined by applications for reliable detection. Recently, detection of the other one kind of events, called the continuous object, such as wild fire and bio-chemical material has been receiving increased attention. Unlike the individual objects, a continuous object might cover a wide area and it could dynamically alter its own shape according to physical environments, e.g. wind, geographical features, and so on. Hence, the continuous object detection reliability can not be estimated by the indicator for the individual objects. In this paper we newly define the reliability indicator for continuous object detection. Then, we propose error recovery and revision scheme based on the estimation result from the novel indicator. Simulation results prove that the proposed scheme provides high reliability with respect to continuous object detection.

For reliable event detection in wireless sensor networks, a sink requires collective information reported by sensor nodes sensing an event. In other words, the sink has to receive a certain amount of data dealing with the event for reliable event detection. Existing studies propose quantity-based event reliability protocols that improve event reliability by increasing the number of data successfully transmitted by controlling transport process. These studies present diverse schemes to successfully transmit as many reporting data as possible such as diversification of routing path for congestion avoidance and control of data reporting frequency rate for transport error compensation. However, since it frequently happens that wireless sensor networks with restricted capacity cannot deliver more than required amount of data due to data collision and congestion, the quantity-based event reliability protocols have limitation to raise the possibility of event detection. In this paper, we proposes a Quality-based Event Reliability Protocol (QERP) utilizing a property that the reporting data from sensor nodes are different in the contribution degree (CD) for event detection according to their environmental conditions. QERP selects sensor nodes to send their reporting data according to CD, and differentially transports them by CD-based buffer management and load balancing. Simulation results show that QERP detect more reliably and energy-efficiently an event than quantity-based event reliability protocols.

For WSNs, many data dissemination protocols have been proposed for mobile sink groups, in which sinks are spatially apart each other in their close proximity and move together according to group mobility. Most previous works cannot be directly applied to mobile sink groups due to the control overhead caused by the individual mobility in the group. M-geocasting protocol considers both of data dissemination and group mobility, but regional flooding leads to energy inefficiency. Energy consumption is increased in proportion to the spatial size of the group. In addition, the more frequent events generated in a source have more potential of broadcast storms and failures in data reception in some sinks exist in the group. In the paper, we propose an energy efficient scheme for data dissemination called Pipe Based Data Dissemination (PBDD), in which flooding combines with a virtual pipe, preventing the problems in flooding and data loss in group mobility. The virtual pipe is a unit of data storage for stable data dissemination, while flooding is utilized only for location discovery. Simulation results show that the PBDD outperform the existing protocols in terms of energy consumption and successful delivery rate.

There have been proposed many data dissemination protocols which use routing structures dependent on sinks or events in wireless sensor networks. However, as many mobile sinks and events exist in the network, such protocols are not energy-efficient due to frequent reconstructions of routing structures. Thus, in this paper, to provide the scalability and mobility of sinks and events, we propose new independent structure-based data dissemination protocol which exploits a k-level Independent Grid Structure (IGS) for data dissemination from sources detecting the events to sinks. The proposed protocol needs not to construct any routing structure irrespective of the number and the movement of both sinks and events. The proposed protocol also allows query or report packets to be sent to only a few grid headers in the k-level IGS and provides aggregation and multicasting of report packets by the k-level IGS. Simulation results show that the proposed protocol is superior to other protocols.

In wireless sensor networks, there have recently been studies on mobile sinks groups such as groups of soldiers on battlefields, which are characterized by geographically collective movement. Although the existing protocols for individual mobile sinks can support the mobile sinks groups, they suffer from high congestion and control overhead due to location updates by each sink in the groups. To solve the location update problem by individual sinks, a protocol, called M-Geocasting only updates the region information of the mobile sink groups to sources. However, since M-Geocasting uses the flooding within the group regions for data delivery to member sinks, it excessively consumes the energy of sensor nodes in the group region. Moreover, the flooding potentially causes broadcast storms within the group region when many events exist. Thus, in this paper, we propose an efficient data dissemination protocol which can avoid the flooding within the group region for supporting mobile sink group. The proposed protocol introduces a virtual pipe in the group region for data dissemination as data storage. In the proposed protocol, a source sends data to the pipe and member sinks retrieve data directly from the pipe. Simulation results show that the proposed protocol is superior to the existing protocols in terms of the energy consumption and the data delivery ratio.

Recently, group mobility support of mobile sinks has received increasing interest, and several mechanisms have been proposed. The mechanisms typically follow a strategy that simply adopts flooding. The strategy detects the currently located region of a mobile sink group in flooding, registers the current region to a source, and performs data flooding in the region to disseminate data to the sink group. However, this strategy might cause serious problems in terms of reachability and communication overhead. In the first, although a group could continuously move toward a target point for its own mission, the strategy discretely performs detecting the group region and updating the region information. Namely, data may be delivered the previously current region, i.e. already updated but changed the region. Moreover, in order to obtain the region information of the group, flooding is frequently fulfilled as well as the strategy utilizes flooding for data delivery to the group every time. Therefore, we propose a novel strategy for reachability and low overhead, called X-Geocasting. X-Geocasting merely finds out the region of a group when the group changes direction or movement velocity. Also, instead of fully flooding in group regions, X-Geocasting predictively and flexibly determines the restricted flooding area according to direction and movement velocity. Simulation results prove this proposed group mobility support strategy provides reachability and high energy-efficiency.

Wireless sensor networks consist of a large number of sensor nodes, recharging them is often infeasible. The failure of sensor nodes caused by energy exhaustion or physical destruction may lead to the reduction of sensor areas. In wireless sensor networks, holes can be formed due to void areas in sensor nodes deployment, destruction of sensor nodes, or uneven energy consumption. In such a network, geographic routing is very strong energy-efficient routing scheme without consideration of global network topology. But the hole problem becomes another difficult issue faced by geographic routing. Moreover, the holes make more serious obstacles in multipath routing, that is, multiple paths are eager to bypass the holes simultaneously. It results in more energy consumption or data collision on the edge of holes by the right hand rule and finally cannot construct disjoint multipath. In this paper, we propose the hole detouring strategy to handle the hole problem in disjoint multipath routing. Then our robust disjoint multipath routing scheme based on the hole detouring strategy can efficiently construct disjoint multipath preventing the hole problem and avoiding data collision on the edge of holes. Simulation results present our protocol is superior to the previous works in terms of energy consumption, average delivery delay and show reliable disjoint multipath construction under the hole flexibly.

Real-time data delivery is the most important requirement for mission-critical applications in wireless sensor networks. Since a mobile sink is requested for applications and for energy efficiency in WSNs, an Expect Area-based Real-time Routing protocol (EAR2) is proposed to support real-time routing to the mobile sink. EAR2 is based on an Expect Area (EA) of the mobile sink and exploit flooding of real-time data within EA. However, flooding within EA makes sensor nodes in EA consume much energy. Flooding time within EA may also be difficult to measure and change widely according to time and environment. Thus, to avoid the flooding problems in EAR2, we propose a new real-time routing protocol based on grids for a mobile sink. In addition to EA of a mobile sink, the proposed protocol considers Expect Grids (EGs) of the mobile sink, which are included in EA. Instead of flooding within EA, the proposed protocol exploits multicasting to EGs and one-hop forwarding in a EG because in comparison with flooding, multicasting saves much energy and one-hop forwarding time is easy to measure and changes narrowly according to time and environment. Simulation results show that the proposed protocol is superior to other protocols.

The mobility model of a mobile sink group typically consists of two movement behaviors as follows: a micro-level movement behavior and a macro-level one. In the micro-level, mobile sinks randomly move within a geographically restricted region while all the member sinks in the macro level collectively and slowly move together toward with similar direction. Recently, a group communication protocol has been proposed to support the mobile sink group. It exploits both data dissemination by restricted flooding within the group region for the micro-level movement and periodical updates of the group region to the source for the macro-level movement. However, such mechanism might causes the excessive energy consumption of sensor nodes due to the frequent flooding for both location requests of a leader sink for the group region calculation and data dissemination within the group. Also, since it calculates the group region through current location of member sinks, the group region might be moved in the macro-level even if only a sink moves in the micro-level in practice. It might bring frequent updates of the group information to the long-distance source. In this paper, we propose an energy-efficient group communication protocol that disseminates data without both the flooding and the group region calculation. In the proposed protocol, data of the source is only disseminated to grid headers of virtual grid structure in the group instead of all sensor nodes in the group, and then each member sink directly gets the data from the closest grid header. As the group region update performs locally in grid- level, the communication cost would be significantly reduced. Simulation results demonstrate that the proposed protocol has lower energy consumption than the previous one.

Due to the severe resource constraints of sensor hardware, energy efficiency is a principal factor for detecting and tracking the movement of the large-scale phenomena such as wild fire, poison gas and hazardous bio-chemical material, denoted by continuous objects. In order to save the energy, the selective wakeup approach is effective way in the wireless sensor networks. However, most previous researches concentrated on individual objects such as intruders, tanks, and animals cannot be applied to the continuous object tracking because it is hard to expect that the diffusion of continuous object has the uniform velocity or acceleration. Recently, a prediction-based selective wakeup algorithm, denoted by PRECO is proposed. Nevertheless, this mechanism is still not acceptable. First, its prediction result is very inaccurate because a sensor node calculates next boundary line with only a few data while the continuous objects are pretty flexible and vicissitudinous. Second, its prediction tasks among current boundary nodes should be operated at the same time but it is a hard problem for the nodes to have synchronization in the wireless sensor networks. Therefore, we propose a novel prediction and selective wakeup scheme for energy efficient and accuracy continuous object tracking by using structured clustering. Hence, when objects are detected in some specific area, appointed areas where the target may move activate to keep guard without any complex calculations. Moreover, our scheme is asynchronous so that it is suitable for the sensor networks.

In wireless sensor networks, many studies on data dissemination to individual mobile sinks traditionally rely on a strategy that consists of a virtual infrastructure to serve current location of the mobile sinks and a per-sink foot-print chaining mechanism to support local mobility after location update. To adapt the strategy for supporting mobile sink groups, it might be simply considered to exploit a representative per a mobile sink group in order to representatively register location of the mobile sink group and representatively make the foot-print chain of the sink group. However, the representative manner may lead to considerable problems with respect to efficiency and robustness of data dissemination: inefficient data collection problem, needless location update problem, and relay path loss problem. These problems could be caused from dependency between the group and the representative, i.e. a member sink. Therefore, we propose a novel strategy for data dissemination decoupled with any member sink of a mobile sink group. In order to independently deal with a mobile sink group, the novel strategy is composed of three major mechanisms: 1) representative location update, 2) distributed data collection, and 3) per-group foot-print chaining.

In wireless sensor networks (WSNs), the studies that support sink mobility without location information of sensor nodes traditionally establish a cluster-based virtual infrastructure. The cluster-based infrastructure consists of clusters involving sensor nodes and a shared tree organized by the cluster heads. In the studies, data dissemination from a source node to a mobile sink is performed via the shared tree. The mobile sink makes connection from the current standing cluster into the root of the shared tree; the source transmits data to the root; and the root delivers the data to the mobile sink. Namely, the data from a source may always be detoured to a mobile sink via the shared tree. According to a change of the current standing cluster, the mobile sink could frequently remake connection into the root; thus, excessive energy consumption by the detour problem might seriously happen. In this paper, we propose a communication protocol that provides the shortest path from a source to a sink by exchanging a routing table between neighboring cluster heads. The routing table contains the cluster ID of a neighbor cluster and hop-count from the neighbor cluster to the other clusters. A sink registers the cluster ID of the current standing cluster into the root of the shared tree, and a source then obtains the cluster ID. Thus, the source can deliver data directly to the current standing cluster of the mobile sink. Simulation results show that the proposed protocol is superior to the existing protocol.

Real-time data delivery to a multicast group may be defined as data dissemination to each member in the multicast group within the desired time deadline. The hardest part of this mission is to enforce this real-time constraint in the communication between a source and the furthest member since an end-to-end delay is proportional to a physical distance in wireless sensor networks. We may call it the critical distance. This must be most important constraint for real-time multicasting. That is, the delivery distance from a source to each member must not be longer than the critical distance even by any reason. However, since the traditional multicasting protocols lay the strong emphasis only on communication cost rather than distance, they may violate the real-time constraint related to the critical distance. In this paper, we propose a novel multicasting scheme satisfying the real-time constraint.

In wireless sensor networks, a mobile sink group have geographically collective movement and member sinks of the group try to get same data to execute a communal mission. In order to support the mobility for such groups, it is needed to get the current location of a mobile sink group and then to offer the location to a source. Previous works for mobile sink groups provide region information of a sink group to a source. To provide the information, the previous works calculate a region including all member sinks by flooding; then, it notifies this region information to a source. However, flooding and location updates are periodically performed regardless of the group movement so that it causes considerable overhead in terms of energy consumption. In this paper, we propose an energy-efficient scheme supporting mobile sink groups without periodic flooding and location update. The proposed scheme calculates a location of a group without large energy consumption due to flooding. It exploits the inherent property of mobile sink groups which could approximate entire group movement by only partial member sinks movement. Also, the scheme learns group location by back-propagation learning method through exploiting overhearing feature in wireless communication environment. Our simulation studies show that the proposed scheme significantly improves in terms of energy consumption compared to the previous work.

As the mobile Internet increases with the popularization of smartphones, the conventional services are gradually being expanded to the wired and wireless integrated environment. These changes in the network environment require a new paradigm for the pursuit of safe and stable communication. In this paper, we propose a Seamless and Secure service Framework (SSF) that can maintain a sustainable secure relation between the user terminal and the sensitive service system by using both personal and network information. Typical examples of the SSF are the secure payment of bills and authentication. The SSF can block at the root the illegal use of the service (by a third party) even if personal information is leaked, as long as the user terminal is not lost. In addition, the SSF can provide a seamless service environment even if the access network is changed by movement of a terminal with the multiple network interfaces within the heterogeneous network environment.

Typical real-time routing data dissemination schemes employ 1-hop transmission speed based on the 1-hop lookahead manner that proactively obtains information of 1-hop neighbor nodes and selects one that satisfies a desired delivery speed as next hop. To improve performance of 1-hop lookahead based real-time routing protocols, THVR (Two-Hop Velocity-based Routing) is proposed. THVR reduces deadline miss ratio that the ratio of the number of data that exceeds the time limit to total number of sending data via routing decision based on 2-hop neighborhood information obtained from the 2-hop lookahead information. However, since the 2-hop lookahead manner makes every sensor node proactively obtain 2-hop neighborhood information whether the sensor node has data to forward or not, THVR carries two inefficiencies: heavy control message exchange overhead and high computing complexity. In this paper, we propose a noble real-time routing protocol based on reactive and restricted zone search. The proposed protocol minimizes the deadline miss ratio and eliminates the two inefficiencies mentioned above by on-demand multi-hop lookahead. In the proposed scheme, reactive multi-hop neighborhood information obtainment is fulfilled only by a small number of sensor nodes within a restricted zone around a data forwarding path from the source to the destination.

There have been many geographic multicasting protocols proposed for wireless sensor networks (WSNs). These protocols tend to exploit a SOurce-initiated Geographic Multicasting (SOGM) approach which consists of three phases: first, a source collects the position information of all sink nodes; second, the source constructs a multicast tree through the position information; third, the source forwards data down the multicast tree. However, if a multicast group contains many mobile sinks, frequent movement of the sinks cause a huge number of link failures of the multicast tree. To fix them, the SOGM approach requires a great deal of delivery of position registration and update messages to the source, thus leads to significant energy consumption of the sensor nodes in the vicinity of the source. Moreover, since each sink asynchronously updates one's new position to the source, it is difficult for the source node to find an opportune time for reconstructing the multicast tree. In this paper, we propose a SInk-initiated Geographic Multicasting (SIGM) protocol for WSNs which can avoid these problems faced by the SOGM approach. The SIGM allows sinks to construct their own data delivery paths to a source, and a multicast tree is automatically constructed by merging the data delivery paths. Simulation results show that the proposed protocol is superior to other protocols in term of average energy consumption, it thus prolongs the network lifetime.

In wireless sensor networks, the studies that support sink mobility without global position information exploit a Backbone-based Virtual Infrastructure (BVI) to avoid the routing structure construction per each mobile sink by full network flooding. The BVI approach typically considers one-hop clusters and a backbone structure-based tree configured by the cluster heads (CHs). For data dissemination to a mobile sink, the head of the cluster where the mobile sink exists registers the backbone structure on behalf of the sink, and then source nodes generate the data to their CHs via the tree. Finally, the CHs deliver the data to the mobile sink. However, the one-hop cluster makes the tree organized by too many CHs so that it causes large location registration overhead according to movement of the sink. Moreover, the data delivery via the tree with a large number of CHs might lead to data delivery from source nodes to the sink though detour paths due to always delivering data via the tree. Namely, although the source nodes exist at nearest clusters from the cluster attached by the sink, if they are located in different branch of the tree, the data should be delivered via detour paths on the tree. Therefore, we propose a novel BVI-based communication protocol to support sink mobility without global position information. To reduce the number of CHs, we consider multi-hop clusters. Also, to avoid the location registration of a mobile sink to the whole CHs, we uses a rendezvous CH on which queries of the mobile sink and reporting data of a source node meet. However, such a manner also has data detour problem that the source node sends data packets to the mobile sink via the rendezvous CH. Thus, we present a scheme to find a path with fewer hop-counts between CHs where the source node and the mobile sink are located in. Simulation results show that the proposed protocol is superior to the existing protocols in terms of the control overhead and the data delivery hop counts.

In order to provide context-aware services, context modeling is one of the most important tasks. Ontology has been widely accepted for the context modeling but it brings some overheads in the process of reasoning large-scale and dynamic information. In mobile networks, especially, ontology should be verified to be applicable for Context-aware Services since real-time responsiveness for large scale moving users is highly required to be guaranteed. This paper proposes an efficient context model to overcome the limitation of ontology. For the purpose, we design a conceptual context model and compare the processing time of the context-aware mobile service system implying the three different context modeling approaches ontology, database, and proposed hybrid modeling. As the result of performance evaluations, the proposed hybrid model shows faster processing time among them and lesser affected by the major metrics of mobile services changeability and number of users than the two existing models. Based on the experimental results, we expect that the proposed hybrid model is very useful and efficient for fast responsiveness to support Context-aware Services for large scale users in mobile networks.

In many applications of Wireless Sensor Networks (WSNs), the sensing data are disseminated from a source to multiple mobile sinks. Since WSNs consists of a number of sensor nodes with limited capabilities, previous studies mainly discuss on how to send the data efficiently and do not consider the group mobility of mobile sinks that move together staying closely and randomly move within a geographically restricted region. Although the existing multicasting protocols could be applied, they suffer from high congestion and control overhead due to location updates by individual mobile sinks. Geocasting protocols are effective for data delivery to a sink group within a restricted region, but do not guarantee since they only focus on transmitting data to all nodes within a stationary region. Therefore, we propose Region Based Data Dissemination (RBDD) scheme to address these problems. RBDD provides efficient data dissemination scheme for mobile sink groups, so it guarantees data transmission when a sink group does not only move as a whole, but its member sinks also move inside of the region or outside of it. Simulation results show that RBDD guarantees data delivery to a mobile sink group.

Data packets in multi-hop wireless sensor networks require a variety of Communication Reliability (CR) according to applications. Recently, a scheme for supporting a desired CR, called AC, has proposed. In order to support the desired CR, AC simply maintains 100% of data packets of a source at intermediate nodes on a routing path which do not satisfy the desired CR. However, since AC does not consider the link quality of each intermediate node on the routing path, it highly increases the number of total packets which are transmitted on the routing path for achieving the desired CR. To solve the high number of totally transmitted packets in AC, we propose an effective transmission scheme, MTTP, which can reduce the number of totally transmitted packets for achieving the desired CR. By geometric programming, MTTP allocates an optimized one-hop packet transmission rate of each wireless link by considering the quality of wireless links on the routing path. However, AC and MTTP consider only one next-hop node on the routing path even though one node has many one-hop neighbors in practice. Accordingly, we propose another scheme, MTTP_Prime, which consider many one-hop neighbors. By dynamic programming, MTTP_Prime selects a routing path with optimized one-hop packet transmission rates in terms of the number of totally transmitted packets. Simulation results verify that MTTP is superior to AC, and MTTP_Prime is superior to MTTP.

This paper proposes a novel detection and tracking scheme for continuous objects in wireless sensor networks, such as wild fire and bio-chemical material. Unlike previous works, the scheme takes into account a two-tier grid structure in order to achieve flexible and reliable detection and tracking. Firstly, for flexibility, the scheme proactively constructs a coarse-grained grid structure and then, once a continuous object appears, fine-grained grid structures are reactively established within coarse-grained grid cells only around the continuous object. Secondly, with respect to reliability, minute grid cells of the fine-grained grid structures are able to provide detailed shape of boundary of the continuous object; to quickly deal with diffusion of the continuous object the scheme prepares the fine-grained grid structures into next coarse-grained grid cells toward diffusion direction of the continuous object.

Due to the severe resource constraints of sensor hardware, energy efficiency is one of critical factors for monitoring the movement of the large-scale phenomena such as wild fire and hazardous bio-chemical material, denoted by continuous objects. In order to save energy, most of existing research on tracking the continuous objects focuses on finding the ways to minimize the communication cost through the effective data delivery such as data aggregation and reducing the number of reporting nodes, and not much work has been done on sensor state scheduling. Energy efficiency is expected to improve if only sensor nodes near the boundary of continuous object actively participate in tracking process, while other sensor nodes stay on sleep state for energy saving. In this paper, we propose a predictive continuous object tracking scheme, called PRECO, which uses minimum set of active sensing nodes to reduce energy consumption. The proposed scheme predicts the future boundary line, which provides the knowledge for a wake-up mechanism to decide which sleeping nodes need to be activated for future tracking. The proposed algorithm is verified with simulation results that total energy consumption can be dramatically reduced under acceptable boundary detection accuracy.

There have been many routing protocols proposed for data dissemination to multiple mobile sinks in Wireless Sensor Networks (WSNs), and the protocols regard each sink as an individually distributed single entity without relationship of each other. Recently, mobile group entities have been introduced in WSNs. A number of mobile sinks move together in a group manner, and mobile sinks in the group stay closely, and they randomly move within a geographically restricted region. Although the existing multicasting protocols could be applied in such a group communication application, they suffer from high congestion and control overhead due to location updates to a source by individual mobile sinks. Geocasting protocols are effective means for delivering data packets to a sink group within a restricted region, but do not guarantee successful data delivery to a mobile sink group since they only focus on transmitting data to all nodes within a stationary region. This paper propose Region-Based Data Dissemination (RBDD) scheme to address these problems. RBDD first determines the group region based on current locations of mobile sinks in a group, and advertises the information of the group region to sources. It then directly transmits data to a group of mobile sinks through restricted flooding only within the region. Simulation results show that RBDD guarantees data delivery to a mobile sink group.

For multicast applications with large-scale groups in large-scale wireless sensor networks, it is an important issue for energy saving in geographic multicasting both to obtain location information of destination nodes and to construct the geographic multicast tree efficiently. To address this issue, there have been proposed global search based hierarchical geographic multicasting protocols. Such protocols divide the whole network into many multiple small areas and a leader node in each area manages the location information of destination nodes in its area. However, since they find location information of such leader nodes through global location search at a source, they consume much energy. Also, since they exploit hierarchical geographic multicast trees that have a higher tree consisting of the source node and the leader nodes and a lower tree consisting of a leader node and destination nodes in the area of the leader node, they consume more energy due to data detouring. To solve the problems of global search based hierarchical geographic multicasting protocols, we propose a local search based consecutive geographic multicasting scheme. Through avoiding the global search and removing the data detouring, the proposed protocol saves much energy of sensor nodes. Simulation results show that the proposed protocol is superior to the existing protocols.

Wireless sensor networks may be utilized for various application areas such as health, military, home, and so on. In the wireless sensor networks, data transmission typically relies on multi-hop communication with high packet loss rates on wireless links so that reliable end-to-end data transmission is desirable. Recently, in order to achieve desired Communication Reliability (CR) levels of the various sensor network applications, a flexible loss recovery mechanism, called Active Caching (AC) is proposed. With respect to a desired CR of an application, when the packet delivery rate during multi-hop transmission from a source to an intermediate node decreases below the CR, AC retransmits lost packets from the source to the intermediate node so that the intermediate node has all data packets just like the source node. Then, during the data transmission from the intermediate node to the destination, if the packet delivery rate at another intermediate node falls below the CR, the new intermediate node recovers the lost packets from the previous intermediate node, not from the source node. Namely, AC flexibly caches all data packets at some intermediate nodes on the routing path in order to achieve the CR. However, AC does not consider the loss rate of each wireless link on the multi-hop routing path in terms of the loss recovery. Since the lost packets are requested and retransmitted via the multi-hop routing path, AC may cause a lot of retransmissions of the lost packets and thus increasing the number of totally transmitted packets. Therefore, we propose a strategy to minimize the number of totally transmitted packets when all data packets from a source are delivered to a destination with a desired CR. In order to minimize the number of totally transmitted packets, the strategy allocates an optimized one-hop packet transmission rate per each wireless link calculated by geometric programming.

In this paper, we investigate the use of explicit disjoint for the multipath routing to achieve cost-efficient operation of wireless sensor networks. The focus is on constructing completely disjointed multiple paths between the source of sensing stimulus and the destination of gathered sensor data. We propose simple schemes for multipath construction based on explicit multiple anchor nodes. For the fully disjointed multipath construction, we exploit the logical and physical schemes. The logical method classifies a multipath through the pipeline of the area where there is at least one sensor. The physical approach comprises completely disjoint multiple paths to be comprised at the source level based on the geographic routing, intermediate node side, and anchor node side and destination node side. We propose explicit multiple paths to comprise a disjoint multipath so that we removes the flooding overhead used in the multipath discovery process. The proposed scheme constructs the distributed multiple paths with data transmission through the localized information exchange between neighbor nodes. Our simulation results show the fundamental importance of an explicitly disjointed multipath proposed in this paper. For example, one of our results shows that the proposed scheme significantly reduces the signaling overhead compared to the existing multipath routing methods when there are many nodes in WSN. The simulation result also shows that the proposed scheme, compared to the explicit disjoint multiple paths, is more cost efficient than an existing multipath scheme.

In wireless sensor networks, with respect to a desired time deadline real-time data dissemination schemes achieve that by a spatiotemporal communication approach forwarding data from a source to a destination with a delivery speed. The delivery speed is typically obtained from both the static distance from the source to the destination and the interval of the time deadline. However, in case of real-time routing to a mobile sink, since the mobile sink randomly moves around, the distance from a source to the mobile sink would be dynamically changed. Hence, we propose a new real-time routing scheme considering the dynamic distances by the mobile sink. In the scheme, the source calculates an expected area of the mobile sink by the moving speed of the sink; then, the data delivery speed is obtained from the worst case distance from the source to the farthest position on the area. The source transmits data to expected area with the delivery speed, and the first sensor node within the area then floods in the area to deliver the data to the mobile sink that is dynamically located within the area.

Dynamic spectrum access (DSA) has received much attention in recent years as an effort to enhance the spectrum utilization. Primary-secondary usage (PSU) of spectrum is an option of DSA which gathers much study interest. Some modes of secondary usage of spectrum are granted on the condition that the secondary user (SU) releases the spectrum resource immediately whenever the primary user (PU) requests. The SU may hop to an idle spectrum resource, if one is available, or the call is dropped. This spectrum handoff (SH) let the ongoing call continue the session with some degradation of Quality of Service (QoS) for a while. However if the spectrum resource consists of more than one spectrum blocks (SBs) as Public-Private Partnership (PPP) in the upper 700MHz band as Federal Communications Commission (FCC) revised lately, we may reduce the SHs by employing the proposed Cascaded Resource Allocation (CRA) algorithm. In CRA, the SBs are prioritized and the users' accesses are allocated to the SBs considering the priority of the SBs. In this paper we present a generalized model to efficiently make use of multiple SBs and a basic analytical model for prioritized resource access. The performance of CRA is measured by analyzing Markov modulated Poisson process (MMPP) and simulation results.

In order to monitor continuously moving phenomena such as wile fire and hazardous bio-chemical material in wireless sensor network, boundary tracking approach has been widely used by reason of its huge scale and extensive diffusion property. With the boundary tracking scheme, the energy efficiency is expected to improve if only sensor nodes near the boundary of continuous object actively participate in tracking process, while other sensor nodes stay in sleep mode for energy saving. In this paper, we propose a predictive continuous object tracking scheme, which uses minimum set of active sensing nodes to reduce energy consumption. The proposed scheme predicts the future boundary line, which provides the knowledge for a wake-up mechanism to decide which sleeping nodes need to be activated for future tracking. The proposed algorithm is verified with simulation results that total energy consumption can be dramatically reduced under acceptable boundary detection accuracy.

There have been proposed many geographic multicasting protocols for wireless ad hoc sensor networks. Most of these protocols tend to exploit a Source-initiated Geographic Multicasting (SGM) approach which consists of three phases: first, a source collects the position information of all destination nodes; second, the source constructs a multicast tree through the position information; third, the source forwards data down the multicast tree. However, if a multicast group contains many mobile destinations, the SGM approach may cause a great deal of delivery of position registration and update messages to the source, thus lead to significant energy consumption of the sensor nodes in the vicinity of the source. In addition, high data delivery latency is another problem since the data delivery is triggered after the source obtains the position of all destinations and constructs a geographic multicast tree. Moreover, since each destination asynchronously updates one's new position to the source, the source node in the SGM approach is difficult to find an opportune time for reconstructing the multicast tree. In this paper, we propose a Destination-initiated Geographic Multicasting (DGM) protocol which can avoid these problems faced by the SGM approach. The DGM allows destinations to construct their own data delivery paths to a source, and a multicast tree is automatically constructed by merging the data delivery paths, and then, the source node forwards data to them down the multicast tree. In the DGM, we also propose a round-based virtual infrastructure with a radial shape for increasing the merging probability of data delivery paths and reducing reconstruction ratio of the multicast tree due to mobility. Simulation results show that the proposed protocol is superior to other protocols in term of average data delay and average energy consumption.

Proxy Mobile IPv6 (PMIPv6) is designed to provide mobility service to IPv6-nodes in a network domain by network-based management which does not require the nodes to be involved in IP mobility management. In other words, the PMIPv6 can support roaming within a PMIPv6 domain, i.e. intra-domain roaming, transparent to mobile nodes. Recently, next generation wireless networks, such as 802.16e and Super 3G/3.9G, adopt the PMIPv6 as a management solution of the IP mobility. Such extensive adoption of the PMIPv6 might lead to frequent roaming of IPv6-nodes not only within a PMIPv6 domain but also between PMIPv6 domains. However, for the roaming between PMIPv6 domain, i.e. inter-domain roaming, existing solutions take interworking between PMIPv6 and MIPv6 into consideration. It means that every mobile node should involve IP mobility management although the nodes merely move around among PMIPv6 domains which provide the transparent node mobility service. Hence, we propose a network-based roaming mechanism between PMIPv6 domains to offer transparent mobility support to IPv6-nodes. The inter-domain mechanism takes into account concatenated tunnels between home domain and visited domain. The tunnels would be established by signaling among routers in the home and visited PMIPv6 network domains.

This paper proposes a novel detection and tracking scheme for large-scale phenomena, called continuous objects, in wireless sensor networks, such as wild fire and bio-chemical material. Unlike previous works, the scheme takes into account a two-tier grid structure in order to achieve flexible and reliable detection and tracking. Firstly, for flexibility, the scheme constructs a coarse-grained grid structure and then, once a continuous object appears, fine-grained grid structures are established within coarse-grained grid cells only around the continuous object. The fine-grained grid structures could be constructed with dynamic grid cell size according to various requirements. Secondly, for reliability, minute grid cells of the fine-grained grid structures are able to provide detailed shape of boundary of the continuous object; to quickly deal with diffusion of the continuous object the scheme prepares the fine-grained grid structures into next coarse-grained grid cells toward diffusion direction of the continuous object.

In wireless sensor networks, real-time data delivery schemes typically achieve a desired delivery speed by proactively performing one-hop lookahead. Recently, to reduce the deadline miss ratio against the desired delivery speed, a study has proposed a real-time routing protocol based on proactively performing twohop lookahead. However, the recent study might cause heavy message exchange overhead and high computing complexity to proactively carry out obtainment of two-hop neighborhood speed information in the entire sensor network whether data are delivered or not. Moreover, although multi-hop lookahead provides the least deadline miss ratio, due to the restriction from the overhead and the complexity, the recent study merely adopts the two-hop lookahead manner. In this paper, we propose a novel real-time routing protocol. The proposed routing protocol adopts on-demand neighborhood information obtainment only around data forwarding paths. The on-demand information obtainment is performed in multi-hop lookahead. Hence, the proposed routing protocol is able to provide the least deadline miss ratio to realtime data delivery. Simulation results prove that the proposed routing protocol offers better performances with respect to deadline miss ratio, total communication costs, energy efficiency, and network lifetime.

In wireless sensor networks, a geographic routing requests source nodes (sensor nodes) to know location information of destination nodes (sinks) to send their data. To address this issue, many sink location service schemes have been proposed in the literature. They are designed to support only one communication mode such as unicast, anycast, manycast, or multicast communication modes. However, because an application can have one or more communication modes or a sensor network can operate several applications with each communication mode, it is necessary for a scheme to support all communication modes. Hence, we propose a general sink location service scheme for supporting all communication modes. The proposed scheme modifies the basic idea of the existing one proposed for unicast communication mode and extends it for supporting all communication modes. Simulation results show that the proposed scheme is superior to other sink location service schemes when supporting all communication modes.

Geographic routing has been considered as an efficient, simple and scalable routing protocol for wireless sensor networks, since it exploits pure location information instead of global topology information to route data packets towards a static sink. Recently, a number of research works have shown that mobile sinks can achieve high energy efficiency and load balance than static ones. In order to receive data packets continuously, a mobile sink must update its location to the source frequently. However, frequent location updates of mobile sinks may lead to both rapid energy consumption of the sensor nodes and increased collisions in wireless transmissions. The authors propose a novel geographic routing for mobile sinks to address this issue. The proposed scheme takes advantage of wireless broadcast transmission nature of wireless sensor nodes. When a sink moves, the new location information is propagated along the reverse geographic routing path to the source during data delivery. Analysis and simulation results indicate that elastic routing is superior to other protocols in terms of control overhead, data delivery delay and energy consumption.

Geographic routing has been considered as an efficient, simple, and scalable routing protocol for wireless sensor networks since it exploits pure location information instead of global topology information to route data packets. Geographic routing requires the source nodes to be aware of the location of the sink nodes. How source nodes efficiently obtain the sink location information has been merely studied yet. In this paper, we propose a Sink Location Service via Inner Rectangular in Wireless Sensor Networks. A source node and a sink node send location queries and location announcement messages to specified direction respectively by geographic routing; thus, a sink location query path and a sink location announcement path is generated. The node located on a crossing point of these two paths informs the source node about the sink location information. Then the source node sends data to the sink node by geographic routing. The proposed scheme constructs a virtual restricted linear flooding zone inside the network to guarantee the existence of the crossing point. Simulation results show that proposed scheme is reliable and efficient than the existing protocols.

We propose a communication mechanism to support mobility of loosely coupled mobile users in sensor applications with multiple sources. First, we examine problems for mobility support of the loosely coupled users in wireless sensor networks with multiple source nodes, and then study the dynamic sink communication model to support a mobile user with sink-oriented tree based data gathering from multiple sources and data-centric unicasting. Finally, we present an energy-efficient solution to support the loosely coupled mobile users through single data-gathering tree establishment with a distributed manner and the gathering tree based data-centric multicasting.

This paper addresses issues for tracking and monitoring continuous objects, such as poison gas, biochemical, and chemical liquid in wireless sensor networks. These continuous objects are quite different from the individual objects, such as people, animals, and vehicles in that they are continuously distributed across a region and usually occupy a large area. Accordingly, they are detected and sensed by many sensor nodes, and their sensing data are redundant and highly correlated. Hence, there needs any efficient scheme on collecting and aggregating locally their sensing data and generating the data report. The continuous objects also tend to diffuse, changes in shape, increases the size, even splits into multiple smaller continuous objects, or join together one continuous object. Accordingly, there also need any efficient scheme to manage efficiently the dynamic change of shape of the continuous objects. Therefore, we introduce dynamic rectangle zone-based collaboration mechanism for detecting, tracking, and monitoring the continuous objects taking into account the dynamic change of their shape. The proposed mechanism constructs a dynamic rectangle zone included the area occupied by one continuous object. One center node in the zone collects and aggregates the sensing data from sensor nodes which detect the continuous object. The dynamic rectangle zone change newly according to dynamic change of the continuous object and the center node is also altered by another node to minimize the energy consumption for collecting the sensing data. Through simulation results, we also evaluate how environmental factors and control parameters affect the performance of the proposed mechanism.

In delay-tolerant wireless sensor networks, reporting data from a source node to a sink may be delayed to satisfy certain criterions, for example, high energy-efficiency, low algorithm complexity and so on. Sensed data in such networks accumulate on a sensor node during time delayed. It means that even a single failed node may cause a massive-data loss. This paper proposes a backup scheme to minimize data losses caused by failed nodes in wireless sensor networks using the delayed report. The proposed scheme can safely preserve data and consume less energy by backuping a single data to multiple nodes that exist in the one-hop distance from the source node. Multiple backup nodes do not only store and recover backup data but also distributedly report their backup data to the sink instead of the source node. As a result, the energy consumption for data report is not concentrated to the source node and is distributed to backup nodes. Such approach suggests the new potentiality of a backup scheme in error-scarce network.

Typical multicasting saves efficiently both bandwidth and energy in static wireless sensor networks. Such benefits make the research of multicast which is a transmission from a data source to multiple destinations (sinks), actively. Most of these researches focused on the way how to make efficient multicast tree only, they are weak for supporting mobile sinks. In practical applications, sinks move around and collect information from a sensor field. If the mobile sinks apply to these approaches, frequent entire multicast tree reconstructions are needed to support mobile sinks. Unfortunately, it leads to exhaustion of sensors' limited power supply, consequently it reduces whole network lifetime. In this paper, we propose an energy-efficient multicast protocol to support multiple mobile sinks by the local multicast tree reconstruction, called Local Updated-based geographic Multicasting for Mobile sinks (LUMM) for wireless sensor networks. A value of BOD (benefit of distance) used a standard from a local multicast tree reconstruction with minimal overhead. Our simulation results show that LUMM support the mobility of sinks efficiently.

Geographic routing has been considered as a scalable approach in ad-hoc and sensor networks since it exploits pure position information of neighbors and a destination node instead of global topology information to route data packets. To obtain the position information of the neighbors, many geographic routing protocols assume that each node exchange periodically its own position information with its neighbors. However, these periodically position exchanges in regions without packet forwarding make nodes consume unnecessary energy. In addition, given that the nodes have mobility, when a node forwards a packet, the position information of its neighbor nodes may be invalid. Hence, in these mobile networks, it is more efficient that a mobile node collects the position information of its neighbors when it needs to forward a packet. Because every sender node in geographic routing also selects the nearest neighbor node to the destination node as the receiver node, obtaining the position information of only closer neighbor nodes to the destination node can save more wireless resources than obtaining that of all neighbor nodes. In large-scale networks, because many wireless collisions can happen due to position exchanges of many neighbor nodes, they should share limited wireless resources. Therefore, we propose a mechanism to solve these issues of geographic routing in large-scale mobile networks. Simulation results show that the proposed mechanism has better performance than the existing geographic routing protocols.

Most existing geographic routing protocols on sensor networks concentrates on finding ways to guarantee data forwarding from the source to the destination, and not many protocols have been done on collecting and aggregating data of sources in a local and adjacent region. However, data generated from the sources in the local and adjacent region are often redundant and highly correlated. Accordingly, data collection and aggregation of the region in the sensor networks is important and necessary to save the energy of sensor nodes. We introduce the concept of a local sink to address this issue in geographic routing. The local sink is a sensor node in the region, in which the sensor node is temporarily selected by the global sink for collecting and aggregating data from source nodes in the region and delivering the aggregated data to the global sink, in geographic routing. We also design a model to determine an optimal location of the local sink and propose a mechanism to collect data through the local sink. Simulation results show that the proposed mechanism with the local sink is more efficient in terms of the energy and the data delivery ratio than the existing mechanism in a geographic routing.

In many sensor applications such as intruder tracking, reliable data dissemination is necessary. Existing studies in ad hoc networks generally apply end-to-end control for reliability. This approach however could not adapt to wireless sensor networks (WSNs). Existing studies in WSNs generally apply multi-path approach for reliability. This approach however only increases probability but could not assure data dissemination. In typical WSNs, data are delivered from a source node to a destination node on routing path that is fixed within a certain period of time. This routing path is well-matched with notion of virtual circuit. Approaches based on virtual circuit traditionally use hop-by-hop control for reliable data dissemination. In this paper, we apply notion of virtual circuit to WSNs and propose hop-by-hop control for reliable data dissemination. The proposed scheme consists of three major functionalities: virtual circuit construction, hop-by-hop control, and virtual circuit management. Virtual circuit construction make sure constructing fixed routing path by routing table. Hop-by-hop control guarantees data transmission between two nodes, i.e. one hop, on virtual circuit by error detection and retransmission. Virtual circuit management prevents disconnecting circuit by reconstructing circuit. Simulation results show that the proposed scheme is efficient in terms of data delivery ratio and energy consumption.

In wireless sensor networks, groups of mobile users interested in equivalent information could be classified into two categories according to existence of direct communication channel among the users: 1) loosely coupled user group and 2) tightly coupled user group. The loosely coupled group means that a mobile user should communicate with others via a wireless sensor network for querying, gathering, and sharing of information interested from the group. Several information communication mechanisms have already been proposed to support mobility of the loosely coupled user groups. However, the mechanisms may not suit in case of sensor applications with multiple data sources since those are usually construct a network structure per each source. Namely, according to the mechanisms, too many network structures for the many data sources could be constructed and it may causes excessive computing overhead and energy exhaustion of sensors. Therefore, we propose an information communication mechanism to support mobility of loosely coupled mobile users in sensor applications with multiple sources. First, we examine the problems for mobility support of the loosely coupled groups in wireless sensor networks with multiple source nodes, and then study the dynamic sink communication model for data gathering from multiple sources and data delivery to a mobile user. Finally, we present an energy-efficient solution to support mobility of loosely coupled groups based on data gathering tree establishment via distributed manner and tree-based data multicasting.

Future wireless communication systems are expected to be comprised of multiple overlay networks, in which different kinds of Radio Access Technologies (RATs) are being deployed in overlay. Since efficient use of multiple RATs may result in economical benefits to users and network operators, RAT selection, or joint radio resource management, is an important issue. For the sake of proper RAT selection, users' velocity and network load status are considered as vital parameters. In this regard this paper proposed a mobility model to reflect both individual user's velocity and collective network load according to zones. To cope with different coverage size of RATs and supporting velocity of mobile nodes we employ probabilistic change of velocity according to user's position. We first divide the whole simulation area into zones according to users' mobility pattern and define probabilistic zone transition model (PZTM). We believe the proposed mobility model is consistent with real life as well.

In large scale Internet network, the research in area of event detection and report publish/subscribe communications paradigm is being progressed. Data-centric is the basic characteristic of data transmission mode of the publish/subscribe communications paradigm. Such characteristic coincides with the wireless sensor network. The publish/subscribe communications paradigm performs task in manner of space, time and synchronous decoupling. The publish/subscribe communications paradigm with such property is tend to be applied to the wireless sensor network. However, existing algorithms do not satisfy the three decoupling modes in wireless sensor network. Therefore, this paper applies the publish/subscribe communications paradigm to the wireless sensor network and proposes a model to solve the energy consumption problem. The proposed communication model satisfies the three decoupling modes by using Embedded Grid Structure (EGS) in the wireless sensor network. Simulation results show that proposed model is energy-efficient compared with other protocols.

We propose a communication mechanism to support mobility of loosely coupled mobile users in sensor applications with multiple sources. First, we examine problems for mobility support of the loosely coupled users in wireless sensor networks with multiple source nodes, and then study the dynamic sink communication model to support a mobile user with sink-oriented tree based data gathering from multiple sources and data-centric unicasting. Finally, we present an energy-efficient solution to support the loosely coupled mobile users through single data-gathering tree establishment with a distributed manner and the gathering tree based data-centric multicasting.

In mobile broadband wireless access networks such as Mobile WiMAX, idle mode is defined to save radio resources and reduce power consumption when a mobile station is not involved in packet transmission and reception. In order to support idle mode, location update and paging should be supported, where location update and paging overheads are affected by paging group size. In this paper, we propose a hierarchical paging group ID structure, an adaptive location update algorithm based on the paging group structure, and a predictive paging scheme for large size paging groups. The performance of the proposed scheme is compared with conventional scheme from the aspect of location update and paging signaling overheads. Numerical results show that the proposed scheme performs well for varying the velocity of mobile stations.

Typical information communication for large-scale wireless sensor networks may be performed in a data-centric routing manner. The data-centric routing manner well matches the publish/subscribe communication paradigm operated by a contention-based networking. The publish/subscribe paradigm provides decoupling properties for data-centric networking: space, time, and synchronization decoupling. For large-scale applications in which many publishers and subscribers are participated in interworking of information, the decoupling properties proffer salability. However, most existing communication schemes for the large-scale sensor networks do not fully satisfy the decoupling properties. The schemes construct network structures based on publishers or subscribers known as event sources and sinks respectively. Such dependency of network structures causes that network structures are established in proportion to the number of sinks or sources, i.e. space dependency. Also, originating sinks or sources of structures are always joined with the structures and manage the interworking information, i.e. dependency of time and synchronization. Hence, the communication schemes should take into account a network structure independent of the publishers and subscribers. In this paper, we propose a novel communication scheme decoupled with sinks and event sources, called ARBITER. ARBITER constructs a shared virtual grid with level value k from center point, k = 0. It then arranges storage nodes and transit nodes at level 1 cross points and over level points respectively. Sinks query to the storage nodes through the transit nodes and receive interesting information via requesting paths. Sources store sensed data to the storage nodes by the transit nodes. Our simulation proves that ARBITER shows better performance in terms of scalability, data responsibility, and mobility support.

Geographic routing has been considered as an efficient, simple, and scalable routing protocol for wireless sensor networks since it exploits pure local location information instead of global topology information to route data packets. Geographic routing requires the sources nodes to be aware of the location of sinks. Most existing geographic routing protocols merely assume that source nodes are aware of the locations of sinks or can get the locations of sinks by some service. How can source nodes get the locations of sinks was not addressed in detail. In this paper, we propose a circle path based sink location service for geographic routing in wireless sensor networks. In this scheme, a source node sends a sink location query (SLQ) message to the predefined base node and sends another SLQ message to a node on the edge of the sensor network, thus generating a SLQ path; a sink node sends a sink location announcement (SLA) message along a circle path, the centre of the circle path is the predefined base node. By this way we can guarantee the SLQ path and SLA path have at least one crossing point. The node located on the crossing point of the two paths informs the source node the sink location. How to achieve this procedure in any irregular profile sensor network is another challenge of this paper. Simulation results show that our protocol is significantly superior to other protocols in terms of energy consumption and control overhead.

Many dissemination protocols on the mobility support in wireless sensor networks have been designed based on the assumption that the movement trace of sinks is random. However, the mobility of the sinks in many applications, for example, the movement traces of a soldier on operation in a battle field or a firelight on rescue operation in the disaster area, can be determined in advance since they move in accordance with the decided operation or the drill regulation to perform their task. In this paper, we propose a Predictable Mobility-based Data Dissemination protocol (PMDD) that enables data to directly route from source nodes to moving sinks by taking into consideration predictable movement behavior of the sinks. We also compare the performance of the PMDD with those of other dissemination protocols with random movement behavior of the sinks, and show the superiority of the PMDD based on network lifetime, data delivery ratio, and delay latency.

Typical wireless sensor networks consist of sensor nodes and base-stations (sinks). The sensors, sinks, and user nodes can orthogonally provide their own mobility environments. The existing studies take only sensor mobility, sink mobility, and event mobility into account. Inquirer mobility, however, can be possibly suggested as one of the mobility models. An inquirer is one of the existing entity for sensor networks as a user. Inquirer mobility and routing mechanism to support it are proposed in this paper. For that, possible mobility environment and characteristics are also analyzed. At the end of this paper, excellence of the proposed routing model is proved through simulation results.

Sensor networks are composed of a great number of sensor nodes. Since all sensor nodes are energy-restricted and hard to recharge, it is very important. However, the energy consumption may significantly increase if mobile sources or sinks exist in sensor networks. The reason is that the routing information for mobile sources and sinks needs to be update frequently for efficient data delivery. The routing algorithm supporting mobile sinks should consider not only continuous data delivery but also the energy consumption of sensor nodes. However, most of the existing research e.g. Fan Ye, et al. (Set. 2002), Zehua Zhou, et al., (Jun 2006) focuses on even energy consumption while the mobility of sinks and sources is rarely consider. In this paper, we propose an efficient routing protocol with multiple virtual grids to reduce energy consumption and improve packets delivery efficiency. Simulation results show that our algorithm can guarantee high data delivery ratio and lower average delivery delay, while consuming lower energy than existing routing protocols in sensor networks.

Fast Mobile IPv6 has been proposed to reduce latency and packet loss inherent to the handover process. However the previous research did not consider the packet loss according to the tunnel management for Fast Mobile IPv6. In the procedure of binding updates and fast binding updates, a mobile node has to establish new tunnels after receiving binding acknowledgement messages. While completing the tunnel creation and routing update, the mobile node can not handle packets incoming and outgoing through the new tunnels. This drawback causes packet loss of impeding the seamless handover. To reduce this packet loss, we have developed an effective tunnel management scheme called Dual Mode Tunneling (DMT). It employs decapsulation-only tunnels before using typical tunnels which can do an encapsulation and decapsulation. Through implementation and experimental study for vertical handover between 3G long term evolution and wireless local area network, we have evaluated the performance of the proposed scheme.

Void areas (holes) as an inevitable phenomenon exist in geographic routing of wireless sensor networks, because the unpredictable and harsh nature application environment or uneven energy consumption. Most of the existing schemes for the issue tend to construct a static detour path to bypass a hole. The static detour path may lead to uneven energy consumption of the nodes on the perimeter of the hole; thus it may enlarge the hole. At the same time, traffic would concentrate on the peripheral node of the hole; thus the nodes on the perimeter of the hole tend to be depleted quickly. In previous work, we have proposed a hole geometric model to reduce the energy consumption and packet collisions of the nodes on the hole boundary. This scheme, however, still has the static detour path problem. Therefore, we extend the previous work by constructing a dynamic detour path hole geometric model for wireless sensor networks in this paper. The location of hole detour anchor is dynamically shifted according to Gaussian function, just generating dynamic hole detour paths.

Geographic routing has been addressed in many literatures of ad hoc sensor networks due to its efficiency and scalability. Void areas (holes) bring geographic routing several problems such as excessive energy consumption and data congestion of hole boundary nodes. Holes are hardly avoided in wireless sensor networks because of various actual geographical environments, e.g., puddles, buildings or obstacles, or uneven energy consumption, even physical destruction. To bypass holes, most existing geographic routing protocols tend to route data packets along the boundaries of holes by perimeter routing scheme. This scheme consumes more energy of the nodes on the boundaries of holes, thus possibly enlarging the holes, we call this hole diffusion problem. In this paper, we propose anchor node based virtual modeling of holes in wireless sensor networks to solve the hole problems faced by geographic routing in wireless sensor networks. Simulation results show that the proposed protocol is superior to other protocols in terms of packet deliver ratio, control overhead, average delivery delay, and energy consumption.

Mobile IPv6 (MIPv6) used to support IP mobility in heterogeneous network such as the universal mobile telecommunications system (or long term evolution system) and 802.11 wireless local area networks (WLANs). But MIPv6 has well-known packet loss during movement detection and binding update, but it has another packet loss while creating new tunnel and updating routing path. That is, when the home agent sends a binding acknowledgement (BA) message to mobile node after receiving a binding update (BU) message, the new tunneled packets are also sent to MN with the BA message. After receiving the BA message, the MN creates new tunnel and modifies routing information. But while completing these procedures, the MN can not handle new tunneled packets incoming together the BA message. To solve this problem, this paper proposes the dual tunneling mechanism(DTM) to reduce the additional loss using the reception- only tunnel. In this paper, we analyze the packet delay time in overlay and non-overlay network in case of general mobile IPv6 and DTM, and observe the handover experimental result for the 3G LTE-WLAN network.

This paper proposes an effective resource management scheme using vertical handoff and fairness concepts to prevent hot-spot cell and satisfy the various QoS requirements of users in 4G wireless networks. When the networks adapt available resources and QoS threshold to meet users' multiple QoS constraints, the occurrence of hot-spot cell in high-loaded traffic regions with time variable traffic conditions is unavoidable. The hot-spot cell cause serious lowering of resource utilization and system throughput in overall networks. In order to prevent the hot-spot cell and enhance resource utilization and system throughput, this paper uses vertical handoff decision function by inter-cell and inter-service fairness concepts. In order to verify the performance of proposed scheme, the simulation and numerical analysis are performed.

Main idea of Fast MIPv6 (FMIPv6) is the new address pre-configuration on the link of the current access router by the aid of predictive link layer triggers. If the link layer triggers are not available prior to the link layer handover, the FMIPv6 reverts to the reactive mode. In this case, the MN performs the address configuration after connecting to the new access router. It causes additional packet loss and signaling overhead. Also, too early link layer triggers increase the service delay time and the buffer space. In this paper, we propose the definitive link layer triggering criterion to support the predictive handover in FMIPv6. We consider the handover scenario from WLAN to a cellular network which is most common access networks in wireless worlds. To provide the best time on which the link layer triggers initiate, we introduce a remaining link lifetime which considers the received signal strength variation rate. The performance evaluation shows that the proposed algorithm substantially reduces the handover latency with guaranteeing the predictive mode FMIPv6.

Geographic routing is attractive in wireless sensor networks especially for scalability, as it is possible to scale the network size without increasing the signaling overhead, because routing decisions are inherently localized. Geographic routing requires the sources nodes to be aware of the location of the sinks. Most of existing geographic routing protocols merely assume that the sources can get the location of sinks by some location service. How can source nodes obtain the location of sinks is not addressed in detail. In this paper, we propose an anchor node based sink location dissemination scheme for geographic routing in wireless sensor networks. In this scheme, a source node and a sink node send sink location announcement and query messages along two paths respectively by geographic routing. The node located on the crossing point of the two paths informs the source about the sink location. The challenge of this paper is that how to guarantee these two paths having at least one crossing point in any irregular profile of sensor network. Simulation results show that our protocol is significantly superior to other protocols in terms of energy consumption and control overhead.

Geographic routing has been addressed in many literatures of ad hoc sensor networks due to its efficiency and scalability. Void areas (holes) bring Geographic routing some problems such as data congestion and excessive energy consumption of hole boundary nodes. Holes are hardly avoided in wireless sensor networks due to various actual geographical environments, e.g., puddles, buildings or obstacles, or uneven energy consumption, even physical destruction. To bypass a hole, most existing geographic routing protocols tend to route data packets along the boundary of the hole by perimeter routing scheme. This scheme, on one hand, consumes more energy of the nodes on the boundary of the hole, thus possibly enlarging the hole, we call this hole diffusion problem; on the other hand, it may incur data congestion if multiple communication sessions are bypassing the hole simultaneously. In this paper, we propose efficient hole detour scheme to solve the hole problems faced by geographic routing in wireless sensor networks. Simulation results show that the proposed protocol is superior to other protocols in terms of packet deliver ratio, control overhead, average delivery delay, and energy consumption.

In wireless sensor networks, a communication model that separate a sink collecting information from sensor nodes and a user using it has been proposed. In the model, a mobile user appoints a neighborhood sensor node as a dynamic sink, and the dynamic sink collects data from all sensor nodes and forwards the aggregated data to the mobile user. In this paper, we expand the model for single mobile user to support multiple mobile users. A core of the novel model is mapping between single dynamic sink and multiple mobile users. Namely, multiple mobile users appoint a dynamic sink and the sink collect information from all sensor nodes and forward them to the multiple mobile users. To design effectively the novel model, two issues should be solved. First, the multiple mobile users without any mutual communication channel should efficiently choose and appoint only one dynamic sink. Second, the single dynamic sink should forward the collected information to the multiple mobile users. This paper proposes a solution for those issues. The solution consists of three schemes: 1) data collection scheme, 2) tree-based multicast scheme, and 3) user mobility support scheme. The data collection scheme is to solve the first issue and the tree-based multicast scheme is to solve the second issue. Also, the user mobility support scheme is to guarantee data forwarding to mobile users.

Geographic routing has been considered as an efficient, simple, and scalable routing protocol for wireless sensor networks since it exploits pure location information instead of global topology information to route data packets. Geographic routing requires the sources nodes to be aware of the location of the sinks. How can source nodes get sinks locations with low overhead is a difficult issue in wireless sensor networks. In this paper, we propose a Sink Location Service for geographic routing in wireless Sensor Networks. In this scheme, a source node and a sink node send sink location announcement and query messages along two paths respectively by geographic routing. The node located on the crossing point of the two paths informs the source about the sink location. Then the source can send data packet to the sink by geographic routing. How to guarantee that these two paths have at least one crossing point in any irregular profile of sensor network is the challenge of this paper. Simulation results show that our protocol is significantly superior to other protocols in terms of energy consumption and control overhead.

Void areas (holes) are hardly avoided in wireless sensor networks because of various actual geographical environments, e.g., puddles, buildings or obstacles, or uneven energy consumption. To bypass holes, most existing geographic routing protocols tend to route data packets along the boundaries of holes by perimeter routing scheme. Such a scheme depletes the energy of nodes on the boundary of holes faster than others and is likely to result in earlier deaths, thus enlarging the hole sizes, a phenomenon we call the hole diffusion problem. Routing along the hole boundary may also lead to increased collisions especially if multiple data streams try to bypass a hole simultaneously. In this paper, we propose virtual circle based geometric modeling of holes for geographic routing to address these problems in wireless sensor networks. Our proposed algorithm avoids routing on the hole perimeter by selecting appropriate intermediate anchor nodes (close to the hole boundary) and routing via this anchor node. We show by simulation that our proposed algorithm provides significant savings in energy consumption, shorter routing delays, higher packet delivery ratio, all with comparable control overhead as compared with state-of-the-art techniques.

Wireless sensor networks traditionally consist of sensors perceiving data and sinks gathering the data. In addition, users receive required information from the sinks via infrastructure networks. The users, however, should receive the information from the sinks through multi hop communications of disseminated sensor nodes if such users move into the sensor networks without infrastructure networks. Unlikely, the previous works only considered mobility of sinks, which function users. Nevertheless, it is difficult for such approaches to mobility to exploit the existing data-centric routing algorithms and also for the mobile sinks to function as gateways to connect with infrastructure. To improve the shortcomings, we suggest a novel viewpoint of mobility for wireless sensor networks and propose a solution to support the mobility with multiple static sinks in this paper. The multiple static sinks, which are connected with each other via infrastructure, provide high throughput and low latency. Furthermore, they improve hotspot problems and prolong network lifetime. The proposed mechanism finally is evaluated by simulation results about throughput, latency, and network lifetime.

Wireless sensor networks are composed of a great deal of energy restricted sensor nodes and targets (events) at long- term usage such as environment monitoring. The failure of sensor nodes caused by energy exhaustion or physical destruction may lead to the reduction of sensor areas. In the wireless sensor networks, the nodes located on the edge of holes are relatively weaker than other sensor nodes since the geographic routing scheme tends to route data packets along the edge of holes by the right hand rule. It results in more energy consumption or even exhausts the energy of the hole edge nodes, so it may enlarge the holes. We call this, aholediffusionproblem. The right hand rule may also lead to data collisions on the hole edge nodes if multiple communication sessions need to bypass a hole simultaneously. In this paper, we propose hole modeling to handle the hole problem in wireless sensor networks. Our hole modeling can efficiently prevent the hole diffusion, avoid the local minimum faced by geographic routing protocols, and reduce data collisions on the hole edge nodes. Simulation results present our protocol is superior to the previous works in terms of control overhead, average delivery delay and energy consumption.

Void areas (holes) are hardly avoided in sensor networks either because of various actual geographical environments, e.g., puddles, buildings or obstacles, or uneven energy consumption. To bypass holes, most existing geographic routing protocols tend to route data packets along the boundaries of holes. Generally, a data packet will be either forwarded along a hole boundary by the right hand rule or pushed back to find another route to its destination when the data packet encounters the hole boundary. The right hand rule, on one hand, consumes more of the nodes' energy on the boundaries of holes, thus possibly enlarging the holes; on the other hand, it may incur data collisions if multiple communication sessions share the same boundaries of holes simultaneously. In this paper, we will propose a hole geometric modeling to solve hole problem in wireless sensor networks. Our hole geometric modeling has two goals: one is to prevent data packets from traveling along the boundaries of holes; the other is to avoid the problem of local minimum phenomenon. By achieving the first goal we can not only reduce the energy consumption of the nodes on the boundaries of holes, thus preventing holes' diffusion, but also reduce the data collisions in the nodes on the boundaries of holes. The second goal can reduce the packets rerouting overhead.

Overlay multicast protocols in mobile ad hoc networks (MANET) have advantages that are low overhead and robustness in dynamic network topology by using the unicast routing protocol between group members. However, overlay data paths in overlay multicast can remain static even though the underlying physical topology is changing. Overlay multicast may lead to sub-optimal overlay data paths, since the communicating group members are not aware of the underlying physical topology. Therefore, overlay multicast protocols requires periodic control messages for the overlay data path management in dynamic environment. In this paper, we propose an efficient overlay multicast protocol (EOMP) using unicast routing information. Multicast state information of each group member in EOMP is created by its unicast routing table. Therefore, multicast data packets between group members are delivered through the overall optimal paths in physical networks. Meanwhile, the overlay data path in EOMP can be managed without periodic control messages in the dynamic environment. Finally, we evaluate EOMP performance with other multicast protocols proposed for ad hoc networks. Simulations show enhanced results of proposed protocols

Recently, Internet connectivity in mobile ad hoc network (MANET) has been studied extensively in order to support ubiquitous Internet services to MANET users and provide interworking with other networks such as wireless local area network (WLAN) and cellular networks to extend the coverage of these networks. Although there have been a lot of works on connecting MANET with Internet, few works have been performed on the detailed performance analysis of the effect of routing path discovery for Internet connection from MANET with reactive routing protocol such as ad hoc on demand distance vector (AODV) protocol from the aspect of routing discovery delay and control overhead. In this paper, we propose a hierarchical mobile AODV6 network architecture, which combines the concept of hierarchical Mobile IPv6 and AODV ad hoc routing protocol. In the proposed architecture, Internet gateway performs the role of mobility anchor point (MAP) of hierarchical mobile IP (HMIP), and a novel routing path discovery and data delivery scheme is proposed by managing address information of connected nodes in Internet gateway. Then, the performance of the proposed scheme is analyzed in terms of routing path discovery overhead and control packet overhead for Internet connection from AODV6 node. The result shows that the proposed scheme has lower control packet overhead and routing path discovery delay compared with conventional AODV6 scheme

Typical sensor networks consist of a user, a sink, and a number of sensor nodes. The traditional communication architecture usually assumes that there is a legacy networks between a user and a sink. However, in many actual applications users like firefighters and soldiers move around sensor fields and they may not have any direct communication through legacy networks. In other words, a sensor network is the only communication channel between a user and a sink in a practical sensor field. Thus, it is essential to deliberate a novel architecture for the user mobility issue. In this paper, we present a novel communication architecture where a user operates around an infrastructureless sensor field. We, then, propose a new networking model to support user mobility on the novel architecture, named dynamic sink model. In the model a sink is temporarily selected among generic sensor nodes by a user when the user wants to get information from a sensor network. The selected sink gathers data from sensor nodes for interested tasks and propagates collected information to the user via the sensor network. We evaluate and analyze performance of the proposed dynamic sink model on the novel architecture with regard to efficiency of energy consumption, average delay, and delivery ratio, compared with the common static sink model on typical communication architecture

Stable multicast data delivery structure contributes high data delivery ratio and low control overhead in Mobile Ad Hoc Networks (MANETs). Due to dynamic topology of MANETs, to construct a stable multicast data delivery structure becomes a challenge in ad hoc environment. In this paper, we propose a stable overlay multicast protocol for MANETs based on modified Delayed Forwarding mechanism. In this protocol, each member node precalculates its stability according to remaining battery and local mobility of itself. A source rooted overlay multicast tree is created if source has to send data packets. The overlay creation follows the stability of each member node. By using modified Delayed Forwarding mechanism, a member node with relatively high stability will have highly populated subtrees, by this way to improve multicast routing stability. Data packets are transmitted via IP-in-IP tunnels between member nodes in the overlay tree.

A characteristic of mobile ad hoc networks, mobility leads to frequently update multicast routing information based on network multicasting. For the reason, comparatively lots of control signaling messages are generated, so bandwidth of wireless media and limited battery power of mobile nodes are inefficiently consumed. To improve the shortcomings, overlay multicast protocols on application layer has been proposed; however, some of them have another shortcoming which is that the number of unnecessary data forwarding among multicast members increases. Additionally, they hardly support network scalability. Thus, this paper proposes an implicit cluster-based overlay multicast protocol exploiting tree division (ICOM-TD) for mobile ad hoc networks to improve their shortcomings. Finally, we evaluate performance of ICOM-TD through numerical analysis about complexity of multicast routing and simulation in comparison with existing multicast mechanisms for ad hoc networks on end-to-end time delay, packet overhead, and delivery ratio.

Typical sensor networks consist of users, sinks, and a number of sensor nodes. The traditional architecture usually assumes that there is a legacy network between users and sinks. However, practical users like firefighters and soldiers move around sensor fields and they might not have any direct communication through legacy networks. In other words, sensor networks are the only communication channel between users and sinks in practical sensor fields. Now there are no researches with respect to architecture to support the user mobility. Thus it is necessary to deliberate a new architecture for such the issue. In this paper, a novel communication architecture was presented where a user operates around an infrastructureless sensor field. A new networking model was then proposed, named dynamic sink model, to support user mobility on the novel architecture. In the model a sink is temporarily selected among generic sensor nodes by a user when the user wants to get information from a sensor network. The chosen sink gathers data from sensor nodes for interested tasks and propagates collected information to the user via the sensor network. The performance of the dynamic sink model on the novel architecture was evaluated and explored with regard to average delay, delivery ratio, and network lifetime compared with the common static sink network model on typical communication architecture.

The previous tree-based and mesh-based multicasting in mobile ad hoc networks need to be improved because of their shortcomings of the mechanisms. One of them is lots of signaling overheads to modify multicast trees due to dynamic topology, and the other is inefficiently exploiting wireless network resources for delicately set paths. For the reason, overlay multicast mechanisms in mobile ad hoc networks are proposed to improve such shortcomings, yet they also result in the other problems, which are network scalability and inefficient transmission among dense multicast members. In this paper, An overlay multicast mechanism based on single-hop clustering and tree division (OMCD) in mobile ad hoc networks is proposed to improve all the problems. The OMCD exploits single-hop clusters to manage dense multicast members and to reduce overheads by broadcasting. The clusters are created and delegated by cluster leaders, based on location information. Also, multicast sources in OMCD deliver multicast data to only the leaders through overlay multicast tree (OMT) but not all multicast members. Finally, performance of the proposed OMCD is also evaluated by analysis and simulation in the end of this paper

In IEEE 802.16e Mobile Wireless Metropolitan Area Networks (MAN) system, idle mode and paging are defined in order to save battery power of MS and scarce radio resource. Current IEEE 802.16e standard, however, only specifies physical (PHY) layer and medium access control (MAC) layer protocols and mechanisms on idle mode management and paging in network layer have not been completed yet. In this paper, two alternative registration and paging schemes are proposed in order to support idle mode in IEEE 802.16e Wireless MAN system with location server (LS) and paging controller (PC). These mechanisms can be used in implementing network entities for IEEE 802.16e Wireless MAN system. The performance of the two schemes is analyzed based on mathematical analysis. The results show that there is a tradeoff between two schemes based on mobility and traffic characteristics of MS.

In this paper, we give a framework to reduce delivery failure influence in overlay multicast. Unlike previous efforts based on duplicated forwarding, our scheme builds another type of overlay data delivery tree (DDT), which is adaptively reconstructed based on the number of measured packet delivery ratio while guaranteeing end-to-end delay bound. Through practical simulation results, we analyzed packet delivery ratio, control overhead, end-to-end delay and number of replicated packets.

Due to unpredictable topology change and frequent link failure, it is becoming evidently a major challenge to provide a stable route between source and destination in mobile ad hoc networks (MANET). Unlike previous multipath routing schemes for redundancy and unicast routing protocol utilizing longest route expiration time supported by GPS, we develop a framework to establish the most stable route based on measured frequency of link failure, and available battery, as well as the number of actual connections. To evaluate the performance of the proposed scheme, we also provide practical simulation results with multipath routing and unicast routing protocol in terms of packet delivery ratio, control overhead, and hop counts, as well as end-to-end delay. Through analysis of simulation results, we demonstrate that our scheme shows better performance than the general unicast routing protocol as well as similar packet delivery ratio to the multipath routing protocol with less maintenance overhead.

Various ALM (application layer multicast) mechanisms have been suggested to remove the barriers that block deployment of IP multicast. However, most ALM mechanisms do not consider the host group model, which is not a problematic portion, but advantageous feature of traditional IP multicast in terms of scalability, robustness, security, and transparency. Furthermore, those mechanisms build an overlay multicast network for data delivery mostly based on a simple measurement, with a few metrics, without directly considering the IP network topology. Thus, they might suffer some inefficiency, such as long join delay and large control overhead. We propose a scheme to take advantages of both IP multicast and ALM, based on two principal design factors. By adopting the host group model, our scheme can inherently acquire network topology information used to get rid of application level routing inefficiency, and to gain additional efficiency for many group members. Also, we exploit topology-awareness to reduce join delay and localize group members so that controls for setting up and maintaining overlay networks can be limited in a domain. Overall network performance is enhanced with our scheme by building an overlay network based on performance factors associated with network characteristics using a hierarchical structure.

Fair call admission control (CAC) for heterogeneous services with different traffic properties, such as wideband and narrowband calls, is an important subject in wireless networks. B.M. Epstein et al. (see IEEE JSAC, vol.18, no.3, p.523-34, 2000) proposed a novel CAC scheme, independent multiclass one-step prediction with complete sharing and reservation (IMOSP-CS and IMOSP-RES), which ensures that wideband calls are not blocked more than narrowband calls. However, such an IMOSP algorithm can often lead to some abnormalities, not guaranteeing call blocking probability (CBP) fairness and high resource utilization, depending on traffic behavior. It is mostly because the resource adjustment algorithm in IMOSP simply increases or decreases only one bandwidth unit independent of traffic properties. These abnormalities can be easily seen where offered traffic load between services differs greatly. We propose a novel CAC scheme to admit wideband and narrowband calls fairly regardless of traffic behavior. Also, we propose a new resource management algorithm to enhance utilization. These improvements are largely dependent on seeking a reservation partition for each class based on prediction and measurement. Simulation results demonstrate that our CAC scheme actually achieves CBP fairness for wideband and narrowband calls and also improves resource utilization.

We propose a new adaptive and predictive measurement-based fair call admission control policy. The objective of a new admission policy is to reduce computation overhead and rapidly re-allocate resources to meet desired quality of service (QoS) demands. With numerical analysis, we evaluate QoS constraints by using queuing model which is described by a two-dimensional continuous-time Markov chain. By comparing results of analytical model with one of event-driven simulation, we validate the accuracy.

Previous multicast schemes for MANET (mobile ad hoc networks) are mostly classified as tree-based schemes and mesh-based schemes depending on their multicast delivery structure. Tree-based schemes cannot cope with network mobility due to frequent tree reconfiguration. On the other hand, mesh-based schemes waste unnecessary resource due to delivery along multiple paths. We propose to use an overlay multicast to handle network mobility efficiently with minimized resource. In our scheme, DDT (data delivery tree) can remain static as long as unicast route between members that are related to data forwarding remains reachable. Thus, it can not only minimize the effects of network mobility, but also bring about low additional control overhead. Such distinct advantages are specifically evaluated through the results of the simulation.

We propose an admission control scheme for guaranteeing the mobile QoS in mobile IP networks. The proposed scheme considers the tunnel reservation for keeping handoff dropping probability below predefined values. It reserves resources dynamically by estimating the number of mobile users and mobility features in each mobility agent. We propose mobility entities that depict mobility features and the history which has statistical mobility information in each mobility agent. We describe the requirements for macro mobility considerations and prove that our scheme satisfies them. With the mobility entities and the history, our scheme makes a history tuple to predict a mobility feature of the next time. It can be applied to a real world, because it reflects mobility features of each mobility agent to measure and analysis mobility entities. It provides an adaptive reservation scheme which allocates additional resources depending on a measured handoff dropping probability even if a handoff probability is changed unexpectedly.

The differentiated service architecture is based on a simple model by applying a per-class service in the core node of the network. However, due to the simplified network behavior, the network structure and provisioning were more complicated. If a service provider wants the dynamic provisioning or better bandwidth guarantee, signaling protocol with QoS parameters or admission control method should be deployed in DiffServe network. However, these methods increase the complexity. Therefore, we propose the dynamic provisioning mechanism based on the centralized bandwidth broker and distributed measurement based on the centralized bandwidth broker and distributed measurement based admission control and movable boundary bandwidth management to support heterogeneous QoS requirements in DiffServe networks.

This paper introduces the Electronic Commerce Payment System-Telephone Number (ECPS-TN) with a deferred payment method that bills the price of merchandise in electronic commerce shopping mall based on business to customer (B2C) together with a telephone bill, and presents its configurations, functions, and performances. The ECPS-TN consists of a server and gateway system that presents the service of ECPS-TN which can be linked by the present electronic commerce shopping mall of the Web/Merchant server, customer management and billing system, and the TCP/IP. By introducing a different payment method from the present payment such as credit card, electronic money wallet, and on-line depositing, it can not only serve a variation of payment but also secure a member of service for almost of users by using the system that bills the price of merchandise in electronic commerce shopping mall together with the number of public switched telephone network/integrated service digital network (PSTN/ISDN) which belongs to an average Internet user.

Mobile IP (MIP) is proposed to ensure packet routing to a mobile host in the Internet regardless of the attachment point. MIP defines two functional entities, home agent (HA) and foreign agent (FA) to manage the mobile host location. Also, MIP defines the tunneling mechanism to deliver packets that are destined for the mobile node's home address. This tunneling mechanism has difficulties in adapting to the IntServ and DiffServ Internet service architectures. Since both services identify the service session as three-tuples - destinations IP address, IP protocol number and destination port - a new different service session must be defined over the IP tunnel. Current MIP QoS works concentrate on how to guarantee QoS over the IP tunnel and map it to the end-to-end service session, but seem to neglect the host mobility supporting protocol. We regard this protocol as an important factor. The current protocol has a hierarchical architecture with both micro and macro mobility. So, if MIP QoS can be organized in the same hierarchical architecture, better QoS can be obtained. Since MIP can support host mobility in a macro network, IntServ and Diffserv must be applied in this section. However, since several schemes are proposed to support fast handoff in the micro level, several QoS mechanisms may be applied in this level. This paper specifics a hierarchical scheme which uses not only aggregate RSVP flows between domain level agents, but also a specific local policy between domain level agent and mobile host in a domain.

This paper proposes the TPED MBAC (two-phase edge-to-edge distributed measurement based admission control) mechanism that provides the guarantee of user QoS requirements and the fairness of blocking probability between flows traversing different path lengths in large IP networks. The proposed mechanism has two provisioning phases, the quantitative provisioning phase and the qualitative provisioning phase, in admission control and performs WRR scheduling based on the hop counter for probing packet transmission. Additionally, the proposed mechanism uses the optimized probing packet rate instead of the peak rate. For the performance evaluation of the proposed mechanism, we present simulation results in terms of the fairness of blocking probability and the loss probability using the ns-2 simulator.

ATM rate-based flow controls can effectively reduce cell losses and buffer requirement in ATM switches, and thus enhance overall performance in ATM networks. However, many simulation studies show that the performance of TCP can be reduced over ATM networks in some situation like network congestion. This comes from the absence of direct channel between TCP and ATM protocol stack. That is, the ATM layer in a host does not notify TCP of the congestion information from ATM networks through resource management (RM) cells. So, TCP may generate vast packets regardless of present network status. In this paper, we introduce the direct mechanism, interoperative method between TCP and ATM protocol stack and perform a simulation in order to justify our mechanism. The simulation results, by SIMNET from NIST, show that the TCP adopting mechanism has better performance over that only with ATM congestion control mechanism.