The proliferation of mobile and IoT devices has sparked growing interest in multi-device interaction, where a single app operates across multiple devices to leverage their diverse capabilities. However, the current methods of app development and usage remain bound to a single-device paradigm, rendering multi-device apps difficult to implement and deploy. This paper presents COMET , a novel mobile app framework that enables the dynamic distribution of app components across multiple devices at runtime, supporting a wide range of multi-device scenarios, including collaborative applications, smart environments, and interactions across heterogeneous personal devices. COMET enables developers to specify distributable components using lightweight annotations and employs build-time code instrumentation to automate the deployment and execution of selected components onto remote devices. This approach supports multi-device interaction with minimal developer effort and without requiring system-level modifications. To realize this, COMET addresses four key challenges: (i) the static partitioning of app components and extraction of their dependencies at build time, (ii) efficient execution of these components on remote devices, (iii) preservation of intercomponent communication across devices, and (iv) synchronization of distributed components that share a global state. We implemented a prototype of COMET on Android and evaluated it using real-world apps. Our evaluation with eight case-study apps shows that component distribution completes within 251.8 ms. A user study with 15 participants further demonstrates that COMET provides intuitive multi-device interaction with acceptable responsiveness.

This research addresses the critical health risk of falls in the elderly through the development of an innovative fall recognition system. The proposed methodology incorporates data augmentation, joint angle extraction, velocity, acceleration, and spatial feature analysis. RNN embeddings capture temporal dependencies, while a hybrid optimization model Minkowski Distance in Locust Movement with Aquila (MDLMA), combining Artificial Locust Swarm Optimization (ALSO) and Aquila Optimizer (AO) facilitates effective feature selection. The Graph-Based Hierarchical Temporal Network (GHTNet) integrates graph convolutional networks, bidirectional Long Short-Term Memory (Bi-LSTM) layers with Residual Blocks, and Attention-Weighted Fusion for adaptive spatial and bidirectional temporal modelling. The system culminates in a fully connected layer for precise fall classification, ensuring robustness and efficiency in detection.

Ultra-wideband technology has the potential to provide precise real-world localization. However, due to Non-Line-of-Sight propagation, the transmitted packet can be incomplete or lost during the ranging, which may lead to communication failure. To minimize this, we propose the scheduled signal reception technique. The proposed approach is tested in a real-world environment with Qorvo DWM3001C modules. The experimental results verify its efficiency, offering a practical solution for UWB-based localization, particularly in dynamic circumstances.

In this paper, we propose LUVI, Lightweight UWB-VIO relative positioning method for indoor localization. Recent designs of handheld and embedded devices feature various technologies which have the means to enhance localization performance in indoor environments. These include visual odometry based on cameras and augmented reality, and communication hardware such as UWB. Integration of such technologies to exploit their advantages allows us to compensate for each other's errors in measurement. This improves the overall function of future services, such as visual representation of sensing information from sensors in areas that are not physically visible. However, existing work cannot fully exploit these technologies to high extent, often inducing high errors or wasted resources. LUVI is a novel localization method which estimates the location of a target object using relative coordinates of estimator devices without the aid of definitive coordinates. LUVI focuses on utilization of lightweight management of virtual anchors for localization, with functions that reduce the computing and communication complexity while maintaining the accuracy and improving energy efficiency of the localization. Our work has been fully implemented and tested in several indoor environments, showing robustness to NLOS while significantly reducing computational complexity, and up to 30% lower average error.

Federated Learning (FL) is an emerging machine learning technique used to train big data in resource-constrained situations. However, three main challenging issues are identified regarding communication resources in FL. First, the parameter server (PS) that collects user devices’ models is in the remote cloud. In the process of aggregating the model, the issues may burden the path links between the PS and high-traffic local nodes. Second, the network can be congested owing to the large size of the model parameters. Third, PS-side links may be highly stressed if the number of participating clients is large. In the present study, we propose a resource efficient FL scheme, in which clusters’ clients are based on the location, and the communication range of each client, which selects partial clients in a cluster, updates the model by exploiting the Pareto principle. Simulation results show that our proposed scheme reduces wireless network traffics while maintaining a slightly higher accuracy than the legacy FL mechanism.

Over the several years, lots of researches have focused on routing protocol for Mobile Ad-Hoc Networks (MANET). Optimized Link State Routing Protocol (OLSR) is one of the typical routing protocols standardized by IETF, but it is known to be vulnerable to many type of security attacks. In this paper, blockchain technology is applied to OLSR to complement security vulnerabilities and reduce the computational overhead in existing security solutions.

In this poster, we propose a sensor localization system assisted by wireless communication and augmented reality (AR) suitable for disaster relief applications. Generally, disaster environments are considered extremely hazardous and deteriorated, with unpredictable effects to human mobility and digital devices. To maximize the safety and efficiency of first responders, deployment of wireless sensors are of utmost importance, as sensor nodes can provide sensing information as well as location information. We analyze the issues and challenges that need to be tackled for high accuracy localization of sensor nodes in such environments, and then propose a system that we plan to develop in the near future.

Ultrawideband (UWB) based localization has the potential to be used in a variety of applications due to its high accuracy. For robust and high performance in real environment, the most challenging issue is the detection and mitigation of noise from non-line-of-sight (NLOS) signals. Current researches use channel state information, particle or Kalman filter, and statistics based approaches for the NLOS noise detection and mitigation. These solutions show high accuracy in some applications; however, they need additional hardware and work in static environment only. We propose an NLOS mitigation algorithm that does not need any additional hardware andworks in dynamic environment with mobile obstacles. The main idea of the algorithm are to estimate the NLOS bias by repetitively comparing the intersection of the hyperbolas with intersections of circles. The proposed approach is tested for Decawave UWB testbed. Experimental results show that the proposed scheme works well in different dynamic scenarios as compared to the localization scheme without NLOS noise mitigation.

WLAN based localization is a key technique of location‐based services (LBS) indoors. However, the indoor environment is complex; received signal strength (RSS) is highly uncertain, multimodal, and nonlinear. The traditional location estimation methods fail to provide fair estimation accuracy under the said environment. We proposed a novel indoor positioning system that considers the nonlinear discriminative feature extraction of RSS using kernel local Fisher discriminant analysis (KLFDA). KLFDA extracts location features in a well‐preserved kernelized space. In the new kernel featured space, nonlinear RSS features are characterized effectively. Along with handling of nonlinearity, KLFDA also copes well with the multimodality in the RSS data. By performing KLFDA, the discriminating information contained in RSS is reorganized and maximally extracted. Prior to feature extraction, we performed outlier detection on RSS data to remove any anomalies present in the data. Experimental results show that the proposed approach obtains higher positioning accuracy by extracting maximal discriminate location features and discarding outlying information present in the RSS data.

Abstract Routing Protocol for Low Power and Lossy Networks (RPL) has been standardized by the Internet Engineering Task Force to efficiently manage the functions of the network layer when providing Internet connectivity for wireless sensor networks. RPL has been designed for constrained devices and networks. Owing to their constrained nature, RPL‐based networks can be exposed to a wide variety of security attacks. One of the most serious attacks in RPL is a black hole attack, where a malicious node silently drops all the packets that it is supposed to forward. This paper proposes a mitigation technique against black hole attack with low packet loss and high reliability. The proposed technique consists of a local decision and a global verification process. First, each node observes the communication behavior of its neighboring nodes by overhearing packets transmitted by its neighbors and attempts to identify suspicious nodes based on their behavior. In the second process, if a node identifies a suspicious node, then it verifies whether the suspicious node is a black hole. We demonstrate that the proposed approach increases packet delivery rate significantly and detects black hole attack effectively. Copyright © 2016 John Wiley & Sons, Ltd.

Integration of sectored-antenna in wireless networks improves network performance through increased network capacity, extended transmission range and reduced energy consumption. However, incorporating sectored-antenna makes the trivial process of discovering neighbors even more challenging and complicated. Moreover, due to the frequent changes in network topology, a continuous and self-adaptive neighbor discovery protocol is highly sought-after. In this paper we present a novel neighbor discovery protocol for wireless ad hoc networks with sectored-antennas. The novelty of the proposed protocol lies in three aspects. Firstly, it considers the neighbor discover as an ongoing or continuous process instead of a onetime network bootstrap activity. Secondly, the protocol leverages the in-network information to adapt itself according to the network dynamics. Finally, by adjusting the frequency and length of the neighbor discovery process, the protocol reduces the discovery time and the communication overhead. Through extensive simulation-based study it is shown that the proposed protocol outperformed the pure random, scan-based approach in terms of discovery latency while significantly minimizing the communication overhead.

The introduction of ubiquitously connected mobile computing platforms acted as a catalyst for accessing and enjoying multimedia/visual contents on a more diverse set of computing environments than ever before. Recently, with the standardization of various protocols, a number of screen sharing services have been introduced, in which the contents of a mobile computing platform's screen is shared with a neighboring device [1]. With these services, data contents collected from various external sensing sources, can be captured at a mobile platform and (visually) shared easily with others using direct wireless connections. However, a previously unconsidered technical issue begins to impact the user experience levels of these multimedia/screen sharing mobile services. Specifically, we begin to notice energy efficiency as an important performance factor to consider when utilizing visual contents on mobile platforms with resource limitations. Actively using computational resources for visual applications lead to device heating and shorter battery life-times, as well as increased use of the wireless bandwidth when downloading or sharing the visual contents.

Conjunction of USB applications with wireless technologies leads us to USB over Wi-Fi through the means of Wireless Serial Extension (WSE). However, USB and Wi-Fi has distinct data prioritization methods, which causes problems in existing QoS protocols when the two technologies are used together. To solve this problem, this poster proposes and evaluates the dynamic QoS adaptation scheme, which intelligently maps the data of USB with the weighted transmission queues of enhanced distributed channel access (EDCA) mechanism.

Topology control offers many advantages for wireless networks such as reduced energy cost, simplified communication graph and network-wide connectivity. There are mainly two methods for managing the network topology. In clustering, a hierarchy of backbone nodes is selected to improve on the systems scalability and network lifetime whereas in power control each node adjusts its transmission power to achieve certain desirable properties of the resulting topology. While the focus of the former approach is to find an ideal number of the backbone nodes, the main objective of the later approach is to estimate a minimal power level which can solve multi-objective design problem. There have been several topology control protocols proposed however they miss the potential of combining both approaches. In this paper we propose Two-Tiered Topology Control (TTTC) protocol, a generic framework which combines the clustering and power control approach towards topology control and evaluate different conditions under which it performs well. TTTC operation is divided into two phases. During the first phase, a parameterized clustering algorithm is executed to obtain clusters of varying properties. At the end of first phase, the network is organized into two tiers. The backhaul-tier consists of cluster-head nodes while the connectivity-tier contains the cluster-members. In the second phase, each cluster-head runs a local MST-based power control algorithm. Simulation results show that proposed framework achieves efficient trade-off in terms of energy cost, neighbor count and hop count while maintaining fully connected network. Moreover, the framework relies on local available information with lower communication overhead.

This paper focuses on improving the reliability of packet transmission in wireless CCN. Various studies on wireless CCN have been conducted; however, only a small number have addressed such an issue of reliability. Due to the packet size limitation of the MAC layer, a segment from the upper layer needs be fragmented into smaller pieces. The problem is that a receiver cannot rebuild the segment even when only a single fragment is lost. Of course, the traditional CCN provides a solution with interest retransmission. However, this scheme causes a significant network overhead as it requires all the fragments, even the one(s) successfully transmitted, to be requested for retransmission. To solve this problem, we propose a novel scheme in which only missing fragments are requested. We compare the proposed scheme to the interest retransmission mechanism by means of implementation in order to analyze its effectiveness.

This poster proposes an adaptive flow control scheme for reliable packet delivery of Universal Serial Bus (USB) services when they are transmitted through wireless medium. In the future, USB can be utilized with the Wi-Fi technology to provide Wi-Fi USB (WSB). However, the data transmission of Wi-Fi and USB are asynchronous due to their different Medium Access Control (MAC) characteristics, which may result in buffer overflow. To prevent buffer overflow, we propose an adaptive flow control scheme that can select between the various transmission speeds of USB to match with the bandwidth provided by the Wi-Fi layer. Preliminary results of the proposed scheme evaluated via the NS-3 shows that the packet delivery ratio of USB data can be substantially increased, thus providing better USB reliability.

The capability to interconnect directly with neighboring wireless devices coupled with improvements in high-speed wireless connections, and the wide distribution of high-quality multimedia has led to the design of standards such as the WiFi-based Miracast [1], which allows handheld mobile devices to share their screen contents with larger-sized display devices (e.g., smart TVs). Such screen sharing capabilities allow various multimedia files to be easily accessed through mobile platforms, and played (in real-time) through larger screens; thus, has the potential to enable a variety of attractive entertainment applications. While widely available on all Android-based mobile devices (4.2 or recent), the Miracast standards introduce a significant level of inefficiency as it deals with different types of multimedia contents.

The peer-to-peer and ad-hoc networking allows content dissemination and sharing among mobile devices without depending on any infrastructure. However, mobile devices still encounter content sharing issues in highly dense networks. Therefore, we develop a new architecture which creates self-organizing ad-hoc network with content centric networking over Wi-Fi Direct on smartphones. It enables nodes to build multiple groups using different channels for providing Wi-Fi Direct based multi-hop communications. The proposed architecture can achieve not only power efficiency for energy constrained devices but content sharing efficiency from content-centric networking properties. Our simulation study using NS-3 with CCNx shows significantly improved performance of the proposed solution.

Content-centric networking (CCN) is a new networking paradigm to resolve the data traffic explosion problem of the Internet caused by rapid increase in file sharing and video streaming traffic. Networks with CCN avoid delivery of the same contents on one link as many times as they are requested, as contents can be stored and transferred by the cache of CCN routers. Two major features that are currently considered in CCN are in-network caching and content-aware routing. Even though both aspects are important, there is little work on the comprehensive interaction between them. In this paper, we propose the cache capacity-aware CCN which consists of selective caching and cache-aware routing methods that interacts with each other to encompass cache management and cache-aware request forwarding. The main motivation of the proposed scheme is to utilize the network caches evenly and redirect a content request based on the past forwarding of the desired contents (or chunks). To enable this function, we utilize a cache capacity metric which is collected on forwarded content requests and reflected in the content replication with popularity information from content server. We evaluate the proposed scheme against existing cache replication algorithms and show that it leads to better utilization of network caches with significant performance improvements.

Research presented in this paper enhances the power management schemes of Wi-Fi Direct to provide better services for a wider range of Wi-Fi Peer-to-peer (P2P) applications. Although the Wi-Fi Direct defines two power management schemes to provide energy efficiency in P2P devices, neither is enough to meet power efficiency and reliability requirements for various services. To alleviate this problem, the proposed scheme recognizes the properties of applications and dynamically adjusts the duty cycle of P2P devices. The proposed scheme is compared with the schemes in Wi-Fi Direct to analyse its effectiveness.

Wireless Mesh Networks are suitable for providing the Smart Grid communications required for high reliability and network capacity. However there still exist several problems disturbing network reliability. In this demonstration, we propose reliable Wireless Mesh Network architecture based on IEEE 802.11s system. We will present our system architecture to increase communication reliability and evaluate the performance by implementing testbed installation.

This paper focuses on enhancing IEEE 802.11e EDCA for improving reliability in Smart grid networks. 802.11e can support prioritized QoS to differentiate traffic and guarantee fairness for delay-stringent applications. However, this may pose serious problems when applied to Smart Grid environments which support applications that have strict reliability requirements. To solve this problem, we suggest a contention mitigated EDCA algorithm (CM-EDCA), which utilizes packet collision and MAC retransmission parameters to change the packet priority and reduce packet collisions. The proposed scheme is compatible with IEEE 802.11e and easy to implement for Smart grid devices. Simulation studies show improved reliability compared to the existing methods in IEEE 802.11e.

We propose and demonstrate an adaptive wireless mesh network architecture for public surveillance and monitoring. The proposed architecture is based on IEEE 802.11s WLAN mesh network, which is enhanced to provide adaptation depending on the environment of the network. We first introduce the implementation architecture of the adaptive mesh, and then describe the demonstration of the network on the wireless mesh camera sensor testbed.

In video surveillance and monitoring systems based on wireless mesh networks, large volumes of multimedia data with different priorities and time demands are generated by video cameras and wireless sensors. Hence, one of the key issues is how to alleviate network congestion for highly reliable transfer of multimedia data towards gateways. This paper proposes a solution for utilizing multiple gateways to divert data streams and alleviate traffic congestion near a specific gateway. With a new routing protocol, named “Multi-Gateway Routing with Congestion Avoidance (MGR-CA)”, network congestion can be predicted in a distributed manner and amounts of data traffic transmitted to the congested path are redirected to an alternative gateway based on the severity of congestion. Preliminary testbed experiments are made to show the performance of our scheme.

Geocasting is an efficient mechanism for disseminating messages towards a specific geographical region. Since its packet forwarding is based on the location information of nodes, it does not require any periodic or on-demand path updates. Especially, geocasting is suitable for several applications in tactical ad hoc networks such as alarms for chemical and missile attacks, guerrilla detection or a local weathercast. However, traditional geocast protocols proposed for pure mobile ad hoc networks are inadequate to meet high demands of reliability in military applications. In this study, the authors propose even more efficient and reliable dual-path geocasting protocol which utilises two independent paths and novel acknowledgement mechanisms to improve the chances of successful message delivery. The authors investigate how to locate this dual path to achieve the best performance by means of destination points. The authors’ comprehensive simulation study using ns-2 shows that the proposed scheme results in high delivery ratio with low packet overhead and latency.

In numerous sensor network applications, a group of nodes surrounding an event (forming an active region) must collaborate to collect locally generated data, reliably and efficiently. Active regions are often characterized by intense data transfer, packet collisions and congestion, resulting in significant network performance loss. Previous studies dealt these scenarios either at the application or network layers, where potential performance gains at the MAC layer were not considered. In this paper, a cross-layer communication protocol Event-Centric MAC (EC-MAC) is introduced in which the channel access time is divided into two intervals. During slot reservation interval, all nodes within an active region collaborate to construct a Transmit/Receive schedule on-the-fly. Once the schedule is in place, data forwarding is performed during the data transmission interval towards a designated root node. By allowing contention-free channel access, EC-MAC outperforms fully awake and LPL-based MAC protocols in terms of both energy efficiency and data throughput.

Vehicular sensor networks (VSN) has recently become a hot research topic in the field of wireless networking, as this promising technology has potentials to provide variety of applications and safety to drivers on the road. As promising it is, VSN also introduces many new challenges to the table. For example, the vehicle mobility creates a very unique topology with frequent network disconnections, which may pose problems when existing network protocols for general ad hoc networks are applied. Majority of the research related with VSN limit their data harvesting schemes to only single-hop or short distance transmissions. Therefore these works cannot meet real-time requirements nor support applications where data must be transmitted in multi-hop. The authors believe such problems can be alleviated by our proposed scheme, named ‘multi-hop data harvesting’ (MDH). The simulation studies conducted using QualNet 4.0 simulator shows the effectiveness of the proposed scheme.

In a wireless sensor network application for tracking multiple mobile targets, large amounts of sensing data can be generated by a number of sensors. These data must be controlled with efficient data aggregation techniques to reduce data transmission to the sink node. Several clustering methods were used previously to aggregate the large amounts of data produced from sensors in target tracking applications. However, such clustering based data aggregation algorithms show effectiveness only in restricted type of sensing scenarios, while posing great problems when trying to adapt to various environment changes. To alleviate the problems of existing clustering algorithms, we propose a hybrid clustering based data aggregation scheme. The proposed scheme can adaptively choose a suitable clustering technique depending on the status of the network, increasing the data aggregation efficiency as well as energy consumption and successful data transmission ratio. Performance evaluation via simulation has been made to show the effectiveness of the proposed scheme.

While a network with stationary nodes can provide large capacity in many current wireless systems, a network with mobile users suffers from severe performance degradation. This happens due to quick channel variation and its resulting protocol overheads that are especially large for multiuser multiple-input multiple-output (MIMO) systems. In this paper, we propose a relay-assisted multiuser MIMO downlink system to support highly mobile wireless access. Through a theoretical throughput analysis that explicitly considers the protocol overheads, we show that the MIMO relay significantly enhances the sum throughput of the system.

In this paper, we propose the EDCA-TM, a new architecture which tunes the enhanced distributed channel access (EDCA) for multi-hop networks. In EDCA-TM, we suggest a new module for dynamic access category adaptation (DACA) over the existing channel access mechanism such as EDCA. It processes received data packets for assigning an appropriate access categories (AC) to provide delay and rate guarantee to the QoS traffic. In addition, we adopt the earliest deadline first queuing (EDF) scheme to reschedule buffered packets in the AC queues according to their urgency for actual transmission. We have simulated our proposal in the network simulator, ns-2.31, and compared it with EDCA and APHD. Results show that our schemes outperform existing protocols and provide quality service for the traffic flows within the stated requirements.

This paper proposes a novel multi-hop data dissemination method using data replication technique to collect sensor data in vehicular sensor networks (VSN). Currently, existing network protocols for general sensor networks pose problems when used in VSN applications. Even the majority of research based on VSN network protocols has some problems, as they limit their data harvesting schemes to only single-hop or short distance transmissions, or use high-cost relay stations to support multi-hop cases. As a result, these works cannot completely solve some critical issues in VSN, such as data transmission delay, packet overhead, and network connectivity. We believe such problems can be alleviated by our scheme, which uses replicas in a multi-hop data dissemination scheme. Our simulation study conducted using the QualNet 4.0 simulator shows the effectiveness of the proposed scheme.

Abstract Using directional antennas can be beneficial for wireless ad hoc networks consisting of a collection of wireless hosts. The most important benefit includes a reduction of the radio interference. Thus, it can significantly increase the spatial reuse, thereby improving the network throughput. To best utilize directional antennas, a suitable Medium Access Control (MAC) protocol must be designed. Current MAC protocols, such as the IEEE 802.11 standard, do not benefit when using directional antennas, because these protocols have been designed for omnidirectional antennas. In this paper, we present modified MAC protocols suitable for 802.11 based ad hoc networks using directional antennas. Our comprehensive simulation results demonstrate the performance improvement obtained with the proposed protocols. Copyright © 2007 John Wiley & Sons, Ltd.

Recently, wireless sensor networks have gained increasing attention from the industry as well as academia. Various research issues related with sensor networks are intensively proposed, and they are evaluated by some network simulators or real sensor platforms. One of the well-known simulators for wireless sensor networks is called TOSSIM. It can simulate with TinyOS source codes on the real testbed without any significant modifications. Although TOSSIM's architecture and interfaces are well designed for wireless sensor networks based on IEEE 802.15.4 standards, its current RF model is too simple to support main features of the PHY stack of the IEEE 802.15.4. In order to enhance the accuracy of wireless simulation results and implement IEEE 802.15.4 standard, we design a new wireless propagation model and RF physical stack based on the two-ray ground path loss model and CC2420 RF transceiver. Our work contributes on the performance evaluation areas of wireless sensor networks and IEEE 802.15.4 WPAN standard using simulations.

This paper considers the problem of geocasting in mobile ad hoc networks. Geocasting, a variation on the notion of multicasting, is a mechanism to deliver messages of interest to all nodes within a certain geographical target region. Although several geocasting protocols have already been proposed for mobile ad hoc networks, with the goal of achieving an efficient message delivery, most of these algorithms consider a "single" target region only and therefore multiple transmissions should be initiated separately by the message source when more than one target regions need to receive the same geocast messages. This causes significant performance degradation, especially as the number of geocast regions increase. To solve this problem, we propose a novel scheme driven by geometry, named GGP (geometry-driven geocasting protocol). In this scheme, the geometric concept of "Fermat point" is utilized to determine the optimal junction point among multiple geocast regions from the source node, and hence to reduce the overhead of message delivery, while maintaining a high delivery ratio

Service discovery is an important problem in a self-configurable ad hoc network, where each mobile node is required to automatically discover and provide the available network services among themselves. Several protocols have been presented, with a goal of achieving efficient service discovery in mobile ad hoc networks. Basically, we have the same objective of developing an efficient protocol, but with an integrated approach. Our work is motivated by the observation that the current protocols mostly assume the existence of some routing protocols underneath, separated or loosely coupled from the service discovery protocol. We argue that, however, such an assumption clearly causes the problem of "inefficiency" because both protocols are based on a network-wide flooding mechanism, resulting in unnecessarily large number of redundant packet floods. In this paper, we propose a novel approach of integrating these two different but similar discovery protocols for services and routes. Our simulation results show that the proposed integrated scheme, named as HAID (hybrid adaptive protocol for integrated discovery), can reduce network overhead as well as end-to-end delay in mobile ad hoc networking environments.

The exponential growth of mobile data users and services places a heavy burden on the limited wireless bandwidth of cellular data networks. The situation will be exacerbated with the advent of high bandwidth multimedia applications for mobile devices. We propose an architecture called the cellular-based ad hoc peer data sharing system (CAPS) to reduce the load on the cellular network while improving request response times. In CAPS, mobile hosts in a cellular network form an overlay multihop wireless network. This ad hoc network acts as a 'virtual cache' that enables data sharing among mobile hosts. Participating mobiles share the contents of their local caches with other mobiles. A subset of mobile hosts keep track of the location of objects with minimal overhead. Using CAPS, popular objects can be obtained over the ad hoc network without accessing the cellular infrastructure, thereby reducing the load on the cellular network and improving data access latency. We have extensively evaluated the performance of this architecture through simulations in ns-2 across a wide range of scenarios, and find that CAPS reduces the timeouts of the user requests by 70-90% and reduces the load at the base station by up to 60%.

Access to data services via wireless LANs at private (e.g., corporations or home) and public "hot-spot" (e.g., hotels and airports) setting is becoming a common place daily. Data access via (for profit) public wireless LAN (PWLAN) installations is typically based on user subscription and preconfigured services profiles pertaining primarily access to the global Internet. The goal of the ts-PWLAN project is to define an architecture and a prototype implementation that enables the provision of premium and non-premium tiers of services to transient and non-transient users. ts-PWLAN provides for dynamic renegotiations of tier of services and enables various billing modes, e.g., based on connectivity time and usage, thus enabling service providers to increase their revenue opportunities via multiple service offerings.

This paper considers the problem of providing a geocast service in mobile ad hoc networks and presents a novel geocasting algorithm combining unicasting and flooding. Geocast is useful for sending messages to everyone in a specified geographical region. The proposed protocol is named GeoTORA, because it is derived from the TORA (unicast) routing protocol. Flooding is also incorporated in GeoTORA, but it is limited to nodes within a small region. This integration of TORA and flooding can significantly reduce the overhead of geocast delivery while maintaining reasonably high accuracy.

Using directional antennas can be beneficial for wireless ad hoc networks consisting of a collection of wireless hosts. To best utilize directional antennas, a suitable medium access control (MAC) protocol must be designed. Current MAC protocols, such as the IEEE 802.11 standard, do not benefit when using directional antennas, because these protocols have been designed for omnidirectional antennas. In this paper, we attempt to design new MAC protocols suitable for ad hoc networks based on directional antennas.

A mobile ad hoc network consists of wireless hosts that may move often. Movement of hosts results in a change in routes, requiring some mechanism for determining new routes. Several routing protocols have already been proposed for ad hoc networks. This paper suggests an approach to utilize location information (for instance, obtained using the global positioning system) to improve performance of routing protocols for ad hoc networks. By using location information, the proposed Location-Aided Routing (LAR) protocols limit the search for a new route to a smaller "request zone" of the ad hoc network. This results in a significant reduction in the number of routing messages. We present two algorithms to determine the request zone, and also suggest potential optimizations to our algorithms. 1 Introduction Mobile ad hoc networks consist of wireless mobile hosts that communicate with each other, in the absence of a fixed infrastructure. 1 Routes between two hosts in a Mobile Ad hoc NETwork...