Achieving low delay and high data rate communication in 5 G requires preventing persistent queue backlogs at path bottlenecks. A key indicator of queue buildup is an increase in one-way delay (OWD) of packets. However, accurately measuring OWD is challenging due to synchronization issues between the sender and receiver. Moreover, using OWD to infer the onset of queueing can be inefficient. For instance, congestion control mechanisms that rely on latency as a congestion signal may result in cellular network underutilization, see, e.g., [1]. Thus, to develop more efficient rate control approaches, it is crucial not only to estimate OWD accurately but also to perform a more fine-grained analysis that provides detailed insights into the queue status. This paper presents a framework for modeling OWD in 5 G edge networks, where the wireless link is typically the path bottleneck. We demonstrate that OWD is dominated by queueing delay (QD), particularly at high data rates. We analyze QD by decomposing it into two main components: aggregation delay and channel access time. Aggregation delay can be accurately measured at the user equipment (UE), and channel access time can be estimated based on network conditions. Our key contribution shows that QD, while challenging to measure directly at the base station (BS), can be closely approximated by combining these components. We validate this model through NS3 simulations under varying network loads and single- and multi-UE scenarios. This framework provides a foundation for developing advanced mechanisms for congestion control and bottleneck detection in 5G networks.

Accurate reliability modeling for ultra-reliable low latency communication (URLLC) and hyper-reliable low latency communication (HRLLC) networks is challenging due to the complex interactions between network layers required to meet stringent requirements. In this paper, we propose such a model. We consider the acknowledged mode of the radio link control (RLC) layer, utilizing separate buffers for transmissions and retransmissions, along with the behavior of physical channels. Our approach leverages the effective capacity (EC) framework, which quantifies the maximum constant arrival rate a time-varying wireless channel can support while meeting statistical quality of service (QoS) constraints. We derive a reliability model that incorporates delay violations, various latency components, and multiple transmission attempts. Our method identifies optimal operating conditions that satisfy URLLCIHRLLC constraints while maintaining near-optimal EC, ensuring the system can handle peak traffic with a guaranteed QoS. Our model reveals critical trade-offs between EC and reliability across various use cases, providing guidance for URLLCIHRLLC network design for service providers and system designers.

Many Internet of Things smart-* applications are being powered solely through ambient energy-harvested energy. These applications require periodic data collection with low latency and high reliability. Since the energy is harvested in small amounts from ambient sources and is stochastic in nature, it is extremely challenging to achieve low latency and high reliability for such applications. To this end, we propose a distributed, energy-management module called ReNEW, for Constructive Interference (CI) based protocols that utilizes the available energy effectively in order to achieve our target of increased reliability in EH-WSN, especially in the low harvesting regimes. We choose CI-based protocols to leverage the low latency guarantees. Specifically, we propose a Markov decision model to maximize the energy utility in the infinite horizon by allocating energy optimally. To this end, we also propose a threshold optimal policy. As we find that just a energy scheduler cannot achieve the goal, we also propose distributed techniques to conserve energy on the redundant nodes in the network, and dynamically activate them based on feedback. We also improve the performance of CI by adapting the transmit powers on nodes. We implement and evaluate ReNEW on Indriya testbed for real-world scenarios. We show that in a network of 20 source nodes out of the 30 nodes in the network can perform periodic data collection with an improvement of 2.5 times higher packet reception ratio as compared to LWB. This is one of the worst case scenarios as the harvested energy is as low as 50uJ/s and packets of size 100 B is sent every 30 s. Furthermore, in this scenario, ReNEW saves around 25% higher residual energy on the average as compared to the standard LWB. In a nutshell, by integrating ReNEW with CI based protocols, we enable guaranteed latency and increased reliability for the batteryless EH-WSNs.

The constructive interference (CI) phenomenon has been exploited by a number of protocols for providing energy-efficient, low-latency, and reliable data collection and dissemination services in wireless sensor networks. These protocols consider CI to provide highly reliable packet delivery. This has attracted attention to understand the working of CI; however, the existing works present inconsistent views. Furthermore, these works do not study in the real-world settings where the physical conditions of deployment and unreliable wireless channels also impact the performance of CI. Therefore, we study the phenomenon of CI, considering a receiver's viewpoint and analyze the parameters that affect CI. We validate our arguments with results from extensive and rigorous experimentation in real-world settings. This paper presents comprehensive insights into the CI phenomenon. With the understanding, we develop the destructive interference-based power adaptation (DIPA), an energy-efficient and distributed algorithm, that adapts transmission power to improve the performance of CI. Since CI-based protocols cannot have an explicit acknowledgment packet, we make use of destructive interference on a designated byte to provide a feedback. We leverage this feedback to adapt transmission powers. We compared CI with and without DIPA in two real-life testbeds. On one testbed, we achieve around 25% lower packet losses while using only half of its transmission power for 64-B packets. On the other testbed, we achieve 25% lower packet losses while consuming only 47% of its transmission power for 128-B packets. Existing CI-based protocols can easily incorporate DIPA into them to achieve lower packet losses and higher energy efficiencies.

Channel congestion is one of the most critical issues in IEEE 802.11p-based vehicular communications as it leads to the unreliability of safety applications. As a countermeasure, many Decentralized Congestion Control (DCC) algorithms have been proposed. One of the most prominent DCC algorithms is the message-rate based LIMERIC. Recently, algorithms have also been proposed to support higher vehicle density (better scalability). One of such algorithms is the combined message-rate and data-rate based congestion control algorithm (MD-DCC). MD-DCC can support around 2.7 times higher vehicular density than LIMERIC. However, if LIMERIC has been deployed, can MD-DCC be introduced and coexist well with LIMERIC. The objective of this paper is to investigate how MD-DCC coexists with LIMERIC. Given a scenario where vehicles may use either LIMERIC or MD-DCC, we study the impact of coexistence on channel load, fairness and reliability of vehicles at different densities. Simulation studies show that there is no significant degradation of reliability both for LIMERIC and MD-DCC at different densities. On the contrary, coexistence can improve the reliability of LIMERIC vehicles. Furthermore, MD-DCC can support vehicles at large densities even when it coexists with LIMERIC retaining its scalability. However, fair allocation of resources is not guaranteed when LIMERIC and MD-DCC coexist.

Ambient energy-harvesting technology is a promising approach to keep wireless sensor networks (WSNs) operating perpetually. Depending on the harvesting source nodes can either be active (alive) or inactive (dead) at any instant in such Energy-Harvesting WSNs (EH-WSNs). Thus, even in a static deployment of EH-WSNs, the network topology is no longer static. A popular method to increase energy-efficiency in WSNs is by employing topology control algorithms. Most of the topology control algorithms in the literature cannot handle the situation when nodes have different energy-levels, and when number of active nodes varies with time in EH-WSN. To address this issue, we present two localized energy based topology control algorithms, viz., EBTC-1 and EBTC-2. EBTC-1 is for convergecast applications of WSNs and EBTC-2 is for a generic scenario where all nodes are required to be connected. While typical topology control algorithms select a particular number of neighbors, the distinguishing feature of both these algorithms is that they select neighbors based on energy-levels, and render the global topology strongly-connected. Simulation results confirm that EBTC-1 and EBTC-2 reduce the transmission power and they let nodes have neighbors with high remaining energy. Results show that our proposed algorithms increase at least 33% in the remaining energy per neighbor. In addition, in terms of energy consumption and fault-tolerance, our proposed algorithms typically achieve 1-connected topology using 74% less energy compared to K-Neigh.

Constructive Interference (CI) phenomenon has been exploited by Glossy, a mechanism for low-latency and reliable network flooding and time synchronization for wireless sensor networks. Recently, CI has also been used for other applications such as data collection and multicasting in static and mobile WSNs. These applications base their working on the high reliability promised by Glossy regardless of the physical conditions of deployment, number of nodes in the network, and unreliable wireless channels that may be detrimental for CI. There are several works that study the working of CI, but they present inconsistent views. We study CI from a receiver's viewpoint, list factors that affect CI and also specify how and why they affect. We validate our arguments with results from extensive and rigorous experimentation in real-world settings. This paper presents comprehensive insights into CI phenomenon. With this understanding, we improve the performance of CI through an energy-efficient and distributed algorithm. We cause destructive interference on a designated byte to provide negative feedback. We leverage this to adapt transmission powers. Compared to Glossy, we achieve 25% lesser packet losses while using only half of its transmission power.

Communication at mmWave frequencies has been the focus in the recent years. In this paper, we discuss standardization efforts in 60 GHz short range communication and the progress therein. We compare the available standards in terms of network architecture, medium access control mechanisms, physical layer techniques and several other features. Comparative analysis indicates that IEEE 802.11ad is likely to lead the short-range indoor communication at 60 GHz. We bring to the fore resolved and unresolved issues pertaining to robust WLAN connectivity at 60 GHz. Further, we discuss the role of mmWave bands in 5G communication scenarios and highlight the further efforts required in terms of research and standardization.

In this paper, we emphasize on indoor networks in 5G era. We explore the possible technologies and architectural solutions for 5G indoor communications. Owing to the fact that requirements for indoor and outdoor communications will be quite different in the next generation networks, we try to define an architectural framework for 5G indoor communications. Our proposed architecture focuses on three aspects of indoor network architecture, namely; air interface, backhaul connectivity and indoor signal distribution.

Ambient energy harvesting for Wireless Sensor Networks (WSNs) is being pitched as a promising solution for long-lasting deployments in various WSN applications. However, the sensor nodes most often do not have enough energy to handle application, network and house-keeping tasks because amount of energy harvested highly varies spatially and temporally. Moreover the ambient source cannot be assumed to be continuously available. When harvested energy is in excess, it is desirable that the nodes take up higher loads. The nodes should switch to highly energy efficient schemes when the energy is not sufficient. Hence harvesting-aware scheduling of tasks is required. The two most important challenges for harvesting-aware scheduling are (a) to determine the amount of energy to be expended in a time slot, and (b) to utilize this energy for execution of tasks maximally. To increase energy utilization for task execution, we decompose application level tasks into subtasks, some of which can be executed concurrently. In this article, we propose a dynamic optimization model, based on Markov Decision Process (MDP) that takes into account priorities and deadlines of the tasks, and stored and harvested energy to derive an optimal scheduling policy. Since the complexity of the MDP is intractable in realtime, we propose a greedy scheduling policy. We compare its performance with the optimal policy.

60 GHz wireless local area networks (WLANs) standards (e.g., IEEE 802.1 lad and IEEE 802.15.3c) employ hybrid MAC protocols consisting of contention based access using CSMA/CA as well as dedicated service periods using time division multiple access (TDMA). To provide the channel access in the contention part of the protocol, quasi omni (QO) antenna patterns are defined which span over the particular spatial directions and cover a limited area around access points. In this paper, we propose an algorithm to determine the beamwidth of each QO level. The proposed algorithm takes into account the spatial distribution of nodes to allocate the beamwidth of each QO level in an adaptive fashion in order to maximizes the channel utilization and satisfy the required link budget criterion. Since the proposed algorithm minimizes the collisions, it also minimizes the average time required to transmit total packets in a QO level. Proposed algorithm improves the average channel utilization up to 20–30% and reduces the time required to transmit total packets up to 40–50% for the given network parameters.

IEEE 802.22 standard is the first worldwide standard using cognitive radio (CR) technology for wireless regional area networks (WRANs). Orthogonal frequency-division multiple access (OFDMA) is employed for point-to-multi-point (P2M) communication between base stations (BS) and customer premises equipments (CPEs) in WRANs. The large coverage of a single cell (up to 100 km of radius) is the unique feature of WRANs. However, channel reuse is not considered, i.e., in one slot the channel can be allocated to only one CPE, and every intra-cell packet needs to be routed through the BS. Therefore, device-to-device WRAN (D2DWRAN) has been proposed to support direct intra-cell CPE-CPE communication. Power control strategies are used to achieve higher reuse of OFDMA slots. In this paper, we take one step further to enhance the network capacity by adopting multichannel management (MCM) with infrastructure support. This enables multiple operating channels to be used simultaneously in D2DWRANs. New channel switching strategies are also studied. We implement a MCM scheme in an OFDMA setting for D2DWRANs, and examine it in the upstream (US). For downstream (DS), there are already many proposals in the literature, which can be adopted directly by D2DWRAN. The simulation results show that MCM scheme significantly improves the network performance compared to single-channel D2DWRANs and WRANs.

IEEE 802.22 wireless regional area network (WRAN) standard employing cognitive radios is gaining much attention recently. The WRAN standard targets reuse of unused TV channels. We propose a device-to-device wireless regional area network (D2DWRAN) to extend the capacity of IEEE 802.22. Network capacity can be increased by supporting direct intra-cell device to device (D2D) communication through channel reuse and also with aggregation of nonadjacent multiple operating channels. Self-coexistence of neighboring IEEE 802.22 cells is a major challenge in WRANs, since the availability of channels varies frequently and channels are reused by every cell as much as possible. Currently, IEEE 802.22 does not consider D2D communication. We propose a two-tier spectrum sharing mechanism for channel allocation in D2DWRANs - both at intra-cell and inter-cell levels. Algorithms and a thorough analysis are presented. We examine our proposal through simulations. Results show significant performance improvement compared to IEEE 802.22. However, there are many hurdles to cross, such as, coexistence with other cognitive radio networks (CRNs), the intra-cell routing, allocation of other network resources, etc. We believe that further work in this domain can lead to increase in capacity not only in WRANs but also in other cellular networks.

We propose two novel energy-aware routing algorithms for wireless ad hoc networks, called reliable minimum energy cost routing (RMECR) and reliable minimum energy routing (RMER). RMECR addresses three important requirements of ad hoc networks: energy-efficiency, reliability, and prolonging network lifetime. It considers the energy consumption and the remaining battery energy of nodes as well as quality of links to find energy-efficient and reliable routes that increase the operational lifetime of the network. RMER, on the other hand, is an energy-efficient routing algorithm which finds routes minimizing the total energy required for end-to-end packet traversal. RMER and RMECR are proposed for networks in which either hop-by-hop or end-to-end retransmissions ensure reliability. Simulation studies show that RMECR is able to find energy-efficient and reliable routes similar to RMER, while also extending the operational lifetime of the network. This makes RMECR an elegant solution to increase energy-efficiency, reliability, and lifetime of wireless ad hoc networks. In the design of RMECR, we consider minute details such as energy consumed by processing elements of transceivers, limited number of retransmissions allowed per packet, packet sizes, and the impact of acknowledgment packets. This adds to the novelty of this work compared to the existing studies.

Homes, offices and vehicles are getting networked. This will enable context aware, autonomous operation of many support systems that could be controlled remotely. To achieve this there would be a large number of tiny devices - sensors and actuators - which are networked and they are termed generally as Internet of Things (IoT) devices. In future, they will be powered through harvested energy from the ambience to enable perennial lifetime and minimal manual maintenance. Some examples of energy sources are photovoltaic panels and piezoelectric crystals. Several challenges arise due to the nature of sources of energy. One of these challenges is that the devices (nodes) leave and re-enter networks due to fluctuating availability of harvested energy. As a result, the neighbor table maintained at each node changes quite often leading to complications in forming and maintaining routes. In fact initial neighbor discovery (ND) itself is a difficult task. Further, usage of directional antennas would increase the time taken to complete ND. We study such a network through exhaustive simulation study considering various parameters. We demonstrate the benefits and challenges of using directional antennas for ND. We present a scheme that nodes could use to discover their neighbor during initial deployment and another scheme that could be used for subsequent discovery on re-entry into the network. We show that a dedicated ND protocol is necessary for energy harvesting networks and that directional ND is beneficial in these networks under some circumstances.

We propose energy harvesting technologies and cooperative relaying techniques to power the devices and improve reliability. We propose schemes to (a) maximize the packet reception ratio (PRR) by cooperation and (b) minimize the average packet delay (APD) by cooperation amongst nodes. Our key result and insight from the testbed implementation is about total data transmitted by each relay. A greedy policy that relays more data under a good harvesting condition turns out to be a sub optimal policy. This is because, energy replenishment is a slow process. The optimal scheme offers a low APD and also improves PRR.

Even though 60 GHz frequency band has limited coverage, due to the availability of higher bandwidth worldwide (unlicensed, approximately 5 GHz between 57–62 GHz), it is one of the promising candidates for future broadband employing both Fiber and Wireless (Fi-Wi) technology. In this article we briefly explain an in-home radio over fiber (RoF) architecture employing 60 GHz spectrum band. The main challenge for designers of such networks is the additional delay introduced by the optical distribution network. Later in the light of this increased delay, we provide an investigation on the feasibility of applying the IEEE 802.15.3c MAC protocol in such a RoF system at 60 GHz. Mainly, we analyse various ACK mechanisms in the IEEE 802.15.3c when it is used in conjunction with RoF network. The analytical results show that the fiber optic network causes a slight drop in the throughput but it could still be easily used in home networks. This gives us an opportunity to sustain high bandwidth at low cost for home networking, also supporting mobility. Modelling of a RoF system with IEEE 802.15.3c and numerical results thereof are the contributions of this article.

IEEE 802.22 is the first standard to uitilize cognitive radio technology for wireless regional area networks (WRANs). It has adopted a cellular topology containing one base station (BS) and multiple customer premises equipments (CPEs) in a cell. It covers a very large area with radius ranging up to 100 km. Orthogonal frequency-division multiple access (OFDMA) system is employed and it is further slotted in time-domain. In one slot only one CPE can be allocated, and every intra-cell packet needs to be routed through the BS. This point-to-multi-point structure significantly limits the network capacity in the case of CPE-CPE communication, which is predicted to happen, and even the use of OFDMA does not help much. Therefore, peer-to-peer WRAN (P2PWRAN) has been proposed to support direct intra-cell communication in order to extend the network capacity. In this paper, the IEEE 802.22 OFDMA system is adapted to P2PWRAN to support direct CPE-CPE communications. The downstream burst allocation in P2PWRAN is similar to the OFDMA system of IEEE 802.16, which has been widely studied in the literature. Therefore, in this paper we look at the unexplored upstream burst allocation where slots can be reused among CPEs and the BS with power control mechanisms. We propose a burst allocation algorithm that maximizes the network capacity greedily. The algorithm is examined under various conditions such as, number of CPEs, size of requests, length of US subframes and type of requests (CPE-BS or CPE-BS). We also show that our algorithm performs better than the existing solutions.

In a home environment, a Smart Grid Home Area Network (SG-HAN) platform facilitates collection and delivery of power consumption information for load profiling and informed decisions on energy management. However, one of the main challenges in HAN is the overcrowded unlicensed 2.4-GHz ISM frequency band, occupied by several types of radio technologies such as ZigBee, Bluetooth, and WiFi. It is crucial that those technologies coexist peacefully to allow each user of the radio technology to fulfill their communication goals. In this paper, we present a potential coexistence scenario in SG-HAN for homogeneous and heterogeneous wireless technologies. The coexistence impact on SG-HAN performance is then modeled and analyzed. The numerical results show significant performance degradation due to the interference for devices in close proximity with the interfering sources in a spectrum sharing environment where in the worst case scenario, SG-HAN communication is almost impossible.

IEEE 802.22 is proposed for reusing the TV channels with cognitive radio technology to build Wireless Regional Area Networks (WRANs). The cellular topology of a WRAN makes the spectrum management easy. However, this topology reduces the network capacity significantly, because in one slot only one user can be allocated with a channel. Therefore, Peer-toPeer WRAN (P2PWRAN) is proposed, in which direct CPE(Consumer Premises Equipment)-to-CPE intra-cell communication is supported. While increasing the network capacity significantly, reducing the total energy consumption is a challenge.The energy efficiency of nodes in the standard for WRAN is difficult to improve, since the transmission distance of nodes to the BS is relatively static. P2PWRAN enables to achieve higher energy efficiency through better possibilities of channel allocation. Channel allocation influences energy consumption and network capacity significantly. Channel allocation also affects the upper layers, for example the routing protocol. Therefore, guaranteeing the network performance and fairness amongst CPEs, while achieving green networks, needs cross-layer design. In this paper, we define the channel allocation problem in P2PWRAN and we recognize it as a Multi-objective Quadratic Programming (MOQP) problem. An Energy-aware Channel Allocation (ECA) algorithm is proposed for exploiting the P2PWRAN paradigm to achieve the lower communication energy consumption and higher network energy efficiency and throughput than simple greedy policies. ECA jointly considers the network layer and Media Access Control (MAC) layer. By controlling the parameters in ECA, the fairness of channel allocation can also be guaranteed.

We implement two energy models that accurately and comprehensively estimates the system energy cost and communication energy cost for using Bluetooth and Wi-Fi interfaces. The energy models running on a system is used to smartly pick the most energy optimal network interface so that data transfer between two end points is maximized.

Peer to peer wireless regional area network (P2PWRAN) is proposed as an extension to support peer to peer communication based on IEEE 802.22 [1]. Multiple channel allocation and reuse of channels in the same time slot in P2PWRAN significantly increase the network capacity compared to standard IEEE 802.22 networks. One of the key issues in bringing P2PWRAN into reality is building the interference map. The concept of interference map/mapping has been mentioned in literature however, how to build an interference map is still an open issue. Therefore, we propose a simple and self-adapting interference map building protocol (SIMBP) for P2PWRAN, which can also be used in other multi-channel wireless networks with minor modifications. The simulation results show that SIMBP converges under the P2PWRAN setting, and with number of available channels and growing number of nodes, the capacity of the network is reached eventually.

Wireless Regional Area Networks(WRAN), IEEE 802.22 standard, adopts a centralized cellular topology including base station (BS) and customer-premise equipments (CPEs). However this may lead to limited network capacity, since every CPE needs to communicate to the BS and only one channel can be used to communicate in the whole cell per time slot with one BS antenna. Peer to Peer WRAN (P2PWRAN) was proposed [3] to circumvent this, where CPEs can communicate with each other directly. P2PWRAN increases network capacity compared to the standard WRAN because of spatial reuse. Multiple communication channels can be simultaneously allocated and reused in one time slot by the BS and multiple CPEs. In IEEE 802.22b [4], a standard in progress, peer to peer communication plays an important role for enabling smart grids. Channel allocation influences the network performance significantly, therefore, we formulate the spectrum allocation problem in P2PWRAN as a quadratically constrained programming (QCP) problem. It is also proved as a computationally hard problem. The Greedy Coloring Algorithm (GCA) is examined in P2PWRAN channel allocation, and the results show that it may cause severe unfairness in allocation of channels. Thus a Fair Greedy Coloring Algorithm (FGCA) is proposed to guarantee a fair allocation by queuing flows considering previous allocations. However, FGCA guarantees fairness but leads to decrease in performance of P2PWRAN. Therefore, a Trade-off FGCA (TFGCA) is proposed considering fairness and network performance at the same time during allocation. Simulation results show that with the adjustment of two factors in TFGCA, network performance and fairness can be balanced.

The rapid developments in Internet-of-Things (IoT) and Machine-to-Machine (M2M) communication make it necessary to design communication systems operating in different wireless spectrum as an alternative to highly congested wireless access systems. In addition, the deployment of wireless smart meter devices is ramping up and it is expected that such devices will flood the market in the near future competing for the same wireless spectrum. The IEEE 802.11ah standardization task group is developing a global Wireless LAN (WLAN) standard that will allow wireless access using carrier frequencies below 1 GHz in the ISM (Industrial, Scientific, and Medical) band and will help Wi-Fi-enabled devices to get guaranteed access for short-burst data transmissions, such as meter data. In addition to exploiting the underutilized sub 1 GHz spectrum the improved coverage range allows new applications to emerge such as wide area based sensor networks, sensor backhaul systems and potential Wi-Fi off-loading functions. This paper summarizes the IEEE 802.11ah standardization activities in progress and discusses advantages and challenges in the design of physical layer (PHY) and media access control (MAC) schemes in the sub 1 GHz band.

Wireless communication in the sub 1GHz band is going to be one of the key enabler for the wireless smart grid. As part of the smart grid, home area networks (HAN) have to be reliable, robust, and secure. Frequency bands at 2.4 GHz are widely used, e.g., by Wi-Fi and ZigBee systems, but are highly congested. Frequency bands below 1 GHz, such as the ISM (industry, scientific and medical) 920/950MHz bands, offer less interfered wireless channels. There are few wireless transceivers available in the consumer market, which operate in the 950MHz ISM band. However, a thorough performance evaluation of the transmission characteristics is missing. We conducted a performance analysis of 950MHz transceivers which we deployed in a multi-node network setup to emulate a wireless HAN system. We contribute on details regarding the data rate of sub 1 GHz wireless sensors and the related error statistics. We discuss the transmission boundaries and investigate the optimal modulation schemes of sub 1GHz wireless sensors.

One of the sources of the energy waste in wireless sensor networks is idle listening, the time in which a node monitors the free channel. In applications where the events occur sporadically, energy consumption due to idle listening can be further reduced by dual-radio cooperation. In dual- radio cooperation, nodes in the network have two stacks. One stack makes use of a low-power wake-up radio for event-driven communication over the main radio. The other stack may employ any sensor networking medium access control protocol only over the main radio. One of the two stacks can be dynamically operational depending on the rate of the events or the packet arrival rate. When the event rate becomes small, the event-driven stack takes over the operation. If the event rate increases, it could be more efficient to operate the legacy single radio stack. In this paper, we investigate the performance of the dual-radio cooperation in wireless sensor networks. A medium access control protocol is proposed for the dual- radio cooperation to maximize the energy efficiency of the wireless network. We define the critical event rate as the event rate threshold above which the single-radio stack performs better than the dual- radio stack. We analyzed and validated the critical event rate by simulations. We show that 70-97% energy conservation is possible by employing the dual-radio cooperation.

Abstract The newer context‐aware applications require many inputs and amongst them the location information is one of the most important. In the near future, we see the potential in using wireless sensors deployed inside buildings to support in generating the location information besides their other routine tasks. This paper records the efforts involved in designing and prototyping a centralized indoor positioning system for tracking a target's position. We present an in‐depth discussion on the RSSI based positioning algorithms both, range‐based and range‐free. Considering that the signal strength can be distorted heavily due to multi‐path and shadowing, we have proposed the weighing schemes to leverage the credibility of the measured RSSI values. For online tracking, we have also proposed boundary selection and local grid scanning to lower the searching time, and the RSSI data dissemination and collection schemes to reduce traffic overhead. Evaluations have been done in both the field measurements and with an RSSI generator. The generator has been developed to simulate and replace the real measurements for the ease of algorithm design and testing, thus avoiding repetitive field measurements. The results show that positioning systems with adequate accuracy can be built with our proposed schemes. We expect that these proposed schemes to be integrated in multitude of systems with context‐aware applications, which use location information. Copyright © 2010 John Wiley & Sons, Ltd.

In this work, we study the adaptability of well known cryptography algorithms to energy harvesting wireless sensor networks. We are particularly interested in algorithms that have the ability to adapt to varying power in such networks. Our investigations and implementation on hardware platforms indicate that it is optimal to precompute a few key stream bytes, store in memory and later used during the time when the system is low on harvested power level. Our demonstrable setup shows using a precomputed key stream can decrease the energy consumption by 14%. We have implemented the Trivium stream cipher for two different microcontrollers, the MSP430 and the AVR ATmega1281 and show the performance results for these implementations. We have implemented an algorithm based on universal hash functions to provide message authentication with the assistance of stream ciphers. We show that this authentication algorithm has exciting properties for energy harvesting system and more generally for resource constrained devices.

Energy-aware routing is an effective way to extend the operational lifetime of wireless ad hoc networks. In this paper, we propose a new energy-aware routing scheme called Reliable Minimum Energy Cost Routing (RMECR). RMECR finds routes which require least amount of energy for reliable packet transfer in ad hoc networks. It defines the energy cost of packet forwarding by a node as the fraction of remaining battery energy which is consumed by a node to forward a packet. This includes the energy consumed for retransmission of the packet as well, when the packet or its acknowledgment is lost. We show that RMECR can effectively reduce the energy consumption of nodes and balance the traffic load among them. Furthermore, RMECR is able to find reliable routes, in which constituent links require less number of packet retransmissions due to packet loss. This in turn decreases the latency of packet delivery and saves energy as well.

Cognitive Radios (CRs) address spectrum scarcity and under-utilization of the spectrum. Allocating spectrum to CR nodes in a network is neither easy nor straight-forward since spectrum availability is space and time-varying. The Link layer always sets up communication between nodes in a CR ad hoc network by allocating the available spectrum suitably. In a time-slotted model, allocation of channels amongst CR nodes is a NP complete problem. Moreover, since the availability of spectrum is time varying, all the nodes in the network may not be allocated sufficient resources. Thus there is always a possibility that a node may starve compared to its counterparts. In this article, we address the issue of fairness in a CR ad hoc network and propose novel distributed heuristics to allocate spectrum fairly. In literature, max-min, max-sum and max-proportional fairness based schemes are proposed to provide fairness in these CR ad hoc networks. We compare our heuristic results with these schemes, and discuss why our method is significantly better.

60 GHz radio is a very attractive technology for short-range wireless communication due to its capability to provide Gbps data rate. To address the neighbor discovery (ND) problem in 60 GHz networks, we propose a novel analytical framework to investigate the ND performance. The main difficulty in modeling the ND process in a 60 GHz network is the involvement of the directional antennas with gain differences between the antenna's main lobe and side lobes. Different antenna modes - directional or omni-directional - coupled with different ND mechanisms make the analytical study demanding. In this article, we propose a comprehensive theoretical model to demonstrate the performance of ND processes using one-way ND and handshake-based ND mechanisms. Moreover, we combine them with different antenna modes, i.e., directional transmitting with omni-directional listening (DO) and directional transmitting with directional listening (DD) modes. The impact of antenna modes on the ND process is analyzed. Since 60 GHz radio is prone to co-channel interference, we examine a realistic interference-aware link model and antenna pattern via simulation studies. Our work is specifically beneficial to provide guidelines for applying directional neighbor discovery process within 60 GHz wireless networks.

Wireless personal area networks (WPANs) usually have very limited coverage. In this paper, we focus on methods to extend this range through multi-hop communication crossing several inter-connected WPANs called piconets. Multi-hop communication between piconets is possible through the bridge devices. While extending the range of WPANs, bridge devices become the capacity bottlenecks for these connected piconets. Therefore, an unoptimized resource allocation mechanism involving the bridges could degrade system performance severely. In this work we propose a novel resource allocation mechanism that outperforms other schemes proposed so far. Moreover, our scheme is QoS aware due to its cross-layer design. In our proposed scheme, resource allocation cooperates with the route discovery process to mitigate collisions due to inter-piconet resource reservations. Simulation results show that our approach significantly increases network capacity. This work is expected to pave the way for QoS support in WPANs.

Cognitive radios (CRs) address the problems of spectrum scarcity and under-utilization of the spectrum. However, realizing a CR network is neither easy nor straight-forward. The link layer in CR ad hoc networks is responsible for choosing suitable channels, out of the available channels, for setting up communication between nodes. However, the selection of channels amongst the CR nodes in the network is proven to be NP-complete. The need of maximizing the spectrum efficiency in a fair way can be modeled as a graph coloring problem. An edge coloring heuristic and a clique determination heuristic algorithms are proposed in this article. We compare the results of these heuristics with the algorithm proposed in. We also compare the spectrum utilization in all these algorithms.

Cognitive Radios (CRs) address spectrum scarcity and under-utilization of the spectrum. However, realizing a CR network is neither easy nor straight-forward. In particular the link layer should facilitate setting up of communication between nodes enabling sharing of channels, while maximizing the spectrum utilization. We address the problem of allocation of channels to CR nodes. For time-slotted model, allocating the channels among CR nodes is an NP complete problem. We propose novel distributed heuristics, one based on clique sets called Clique Based Heuristic and the second one is a low complexity, locally adapting Localized Heuristic; both use local control channel. We compare the results of these heuristics with the optimal and a distributed graph coloring algorithm proposed in the literature. We also compare the spectrum utilization and overheads for all these algorithms.

The 60 GHz technology has a great potential to provide wireless communication at multi-gigabit rates in future home networks. To maintain the network connectivity with 60 GHz links, which are highly susceptible to propagation and penetration losses, is a major challenge. The quality and the robustness of the 60 GHz links can be improved by employing relay nodes in the network. In this paper, the contribution of relaying to the connectivity and the quality of the 60 GHz radio links is studied by modeling three indoor scenarios. It is analytically and through simulations shown that having a relay node in a 60 GHz network decreases the average freespace path loss 33% in the worst case scenario. The effects of relay device position and the obstacle density on the improvement of the average received signal level are investigated with a verified 3D ray tracing tool. A comparative simulation study on the performance of different relay configurations under various network conditions is conducted. The results yield that even a single relay device positioned at the height of other nodes can improve 50% of the links in considerable levels in a 60 GHz indoor network. It is also shown that additional relay nodes do not contribute to 60 GHz indoor connectivity significantly, if there are two properly positioned relay devices in a network which is moderately populated.

We study the application of multipath routing to enhance reliability of high quality video in 60 GHz radio indoor networks. We propose a cross-layer approach taking into account the possibility of layered-coding for video stream transportation and the characteristics of 60 GHz radio links based on our earlier studies on the stability of 60 GHz radio links. Further three traffic allocation schemes have been investigated and compared for the best use of multipath capacity.

Wireless indoor networks employing Radio over Fiber technique combining 60 GHz wireless networks with wired networks is a newer solution to provide high definition in-home multimedia applications. About 5 Gbps is available in this band. In 60 GHz band, each antenna can cover a small space such as a single room in a building. Thus more antennas are needed to cover the whole building. This leads to frequent handoffs. In addition, the overlapping between two adjacent cells is normally small; therefore a handoff should be completely done in a relatively shorter time compared to cellular networks. Since there are many research results and commercial systems of wireless indoor positioning, predicting the direction of the movement of a user is very easy. This paper proposes the direction assisted handoff algorithm. In this paper we consider such a scenario and we study direction assisted handoff. The simulation results show that the proposed handoff algorithm can reduce the total number of handoffs while increasing the percentage of successful handoffs.

The emerging high definition in-home multimedia applications require higher capacity from future wireless networks in the indoor environments. In this paper, we consider a novel mesh-like architecture for indoor wireless networks using 60 GHz radio for supporting multimedia applications with sufficient data rate and stringent quality-of-service (QoS) guarantees. We concentrate on studying the application of multipath routing to enhance reliability of transporting high quality video since 60 GHz transmission is highly dependent on line-of-sight (LOS). Based on our previous study on the stability of 60 GHz radios, we propose a cross-layer approach taking into account layered coding technique for video stream transportation. We present our model along with an analysis to assess multipath routing in this scenario. Further, we give an in-depth discussion on two traffic allocation schemes to harness multipath capability.

In this paper, we investigate the robustness of the 60 GHz connectivity in typical indoor environments by analyzing the outage probability. We define three realistic indoor scenarios which may host the 60 GHz networks in the future and perform simulations with a verified 3D ray tracing tool on them. In the first set of simulations, we show the impact of access unit position on the connectivity. In the next step, we show that increasing the obstacle density linearly decreases the outage probability of the 60 GHz network and this decrease is found to be sharper for certain positions of the access point. In the last step, we demonstrate the direct effect of reflective surface availability on the connectivity. A 60 GHz indoor network relying solely on the reflections in the absence of line-of-sight path is very vulnerable to outages even in moderately populated indoor environments.

IEEE 802.15.4 Wireless Sensor Networks (WSNs) share the 2.4 GHz Industrial, Scientific, and Medical (ISM) license-free band with many other wireless technologies such as IEEE 802.11b/g Wireless Local Area Networks (WLANs). Because of the low-power, however, IEEE 802.15.4 WSNs are potentially vulnerable to the interference introduced by the other wireless technologies such as IEEE 802.11b/g WLANs, which have much higher power. Particularly, in the presence of heavy interference, IEEE 802.15.4 nodes can hardly get a chance to access the channel, which could result in discarding a large amount of packets. In this paper, we propose a decentralized approach to help IEEE 802.15.4 nodes mitigate interference. By adaptively and distributively adjusting Clear Channel Assessment (CCA) thresholds of IEEE 802.15.4 nodes in the presence of heavy interference, the approach can substantially reduce the amount of discarded packets due to channel access failures, and therefore significantly enhance the performance of IEEE 802.15.4 WSNs. The approach is robust, responsive and easy to be implemented at a low cost. The effectiveness of the approach is validated by OPNET simulation.

60 GHz radio is a promising technology which can handle the data rate of the order of gigabits-per-second. Hence, it is an attractive candidate for wireless personal area networks (WPANs). Due to the high path loss, directional antennas are recommended for use in 60 GHz systems. To set-up directional communications, it is essential to obtain the knowledge of direction of the surrounding devices. However, a neighbor discovery process using directional antennas is nontrivial. In this paper, we provide a comprehensive investigation of using directional antenna for neighbor discovery process. We demonstrate the performance of neighbor discovery using different antenna modes combining different neighbor discovery mechanisms. Our results may aid in designing directional antennas for 60 GHz WPANs.

User centered personal network (PN) interconnects various devices belonging to a user in different geographic locations, such as home, office, car, etc., to form one network to improve the quality of life of the user. In PNs, the user's devices move in different groups, where these groups merge and split. A PN mobility model (PNMM) has been proposed to model the devices' movements in PNs. In this paper, PNMM has been evaluated: stability evaluation proves that PNMM maintains a long-term steady state. The impact of PNMM on the performance of protocols designed for PNs has been discussed in this paper. Simulation results give insights of the performance of the PN clustering protocol, and provide guidelines for future design of clustering in PNs.

A personal network (PN) is a network of personal devices regardless of their geographical locations. A PN may consist of several ad-hoc sub-networks, each of which is referred to as a cluster. Different clusters are connected to each other through their gateways and using interconnecting structures, e.g., the Internet. Inside each cluster, there might be several nodes that are able to act as gateway. Gateway nodes may support different access technologies, such as WiFi, Ethernet, WiMax, etc. It also may happen that a single gateway, which supports several access technologies, is able to connect to different access networks. To benefit from the availability of different gateways and access networks with different characteristics for a PN user, an efficient methodology for gateway and access network selection is needed. In this work, we are motivated to design a generic architectural framework for selecting the best gateway(s) and access network(s) in a PN. Issues, such as characteristics of the gateway nodes and access networks, QoS requirements of the applications, mobility of gateway nodes, dynamism of the PN topology, etc., have been considered in designing the proposed framework. The main advantages of this framework is leveraging the benefits of different alternative solutions, in terms of overhead, efficiency, complexity, and user satisfaction.

Accurate and fast wireless link quality assessment (LQA) for wireless channels would bring huge benefits for mobile multi-hop and multi-rate wireless ad hoc and sensor networks in the form of improved end-to-end performance. In this paper, we propose a novel LQA method based on cross-layer information. The method is implemented in a real test-bed, which is based on IEEE 802.11b/g, and achieved a significant LQA improvement up to 50% in mobile scenarios without introducing overhead. The effectiveness of accurate and fast LQA is demonstrated by feeding it into the routing layer to enable the route decisions to adapt faster during changing situations, especially in mobile scenarios. The experiment results show that the proposed LQA method can lead to faster and smarter routing decisions and higher end-to-end throughput compared to traditional methods, which only use hello packets to determine the link quality in mobile scenario.

Clustering has been used as a fundamental tool to improve scalability in large wireless ad hoc networks. Techniques based on clustering, such as routing, self-organization, context management, service discovery, etc., ensure QoS in wireless ad hoc networks when the number of devices increases. The crucial issue of clustering is the overhead generated during the cluster formation and maintenance phases. An in-depth study of the influence of node mobility on cluster formation and maintenance overhead is still missing. There is little insight into the performance of clustering in the presence of different node mobility patterns. This paper presents a detailed analytical study of the clustering overhead considering node mobility in wireless ad hoc networks, and offers a way to understand how different the node mobility parameters influence the clustering overhead. The analytical results are compared with the simulation results with sufficient accuracy. In summary, this paper provides a fundamental understanding of mobility behaviors of devices and the clustering overhead.

Group mobility has been modeled for simulators to evaluate protocols in wireless ad hoc networks. These mobility models have to be verified in terms of their instant and long-run behaviors. This paper discusses importance and challenges of the stability evaluation for ad hoc group mobility models; proposes analytical technique for the stability of group mobility model and evaluation of the same via simulation. As a case study, we evaluate the personal network group mobility model (PNMM). The evaluation method presented in this paper can be applied to all generic ad hoc group mobility models in terms of stability analysis and simulations.

Personal networks (PN) is a concept in the area of modern communication networks in which devices belonging to a person cooperate to offer services to the person regardless of their geographical locations. A PN may consist of several ad-hoc sub-networks (or clusters) which are interconnected through infrastructure networks such as the Internet. Failure of personal devices due to battery shortage is one of the main threads for service availability in PNs. Power-aware routing (PAR) has been proposed as an effective scheme to prolong the lifetime of battery-operated nodes in wireless ad-hoc networks. This scheme, however, could be utilized in PNs as well, since a PN cluster can be modeled as a wireless ad-hoc network. Aiming at prolonging the lifetime of nodes in PNs, in this paper we propose a PAR algorithm for PNs and we evaluate and compare its performance with the performance of other PAR algorithms proposed so-far for wireless ad-hoc networks. We analyze the effect of node density, routing overhead, heterogeneity of PN nodes in terms of their power supplies, and communication pattern within PN clusters on the performance of the PAR algorithms. Taking into account various parameters, we show that in a PN environment, our proposed scheme can profoundly extend the lifetime of PN nodes compared to the other algorithms. We also show that there can be an optimal value for route refresh interval, as a parameter which affects the generated routing overhead, and the node density of PN clusters, in such a way that the network lifetime is maximized.

To achieve ultra high data rate communications in 60 GHz Wireless Personal Area Networks (WPANs), frame aggregation is devised in IEEE 802.15.3c to increase the MAC transmission efficiency. In this work, we propose a novel statistical model to analyze the behavior of two types of frame aggregation mechanisms: standard frame aggregation and low latency frame aggregation. Through our model, we could fully understand the performance of the frame aggregation mechanisms in terms of transmission delay and system capacity. The accuracy of our model is validated by extensive simulations. Our work provides valuable insights for ultra high performance transmission using 60 GHz radio.

In this paper, we propose a solution to resolve link blockage problem in 60 GHz WPANs. Line-of-Sight (LOS) link is easily blocked by a moving person, which is concerned as one of the severe problems in 60 GHz systems. Beamforming is a feasible technique to resolve link blockage by switching the beam path from LOS link to a Non-LOS (NLOS) link. We propose and evaluate two kinds of Beam Switching (BS) mechanisms: instant decision based BS and environment learning based BS. We examine these mechanisms in a typical indoor WPAN scenario. Extensive simulations have been carried out, and our results reveal that combining angle-of-arrival with the received signal to noise ratio could make better decision for beam switching. Our work provides valuable observations for beam switching during point-to-point communication using 60 GHz radio.

Today, many wireless devices are mobile and battery powered, which means that the service duration is highly dependent on energy consumptions and battery capacities. Based on the fact that battery capacity is still limited, energy saving is an important issue in wireless communication. Many methods have been proposed to save energy in wireless communication, such as power-aware routing and sleep mode. However, another important approach, transmission power adaptation, is not yet well discussed. In this paper, we propose a mechanism that selects the appropriate transmission power level to transmit packets instead of using a fixed default power level for all packets, which is common in IEEE 802.11. Lower transmission power levels may result in more retransmissions, but still consumes less energy. In total, energy can be saved and interference can be reduced by selecting a good transmission power level. We propose a two phase power saving mechanism and implemented it in a real test-bed. To evaluate the performance of our mechanism, we used an indoor environment to carry out measurements. The measurement results indicate that a significant amount of energy can be saved for the transmitter in most scenarios compared to using a fixed transmission power level for all packets.

With the multitude of mobile communication devices supporting users, it is natural to expect that these devices would work ubiquitously anywhere and any time with high data rate support. 60 GHz is an obvious choice for the high data rate indoor communication. In this paper we present an holistic analytical model of 60 GHz link stability for indoor wireless networks. The model is built considering the indoor channel characteristics of 60 GHz radio, the antenna configuration and the mobility of persons. Also, we take an example to show the relevance of our model and its applicability in numerical evaluation.

QoS-sensitive applications transmitted over wireless links require precise knowledge of the wireless environment. However, the dynamic nature of wireless channel, together with its different configurations and types, makes so called link quality estimation (LQE) a difficult task. This paper looks into the design of an accurate and fast LQE method for a multi data rate environment. We investigate the impact of various conditions on the LQE accuracy. In result, two different link quality estimation sources, i.e., based on hello packet delivery ratio and signal strength, are measured and their performances are compared. We find that these two methods are not always accurate. As an improvement we propose an adaptive LQE method that chooses different LQE indicators depending on the wireless environment. The performance of the proposed method is verified via an extensive measurement campaign.

As described in the scope of the IEEE 802.15 working group, impulse radio ultra wide band (IR-UWB) is suitable for many wireless personal area network (WPAN) applications. Due to the short radio coverage of the UWB technology limited by the FCC regulations, IR-UWB devices that participate in a WPAN may not be always reachable within the single hop. The multi-hop capability will be a substantial requirement in IR-UWB based WPAN networks for diverse application scenarios. However, the existing WPAN solutions most target for the single-hop network and the IR-UWB physical features are rarely taken into account in the protocol design. In our research, we focus on how to incorporate IR-UWB devices into a multi-hop WPAN and how to realize data communication between any pair of nodes in the WPAN. The generic network architecture and new data link layer protocols are proposed for solving the multi-hop connectivity problem as well as being optimized for IR-UWB physical features. The approach enables connection oriented transmissions by explicitly scheduling on forwarding paths so as to enhance channel utilization efficiency. The approach fills a research gap between the specific IR-UWB applications and the existing WPAN standards.

VoIP packets, when transported over the Internet, experience loss and variable delay. The effect of the network not only depends on the background flows but also on the parameters of VoIP packets itself, such as VoIP packet size and the packet generation intervals. While higher sized packets experience more losses, they experience less delay jitter and handling them is thus easy at the playout buffer. To investigate the effect of various network conditions on VoIP session holistically, we present a complete end to end study considering various states of the underlying network. We present as a case study of G.711 coded packets generated at 20 and 40 ms intervals for comparison. While packets carrying 20 ms data are better when the network is loaded, 40 ms packetization is favored when the network is not saturated. This affects the jitter and loss thus affecting the quality. We explain this trade-off using mean opinion scores.

In this paper we introduce and examine via simulations, a Markov decision process (MDP) based approach for vertical handover decision-making. We consider here the case of a heterogeneous network environment where both the legacy WLAN and the novel line-of-sight (LOS)- dependent 60 GHz radio systems are deployed to support indoor high quality multi-media applications. The MDP decision approach takes into account multiple factors such as user preference, network situation, device capability and effects of environment. We show its ability to effectively make handover decision in uncertain situations. The method and results herein are applicable, in general, to any other situation where such a decision is to be made.

With the advent of opening up 60 GHz Radio with 5 GHz of available spectrum, many bandwidth-hungry applications can be supported. The immediate concern, however, is the constraint on the line-of-sight transmission as well as the short transmission range of signals. As a result, in an indoor network, a mobile user might experience frequent breaks or losses of connection when one moves from one cell to another. To mitigate this problem, the Extended Cell (EC) architecture is proposed. In this paper, a dynamic Extended Cell formation algorithm is proposed based on the actual floor plan and the traffic situation under the network. Moreover, by applying this dynamic EC formation algorithm, we show that the call blocking probability is reduced. The dynamic EC formation also eases the deployment and maintenance cost due to its adaptability to the changing environment.

The Information Society Technologies (IST) EUROPCOM project designs and develops an Ultra-WideBand (UWB)-based ad hoc network for search and rescue operations in disaster zones, especially indoors. The primary application of the EUROPCOM system is to provide position tracking of rescue personnel within the disaster zone. Currently no such technologies or systems exist, which can provide the envisaged functionality. The paper presents the network architecture that was proposed in the EUROPCOM project. The network architecture defines new physical entities and includes a complete protocol stack - from the physical layer up to the application layer. Each protocol layer was tailor-made to the operational constraints and requirements of the EUROPCOM system. The resulting protocol layers are lightweight, self- adaptive, bandwidth- and energy-efficient.

With the advent of miniaturization and higher computing capabilities of wireless devices, there is an exponential rise in the number of devices such as personal digital assistants, etc. Application development for these devices is the main focus for many device manufacturers and software developers. The applications developed need to be tested and tried before releasing it to the market. There are cross-compilers to produce the binary files of the software applications that can run on these devices. However, it is rather difficult for developers to test it on the actual devices every time a change is made in the program. Further, a wireless network infrastructure should also be in place for testing. To expedite application development FEW-PNets - a Framework for Emulation of Wireless Personal Networks is proposed. It is a networked application to emulate a Personal Network (PN) owned by a person. It supports emulation of the most functions of PNs. We explain our model by emulating simple PN devices. In this article we elucidate the concepts, advantages, application domains and limitations of FEW-PNets.

We propose an architecture using the 60 GHz Radio over Fiber along with a novel concept of forming Extended Cells (EC). Since in the indoor environment, the propagation of millimeter wave signals is strongly hindered by walls, people, furniture, etc., a mobile user might experience frequent loss of connection as soon as one moves from one cell to another. With ECs one can create sufficient overlap areas between cells, thus ensuring a seamless communication environment to achieve lesser handovers and call drop. We illustrate the effectiveness of the proposed architecture through simulation. We continue further to model the mobility of users in the indoor environment to arrive at an expression to find the call blocking probability.

The current service- and device discovery protocols are not platform- and network independent Therefore, proxy servers will be needed to extend the range of IP-based discovery protocols to non-IP domains. We developed an architecture of a proxy that enables UPnP devices and services to be discovered on the Bluetooth network and vice versa, and allows Bluetooth devices and UPnP control points to access and utilize services located on devices in the other network. We managed to keep all functionality needed for effective proxying running on a single device, e.g. the mobile phone or the Residential Gateway. © 2007 IEEE.

Ultra Wide Band (UWB) has recently gained great interest for high data rate short-range WPANs. Designing a MAC protocol for UWB WPANs must take into account the physical layer characteristics. Due to large bandwidth and spreading spectrum, a time hopping impulse radio UWB (IR-UWB) system can accomplish multiple access by using code division multiplexing. Unlike most existing MAC protocols relying on contention access to limit transmissions, the MAC design for impulse radio intends to accommodate simultaneous transmissions. In this paper, we newly propose a MAC scheme for IR-UWB WPANs. This scheme is a hybrid CDMA and TDMA approach based on time hopping spread spectrum and the timing format of IEEE 802.15.3 MAC. The simulation results show that the proposed approach outperforms the existing protocol under our specifications and WPAN scenarios.

Personal network (PN) as a user centric enabler for future 4G wireless communications starts from the user and extends the user's personal area network (PAN) to a global coverage of his personal devices and services in his home, car and office etc. as well as other foreign networks and services regardless of their geographical locations. Personal networks are dynamic in nature and consist of heterogeneous mobile devices and technologies. As a result, one of the main challenges in the development of personal networks is self-organization in order to be adaptive to the dynamics and heterogeneity of personal networks. A framework that consists of different self-organizing functions for personal networks is proposed in this paper. A cross layer function, context awareness, is discussed in details on how personal networks could make use of context information at various layers to facilitate self-organization.

With more and more consumer devices becoming capable of wireless communication, the need for good quality ad hoc networking becomes more imminent. Self-configuring and self-adapting multi-hop networking will provide an excellent solution for wireless personal area networks (WPAN) as well as wireless home networks. In such networks, scalability is rarely believed to be a real issue. Instead, the issues are related to the end-to-end quality due to wireless links with constantly and rapidly changing quality. Hence, the network layer not only needs to adapt accurately but also in time. This paper looks into the design of accurate and fast wireless link quality assessment (LQA) options. We investigate the possibility to use cross layer information to improve this process which can be used by the routing layer to adapt faster and more accurately to changing situations. Experiments are done and the result shows the importance of adapting the new LQA options.

The provision of one-to-many multimedia services to mobile users over scarce wireless resources has to be performed in a cost-efficient way. In addition to various systems optimized for this type of service, such as DVB-H, UMTS was recently enhanced for support of multimedia broadcast and multicast services (MBMS) over the existing infrastructure. Since MBMS provision will reduce the UMTS capacity for its essential point-to-point services, the integration of UMTS and DVB-H may be beneficial. In this paper, we address the integration of DVB-H at the UMTS radio access level. We present an interworking architecture and discuss necessary modifications to UMTS.

The network resources available on a mobile device may be better employed when taking into account the history of mobility patterns of the user. We propose an experience-based mechanism for network resource usage by applications on mobile hosts. It incorporates a machine learning component that adapts the network resource usage given a high-level metric, typically consisting of system as well as application related sub-metrics.

Voice enabled applications over the Internet are rapidly gaining popularity. Reducing the total bandwidth requirement can make a non-trivial difference for the subscribers having low speed connectivity. Voice activity detection algorithms for VoIP applications can save bandwidth by filtering the frames that do not contain speech. In this paper we introduce a novel technique to identify the voice and silent regions of a speech stream very much suitable for VoIP calls. We use an information theoretic measure, called spectral entropy, for differentiating the silence from the speech zones. Specifically we developed a heuristic approach that uses an adaptive threshold to minimize the miss detection in the presence of noise. The performance of our approach is compared with the relatively new 3GPP TS 26.194 (AMR-WB) standard, along with the listeners' intelligibility rating. Our algorithm yields comparatively better saving in bandwidth, yet maintaining good quality of the speech streams.

This paper addresses the issues of designing an infrastructure to support seamless in-building communication at the 60 GHz band. Recently, the 60 GHz band has received much attention due to its 5 GHz of available spectrum. However, the propagation of signals in this band is strongly hindered by attenuation and line-of-sight requirements. The situation gets worse in the in-building environment where signal propagation is obstructed by physical objects such as walls, furniture etc. In this paper, we present a novel radio over fiber (RoF) architecture that is cost-effective and is able to deliver high data-rate of the order of gigabits. To ensure a seamless communication environment at the 60 GHz band, we propose the concept of extended cells (EC) in order to create sufficient overlap areas. Finally, we illustrate the effectiveness of the proposed architecture by simulating an in-building network at the 60 GHz band employing the RoF and EC concepts

Personal networks (PNs) are future communication systems that combine wireless and infrastructure based networks to provide users a variety of services anywhere and anytime. PNs introduce new design challenges due to the heterogeneity of the involved technologies, the need for self-organization, the dynamics of the PN composition, the application-driven nature, the co-operation with infrastructure-based networks, and the security hazards. This paper discusses the challenges of security, service discovery and QoS provisioning in designing self-organized PNs and combines them all into an integrated architectural framework

A personal network is an overlay network which builds on different wireless networking technologies. This overlay network is responsible of glueing the different wireless networking technologies. In this paper, we consider the cooperation of two key technologies to realize a personal network, namely, Wireless Personal Area Network and Universal Mobile Telecommunications System (UMTS). The co-operation poses a new set of problems as these technologies were not designed to intework with each other. In this paper, we describe each of these problems and their solutions.

Personal networks (PN) is a new concept related to pervasive computing with a strong user-focus view. The key to a successful PN realization is a general network architecture that is capable of bridging different current and future technologies and offers a homogeneous and clear view to the end-user. In this paper, we focus on forming a PN by connecting remote personal devices using infrastructure-based IP networks, including 3G networks and WLAN hotspots. One way is to upgrade the current access networks with new functionality to support PNs. Since many devices in PNs are mobile and battery powered, this may help them to achieve a faster service and to save energy. However, to deploy such functionality is not easy and may hamper the adoption of PNs altogether. Therefore, in this paper we study three possible inter-cluster communication architectures that can use current IP networks. To discern the above proposal we also give a detailed picture of PN network architecture supported by infrastructure. We believe that this detailed discussion will help the success of PNs

IP-based radio access networks (RANs) are envisaged to be the next generation access networks in UMTS. In order to provide a satisfactory level of quality of service (QoS) for real-time applications, and efficient network resource utilisation in the IP-based RAN, resource management in Diffserv (RMD) is proposed (A. Bader et al., 2005). RMD is a simple and scalable bandwidth resource management scheme that extends differentiated services for on-demand resource reservation and admission control. We evaluate measurement-based admission control (MBAC) algorithms for RMD. An MBAC algorithm proposed in literature was selected, namely the time scale decomposition (TSD). The main reason for choosing the TSD algorithm is that this algorithm is less dependent on traffic assumptions. In the TSD algorithm, two variants are specified. The first variant is based on per flow measurement statistics (TSD-FE criterion), which is not scalable. The second one uses aggregate measurement statistics (TSD-AE criterion). The main disadvantage of TSD-AE is that it provides poor utilisation performance due to inaccurate estimation of traffic statistics. Therefore, we enhance TSD-AE to improve its utilisation performance. A performance evaluation of different variants of TSD is conducted, the results show that our proposal, the TSD-EAE outperforms TSD-AE

Next-generation communications networks will comprise third-generation (3G) cellular and multi-hop ad hoc networks, in particular, the Universal Mobile Telecommunications System (UMTS) and the IEEE 802.11 ad hoc networks. The paper has evaluated the performance of transmission control protocol (TCP) over an integrated UMTS and IEEE 802.11 multi-hop ad hoc network for bulk data transfers. The IEEE 802.11b was used. The TCP performance was evaluated for four dedicated UMTS radio channels with bit rates ranging from 64 kb/s to 2 Mb/s with varying block error rates. The throughput simulation results show that the UMTS radio channel is the performance bottleneck for bit rates up to 128 kb/s. However, for a 2 Mb/s channel, the performance is solely constrained by the IEEE 802.11b multi-hop ad hoc network. We have showed that the performance can be improved by using a larger TCP packet size

Radio over Fiber (RoF) techniques have been developed to combine the mobility of wireless technologies and the huge bandwidth offered by optical fibers. In this paper, we present the concept of a hybrid radio-fiber system using IEEE 802.11 specifications as a solution for future broadband in-house networks. An analysis on the feasibility of applying RoF techniques to the IEEE 802.11’s Medium Access Control (MAC) protocol will be presented. To substantiate our discussion, simulations of the hybrid system have been carried out. The results show that the throughput of a 802.11 cell extended with an optical distribution network does not decrease drastically when the propagation delay increases.

In this paper, we introduce a highly efficient flooding protocol for MANETs using only one-hop hello messages. By simulation, we show that the protocol has a performance close to flooding protocols that use two-hop hello messages. Further, the protocol performs very good even when the node mobility increases. The only "cost" this protocol must pay is an increased end-to-end delay. However, with some clever cross-layer optimization, this delay can be reduced to become comparable with other flooding protocols. Further, the overhead generated for flooding a packet by this protocol is lower than other protocols, if one-hop hello messages are already provided.

Universal Mobile Telecommunications System (UMTS) is a third-generation cellular network that enables high-speed mobile Internet access. This paper evaluates the performance of the transmission control protocol (TCP) Vegas and compares its performance with TCP Reno in a UMTS environment. Bulk data transfer was considered in the simulation with varying radio channel conditions. Data losses were assumed to be only caused by the radio channel. Simulation results show that the performance of Vegas is unexpectedly worse than Reno even though the data losses were completely recovered by the UMTS radio link control layer. This has led us to conduct a detailed investigation on the behavior of Vegas in order to identify the cause of performance degradation in Vegas. The poor performance of Vegas is attributed to the UMTS radio interface characteristics which characterize by large and highly variable TCP round-trip times. The round-trip time variations activated Vegas' congestion avoidance and the sender would interpret the round-trip time variation as a sign of network congestion. Consequently, the sender shrinks its window size which reduces the transmission rate even though no TCP packet losses occur. Furthermore, a sudden increase in the instantaneous round-trip time can trigger spurious timeouts at the TCP sender using Vegas which performs unnecessary retransmissions. Spurious timeouts can lead to significant throughput reduction. Reno, on the other hand, does not show any abnormality and delivers the expected performance

This paper considers the basic access mechanism in asynchronous transfer mode (ATM)-oriented rings which, like Orwell, ATM ring, and ALine, apply destination release of used slots. The released slots may be reused by the destination station, or in some protocols, they must be given to the next station. Such a mechanism can be modeled by a multiple-server multiqueue system, where switchover times between consecutive polling instants of the queues are nonzero. The server polls the queues according to a certain polling discipline, which is dependent on the service time. This paper presents approximate mean minipacket waiting times in such systems. The approximation is based on a polling queueing model with Markovian server routing. Poisson arrivals and a symmetric workload model for minipackets having a full and partial traffic matrix are assumed. The performance characteristics are compared between the alternative options.

The ability of error recovery mechanisms to make the Fiber Distributed Data Interface (FDDI) satisfy real-time performance constraints in the presence of errors is analyzed. A complicating factor in these analyses is the rarity of the error occurrences, which makes direct simulation unattractive. Therefore, a fast simulation technique, called injection simulation, which makes it possible to analyze the performance of FDDI, including its fault tolerance behavior, was developed. The implementation of injection simulation for polling models of FDDI is discussed, along with simulation results.>

Multiple access to a single user-network interface (UNI) is a cost-effective solution for the provision of B-ISDN services in customer premises. In a multiple access configuration, a fairly shared access must ensure that each terminal will get a guaranteed bandwidth to provide an acceptable quality of service (QoS) and that the allocation of the remaining bandwidth will result in the same improvement of QoS for all the terminals. An approach to allocating the remaining bandwidth is proposed. It is based on both the guaranteed bandwidth required by the terminal and the probability that the terminal's bit rate exceeds its guaranteed bandwidth. The basic generic flow control (GFC) protocol mechanism and the GFC field settings for a dual-bus customer premises network (CPN) are described.>

The structuring, services, and major protocol functions that are required in the upper layers of the OSI reference model in order to support end-to-end multimedia communication, assuming a simple transport service, are examined. It is assumed that variable-bit-rate (VBR) coding techniques will be used in future multimedia systems. Mutual stream synchronization, integral management, and multiparty connections, which appear to be crucial issues in multimedia communication, are addressed. Important implementation and performance issues are discussed.>

Performance of the Cambridge Fast Ring (CFR), a high-speed slotted ring with normal slots, is studied. It is shown that the CFR can be represented by a multiqueue multiple cyclic server model with a 1-limited service discipline and with a restriction that only one server at a time can be serving a queue. Exact necessary and sufficient stability conditions are stated. An approximate analytic M/G/1 vacation model in which analysis concentrates on one station while the others are represented by a vacation period is developed to estimate the expected message waiting times. It is shown that the model is accurate and usable over a wide range of parameters. A performance evaluation of the CFR based on this model is presented. The performance is compared to that of a variant which does not restrict the number of slots a station may simultaneously use.>

Two access mechanisms complementary in performance are the token ring and the slotted ring. While the token ring outperforms the slotted ring for long messages, the latter performs significantly better for short messages. The paper shows that the factor that causes this difference is the number of tokens on the ring. It proposes a new network design in which the number of tokens has been made adaptive, resulting in a network that can be made to behave like both the token ring and the slotted ring, or anything in between, i.e. it performs optimally for any given message length. The paper presents first simulation results that show the performance gain that is achieved by using this principle. Further, it introduces a new priority mechanism in which an upper bound for the access delay of high priority messages is guaranteed.>

The slotted ring protocol which is evaluated in this paper is suitable for use at very large transmission rates. In terms of modelling it is a multiple cyclic server system. A few approximative analytical models of this protocol are presented and evaluated vs the simulation in this paper. The cyclic server model shows to be the most accurate and usable over a wide range of parameters. A performance analysis based on this model is presented.

The performance of a number of slotted-ring protocols supporting integration of synchronous and asynchronous traffic in high-speed local area networks (HSLANs) is evaluated. They are the Cambridge fast ring, a variant of the Cambridge fast ring, and Orwell. The performance of their basic access mechanisms is compared and contrasted with that of the multiple-token ring. The effect of a uniframe scheme for supporting synchronous traffic is examined. A delay analysis of the integrated-services slotted-ring protocols is presented.>

The integration of voice and data transmission on a CSMA/CD LAN with message priority and deterministic collision resolution is studied. As a result an efficient Stream Traffic Protocol using hybrid switching and implicit token passing is designed. The performance of the protocol both for voice and data is analysed using a discrete event simulation model. The protocol increases the system capacity for voice while the strict real-time constraints for its transmission are still met. It supports a number of subscribers comparable with the equivalent to the capacity of a small PABX, with a good performance for data. The work is part of an overall project of an integrated services LAN offering ISDN S-interfaces.