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Abstract: Wireless mesh networking is an economic and convenient way to provide last mile Internet access through ad hoc peer-to-peer communication links. However, without systematic network configuration and channel resource management, these networks suffer from scalability, performance degradation and service disruption issues due to overwhelming co-channel interference, unscrupulous channel utilization and inherent network mobility. The IEEE 802.11 DCF and EDCA mechanisms based on CSMA/CA are the most widely used random channel access mechanisms, but unfortunately these cannot effectively eliminate hidden terminal and exposed terminal problems in multi-hop scenarios. Social network analysis techniques proposed for economic and social studies have recently been shown to be a successful approach for characterizing information propagation in multi-hop wireless networks. We propose a set of efficient resource allocation algorithms and channel access scheduling protocols based on Latin squares and social centrality metrics for wireless mesh networks (WMNs) with multi-radio multi-channel (MRMC) communication capabilities, called , which can coexist with IEEE 802.11 DCF and be effectively applied in large scale WMNs. Based on interference information provided by the interference graph, uses nodal degree centrality to form cliques for intra-cluster communication, and betweenness centrality to choose bridge nodes to form cliques for inter-cluster communication in WMNs, and then applies Latin squares to map the clique-based clustering structure to radios and channels for wireless communication purposes. Afterwards, again applies Latin squares to schedule the channel access amongst nodes within each cluster in a collision-free manner. We evaluate using simulations, and results show that achieves much better performance than existing IEEE 802.11 standards and other multi-channel access control protocols. [Copyright &y& Elsevier]

Abstract: Wireless data broadcast is an important data dissemination method for distributing public information to mobile users. Due to the exponentially increasing number of mobile network users, it is necessary to develop efficient data retrieval protocols for end users to download data items effectively. In this paper, we concentrate on investigating scheduling algorithms for retrieving a set of data items from a multichannel wireless data broadcast system. As we know, the most important issues in mobile computing are energy efficiency and query response efficiency. However, in data broadcast the objectives of reducing access latency and energy cost can be contradictive to each other. Consequently, we define a new problem named Minimum Constraint Data Retrieval Problem (MCDR). We prove that MCDR is NP-hard, and then show a fixed parameter tractable algorithm which can balance two factors together. It has computational time , where is the number of channels, is the number of required data items, is the maximal time slot, and is the maximal number of channel switches. [Copyright &y& Elsevier]

Channel assignment is a crucial problem for wireless networks, especially for noncooperative wireless networks, in which nodes are selfish. While there have been a few studies of noncooperative, multiradio channel assignment, most existing studies are restricted to single collision domains only. In this paper, we study the design of incentive-compatible protocols for noncooperative, multiradio channel assignment in multiple collision domains. First, we show the necessity of designing incentive-compatible protocols for this problem. Specifically, we show that, if no incentive-compatible protocol is deployed, Nash Equilibria (NEs) may have undesired properties, such as Pareto suboptimality and low throughput. To prevent the system from converging to the NEs with undesired properties, we propose an incentive-compatible protocol for channel assignment in multiple collision domains. We rigorously show that our protocol guarantees that the system converges to NEs that are Pareto-optimal and have the maximum system-wide throughput. Our simulation results also verify that our protocols are effective in ensuring that the system converges to the desired NEs. [ABSTRACT FROM AUTHOR]

Abstract: The underground communication in tunnels and mines is very challenging due to the hostile nature of the environments and to the propagation issues that electromagnetic waves suffer there. Communication is often unidirectional (e.g. in mines) or very costly (e.g. leaky feeder in road tunnels) and hard to install and maintain. This work proposes the use of multi-hop ad-hoc networks to provide multimedia communication between mobile nodes in such a hostile environments, relying on a complete hardware/software, cheap and easy-to-setup platform that can be used both as temporary or fixed infrastructure or as communication backbone in emergency scenarios like mine accidents or a tunnel collapse. The communication is based on the Real-Time Multi-hop Protocol (RT-WMP) and its QoS extension executed over several nodes equipped with specific hardware. This protocol manages delay sensitive messages and the node mobility across the network while the QoS extension is responsible for allowing the end-to-end voice communication. The specific topology and situation have driven to a specialization of RT-WMP to better perform in this type of environments, taking advantage of the a priori (partial) knowledge about the topology. This proposal was tested in a real application in the Somport tunnel, the about 8km-long railroad linking Canfranc, Spain with Pau, France. [Copyright &y& Elsevier]

Abstract: Security protocols operating over wireless channels can incur significant communication costs (e.g., energy, delay), especially under adversarial attacks unique to the wireless environment such as signal jamming, fake signal transmission, etc. Since wireless devices are resource constrained, it is important to optimize security protocols for wireless environments by taking into account their communication costs. Towards this goal, we first present a novel application of a signal-flow-based approach to analyze the communication costs of security protocols in the presence of adversaries. Our approach models a protocol run as a dynamic probabilistic system and then utilizes Linear System theory to evaluate the moment generating function of the end-to-end cost. Applying this technique to the problem of secret key exchange over a wireless channel, we quantify the efficiency of existing families of key exchange cryptographic protocols, showing, for example, that an ID-based approach can offer an almost 10-fold improvement in energy consumption when compared to a traditional PKI-based protocol. We then present a new key exchange protocol that combines traditional cryptographic methods with physical-layer techniques, including the use of “ephemeral” spreading codes, cooperative jamming, and role-switching. Utilizing signal flow analysis, we demonstrate that this new protocol offers performance advantages over traditional designs. [Copyright &y& Elsevier]

We study the capacity scaling laws for the cognitive network that consists of the primary hybrid network (PhN) and secondary ad hoc network (SaN). PhN is further comprised of an ad hoc network and a base station-based (BS-based) network. SaN and PhN are overlapping in the same deployment region, operate on the same spectrum, but are independent with each other in terms of communication requirements. The primary users (PUs), i.e., the ad hoc nodes in PhN, have the priority to access the spectrum. The secondary users (SUs), i.e., the ad hoc nodes in SaN, are equipped with cognitive radios, and have the functionalities to sense the idle spectrum and obtain the necessary information of primary nodes in PhN. We assume that PhN adopts one out of three classical types of strategies, i.e., pure ad hoc strategy, BS-based strategy, and hybrid strategy. We aim to directly derive multicast capacity for SaN to unify the unicast and broadcast capacities under two basic principles: 1) The throughput for PhN cannot be undermined in order sense due to the presence of SaN. 2) The protocol adopted by PhN does not alter in the interest of SaN, anyway. Depending on which type of strategy is adopted in PhN, we design the optimal-throughput strategy for SaN. We show that there exists a threshold of the density of SUs according to the density of PUs beyond which it can be proven that: 1) when PhN adopts the pure ad hoc strategy or hybrid strategy, SaN can achieve the multicast capacity of the same order as it is stand-alone; 2) when PhN adopts the BS-based strategy, SaN can asymptotically achieve the multicast capacity of the same order as if PhN were absent, if some specific conditions in terms of relations among the numbers of SUs, PUs, the destinations of each multicast session in SaN, and BSs in PhN hold. [ABSTRACT FROM AUTHOR]

Abstract: As the demand for mobile ad hoc wireless network (MANET) applications grows, so does their use for many important services where reliability and stability of the communication paths are of great importance. Therefore, a MANET must be able to establish reliable communication channels which are protected by failure recovery protocols. One approach for existing failure recovery protocols is based on using backup paths, or multi-paths. This technique provides for more stable communication channels for wireless services, in particular for MANET applications. But work on such multi-path protocols has focused on stability in the presence of link failure for MANETs. In this paper, we extend such protocols to maintain connection stability in the presence of node failure. Our work is focused on protecting the route of mobile wireless communications in the presence of node failure in order to improve their use in MANETs applications by discovering efficient stable communication channels with longer lifetimes and increased number of packets delivered. [Copyright &y& Elsevier]

Abstract: This paper considers a field with a number of isolated wireless sensor networks served by some mobile mules and base stations (BSs). Sensing data needs to be carried by mobile mules to BSs via opportunistic contact between them. Also, such contact may not be frequent. Thus there are four types of communications in this environment: (i) inter-node communications within a WSN, (ii) opportunistic WSN-to-mule communications, (iii) opportunistic mule-to-mule communications, and (iv) opportunistic mule-to-BS communications. In such disconnected WSNs, since sensors’ memory spaces are limited and data collection from isolated WSNs to mules and then to BSs relies on opportunistic communications in the sense that contact between these entities is occasional, storing and collecting higher-priority data is necessary. Therefore, there are two critical issues to be addressed: the data storage management in each isolated WSN and opportunistic data collection between these entities. We address the storage management problem by modeling the limited memory spaces of a WSN’s sensor nodes as a distributed storage system. Assuming that there is a sink in the WSN that will be visited by mobile mules occasionally, we address three issues: (i) how to buffer sensory data to reduce data loss due to a shortage of storage spaces, (ii) if dropping of data is inevitable, how to avoid higher-priority data from being dropped, and (iii) how to manage the data nearby the sink to facilitate the downloading jobs of mules when the downloading time is unpredictable. We propose a Distributed Storage Management (DSM) strategy based on a novel shuffling mechanism similar to heap sort. It allows nodes to exchange sensory data with neighbors efficiently in a distributed manner. For the opportunistic data collection problem, based on a utility model, we then develop an Opportunistic Data Exchange (ODE) strategy to guide two mules to exchange data that would lead to a higher reward. To the best of our knowledge, this is the first work addressing distributed storage strategy for isolated WSNs with opportunistic communications using mobile mules. We conduct extensive simulations to investigate the merit of DSM and ODE. The simulation results indicate that the level of data importance collected by our DSM is very close to a global optimization and our ODE could facilitate delivery of important data to BSs through mules. We also implement these strategies in a real sensor platform, which demonstrates that the simple and lightweight protocols can achieve our goals. [Copyright &y& Elsevier]

IPv6 mobility management is one of the most challenging research topics for enabling mobility service in the forthcoming mobile wireless ecosystems. The Internet Engineering Task Force has been working for developing efficient IPv6 mobility management protocols. As a result, Mobile IPv6 and its extensions such as Fast Mobile IPv6 and Hierarchical Mobile IPv6 have been developed as host-based mobility management protocols. While the host-based mobility management protocols were being enhanced, the network-based mobility management protocols such as Proxy Mobile IPv6 (PMIPv6) and Fast Proxy Mobile IPv6 (FPMIPv6) have been standardized. In this paper, we analyze and compare existing IPv6 mobility management protocols including the recently standardized PMIPv6 and FPMIPv6. We identify each IPv6 mobility management protocol's characteristics and performance indicators by examining handover operations. Then, we analyze the performance of the IPv6 mobility management protocols in terms of handover latency, handover blocking probability, and packet loss. Through the conducted numerical results, we summarize considerations for handover performance. [ABSTRACT FROM PUBLISHER]

Radio Frequency Identification (RFID) is a technology that is very popular due to the simplicity in its technology and high adaptability in a variety of areas. The simplicity in the technology, however, comes with a caveat - RFID tags have severe resource restrictions, which make them vulnerable to a range of security attacks. Such vulnerability often results in the loss of privacy of the tag owner and other attacks on tags. Previous research in RFID security has mainly focused on authenticating entities such as readers / servers, which communicate with the tag. Any security mechanism is only as strong as the encryption keys used. Since RFID communication is wireless, critical messages such as key exchange messages are vulnerable to attacks. Therefore, we present a mutual authentication protocol that relies on independent generation and dynamic updates of encryption keys thereby removing the need for key exchange, which is based on the concept of gene mutation and transfer. We also present an enhanced version of this protocol, which improves the security offered by the first protocol. The novelty of the proposed protocols is in the independent generation, dynamic and continuous updates of encryption keys and the use of the concept of gene mutation / transfer to offer mutual authentication of the communicating entities. The proposed protocols are validated by simulation studies and security analysis. [ABSTRACT FROM AUTHOR]

With the explosive growth and wide-spread use of smartphones with Wi-Fi enabled, people are used to accessing the internet through Wi-Fi network interfaces of smartphones. Smartphones periodically transmit Wi-Fi messages, even when not connected to a network. In this paper, we describe the Mo-Fi system which monitors and aggregates large numbers of continuous Wi-Fi message transmissions from nearby smartphones in the area of interest using nonintrusive Wi-Fi sniffer sensors. In this paper, we propose an optimized Wi-Fi channel detection and selection method to switch the best channels automatically to aggregate the Wi-Fi messages based on channel data transmission weights and human presence activity classification method based on the features of human dwell duration sequences in order to evaluate the user engagement index. By deploying in the real-world office environment, we found that the performance of Wi-Fi messages aggregation of CAOCA and CACFA algorithms is over 3.8 times higher than the worst channel of FCA algorithms and about 76% of the best channel of FCA algorithms, and the human presence detection rate reached 87.4%. [ABSTRACT FROM AUTHOR]

In wireless sensor networks (WSN), Sybil attack can destroy the routing and data distributed storage mechanisms through fabricating identity information of legitimate nodes. This paper presents a chain key predistribution based approach against Sybil attack. To enhance the security of common keys between neighboring nodes, during the chain key predistribution phase, our approach uses a lightweight hash function to generate several chain keys by hashing the unique identity information of every node sequentially in the trusted base station. These chain keys construct a pool of chain keys. During the pairwise key authentication establishment phase, a node-to-node chain key based authentication and exchange (CK-AE) protocol is proposed, by which each node can share the unique pairwise key with its neighboring node. The CK-AE protocol is provably secure in the universally composable security model (UCSM). Finally, we analyze our approach from the resilience of network and the performance overhead, and the results show that our approach can not only enhance the ability of resilience to Sybil attack, but also reduce the communication overhead significantly at the cost of a certain amount of computational overhead. [ABSTRACT FROM AUTHOR]

The vehicular mobility is reflection and extension of the human social activity. Since human trajectories show a high degree of temporal and spatial regularity, thus vehicular driving paths are predictable to a large extent. In this paper, we firstly analyze the predictabilities of different types of vehicles and then propose a new driving path predication based routing protocol (DPPR). With hello messages to broadcast vehicles' driving path predication information to neighbor vehicles, DPPR can observably increase the successful ratio to find the proper next hop vehicles that move toward the optimal expected road in intersection areas. In roads with sparse vehicle density, DPPR utilizes vehicles to carry messages to roads with high vehicle density while the messages' forward paths partially coincide with the vehicles' driving paths. Moreover, as to messages that can tolerate long delay, they can be carried to destinations by vehicles whose driving paths will pass the messages' destination in order to optimize bandwidth utilization. Simulation results demonstrate the effectiveness of the proposed DPPR protocol. [ABSTRACT FROM AUTHOR]

Intervehicle communication gives vehicles opportunities to exchange packets within the limited radio range and self-organized in Ad Hoc manner into VANETs (Vehicular Ad Hoc Networks). However, due to issues such as the high mobility, insufficient market penetration ratio, and lacking of roadside units, connectivity is actually a big problem in VANETs. In addition, relying only on the direct connectivity in most of the previous works, say broadcasting which provides one-hop connections between nodes is far from the continuously growing application demands in VANETs, such as inter-vehicle entertainments, cooperative collision avoidances, and inter-vehicle emergency notifications. Therefore, the indirect connectivity from multihop forwarding is also a necessary complement especially for the case where direct connection is hardly achieved. In this paper, we define a new metric, that is, available connectivity, to consider both direct and indirect connectivity. After analyzing the statistical properties of direct and indirect connectivity in vehicular environment, the available connectivity is proposed and quantified for practical usage. Numerical results show that our available connectivity could provide correct and useful references for protocols design and performance improvements of different applications. [ABSTRACT FROM AUTHOR]

Due to the potentials in promoting the driving safety and easing the traffic congestion, vehicular networks, especially vehicle-to-vehicle (V2V) communications, have recently been receiving much attention. The data dissemination protocol for V2V applications should not only provide end-to-end transmissions with low error probability and high throughput but also offer antieavesdropping capabilities. To achieve this goal, we in this paper propose a secrecy-enhanced relaying protocol for vehicular environments. Based on the network topology and the velocity of the moving vehicles, the proposed scheme first generates the relay candidate set, from which a single relay is then selected opportunistically to assist the source. By using the superposition coding strategy, the selected relay jointly sends the source message and the artificial interference to enable secure communications. We derive the tight closed-form expressions for the upper and lower bounds of the secrecy outage probability, based on which we analyze the diversity order of the system. The method to generate the interference signal is introduced, and the choice of superposition weight factor is also given. The analytical and simulation results show that the proposed relay-aided protocol yields a better performance than the competing alternatives in terms of both the secrecy performance and the implementation complexity. [ABSTRACT FROM AUTHOR]

Data broadcast is a fundamental operation in wireless sensor networks (WSNs). The existence of wireless interference makes it nontrivial to design a minimum-latency broadcast scheme, which is known to be NP-hard. Existing works all assume strict time synchronization and provide centralized TDMA scheduling algorithms. However, WSNs in practice are more likely to be distributed asynchronous systems. In this paper, we investigate the problem of data broadcast with minimum latency for distributed asynchronous WSNs. To this end, we propose a Distributed Asynchronous Broadcast (DAB) algorithm which crucially leverages an elaborately optimized carrier-sensing range together with collision-backoff schemes to coordinate the transmissions among the nodes on a predetermined broadcast backbone. Theoretical analysis shows that DAB is order-optimal and achieves constant factor approximation to the optimal delay. We then conduct extensive simulations to evaluate the practical capability of DAB in asynchronous WSNs and the results corroborate our theoretical analysis. [ABSTRACT FROM AUTHOR]

Mobile ad hoc networks (MANETs) are formed by wireless mobile devices that do not require a predefined infrastructure and where all nodes are at the same level without the need of a central coordinator. The routing is an important task in this kind of networks because of highly dynamic environments and other characteristics. Routing consists of sending the information from sender nodes to destination nodes in a multihop manner. There are different techniques to solve the routing problem. We rely on bioinspired algorithms, those that take into account the behavior of certain animals to solve it. Specifically we design a novel routing algorithm based on Ant Colony Optimization (ACO) which uses the concepts of Swarm Intelligence and analyzes the behavior of ants at the time of obtaining the food. In this work, we present Hybrid ACO Routing (HACOR), a bio-inspired protocol based on ACO. In the simulation results, we observe how this protocol performs significantly better compared to a state-of-the-art routing protocol, according to the analyzed metrics. [ABSTRACT FROM AUTHOR]

In wireless sensor network, when these sensors are wrongly placed in an observation region, they can quickly run out of batteries or be disconnected. These incidents may result in huge losses in terms of sensing data from numerous sensors and their costs. For this reason, a number of simulators have been developed as tools for effective design and verification before the actual arrangement of sensors. While a number of simulators have been developed, simulation results can be fairly limited and the execution speed can be markedly slow depending on the function of each simulator. In this regard, to improve the performance of existing simulators, this research aimed to develop a parallel calculation simulator for independent sensor (PCSIS) that enables users to selectively use the GPU mode and, based on this mode, enables parallel and independent operations by matching GPU with many cores in order to resolve the slowdown of the execution speed when numerous sensor nodes are used for simulations. The PCSIS supports the GPU mode in an environment that allows the operation of compute unified device architecture (CUDA) and performs the parallel simulation calculation of multiple sensors using the mode within a short period of time. [ABSTRACT FROM AUTHOR]

We consider the use of spatial diversity to improve the performance of analog joint source-channel coding in wireless fading channels. The communication system analyzed in this paper consists of discrete-time all-analog-processing joint source-channel coding where Maximum Likelihood (ML) and Minimum Mean Square Error (MMSE) detection are employed. By assuming a fast-fading Rayleigh channel, we show that MMSE performs much better than ML at high Channel Signal-to-Noise Ratios (CSNR) in single-antenna wireless systems. However, such performance gap can be significantly reduced by using multiple receive antennas, thus making low complexity ML decoding very attractive in the case of receive diversity. Moreover, we show that the analog scheme can be considerably robust to imperfect channel estimation. In addition, as an alternative to multiple antennas, we also consider spatial diversity through cooperative communications, and show that the application of the Amplify-and-Forward (AF) protocol with single antenna nodes leads to similar results than when two antennas are available at the receiver and Maximal Ratio Combining (MRC) is applied. Finally, we show that the MMSE implementation of the analog scheme performs very close to the unconstrained capacity of digital schemes using scalar quantization, while its complexity is much lower than that of capacity-approaching digital systems. [ABSTRACT FROM PUBLISHER]

Control channel is used to transmit protocol or signal information between wireless network nodes and is a key component of wireless network. Compared with data information, protocol or signal information is usuallymuch less, so the spectrumbandwidth requirement of control channel is also much less than that of data channel. In order to optimize the usage of the limited spectrum resources, this paper focuses on the issue of control channel selection. We propose a greedy algorithm which minimizes the total spectrum bandwidth of the set of control channels. The oretical analysis proves that the proposed algorithm can achieve the optimal set of control whose sum of the spectrum bandwidth is the minimum. Simulation results also show that the proposed algorithm consumes less spectrum resources than other algorithms in the same wireless network environment. [ABSTRACT FROM AUTHOR]

The constantly increasing demand for capacity in modern communication systems such as wireless backhaul has led to the employment of frequencies above 10 GHz where the dominant fading mechanism is rain attenuation which is usually modelled as a lognormal random variable (when expressed in dB - log-lognormal in linear scale). In addition, in the context of green communications the use of cooperative diversity techniques can be considered as an important tool which improves the performance, reliability and efficiency of such systems. In this paper, the outage performance analysis of a cooperative system operating at frequencies above 10 GHz is presented, where the propagation medium consists of spatially correlated fading channels. In addition, the energy and spectral efficiency of various multiple-access protocols as well as different relay retransmission and receiver combining techniques are investigated. Moreover, it is proposed that the high correlation coefficient between various rain fading channels can be exploited by the relay to estimate the rain fading of the next hop. Extended numerical results present the impact of various system parameters on the end-to-end performance. Finally, comparison with an energy- and bandwidth- equivalent direct link highlights the system parameter regions where cooperative diversity offers gains over non-cooperation. [ABSTRACT FROM AUTHOR]

Sleep scheduling is a widely used strategy for saving the energy of sensor nodes and prolonging the lifetime of a wireless sensor network (WSN). The lower the duty cycle is, the longer the network lifetime will be. However, sleep scheduling brings great challenges to the design of efficient distributed routing protocols for multi-hop duty-cycled WSNs. This issue has attracted much attention and various routing protocols have been proposed. In this article we first summarize the fundamental issues in the design of routing protocols for such networks, and then classify existing protocols based on different design criteria. We then present a survey of state-of-the-art routing protocols in this area. We illustrate how different protocols work and discuss their merits and deficiencies. Finally, we point out some future directions for routing in duty-cycled wireless sensor networks. [ABSTRACT FROM PUBLISHER]

With the rapid advancement of wireless networking technology, networks have evolved from static to dynamic. Reliability of dynamic networks has virtually become an important issue. Fortunately, a solution to the above issue can be derived from solutions to the Byzantine Agreement (BA) problem. BA problem can be solved by protocols that make processors reach an agreement through message exchange. Protocols used to solve the problem can be divided into Immediate Byzantine Agreement (IBA) protocols and Eventual Byzantine Agreement (EBA) protocols. In IBA protocols, the number of rounds of message exchange is determined by the total number of processors in the network. Even if no faulty processor is present in the network, IBA protocols still require a fixed number of rounds of message exchange, causing a waste of time. In contrast, EBA protocols dynamically adjust the number of rounds of message exchange according to the interference of faulty processors. In terms of efficiency, EBA protocols certainly outperform IBA protocols. Due to the fact that the existing EBA protocols have been designed for static networks, they cannot work on dynamic networks. In this paper, we revisit the EBA problem in dynamic networks to increase the reliability of dynamic networks. Simulations will be conducted to validate that the proposed protocol requires the minimum rounds of message exchange and can tolerate the maximum number of malicious faulty processors compared to other existing protocols. [ABSTRACT FROM AUTHOR]

Performance evaluation of the 802.11 MAC protocol is classically based on the decoupling assumption, which hypothesizes that the backoff processes at different nodes are independent. This decoupling assumption results from mean field convergence and is generally true in transient regime in the asymptotic sense (when the number of wireless nodes tends to infinity), but, contrary to widespread belief, may not necessarily hold in stationary regime. The issue is often related with the existence and uniqueness of a solution to a fixed point equation; however, it was also recently shown that this condition is not sufficient; in contrast, a sufficient condition is a global stability property of the associated ordinary differential equation. In this paper, we give a simple condition that establishes the asymptotic validity of the decoupling assumption for the homogeneous case (all nodes have the same parameters). We also discuss the heterogeneous and the differentiated service cases and formulate a new ordinary differential equation. We show that the uniqueness of a solution to the associated fixed point equation is not sufficient; we exhibit one case where the fixed point equation has a unique solution but the decoupling assumption is not valid in the asymptotic sense in stationary regime. [ABSTRACT FROM PUBLISHER]

In this paper, the weighted average prediction (WAP) is introduced into the existing consensus protocol for simultaneously improving the robustness to communication delay and the convergence speed of achieving the consensus. The frequency-domain analysis and algebra graph theory are employed to derive the necessary and sufficient condition guaranteeing the second-order delayed multi-agent systems applying the WAP-based consensus protocol to achieve the stationary consensus. It is proved that introducing the WAP with the proper length into the existing consensus protocol can improve the robustness against communication delay. Also, we prove that for two kinds of second-order delayed multi-agent systems: 1) the IR-ones with communication delay approaching zero and 2) the ones with communication delay approaching the maximum delay, introducing the WAP with the proper length into the existing consensus protocol can accelerate the convergence speed of achieving the stationary consensus. [ABSTRACT FROM PUBLISHER]

Cooperative techniques have been shown to significantly improve the performance of wireless networks. Despite being a mature technology in single communication link scenarios, their implementation in wider, and practical, networks poses several challenges which have not been fully identified and understood so far. In this paper, the implementation of cooperative communications in non-centralized ad hoc networks with sensing-based channel access is extensively discussed. Both analysis and simulation are employed to provide a clear understanding of the mutual influence between the link layer contention mechanism and relaying protocols. Results show that sensing-based channel access significantly hampers the effectiveness of cooperation by biasing the spatial distribution of available relays, and by inducing a level of spatial and temporal correlation of interference that diminishes the diversity improvement on which cooperative gains are founded. Moreover, the efficiency reduction entailed by several practical protocol issues related to carrier sense multiple access which are typically neglected in the literature is thoroughly investigated. [ABSTRACT FROM PUBLISHER]

We address content discovery in wireless networks with infrastructure, where mobile nodes store, advertise, and consume content while Broker entities running on infrastructure devices let demand and offer meet. We refer to this paradigm as match-making, highlighting its features within the confines of the standard publish-and-subscribe paradigm. We study its performance in terms of success probability of a content query, a parameter that we strive to increase by acting as follows: 1) We design a credit-based scheme that makes it convenient for rational users to provide their content (thus discouraging free-riding behavior), and it guarantees them a fair treatment. 2) We increase the availability of either popular or rare content, through an efficient caching scheme. 3) We counter malicious nodes whose objective is to disrupt the system performance by not providing the content they advertise. To counter the latter as well as free riders, we introduce a feedback mechanism that enables a Broker to tell apart well- and misbehaving nodes in a very reliable manner, and to ban the latter. The properties of our match-making scheme are analyzed through game theory. Furthermore, via ns-3 simulations, we show its resilience to different attacks by malicious users and its good performance with respect to other existing solutions. [ABSTRACT FROM AUTHOR]

We consider the problem of delivering content cached in a wireless network of n nodes randomly located on a square of area n. The network performance is described by the 2^n\times n-dimensional caching capacity region of the wireless network. We provide an inner bound on this caching capacity region, and, in the high path-loss regime, a matching (in the scaling sense) outer bound. For large path-loss exponent, this provides an information-theoretic scaling characterization of the entire caching capacity region. The proposed communication scheme achieving the inner bound shows that the problems of cache selection and channel coding can be solved separately without loss of order-optimality. On the other hand, our results show that the common architecture of nearest-neighbor cache selection can be arbitrarily bad, implying that cache selection and load balancing need to be performed jointly. [ABSTRACT FROM PUBLISHER]

Nowadays, mobile service requests in wireless networking are aimed to the benefit of a good level of satisfaction for the received Quality of Service (QoS) guarantees. In this paper, a new prediction algorithm is proposed, for the pre-reservation of passive bandwidth, when mobile users moves under radio coverage that can be considered as a cellular one (GSM, UMTS, WLAN clusters, etc.). The Hidden Markov Chains (HMC) theory is used to design the predictor, as the main component of the proposed idea, that does not depend on the considered transmission technology, mobility model or vehicular scenario. Mobile ReSerVation Protocol (MRSVP) has been used in order to realize the active/passive bandwidth reservation in the considered network topology. Different simulation campaigns have been carried out in order to appreciate the benefits of the proposed idea. [ABSTRACT FROM AUTHOR]

In November 2011, the IEEE 802.3 Working Group approved the formation of a new Study Group chartered with examination of EPON over Coax (EPoC) technology. This article provides an overview of the market drivers, technical challenges, as well as deployment goals for this new technology. [ABSTRACT FROM PUBLISHER]

Computer networks courses are hard to teach as there are many details in the protocols and techniques involved that are difficult to grasp. Employing programming assignments as part of the course helps students to obtain a better understanding and gain further insight into the theoretical lectures. In this paper, the Partov simulation engine and experience using this engine in a computer networks course are discussed. Since 2009, various programming assignments based on the Partov system have been set to help students in their learning process. Student feedback has been very good; this has been quantified in two surveys in which a majority of students expressed their satisfaction with this approach. [ABSTRACT FROM PUBLISHER]

Wireless Mesh Networks (WMNs) are an important networking infrastructure for providing cost-efficient broadband wireless connectivity to a group of users. WMNs are increasingly being used in urban, metropolitan and municipal area networks for deployment of medical, transport, surveillance systems, etc. The performance and operability of WMNs largely depends on placement of mesh routers nodes in the geographical area to achieve network connectivity and stability. The objective is to find an optimal and robust topology of the mesh router network to support intelligent telecommunication services to clients such as adaptive and flexible wireless Internet access, mobile data, voice, video in addition to supporting other preferred client services. In this work, we propose and evaluate local search methods for intelligent placement of mesh routers in WMNs with a two fold objective: maximizing the size of the giant component in the network and user coverage. Given a grid area where to distribute a given number of mesh router nodes, which can have different radio coverage, and a number of fixed clients a priori distributed in the given area, local search methods explore different local movements and incrementally improve the quality of the router nodes placement in terms of network connectivity and user coverage. We have experimentally evaluated the proposed local search methods through a benchmark of generated instances of varying sizes. Moreover, different distributions of mesh clients (Uniform, Normal, Exponential and Weibull) are used. The experimental evaluation showed the good performance of local search methods for optimizing network connectivity and user coverage in WMNs. [ABSTRACT FROM AUTHOR]

We study fixed data rate communication schemes for wireless relay-interference networks with any number of transmitters, relays, and receivers. The transmitters and the relays have individual short-term power constraints. We analyze both amplify-and-forward (AF) and decode-and-forward (DF) relaying strategies with a two channel use quantized network beamforming protocol. We design the quantizer of the channel state information to minimize the probability that at least one receiver incorrectly decodes its desired symbol(s). Correspondingly, we introduce a generalized diversity measure that encapsulates the conventional one as the first-order diversity. Additionally, it incorporates the second-order diversity, which is concerned with the transmitter power dependent logarithmic terms that appear in the error rate expression. We first show that for AF relays, the maximal achievable diversity in the presence of interference is strictly less than the transmit diversity bound in terms of the second-order diversity. We then prove that it is possible to achieve the transmit diversity bound using DF relays as if there is no interference and as if coding over an arbitrary number of channel uses is allowed. Relay selection provides the best possible diversity gain for both relaying strategies. Finally, we show that all the aforementioned diversity gains can be achieved using distributed decision making with asymptotically zero feedback rate per receiver. Such a performance is made possible by a special distributed quantizer design method we have called localization . [ABSTRACT FROM PUBLISHER]

A wireless sensor network is new technological advancement in wireless communication. Sensor networks are made up of hundreds or thousands of sensor nodes which are densely deployed in a remote environment with the capabilities of sensing, wireless communications and computations. Many different routing, power management and data dissemination protocols have been designed for wireless sensor networks. In this paper a study on layered protocol stack architecture for communication in sensor networks along with the various congestion control algorithms is discussed. [ABSTRACT FROM AUTHOR]

Wireless Sensor Networks (WSN) are collections of sensors that are equipped with a radio and form a wireless network together. In this work we look at communication protocols, which have an obvious effect on the energy within the network, The energy issue is important in WSN, it is generally hard or impractical to charge/replace the exhausted battery, which gives way to the primary objective of maximizing network life time, so that we focused in our Protocol on MAC, consume this protocol the most part of energy from the sensor. In this protocol we proposed an approach for MAC protocol called GSM protocol. In this Protocol, cluster-heads change on a regular intervals To ease the load on the sensors in the network ,the sensors send average of data to avoid large bit of the message, we used own simulation to get the comparison results with "Direct Communication with the base station", we proposed GSP protocol expected to become more effective in reducing energy consumption , by split the cluster into two part that is the default and use the timers for organizing the operations in cluster and avoid the Collision. [ABSTRACT FROM AUTHOR]

Abstract: Recently, many works have been focusing on solving the problem of privacy protection at link-layer level by randomizing all bits of the frames at link layer so that it makes difficult for unintended recipients to associate sequences of packets to their source transmitters. Most existing schemes however assume either the pre-setup for shared secrets between communication entities or the use of public-key infrastructure. These requirements limit the use of the schemes. In this paper, we describe new techniques for protecting the privacy and security of communication entities at wireless link-layer level. Our techniques have a number of crucial advantages. They mitigate the requirement of a key setup or a public-key infrastructure. They provide not only the link-layer privacy, but also the required security properties, including key compromise impersonation resilience, impersonation resistance and forward secrecy. They are simple and relatively fast. [Copyright &y& Elsevier]

This paper proposes a low-cost, low-power, and highcapacity optical-electrical-optical-type reach extender that can provide 3R frame regeneration and remote management to increase the reach and split ratio with no change to a legacy time division multiple access passive optical network. To provide remote management, the extender gathers information regarding optical transceivers and link status per port and then transmits to a service provider using a simple network management protocol agent. The extender can also apply to an Ethernet passive optical network (E-PON) or a gigabit-capable PON (G-PON) by remote control. In a G-PON, in particular, it can provide burst mode signal retiming and burst-to-continuous mode conversion at the upstream path through a G-PON transmission convergence frame adaptor. Our proposed reach extender is based on the quad-port architecture for cost-effective design and can accommodate both the physical reach of 60 km and the 512 split ratios in a G-PON and the physical reach of 80 km and the 256 split ratios in an E-PON. [ABSTRACT FROM AUTHOR]

The preservation of temporal dependencies among a group of processes that exchange continuous media at runtime is a key issue for emerging mobile distributed systems (MDS), such as monitoring of biosignals and interactive multiuser games. Although several works are oriented to satisfy temporal dependencies, most of them are not suitable for MDSs. In general, an MDS is characterized by the absence of global references (e.g. shared memory and wall clock), host mobility, limited processing and storage capabilities in mobile hosts, and limited bandwidth on wireless communication channels. This paper proposes an asymmetric synchronization protocol to be used at runtime in an MDS without using a common reference. One main aspect of our synchronization protocol is that it translates temporal constraints to causal dependencies of the continuous media data as seen by the mobile hosts. We simulate the protocol by considering a cellular network environment and by using MPEG-4 encoders. The simulation results show that our protocol is effective in reducing the synchronization error. In addition, the protocol is efficient in terms of processing and storage costs at the mobile devices, as well as in the overhead attached per message across the wired and wireless channels. [ABSTRACT FROM AUTHOR]

The heterogeneous mobile terminals coexist in the next generation wireless networks. The most common routing schemes for mobile ad hoc networks are designed for homogeneous wireless networks. The heterogeneous wireless network routing protocols are needed urgently in many important applications. This paper im- proves the routing scheme utilizing different capability of terminals and the Hybrid Grid Routing Protocol (HGRP) is proposed. The network is organized in the grid form, that is, the network deployment area is divided into square cells according to the location. Each cell contains one backbone node and several ordinary nodes. This proposed protocol consists of four parts: grid construction, local routing, global routing, and routing correction. Analysis and simulation results indicate that the proposed protocol has the advantages of lower routing cost, lower energy consumption, smaller delay and higher throughput, compared to AODV and ZRP. [ABSTRACT FROM AUTHOR]

Abstract: Ad-hoc networks suffer from the problem of hidden nodes (terminals), which leads to severe degradation of network throughput. This survey gives a comprehensive overview of Medium Access Control (MAC) protocols which directly or indirectly address this problem. The presented protocols are grouped in several categories and are described in the order of their publication date. To give the reader a deep understanding of the progress made in the area of alleviating the hidden node problem a brief summary of the key ideas as well as a detailed comparison of different protocols are presented. Open research directions are also discussed to serve as a starting point for future protocol design and evaluation. [Copyright &y& Elsevier]

In the draft of the IEEE 802.11s standard, a tree topology is established by the proactive tree-building mode of the Hybrid Wireless Mesh Protocol (HWMP). It is used for cases in which the root station (e.g., gateway) is an end point of the majority of the data connections. In the tree topology, the root or central stations (e.g., parent stations) are connected to the other stations (e.g., leaves) that are one level lower than the central station. Such mesh stations are likely to suffer heavily from contention in bottleneck links when the network has a high traffic load. Moreover, the dependence of the network on such stations is a point of vulnerability. A failure of the central station (e.g., a crash or simply going into sleep mode to save energy) can cripple the whole network in the tree topology. This causes performance degradation for end-to-end transmissions. In a connected mesh topology where the stations having two or more radio links between them are connected in such a way that if a failure subsists in any of the links, the other link could provide the redundancy to the network. We propose a scheme to utilize this characteristic by organizing the network into concentric tiers around the root mesh station. The tier structure facilitates path recovery and congestion control. The resulting mode is referred to as Tier-based Proactive Path Selection Mode (TPPSM). The performance of TPPSM is compared with the proactive tree mode of HWMP. Simulation results show that TPPSM has better performance. [ABSTRACT FROM AUTHOR]

Abstract: Various wireless technologies including radio frequency identification (RFID), bluetooth, cellular networks and dedicated short range communications (DSRC) might have an impact on logistics and transport operations. Among them, DSRC stands out as a broadband communications technology which has been designed to provide a general purpose Radio-Frequency (RF) link between vehicles and network infrastructure. As such, DSRC is capable of implementing the physical layer of an Internet Protocol (IP) bearer based network designed to facilitate the monitoring and coordination of portside vehicular traffic. This unprecedented application of wireless networking has the potential to greatly enhance the management of the flow of goods and resources, particularly within large, international ports whose activities comprise multimodal operations such as the use of road haulage to move cargo transported by sea. Given the need for reliable services in non-safety business applications, in this work an Intelligent Transport Systems (ITS) approach is used to address two issues. First, in wireless networks reliable data transfer transport layer services are affected where there is an apparent increase in mobility when access point coverage areas are reduced to counter the effects of path loss in the physical layer. Second, a service provisioning protocol intended for vehicle to infrastructure (V2I) data transfer is proposed to illustrate the importance of cumulative costs in wireless networks used for logistics applications. The analysis covers the average response time for requesting on-demand services within the portside network considered. The results of the analysis confirm the suitability of the approach used to provide a logistics network capable of meeting the requirements demanded in multimodal logistics. [Copyright &y& Elsevier]

Abstract: IEEE 802.11p/WAVE (Wireless Access for Vehicular Environment) is the emerging standard to enable wireless access in the vehicular environment. Most of the research contributions in this area has focused on safety-related applications, while comfort and information/entertainment applications (such as on board Internet access, point-of-interest notification, e-map download) have been considered only recently. Notwithstanding, the user interest in this kind of applications is expected to become a big market driver in a near future. In this paper, an extension to IEEE 802.11p is proposed that is compliant with the multi-channel operation of the WAVE architecture and targets at the support of non-safety applications, while preserving the delivery of safety services. The proposed W-HCF (WAVE-based Hybrid Coordination Function) protocol leverages controlled access capabilities on top of the basic contention-based access of the IEEE 802.11p; it exploits vehicles’ position information and coordination among WAVE providers in order to improve performances of delay-constrained and loss-sensitive non-safety applications. [Copyright &y& Elsevier]

Abstract: With the growing popularity of vehicle-based mobile devices, vehicular networks are becoming an essential part of wireless heterogeneous networks. Therefore, vehicular networks have been widely studied in recent years. Because of limited transmission range of wireless antennas, mobile vehicles should also switch their access points to maintain the connections as conventional mobile nodes. Considering the inherent characteristics of vehicular networks such as dynamic topology and high speed, the question of how to implement handoff protocol under real-time scenarios is very important. IEEE 802.11p protocol is designed for vehicular networks for the long distance transmission. To reduce handoff latency for 802.11p protocol, the authentication phase is waived during the handoff. However, security is also very important for wireless communications, and authentication can forbid access from malicious nodes and prevent wireless communications from potential attacks. Thus, in this paper, a lightweight authentication scheme is introduced to balance the security requirements and the handoff performance for 802.11p vehicular networks. In our scheme, the access points are divided into different trust groups, and the authentication process is completed in a group-based method. Once a vehicle is authenticated by an access point group, during the handoff within the same group, few extra authentication operations are needed. As a result, there is no extra overhead introduced to the authentication servers. Simulation results demonstrate that our authentication scheme only introduces small handoff latency and it is ideal for vehicular networks. [Copyright &y& Elsevier]

This paper reviews quorum systems (QS) from the perspective of cognitive radio networks. Quorum systems were originally developed for and widely used in the scope of operating systems. Recently, quorum systems have been also started to be applied to wireless communications. The objective of this paper is threefold. First, the paper provides survey and guidance on the use of quorum systems. Second, it shows that QS properties provide an interesting alternative towards an asynchronous communication in cognitive radio ad hoc networks (CRANs). Due to properties of quorum systems it is possible to establish CRANs without employing a common control channel (CCC), perfect synchronization, or central controller architecture. QS properties can be efficiently utilized to handle the rendezvous (RDV) problem in CRANs. New RDV protocols must be designed in such a way that there is a guarantee that all nodes meet periodically within reasonable periods of time. Since pseudorandom solutions do not provide this guarantee, systematic approaches are needed such as QSs. Third, we also propose a novel distributed RDV protocol, MtQS-DSrdv, which is based on mirror torus QS and difference set concepts. The proposed protocol guarantees RDVs on all available channels while CR nodes have the same channel set. [ABSTRACT FROM AUTHOR]

It is expected that device-to-device (D2D) communication is allowed to underlay future cellular networks such as IMT-Advanced for spectrum efficiency. This article studies the mechanisms of D2D communication and interference avoidance when the D2D subsystem reuses uplink resources and downlink spectrums with a cellular system, respectively. We firstly propose an effective scheme to establish and maintain D2D communication. Moreover, a novel method to deal with the resource allocation and interference avoidance issues by utilizing the network peculiarity of a hybrid network to share the uplink resource is proposed. Most research focuses on reusing the uplink spectrums, but how to share the downlink frequency bands is seldom addressed. To share the downlink spectrums and avoid the interference to the primary cellular devices, a labeled time slots based mechanism is proposed. Implementation details are described in a real cellular system and simulation results prove that satisfying performance can be achieved by using the proposed mechanisms. [ABSTRACT FROM AUTHOR]

Multipacket reception (MPR) is the capability of simultaneous decoding of more than one packet from multiple concurrent transmissions. Continuous investigations on increasing the reception capability are giving new scientific contributions. In this paper, we provide an overview of MPR-related research work covering (1) the theoretically proved impacts and advantages of using MPR from a channel perspective to network capacity and throughput; (2) the various technologies that enable MPR from transmitter, transreceiver, and receiver perspectives; (3) previous work on protocol improvement to better exploit MPR. Indeed, MPR approaches have been applied in modern wireless mobile systems but the focus of this paper is to discuss MPR in random access wireless networks. Using MPR in suchmultihop environments calls for new adaptation on protocols, especially a cross-layer approach. To this end, we detail a scheduling method that targets full utilization of MPR capability. [ABSTRACT FROM AUTHOR]

Abstract: A Mobile Ad Hoc Network (MANET) is a dynamic wireless network that can be formed without the need for any pre-existing infrastructure in which each node can act as a router. Clustering is a method for hierarchical management of a network. Especially, clustering is often used in MANETs. In order to maintain the stability of clusters, speed of mobile nodes, but not the identity and connectivity, are taken as the basis of clusterhead election. This paper proposes Mobility Entropy-based Clusterhead selection Algorithm for ad hoc networks (MECA). The protocol constructs a new etric of node stability and selects a stable clusterhead with the help of entropy metric to reduce the number of clusterhead reconstruction. It selects the nodes which have the most weight and stability to be the clusterheaders. Simulations demonstrate the performance benefits of our proposal MECA over RSCA in most movement scenarios. [Copyright &y& Elsevier]

Abstract: In Vehicular Ad Hoc Networks (VANETs), Media Access Control (MAC) protocol is indispensable to ensure that the mobile vehicles fairly and efficiently share the wireless spectrum.As for the specific characteristics and the increased attractive services in VANET,few MAC protocols in Mobile Ad Hoc Networks (MANETs) can be suitable and efficient in VANET.We first give a brief introduction related to MAC for vehicular communications. Current MAC schemes for VANET are then presented including some special hot topics such as IEEE 802.11 standards and multichannel-related protocols,followed by a summary on more research proposed in the recent literature. At the end of the paper, we discuss a few challenges faced and point out some future research directions. [Copyright &y& Elsevier]

Abstract: The unprecedented development of communication technology has led to increased complexity of communication protocols and protocol interaction. Correct implementation of communication protocol is very significant. In this paper, we propose a novel test architecture which aims to verify and test IMT-Advanced key technologies of MAC and RRC layer. The proposed architecture contains three parts, including Testing System (TS), Test Adapter (TA) and System under test (SUT). Compared with traditional TTCN-3 test framework a module called TA as a bridge connecting TS and SUT is added into the proposed architecture, which makes testing more simpler and flexible. Properly design of TA enables our architecture support both conformance testing and performance testing, loose the coupling of TS and certain SUT, and become more general-purposed. A test platform is developed and the testing results show that the proposed test architecture is efficient and reliable. [Copyright &y& Elsevier]