Coded diversity for cooperative MISO based wireless sensor networks

Motivated by the recent works on cooperative MIMO, this letter presents a coded diversity based cooperative protocol for wireless sensor networks. In densely deployed sensor networks, nearby nodes form a cluster of virtual antenna array to provide independent fading paths. The source node encodes the information bits with any channel code and forwards a portion of the codeword towards the cooperating nodes. The source and the cooperating nodes transmit different portion of the codeword to achieve a coded diversity at destination. Analysis and simulation show that our proposal can achieve full diversity when code rate is below a certain threshold.     

无线传感器网络中可靠的数据协作传输机制

对基于协作通信的数据传输问题进行了研究,设计了一种适应于无线传感器网络的RBC网络编码方法,提出了一种数据协作传输策略,分析了端到端的中断概率,评估了中继选择过程的有效性,开发了一种ACK-less的基于协作策略的数据传输方法,理论分析和仿真实验表明,所提出的协作数据传输机制,能够更加有效地使用网络资源.     

Virtual MIMO-based cooperative communication for energy-constrained wireless sensor networks

An energy-efficient virtual multiple-input multiple-output (MIMO)-based communication architecture is proposed for distributed and cooperative wireless sensor networks. Assuming a space-time block coding (STBC) based MIMO system, the energy and delay efficiencies of the proposed scheme are derived using semi-analytic techniques. The dependence of these efficiency values on physical channel propagation parameters, fading coherence time and the amount of required training is also investigated. The results show that with judicious choice of design parameters the virtual MIMO technique can be made to provide significant energy and delay efficiencies, even after allowing for additional training overheads.     

Impacts of user-selfishness on cooperative content caching in social wireless networks

Cooperative caching can be an effective mechanism for reducing electronic content provisioning cost in Social Wireless Networks (SWNETs). These networks are formed by a collection of mobile data enabled devices physically gathering in settings such as university campus, malls, airport and other public places. In this paper, we first propose an optimal collaborative object caching policy in order to minimize the object provisioning cost in SWNETs with homogenous user requests and a peer-rebate model for promoting collaboration. Then using an analytical model we study the impacts of user selfishness on the provisioning cost and the earned rebate when certain nodes in an SWNET selfishly deviate from the optimal policy. User selfishness is motivated in order to either increase individually earned rebate or to reduce content provisioning cost. The analytical model is validated by experimental results from simulated SWNETs using the network simulator ns2.     

Asymptotically optimal cooperative wireless networks with reduced signaling complexity

This paper considers an orthogonal amplify-and-forward (OAF) protocol for cooperative relay communication over Rayleigh-fading channels in which the intermediate relays are permitted to linearly transform the received signal and where the source and relays transmit for equal time durations. The diversity-multiplexing gain (D-MG) tradeoff of the equivalent space-time channel associated to this protocol is determined and a cyclic-division-algebra-based D-MG optimal code constructed. The transmission or signaling alphabet of this code is the union of the QAM constellation and a rotated version of QAM. The size of this signaling alphabet is small in comparison with prior D-MG optimal constructions in the literature and is independent of the number of participating nodes in the network     

A cross-layer strategy for cooperative diversity in wireless sensor networks

We investigate the problem of how to minimize the energy consumption in multi-hop Wireless Sensor Network (WSN), under the constraint of end-to-end reliability Quality of Seervice (QoS) requirement. Based on the investigation, we jointly consider the routing, relay selection and power allocation algorithm, and present a novel distributed cross-layer strategy using opportunistic relaying scheme for cooperative communication. The results show that under the same QoS requirement, the proposed cross-layer strategy performs better than other cross-layer cooperative communication algorithms in energy efficiency. We also investigated the impact of several parameters on the energy efficiency of the cooperative communication in WSNs, thus can be used to provide guidelines to decide when and how to apply cooperation for a given setup.     

Mitigating the gateway bottleneck via transparent cooperative caching in wireless mesh networks

Wireless mesh networks (WMNs) have been proposed to provide cheap, easily deployable and robust Internet access. The dominant Internet-access traffic from clients causes a congestion bottleneck around the gateway, which can significantly limit the throughput of the WMN clients in accessing the Internet. In this paper, we present MeshCache, a transparent caching system for WMNs that exploits the locality in client Internet-access traffic to mitigate the bottleneck effect at the gateway, thereby improving client-perceived performance. MeshCache leverages the fact that a WMN typically spans a small geographic area and hence mesh routers are easily over-provisioned with CPU, memory, and disk storage, and extends the individual wireless mesh routers in a WMN with built-in content caching functionality. It then performs cooperative caching among the wireless mesh routers.We explore two architecture designs for MeshCache: (1) caching at every client access mesh router upon file download, and (2) caching at each mesh router along the route the Internet-access traffic travels, which requires breaking a single end-to-end transport connection into multiple single-hop transport connections along the route. We also leverage the abundant research results from cooperative web caching in the Internet in designing cache selection protocols for efficiently locating caches containing data objects for these two architectures. We further compare these two MeshCache designs with caching at the gateway router only.Through extensive simulations and evaluations using a prototype implementation on a testbed, we find that MeshCache can significantly improve the performance of client nodes in WMNs. In particular, our experiments with a Squid-based MeshCache implementation deployed on the MAP mesh network testbed with 15 routers show that compared to caching at the gateway only, the MeshCache architecture with hop-by-hop caching reduces the load at the gateway by 38%, improves the average client throughput by 170%, and increases the number of transfers that achieve a throughput greater than 1 Mbps by a factor of 3.     

无线传感器网络的智能低功耗侦听协议

无线传感器网络MAC层协议低功耗侦听(LPL)使用较长的前导码,在密集部署的无线传感器网络中造成较大的"串音"开销.提出一种智能低功耗侦听协议(SLPL),通过在前导码中嵌入目的地址和前导码长度索引,能有效降低非目的节点的串音开销,减少目的节点的接收开销.理论分析和部署测试表明SLPL的能效比LPL有显著提高,同时测试显示SLPL功耗小于X-MAC协议.     

Systematic energy-balanced cooperative transmission scheme in wireless sensor networks

Energy efficiency is a critical issue in wireless sensor networks(WSNs).In order to minimize energy consumption and balance energy dissipation throughout the whole network,a systematic energy-balanced cooperative transmission scheme in WSNs is proposed in this paper.This scheme studies energy efficiency in systematic view.For three main steps,namely nodes clustering,data aggregation and cooperative transmission,corresponding measures are put forward to save energy.These measures are well designed and tightly coupled to achieve optimal performance.A half-controlled dynamic clustering method is proposed to avoid concentrated distribution of cluster heads caused by selecting cluster heads randomly and to get high spatial correlation between cluster nodes.Based on clusters built,data aggregation,with the adoption of dynamic data compression,is performed by cluster heads to get better use of data correlation.Cooperative multiple input multiple output(CMIMO) with an energy-balanced cooperative cluster heads selection method is proposed to transmit data to sink node.System model of this scheme is also given in this paper.And simulation results show that,compared with other traditional schemes,the proposed scheme can efficiently distribute the energy dissipation evenly throughout the network and achieve higher energy efficiency,which leads to longer network lifetime span.By adopting orthogonal space time block code(STBC),the optimal number of the cooperative transmission nodes varying with the percentage of cluster heads is also concluded,which can help to improve energy efficiency by choosing the optimal number of cooperative nodes and making the most use of CMIMO.     

Locomotion trajectory with cooperative metrics in wireless sensor networks

Detection coverage control is one of the most important topics in the intrusion detection problem of wireless sensor networks (WSN). However, its converse, i.e., to design an object locomotion trajectory in WSN, has not received enough attention. This article proposes a heuristic algorithm, namely, the security & speed (SS) algorithm, to depict such a trajectory that takes into consideration both security and speed. The merit of the SS algorithm is its topology independency. When compared with traditional algorithms, the SS algorithm approaches the optimal trajectory better, and enjoys considerably lower computational load, and a better and adjustable tradeoff between trajectory security and speed.     

一种用于无线传感器网的协作接收方案

无线传感器网中,能量效率是系统设计首要考虑的因素.基于提高无线传感器网能量效率的目的,本文提出了一种简单的协作接收方案并分析了其能量效率,理论分析及仿真结果表明,当通信距离大于某一门限值时采用该接收方案可以有效提高无线传感器网的能量效率.     

Optimal power‐aware relay placement for cooperative wireless sensor networks

We study the problem of optimizing the symbol error probability (SEP) performance of cluster‐based cooperative wireless sensor networks. Recent studies in literature show that an efficient relay selection protocol based on simple geographical information of the nodes to execute cooperative diversity can significantly improve the SEP performance at the destination of such networks. As well, similar line of research on optimal power allocation (for the source and relay nodes) can be found in literature. However, to achieve the best SEP performance at the destination of a cooperative wireless sensor network, joint optimization of power allocation and relay placement should be accomplished. To this aim, we reformulate the SEP of a multi‐hop cooperative communication in a general form and optimize transmitted power level and relay placement simultaneously. This analysis is developed for both amplify‐and‐forward and decode‐and‐forward relaying protocols. Simulation results demonstrate that the proposed joint optimization can effectively improve the SEP performance of the network. Copyright © 2013 John Wiley & Sons, Ltd.     

Spectrally efficient communication for wireless sensor networks using a cooperative MIMO technique

The multi-input multi-output (MIMO) communication framework is adopted for wireless sensor networks by having multiple sensors equipped with single-element antennas cooperate in transmission. A power method-based iterative algorithm is developed that computes the optimal transmit and receive eigen-filters distributively among the sensors while transferring most of the computational burden to the central collector node. Since the proposed algorithm implicitly exploits the channel state information (CSI) both at the receiver and the transmitter, it is expected that the resulting spectral efficiency is higher than what can be achieved by receive CSI-only space-time coding. This intuition is confirmed by employing a variable-rate adaptive modulation scheme for the eigen-transmission and comparing its spectral efficiency with that of orthogonal space time block codes (OSTBCs) at specific target bit error rates. The performance is also evaluated using realistic channel estimation as well as the least mean square (LMS) and recursive least square (RLS) algorithms for iterative eigencoding. This material is based upon work supported by the Air Force Office of Scientific Research under Award No. FA9550-04-C-0074 and Toyon Research Corporation Subcontract No. SC6431-1. Seung-Jun Kim received B.S. and M.S. from Seoul National University in 1996 and 1998, respectively, and Ph.D. from University of California, Santa Barbara in 2005, all in electrical engineering. From 1998 to 2000, he served as a Korea Overseas Volunteer at Chiang Rai Teachers College in Chiang Rai, Thailand. Since 2005, he has been with NEC Laboratories America in Princeton, NJ. His research interests lie in detection/estimation theory, spread-spectrum communications, multiple antenna techniques and cross-layer design. Richard E. Cagley received the B.S. degree in engineering from Harvey Mudd College, Claremont, CA in 1997 and the M.S. and Ph.D. degrees in electrical engineering from the University of California, Santa Barbara in 1999 and 2003 respectively. Dr. Cagley currently holds a position with Toyon Research Corporation, Goleta, CA. Prior to joining Toyon, he held positions with Fujant Incorporated, Jet Propulsion Laboratories, and Qualcomm Corporation. His general research interests are in the areas of physical and MAC layer design for wireless communication. This includes multiuser detection, interference cancellation, space-time processing, spectrum management, and digital receiver design. Ronald A. Iltis received the B.A. (Biophysics) from The Johns Hopkins University in 1978, the M.Sc in Engineering from Brown University in 1980, and the Ph.D. in Electrical Engineering from the University of California, San Diego in 1984. Since 1984, he has been with the University of California, Santa Barbara, where he is currently a Professor in the Department of Electrical and Computer Engineering. His current research interests are in CDMA, software radio, radiolocation, and nonlinear estimation. He has also served as a consultant to government and private industry in the areas of adaptive arrays, neural networks and spread-spectrum communications. Dr. Iltis was previously an Editor for the IEEE Transactions on Communications. In 1990 he received the Fred W. Ellersick award for best paper at the IEEE MILCOM conference.     

无线传感器网络中一种基于OSTBC的高效协作传输技术

针对发端能量受限的无线传感器网络提出了一种基于OSTBC的高效虚拟MIMO协作传输策略.在无线传感器网络的每个簇内采用一种全速率的分布式OSTBC传输方案,同时对调制方式的星座大小进行优化,创建了一种更高效的无线传感器网络和MIMO通信相结合的模型.针对该模型在接收端进行迭代译码,并推导出该系统的总能耗函数和网络时延算式.通过仿真显示,该模型不仅能够极大的降低发端能耗,对任意协作节点数目均能够实现全速率传输,解决了传统分布式空时码用于无线传感器网络时发端的数据积压问题,减小了网络时延.因此本协作传输模型从能量消耗和网络时延两方面对无线传感网的性能进行了提升,能够为无线传感网的应用提供有意义的参考.     

Power control based cooperative opportunistic routing in wireless sensor networks

This paper proposes an approach called PC-CORP (Power Control based Cooperative Opportunistic Routing Protocol) for WSN (Wireless Sensor Networks), providing robustness to the random variations in network connectivity while ensuring better data forwarding efficiency in an energy efficient manner. Based on the realistic radio model, we combine the region-based routing, rendezvous scheme, sleep discipline and cooperative communication together to model data forwarding by cross layer design in WSN. At the same time, a lightweight transmission power control algorithm called PC-AIMD (Power Control Additive Increase Multiplicative Decrease) is introduced to utilize the cooperation of relay nodes to improve the forwarding efficiency performance and increase the robustness of the routing protocol. In the simulation, the performance of PC-COPR is investigated in terms of the adaptation of variations in network connectivity and satisfying the QoS requirements of application.     

Locating the nodes: cooperative localization in wireless sensor networks

Accurate and low-cost sensor localization is a critical requirement for the deployment of wireless sensor networks in a wide variety of applications. In cooperative localization, sensors work together in a peer-to-peer manner to make measurements and then forms a map of the network. Various application requirements influence the design of sensor localization systems. In this article, the authors describe the measurement-based statistical models useful to describe time-of-arrival (TOA), angle-of-arrival (AOA), and received-signal-strength (RSS) measurements in wireless sensor networks. Wideband and ultra-wideband (UWB) measurements, and RF and acoustic media are also discussed. Using the models, the authors have shown the calculation of a Cramer-Rao bound (CRB) on the location estimation precision possible for a given set of measurements. The article briefly surveys a large and growing body of sensor localization algorithms. This article is intended to emphasize the basic statistical signal processing background necessary to understand the state-of-the-art and to make progress in the new and largely open areas of sensor network localization research.     

Supporting cooperative caching in ad hoc networks

Most researches in ad hoc networks focus on routing and not much work has been done on data access. A common technique used to improve the performance of data access is caching. Cooperative caching, which allows the sharing and coordination of cached data among multiple nodes, can further explore the potential of the caching techniques. Due to mobility and resource constraints of ad hoc networks, cooperative caching techniques designed for wired networks may not be applicable to ad hoc networks. In this paper, we design and evaluate cooperative caching techniques to efficiently support data access in ad hoc networks. We first propose two schemes: CacheData, which caches the data, and CachePath, which caches the data path. After analyzing the performance of those two schemes, we propose a hybrid approach (HybridCache), which can further improve the performance by taking advantage of CacheData and CachePath while avoiding their weaknesses. Cache replacement policies are also studied to further improve the performance. Simulation results show that the proposed schemes can significantly reduce the query delay and message complexity when compared to other caching schemes.     

Improving wireless sensor networks performance through epidemic model

Wireless sensor networks (WSNs) encounter a critical challenge of ‘Network Security’ due to extreme operational constraints. The origin of the challenge begins with the entry of worms in the wireless network. Just one infected node is enough to spread the worms across the entire network. The infected node rapidly infects the neighbouring nodes in an unstoppable manner. In this paper, a mathematical model is proposed based on epidemic theory. It is an improvement of the Susceptible-Infectious-Recovered-Susceptible (SIRS) and Susceptible-Exposed-Infectious-Susceptible (SEIS) model. We propose Susceptible-Exposed-Infectious-Recovered-Susceptible (SEIRS) model that overcomes the drawbacks of existing models. The proposed ameliorated model includes a finite communication radius and the associated node density. We obtain basic reproduction number which determines the local and global propagation dynamics of worm in the WSNs. Also, we deduce expression for threshold for node density and communication radius. We investigated the control mechanism against worm propagation. We compare the proposed model with various existing models and evaluate its performance on the basis of various performance metrics. The study confirms melioration in the vital aspects (security, network reliability, transmission efficiency, energy efficiency) for WSNs. The proposed SEIRS model provides an improved technique to restraint worms’ transmission in comparison to the existing models.     

Application modeling for performance evaluation on event-triggered wireless sensor networks

This paper presents an approach for event-triggered wireless sensor network (WSN) application modeling, aiming to evaluate the performance of WSN configurations with regards to metrics that are meaningful to specific application domains and respective end-users. It combines application, environment-generated workload and computing/communication infrastructure within a high-level modeling simulation framework, and includes modeling primitives to represent different kind of events based on different probabilities distributions. Such primitives help end-users to characterize their application workload to capture realistic scenarios. This characterization allows the performance evaluation of specific WSN configurations, including dynamic management techniques as load balancing. Extensive experimental work shows that the proposed approach is effective in verifying whether a given WSN configuration can fulfill non-functional application requirements, such as identifying the application behavior that can lead a WSN to a break point after which it cannot further maintain these requirements. Furthermore, through these experiments, we discuss the impact of different distribution probabilities to model temporal and spatial aspects of the workload on WSNs performance, considering the adoption of dynamic and decentralized load balancing approaches.     

认知无线传感器网络中能耗有效的协作频谱感测算法

提出了一种新的认知无线传感器网络中能耗有效的协作频谱感测算法。首先,为了降低分布式传感节点的能耗,假定传感节点的瞬时信噪比和平均信噪比已知,分析频谱感测节点的能耗与最优检测门限值之间的数学模型。然后,结合感测节点选择和判决门限设定理论,研究基于判决节点选择的有效协作频谱感测方案。理论分析和仿真结果表明,算法有效地降低了认知传感器网络的节点总能耗,提高了能耗效率。