Efficient ARQ protocols for exploiting cooperative relaying in wireless sensor networks

Cooperative relaying is an efficient technique to provide diversity in wireless sensor networks. In this paper, we exploit the limited feedback from the destination and propose a novel cooperative ARQ protocol, which combines the incremental relaying and selection relaying schemes. A relay node is requested to repeat the erroneously received packet, instead of the source node. Both simple and hybrid type I ARQ schemes are studied. An analysis model is established to analyze and compare the data link layer performances of different ARQ protocols in slow fading wireless channel. We prove two SNR thresholds of the relay–destination channel, above which the cooperative ARQ protocols have better performances than the traditional counterparts. In addition, the diversity performances of the various protocols are investigated and it is demonstrated that full order diversity (second-order in this case) can be exploited by the proposed cooperative ARQ protocol. Simulation results are given, which verify the theoretical analysis and comparison.     

Delay and energy efficiency analysis of multicast cooperative ARQ over wireless networks

This paper investigates the performance of multicast cooperative ARQ (MCARQ) in wireless networks for reducing the system’s waiting time and the sum energy, where the delay and energy analytical model are proposed under equivalent service time and ideal Nyquist pulse. The packet transmission process is modulated by a three-state Markov chain, then the steady-state distribution of the MCARQ is obtained by solving the Markov chain. Further, the queue waiting time and energy efficiency of the multicast ARQ (MARQ) and MCARQ are obtained respectively. Theoretical analysis and simulation results demonstrate that the MCARQ protocol has a better performance than the MARQ in delay and energy efficiency. The presented model has potentially applications in practical systems, e.g. Multi-user MIMO communications.     

A bandwidth efficient two-user cooperative diversity system with limited feedback

A two-user cooperative diversity system based on Alamouti signaling was proposed, which utilizes the orthogonal structure of Alamouti signaling to make cooperative users relay on the shared channel resources so that the spectral efficiency of the traditional cooperative system can be improved. When M-ary phase shift keying (M-PSK) modulation and an improved selection decode-and-forward (SDF) relaying protocol with limited feedback are used at the users and m(m ⩾1) receive antennas are configured at the base station, the average bit-error-rate (BER) system performance for statistically similar uplink channels was derived and it was verified by simulations. Under various channel scenarios of interest, numerical and simulation results show that the diversity gain achieved and the BER performance of the proposed system increase with the interuser channel quality, and the full transmit diversity order of two can be obtained for sufficiently high interuser signal-to-noise ratios (SNRs). Supported by the National High-Tech Research & Development Program of China (Grant No. 2006AA01Z270), the National Natural Science Foundation of China-Guangdong (Grant No. U0635003), the Natural Science Foundation of Shaanxi Province (Grant No. 2007F07), the “111” Project (Grant No. B08038), and the Open Research Fund of State Key Laboratory of Rail Traffic Control and Safety, Bejing Jiaotong University (Grant No. RCS2008K003)     

Contention-free MAC protocols for asynchronous wireless sensor networks

A MAC protocol specifies how nodes in a sensor network access a shared communication channel. Desired properties of a MAC protocol are: it should be contention-free (avoid collisions); it should be distributed and self-stabilize to topological changes in the network; topological changes should be contained, namely, affect only the nodes in the vicinity of the change; it should not assume that nodes have a global time reference, that is, nodes may not be time-synchronized. We give a set of TDMA-based MAC protocols for asynchronous wireless sensor networks satisfying all of these requirements. The communication complexity, number and size of messages, for the protocols to stabilize is small, poly-logarithmic in the network size. A preliminary version of the paper appears in the Proceedings of the 18th Annual Conference on Distributed Computing (DISC 2004), LNCS 3704, pp 245–259, Trippenhuis, Amsterdam, The Netherlands, October 2004.     

基于协同分集的无线传感网络路由与信道分析

协同分集是一种新近提出的空域分集技术,它使得终端之间可以共享彼此的天线,为实现多输入多输出(MIMO)提供了有效的方式,适合用于无线Ad hoc网络和无线传感网络中,成为研究热点.在分析协同分集技术的基础上,针对无线传感网络的特点,分析了传感网络中多跳路由算法与协同分集路由算法,给出网络的等效信道模型,并由此讨论使用协同分集对网络能源消耗的影响,讨论了基于协同分集的无线传感网络的实现.分析结果表明,协同分集在无线传感网络中具有较好的应用价值.     

无线传感器网络多径路由协议综述

由于无线传感器网络不同于传统的自组织网络,已有自组织网络路由协议不能有效应用于传感器网络中.文献中已提出不少无线传感器网络路由协议,但这些协议大多针对单路径情况.当链路失效时,单径路由协议需要重新发现新的路由,从而会对传输延时、能耗和可靠性带来较大影响.采用多径路由协议可弥补单径路由协议的不足,有利于提高数据传输的可靠性和实现负载平衡.通过对目前文献中几种典型的多径路由协议的分析和比较,指出进一步研究中值得关注的问题.     

Energy efficient smart-relay-based cooperative MAC for wireless networks

An enormous number of papers investigated wireless cooperative networks over the last few years. Almost all have shown that cooperative transmission improves network performance significantly. However, none of these studies have considered the hidden and exposed terminal problems which appear due to the cooperative mechanisms of relay selection and transmission processes. The hidden terminal problems increase collisions and the exposed terminal problems increase bandwidth wastage, degrading the expected performance of cooperative networks. This paper addresses these problems of traditional wireless cooperative networks. We also propose a protocol called smart-relay-based-cooperative (SRcoop) MAC to optimally reduce the impacts of hidden and exposed terminal problems. We also illustrate an efficient relay selection mechanism that uses a back-up relay to increase transmission reliability. Our innovative model significantly improves the network throughput, end-to-end delay and energy efficiency over traditional cooperative MAC, 2rcMAC, LC-MAC, C-ARQ and Adere et al. protocols.     

Enhanced cooperative communication MAC for mobile wireless networks

In this paper, we propose a new MAC (medium access control) protocol called enhanced cooperative communication MAC (ECCMAC) based on IEEE 802.11. The major objective of ECCMAC is to maximize the benefits of cooperative communication. We first propose a scheme for selecting and maintaining the best relay node. Second, since both cooperative communication and network coding rely on the selection of a relay node, we consider exploiting a network coding technique for additional throughput improvement. Third, to accommodate asymmetric link rates between a sender and a relay node, we employ ECCMAC to measure forward and reverse link rates, whereas prior works have simply assumed symmetric rates. ECCMAC is evaluated in this paper through theoretical analysis, extensive simulation, and simulation with measured data, and the results show that ECCMAC effectively improves wireless network performance.     

Energy-efficient cooperative data aggregation for wireless sensor networks

Recently, cooperative communication mechanism is shown to be a promising technology to improve the transmit diversity only by a single transceiver antenna. Using this communication paradigm, multiple source nodes are able to coordinate their transmissions so as to obtain energy savings. As data aggregation is one of the most important operations in wireless sensor networks, this paper studies the energy-efficient data aggregation problem through cooperative communication. We first define the cooperative data aggregation (CDA) problem, and formally prove that this problem is NP-Hard. Due to the difficult nature of this problem, we propose a heuristic algorithm MCT for cooperative data aggregation. The theoretical analysis shows that this algorithm can reach the approximate performance ratio of 2. Moreover, the distributed implementation DMCT of the algorithm is also described. We prove that both centralized and distributed algorithms can construct the same topology for cooperative data aggregation. The experimental simulations show that the proposed algorithms will decrease the power consumption by about 12.5% and 66.3% compared with PEDAP and PEGASIS algorithms respectively.     

Design and performance evaluation of throughput-aware rate adaptation protocols for IEEE 802.11 wireless networks

Experimental studies have shown that traditional rate adaptation schemes for 802.11 wireless networks suffer from significant throughput degradation in highly congested networks. To address this problem, this paper makes the following two main contributions. First, we design a method to accurately estimate the per-packet transmission times, and we use these measurements to provide a broad classification of the network state and to identify network congestion. Second, we design a new Throughput-Aware Rate Adaptation (TARA) scheme, which uses the congestion estimates to mitigate the negative impact of link-layer collisions on the operations of rate adaptation, without requiring changes in the 802.11 MAC specification. Another key feature of our solution is to minimize probing overheads and limit unnecessary rate decreases by predicting the throughput gain that could be brought about by a change in the transmission rate. Through experiments conducted across a variety of network scenarios and traffic patterns, we show that TARA achieves significantly higher throughput than the other rate adaptation algorithms implemented in the legacy Madwifi driver.     

Gossip-based cooperative caching for mobile applications in mobile wireless networks

Cooperative caching is an efficient way to improve the performance of data access in mobile wireless networks, by cache nodes selecting different data items in their limited storage in order to reduce total access delay. With more demands on sharing a video or other data, especially for mobile applications in an Internet-based Mobile Ad Hoc Network, considering the relations among data items in cooperative caching becomes more important than before. However, most of the existing works do not consider these inherent relations among data items, such as the logical, temporal, or spatial relations. In this paper, we present a novel solution, Gossip-based Cooperative Caching (GosCC) to address the cache placement problem, and consider the sequential relation among data items. Each mobile node stores the IDs of data items cached locally and the ID of the data item in use into its progress report. Each mobile node also makes use of these progress reports to determine whether a data item should be cached locally. These progress reports are propagated within the network in a gossip-based way. To improve the user experience, GosCC aims to provide users with an uninterrupted data access service. Simulation results show that GosCC achieves better performance than Benefit-based Data Caching and HybridCache, in terms of average interruption intervals and average interruption times, while sacrificing message cost to a certain degree.     

基于无线Mesh网路由协议的研究及优化

根据无线Mesh网络的结构特点,对现有的路由协议进行了分析,并针对其中一种典型的路由协议AODV延时过大的缺点进行了优化,即Ⅰ-AODV。其在AODV中引入表驱动的机制,增加维护的邻居节点数目,获得更多节点的路由信息,在路由建立时达到降低网络延时的目的。最后通过仿真软件NS-2进行了模拟测试,测试结果表明,Ⅰ-AODV的网络延时等网络性能明显得到了改善。     

Survey of network coding-aware routing protocols in wireless networks

In recent times, there have been many advances in the field of information theory and wireless ad hoc network technologies. Regarding information theory progression and its connection with wireless ad hoc networks, this study presents fundamental concepts related to the application of the state-of-the-art Network Coding (NC) within wireless ad hoc networks in the context of routing. To begin with, this paper briefly describes opportunistic routing and identifies differentiation between NC-aware and NC-based routing mechanisms in wireless ad hoc networks. However, our main focus is to provide a survey of available NC-aware routing protocols that make forwarding decisions based on the information of available coding opportunities across several routes within wireless ad hoc networks. The taxonomy and characteristics of various representative NC-aware routing protocols will also be discussed. In summary, we provide a comparison of available NC-aware routing schemes and conclude that NC-aware routing techniques have several advantages over traditional routing in terms of high throughput, high reliability, and lower delay in a wireless scenario. To the best of our knowledge, this work is the first that provides comprehensive discussion about NC-aware routing protocols.     

ZigBee-WiFi协同无线传感网络的节能技术

为使无线传感网络实现高效节能,提出一种新颖的基于ZigBee-WiFi协同方式进行的时钟同步机制。ZigBee无线传感节点可以通过内置的接收信号强度寄存器(RSSI),感知同一频段下WiFi周期性发送的信标帧,并用其作为参考时钟,通过补偿校正本地的时钟,但此方法校正后时钟偏差较大;在此基础上提出一种基于状态空间的时钟模型,采用卡尔曼滤波器和离散线性定常系统的二次型最优控制校正算法跟踪并校正状态变量,获得很好的时钟校正精度。分析时钟同步误差与校正周期的关系,综合多方面因素,与工业中常用的异步时钟机制进行对比,比较结果表明,该时钟同步机制使ZigBee网络节能效果显著提高。     

水下无线传感器网络协作式节点定位方法

针对无线传感器网络信标节点受水下条件限制不能布置很多的问题,利用非信标节点参与定位是提高定位精度的一种途径.协作式定位算法就是通过测量所有相邻节点间的信号传输往返时延来计算距离,利用信标节点和未知节点间的距离确定自身初始区域,并利用相邻2个未知节点间的距离来缩小这个区域,用迭代方式提高节点的定位精度.该算法无须额外的硬件支持,仿真结果显示:即使只有很少的信标节点,算法的定位精度也可以超过传统的只用信标节点的定位方式.     

Performance analysis of a random ARQ initialized cooperative communication protocol in shadowed Nakagami-m wireless channel

In this paper, we develop and analyze an energy efficient ARQ (automatic repeat request) initialized transmit diversity protocol for cooperative communications. Medium access control (MAC) layer packet retransmission limit (similar to aShortRetryLimit or aLongRetryLimit [802.11-1997]) has been used as an actuator for transmit cooperative diversity initialization. We take the channel state information (CSI) as a function of retransmission tries and the number of retransmission tries is modeled as a random va...     

Network coding-based cooperative ARQ scheme for VANETs

In this paper we introduce a novel Network Coding-based Medium Access Control (MAC) protocol for Vehicular Ad Hoc Networks (VANETs) that use cooperative Automatic Repeat reQuest (ARQ) techniques. Our protocol coordinates the channel access among a set of relays capable of using network coding in order to minimize the number of the total transmissions, thus enhancing the performance of the network in terms of Quality of Service (QoS) metrics. The proposed solution is compared to other cooperative schemes, while analytical and simulation results are provided to evaluate our protocol.     

基于时分复用的无线传感器网络MAC协议研究

对近年来无线传感器网络(W SNs)的基于时分复用(TDMA)的媒质访问控制(MAC)协议的最新研究进展进行了讨论和综述,描述了设计W SNs的MAC协议应该考虑的问题,详细论述了传感器网络的MAC协议的能量有效性问题,着重对一些具有代表性的基于TDMA的MAC协议进行对比、分析,并在此基础上提出了将来设计这类MAC协议的方向和建议。     

Multicast routing protocols in wireless mesh networks: a survey

Wireless mesh networks (WMNs) introduce a new type of network that has been applied over the last few years. One of the most important developing issues in WMNs is multicast routing, which is a key technology that provides dissemination of data to a group of members in an efficient way. In this article, after an introduction about the structure of a WMN, multicast routing algorithms and protocols in WMNs are surveyed in a detailed and efficient manner. Moreover, effort is made to scale the study into one of the important potential capabilities of multicast routing mechanisms in WMNs, which is taking advantage of using different channels and radios association. While nodes in a single-radio mesh network operating on single-channel have restrictions for capacity, equipping mesh routers with multiple radios using multiple channels can decrease the intention of capacity problem as well as increase the aggregate bandwidth available to the network and improving the throughput. Hence, the purpose of channel assignment is to decrease the interferences while increasing the network capacity and keeping the connectivity of the network. Therefore, this article investigates the multicast protocols considering a definition of three types of WMNs, based on channel-radio association including SRSC, SRMC and MRMC. In its follow, a classification for multicast routing algorithms regarding the achieved optimal solutions will be presented. Finally, a study of MRMC and its relevant problems will be offered, considering the joint channel assignment and the multicast tree construction problem.