Design Considerations for Energy-Efficient Radios in Wireless Microsensor Networks

In the past few years, wireless microsensor networks have attracted a great deal of attention in the research community. This is due to the applications that will be enabled once wireless microsensor networks are in place. The design of wireless microsensor networks, however, represents a difficult challenge. Since many applications require fault-tolerant, long-term sensing, one important challenge is to design sensor networks that have long system lifetimes. Achieving long system lifetimes is difficult because sensor nodes are severely energy-constrained. In this paper, we demonstrate system-level techniques that adapt and tradeoff software and hardware parameters in response to changes in the requirements of the user, the characteristics of the underlying hardware, and the properties of the environment. By using these power-aware, system-level techniques, we are able to reduce the energy consumption of both general, adaptable systems and dedicated point systems. Moreover, given a specific set of operating conditions for a particular system, we show how energy savings of 50% can be achieved.     

无线传感器网络中一种信标节点可迁移的协作定位方法

 提出一种协作定位方法.利用邻居信标交互,获取定位环境信息,并在此基础上实现基于无效信标过滤的信号强度定位.同时,在多种定位方法协作判定下,将精度较高的已定位节点升级为信标节点.仿真结果表明,该方法同加权RSSI及APIT定位方法相比,具有较高的定位精度和定位成功率.     

无线移动传感器网络自适应体系结构的设计

随着无线网络技术的日益成熟及其对小型、微型移动设备的支持,无线移动传感器网络已经逐渐成为一个研究的热点。主要讨论了为无线移动传感器网络设计的一个自适应的体系结构。在该体系结构中,使用了一个区域和核心路由节点相结合的多层结构的方法来增加无线移动网络的信息传输能力、可扩充性和可靠性,并降低网络的能耗,这样就可以适应无线移动网络的高度动态性和移动性。     

无线移动传感器网络自适应体系结构的设计

随着无线网络技术的日益成熟及其对小型、微型移动设备的支持，无线移动传感器网络已经逐渐成为一个研究的热点。主要讨论了为无线移动传感器网络设计的一个自适应的体系结构。在该体系结构中，使用了一个区域和核心路由节点相结合的多层结构的方法来增加无线移动网络的信息传输能力、可扩充性和可靠性，并降低网络的能耗，这样就可以适应无线移动网络的高度动态性和移动性。     

基于容忍覆盖区域的无线传感器网络节点调度算法

节点调度机制是解决无线传感器网络节点能量受限问题的重要方法.传统的位置信息无关的节点调度方案以节点的感知区域覆盖为调度目标,导致处于边界区域的节点由于没有太多机会进入休眠状态而先死亡,进而引起死亡节点向监测中心扩散现象,我们称这种现象为"不均等休眠"问题.针对该问题,从理论上对节点覆盖模型进行分析,提出容忍覆盖区域的概...     

交通路灯监控系统的无线传感网链状路由算法

在交通路灯监控系统中为节省网络节点能耗和降低数据传输时延,提出一种无线传感网链状路由算法（CRASMS）。该算法根据节点和监控区域的信息将监控区域分成若干个簇区域,在每一个簇区域中依次循环选择某个节点为簇头节点,通过簇头节点和传感节点的通信建立簇内星型网络,最终簇头节点接收传感节点数据,采用数据融合算法降低数据冗余,通过簇头节点间的多跳路由将数据传输到Sink节点并将用户端的指令传输到被控节点。仿真结果表明：CRASMS算法保持了PEGASIS算法在节点能耗方面和LEACH算法在传输时延方面的优点,克服了PEGASIS 算法在传输时延方面和LEACH算法在节点能耗方面的不足,将网络平均节点能耗和平均数据传输时延保持在较低水平。在一定的条件下,CRASMS算法比LEACH和PEGASIS算法更优。     

Incentive Mechanism Design for Selfish Hybrid Wireless Relay Networks

Non-cooperative behaviors in communication networks can significantly adversely affect the entire network. Recently, researchers have begun to study such non-cooperative communication systems within a game theory framework and strive to engineer the system to prevent performance degradation under non-cooperative behaviors. The WWAN/WLAN two-hop-relay system described in [1] integrates two types of wireless technologies to improve wireless access throughput and coverage. The relay nodes in the two-hop-relay system can be wireless relay routers deployed by wireless service providers, or dual-mode users who voluntarily relay traffic for other users. However, it is reasonable to assume that all dual-mode terminals are selfish and are not willing to relay for other users without an incentive. In this paper, we will use the basic concepts of game theory, especially the concept of the Nash Equilibrium, to design our scheduling algorithms. Several scheduling algorithms, including the maximum rate C/I scheduler, the proportional fair scheduler, and the round robin scheduler, are examined to understand performance while operating under the assumption that all users are selfish. Under the C/I scheduler or the proportional fair scheduler, Nash Equilibriums exist at the operating points where no user will relay for other users—an undesirable situation. Under the round robin scheduler, selfish users are indifferent on relaying voluntarily or not relaying. Therefore, we are inspired to design a novel incentive scheduler. By applying the proposed incentive scheduler, all selfish users relay cooperatively at the Nash Equilibrium. Hung-yu Wei received a B.S. degree in electrical engineering from National Taiwan University in 1999. He received an M.S. and a Ph.D. degree in electrical engineering from Columbia University in 2001 and 2005 respectively. He is currently an assistant professor at Department of Electrical Engineering, National Taiwan University. His research interests are in cross-layer design issues of wireless mesh networks, and integration of mobile ad hoc networks with cellular networks. Richard D. Gitlin has more than 35 years of experience and leadership in the communications and networking fields. He is currently President of Innovatia Networks, a startup wireless company. Previously he was Vice President, Technology of NEC Laboratories America, Inc. and before assuming this position he was Visiting Professor of Electrical Engineering at Columbia University. After receiving his doctorate in electrical engineering from Columbia, he was with Lucent Technologies for more than thirty-two years, where he held several senior executive positions. He was the Chief Technical Officer and Vice President of R&D, of the Data Networking Systems Business Unit, and Senior Vice President for Communication Sciences Research at Bell Labs, Lucent Technologies where he managed and led research in wireless systems, broadband and optical networking, multimedia communications, and access technologies. He is the co-recipient of three prize paper awards including the 1995 IEEE Communications Society's Steven O. Rice Award, the 1994 IEEE Communications Society's Frederick Ellersick Award, and the 1982 Bell System Technical Journal Award. He is a co-winner of the 2005 Thomas Alva Edison patent award. Dr. Gitlin is the co-author of the text Data Communications Principles, more than 95 technical papers, numerous conference papers and keynote presentations. He holds 43 patents in the area of data communications, digital signal processing, wireless systems, and broadband networking. He is a member of the National Academy of Engineering, a Fellow of the IEEE, and is also an AT&T Bell Laboratories Fellow. Since May 2002, he has served on the Board of Directors of PCTEL [NASDAQ; PCTI], a wireless networking company.     

Distribution of Path Loss for Wireless Personal Networks Operating in a Square Region

Path loss plays fundamental roles in system design, spectrum management, and performance evaluation. The traditional path loss model has a slight inconvenience; it depends on the unknown distance. In this letter, we explore the probability distribution function (PDF) of path loss in an indoor office environment by randomizing out the distance variable. It is shown that the resulting PDF is not Gaussian‐like but is skewed to the right, and both the PDF and the moments are related to the size of the office instead of the unknown distance. To be specific, we incorporate the IEEE 802.15.4a channel parameters into our model and tabulate the cumulative distribution function with respect to different room sizes. Through a simple example, we show how our model helps a cognitive spectrum user to infer path loss information of primary users without necessarily knowing their transmitter‐receiver distance.     

移动代理技术在Ad Hoc无线网络中的应用研究

Ad Hoc无线网络是一组具有路由和转发功能的移动节点组成的一个多跳的临时性自治系统,是一种无中心的无线网络。现有的主动路由协议或者按需路由协议都不能很好地满足Ad Hoc网络的需要。介绍了Ad Hoc无线移动网络和移动代理技术。在分析了现有的2种路由协议后,提出了在按需路由协议中加入移动代理技术来增强Ad Hoc无线网络的性能。在这些结果的基础上,提出了移动代理通信协议。     

Performance Evaluation of Routing Protocols for Ad Hoc Wireless Networks

A mobile ad hoc network is a collection of autonomous mobile nodes that communicate with each other over wireless links. Such networks are expected to play an increasingly important role in future civilian and military settings, being useful for providing communication support where no fixed infrastructure exists or the deployment of a fixed infrastructure is not economically profitable and movement of communicating parties is possible. However, since there is no stationary infrastructure such as base stations, mobile hosts need to operate as routers in order to maintain the information about the network connectivity. Therefore, a number of routing protocols have been proposed for ad hoc wireless networks. In this paper, we study and compare the performance of the following routing protocols AODV, PAODV (preemptive AODV), CBRP, DSR, and DSDV. A variety of workload and scenarios, as characterized by mobility, load and size of the ad hoc network were simulated. Our results indicate that despite its improvement in reducing route request packets, CBRP has a higher overhead than DSR because of its periodic hello messages while AODV's end-to-end packet delay is the shortest when compared to DSR and CBRP. PAODV has shown little improvements over AODV.     

基于跨层设计的无线网络QoS技术

随着多媒体业务的不断发展,如何保证无线网络上的QoS成为一个很重要的问题.基于传统的分层设计方法很难适应快速变化的无线通信环境.主要研究无线网络QoS的跨层设计技术,分析了无线网络的特点及其QoS需求,在此基础上阐述跨层设计的思想和方法,讨论了QoS跨层设计目前存在的问题,对QoS跨层设计技术进行了展望.     

On Increasing Service Accessibility and Efficiency in Wireless Ad-Hoc Networks with Group Mobility

Wireless ad-hoc networks consist of mobile nodes interconnected by multi-hopwireless paths. Unlike conventional wireless networks, ad-hoc networks haveno fixed network infrastructure or administrative support. Because of thedynamic nature of the network topology and limited bandwidth of wirelesschannels, Quality-of-Service (QoS) provisioning is an inherently complex anddifficult issue. In this paper, we propose a fully distributed and adaptivealgorithm to provide statistical QoS guarantees with respect toaccessibility of services in an ad-hoc network. In this algorithm,we focus on the optimization of a new QoS parameter of interest, serviceefficiency, while keeping protocol overheads to the minimum. To achievethis goal, we theoretically derive the lower and upper bounds of serviceefficiency based on a novel model for group mobility, followed by extensivesimulation results to verify the effectiveness of our algorithm.     

Architecture and Experimental Framework for Supporting QoS in Wireless Networks Using Differentiated Services

This paper describes the design and implementation of an enhanced Differentiated Services (Diffserv) architectural framework for providing Quality of Service (QoS) in wireless networks. The Diffserv architecture has been recently proposed to complement the Integrated Services (Intserv) model for providing QoS in the wired Internet. The paper studies whether Diffserv, as defined for wired networks, is suitable for wireless networks. The proposed wireless Diffserv framework takes into consideration several factors, including signaling requirements, mobility, losses, lower wireless bandwidth and battery power constraints. It identifies the need for supporting signaling and mobility in wireless networks. The framework and mechanisms have been implemented in the wireless testbed at Washington State University. Experimental results from this testbed show the validity of the proposed Diffserv model and also provide performance analyses. The framework is also designed to be extensible so that other researchers may use our implementation as a foundation for implementing other wireless network algorithms and mechanisms.     

大规模无线局域网设计与优化算法

归纳了无线局域网系统设计流程,以接入访问点放置问题和信道配置问题为重点,归纳了已提出的目标函数和常见的优化算法,同时介绍了新提出的系统吞吐率最大化和公平性均衡目标函数,以及将接入点放置问题和信道配置问题联合解决的补丁算法.     

A Virtual Topology Based Routing Protocol for Multihop Dynamic Wireless Networks

In this paper, a new hierarchical multihop routing algorithm and its performance evaluation is presented for fully dynamic wireless networks. The routing algorithm operates on a virtual topology obtained by partitioning the routing information for mobile terminals and mobile base stations into a hierarchical, distributed database. Based on the virtual topology, each mobile base station stores a fraction of the routing information to balance the complexity of the location-update and the path-finding operations. Mobility of the network entities changes the load distribution and causes processing and memory bottlenecks in some parts of the network. However, since the network routing elements are also mobile, their movement can be used to distribute the load. Thus, new load balancing schemes are intoduced to distribute the routing overhead uniformly among the mobile base stations. The performance of the hierarchical multihop routing algorithm is investigated through simulations. It is shown that the routing protocol can cope with high mobility and deliver packets to the destinations successfully.     

On the Impact of Quality of Protection in Wireless Local Area Networks with IP Mobility

Wireless local area networks (LANs) are vulnerable to malicious attacks due to their shared medium in unlicensed frequency spectrum, thus requiring security features for a variety of applications even at the cost of quality of service (QoS). However, there is very little work on investigating to what extent system performance is affected by security configurations with respect to mobility scenarios, heterogeneous networks, and different applications. In order to exploit the full potential of existing security solutions, we present a detailed experimental study to demonstrate the impacts of security features on performance by integrating cross-layer security protocols in a wireless LAN testbed with IP mobility. We introduce a quality of protection (QoP) model to indicate the benefits of security protocols and then measure the performance cost of security protocols in terms of authentication time, cryptographic overhead and throughput. Our measurements demonstrate that the effects of security protocols on QoS parameters span a wide range; for example, authentication time is between 0.11 and 6.28 s, which can potentially affect packet loss dramatically. We also find that for the same security protocol throughput in non-roaming scenarios can be up to two times higher than that in roaming scenarios. However, some protocols are robust against mobility with little variation in system performance; thus, it is possible to provision steady service by choosing security protocols when users’ mobility pattern is unknown. Furthermore, we provide observations on cross-layer security protocols and suggestions to the design of future security protocols for real-time services in wireless LANs.

传感器网络节点随机调度算法的覆盖度分析

节点随机调度算法,是一种研究网络局部覆盖的重要方法,它无需知道节点位置信息、简单易用并有较高的实用价值。但是目前对该算法的研究成果均是基于布尔感知模型设计。布尔感知模型尽管简单,但不能真实地反映节点的感知能力。文中首次在概率感知模型下,分析了随机调度算法中网络覆盖度与节点数之间的关系,给出了节点数的下界值,并通过仿真验证了分析的正确性。     

Scheduling in Optical WDM Networks Using Hidden Markov Chain Based Traffic Prediction

This paper presents the design and performance analysis of a predictor-based scheduling algorithm for optical wavelength division multiplexed (WDM) networks. WDM technology provides multiple, simultaneous and independent gigabit-per-second channels on a single fiber. A reservation-based multiple access control (MAC) protocol is considered here for a local area WDM network based on the passive star topology. The MAC protocol schedules reservation requests from the network nodes on the multiple channels. In previous work, we have presented an on-line scheduling algorithm for such a network. We have shown earlier that schedule computation time can significantly affect performance and the scheduling algorithms should be simple for better performance. In this work, we further improve system performance by using a hidden Markov chain based prediction algorithm. The objective here is to reduce the amount of time spent in computing the schedule by predicting traffic requests. Performance analysis based on discrete-event simulation, varying parameters such as number of nodes and channels is presented. The results show that the error of prediction is reasonable for most cases: more than 70% of the time, the error between actual request and predicted request is less than 20%. Network throughput is higher with the proposed prediction algorithm due to pipelining of schedule computation.     

基于联合感知模型的无线传感器网络连通性覆盖协议

本文研究在没有节点位置信息的情况下,如何有效地保证节点采用联合感知模型且节点通信范围多级可调的无线传感器网络的覆盖质量和连通性.给出了在节点随机部署方式下,网络覆盖质量和网络连通性与工作节点个数、监测区域面积和节点性能参数的关系;设计了一个选取最少工作节点保证网络覆盖质量和网络连通性的调度控制算法(SCA),该算法力求...     

Interference in Wireless Multi-Hop Ad-Hoc Networks and Its Effect on Network Capacity

In this paper we propose a new model to calculate interference levels in wireless multi-hop ad-hoc networks. This model computes the expected value of Carrier to Interference ratio (C/I) by taking into account the number of nodes, density of nodes, radio propagation aspects, multi-hop characteristics of the network, and the amount of relay traffic. The expected values of C/I are used to determine network capacity and data throughput per node. Our model uses a regular lattice for possible locations of mobile nodes. This enables us to calculate the expected values of C/I, without having detailed information about movement patterns and exact location of all nodes at any moment. Based on this model we have evaluated effects of variations in the network size, network density and traffic load on C/I, and consequently throughput of the network. Our calculations suggest that interference is upper-bounded in wireless ad-hoc networks that use carrier sensing for medium access control. Further, from the point of view of throughput optimization, our calculations show limits on the network size and input data rates per node.