Two incremental relaying protocols for cooperative networks

The authors investigate a cooperative network with three terminals. By exploiting a simple two-bit feedback message from the destination, two incremental relaying protocols are proposed, namely incremental selection amplify-and-forward (ISAF) and joint incremental selection relaying (JISR) with an aim to balance the load between the source and the relay. The authors derive the asymptotic outage probabilities of the two new protocols and find them to be lower than that of the incremental amplify-and-forward (IAF) protocol, which has been identified as the best protocol so far. Moreover, the spectral efficiencies of ISAF and JISR match that of IAF. Simulation results have verified the asymptotic performance of the protocols and have shown that JISR outperforms ISAF and IAF over all signal-to-noise ratio values.     

Relay-aided opportunistic scheduling in wireless networks

One of the most promising approaches to boost the communication efficiency in wireless systems is the use of multiuser diversity (MUDiv), where the fading of channels is exploited. The mechanism of scheduling the user with the best channel condition is called opportunistic scheduling (OS). In this paper, we propose a novel OS algorithm in wireless networks that reduces the feedback load with the aid of relaying. It is called relay-aided opportunistic scheduling (RAOS). We consider two schemes: non-greedy RAOS and greedy RAOS. In the nongreedy RAOS schemes, we consider two scenario: non-persistent and p-persistent, where the persisting occurs when no feedback is received via a relay. The RAOS algorithm requires users to feedback their signal-to-noise ratios (SNRs) either directly to the access point (AP) or via a relay. Furthermore, We analyse the RAOS algorithm under slow Rayleigh fading assumption and derive the closed-form expressions for the feedback load as well as the spectral efficiency. The result shows that the RAOS algorithm provides 55% feedback load reduction compared with other scheduling algorithms.     

无线非再生中继网络中继区域的计算

引入中继增益和约束参数,提出了一种适用于无线非再生中继网络的中继区域的计算方法.该方法借助误符号率近似解来定义中继增益,利用中继增益和路径损耗模型给出了中继区域及其子区域的闭合表达式及几何解.考虑到无线网络覆盖和天线配置等约束参数对中继区域及子区域的限制,进一步分析了该几何解的组网工程意义.数值与仿真结果表明,提出的中继区域计算方法可适用于各种约束参数下无线非再生网络中继区域及子区域的计算.     

Cooperative wireless networks for better green services

During the last two decades, mobile communication systems (such as GSM, GPRS and 3G networks), wireless broadcasting networks, wireless local area networks (WLAN or WiFi), and wireless sensor networks have been successfully developed and widely deployed through different technological routes for providing a variety of communication services in different application scenarios. While making tremendous contributions to social progress and economic growth, these heterogeneous wireless networks consume a lot of energy in achieving overlapped service coverage, and at the same time, generate strong electromagnetic interference (EMI) and radiation pollution, especially in big cities with high building density and user population. In order to guarantee the overall return on investment (ROI), improve user experience and quality of service (QoS), save energy, reduce EMI and radiation pollution, and enable the sustainable deployment of new profitable applications and services, this paper proposes a cross-network cooperation mechanism to effectively share network resources and infrastructures, and then adaptively control and match multi-network energy distribution characteristics according to actual user/service requirements in different geographic areas. Some idle or lightly-loaded Base Stations (BS or BSs) will be temporally turned off for saving energy and reducing EMI. Initial simulation results show the proposed approach can significantly improve the overall energy efficiency and QoS performance across multiple cooperative wireless networks.     

基于室内传播模型的无线传感器网络节点部署策略研究

为保证在室内部署无线传感器网络节点时实现感知面积完全覆盖特定区域,在2．4GHz的ISM频段,依据对数距离模型,分析了因天线高度不同引起的节点有效覆盖面积的变化问题,讨论了有效通信半径与有效感知半径的关系。在传统的平面节点部署方法的基础上,提出了一种考虑天线高度等环境因素的室内无线传感器网络节点快速部署方案,定义了部署规则和补充规则,从而避免了因天线高度变化而引起的感知黑洞的产生。仿真和试验结果表明该方案可以有效保证规定区域的完全覆盖,具有应用价值。     

机会网络的一种基于消息传播状态的缓存替换方法

针对机会网络在采用"存储-携带-转发"的消息传递方式,节点缓存空间有限的情况下缓存替换方法会对路由协议性能产生很大影响的问题,此文在分析消息在网络中传递特征的基础上,提出了一种分布式的基于消息传播状态的缓存替换(MTSBR)方法.此方法可使节点在缓存空间不够时,优先丢弃复制数量多和传递速率快的消息,从而有效地抑制网络中...     

一种基于协同MIMO的无线传感器网络传输方案

针对无线传感器网络中能量有限和能耗不均衡问题,提出了一种基于协同多输入多输出(MIMO)的无线传感器网络传输方案,此方案利用有限比特的反馈信息实时调整簇头节点(CH)和协同簇头节点(CCHs)的发射功率并动态地更新协同簇头节点,减少协同簇头节点的能耗.在给定误比特率条件下,为使网络总能耗最小,对传输速率和协同簇头节点数进行联合优化,给出了均衡簇内节点能耗的算法.理论分析和仿真结果表明,此方案既能有效降低网络的总能耗,又能均衡网络中节点的能耗.     

Lifetime improvement in wireless sensor networks via collaborative beamforming and cooperative transmission

Collaborative beamforming (CB) and cooperative transmission (CT) have recently emerged as communication techniques that can make effective use of collaborative/cooperative nodes to create a virtual multiple-input/multiple-output system. Extending the lifetime of networks composed of battery-operated nodes is a key issue in the design and operation of wireless sensor networks. The effects on network lifetime of allowing closely located nodes to use CB/CT to reduce the load or even to avoid packet-forwarding requests to nodes that have critical battery life are considered. First, the effectiveness of CB/CT in improving the signal strength at a faraway destination using energy in nearby nodes is studied. Then, the performance improvement obtained by this technique is analysed for a special 2D disc case. Further, for general networks in which information-generation rates are fixed, a new routing problem is formulated as a linear- programming problem, whereas for other general networks, the cost for routing is dynamically adjusted according to the amount of energy remaining and the effectiveness of CB/CT. From the analysis and the simulation results, it is seen that the proposed method can reduce the payloads of energy-depleting nodes by about 90% in the special case network considered and improve the lifetimes of general networks by about 10%, compared with existing techniques.     

无线传感器网络中基于能量有效的按需缓存策略

提出一种能量有效的按需缓存策略BESS,中间节点收到源节点到sink节点数据包后,用二分法根据节点位置选择缓存节点;并由节点剩余能量和能量阈值判断是否应该存储数据项,能量阈值根据每个节点缓存数据项个数不同动态确定;缓存替换中通过建立模型得到影响缓存发现能量的一些因素,根据这些因素构造出缓存替换策略的权值函数.仿真结果表明,与已存在的GCCS策略相比,平均时延降低4.8%～31.6%,平均能耗减少15.1%～35.6%,缓存字节命中率提高3.64%～8.16%.     

基于人类移动模式的机会网络数据分发策略

针对机会网络数据分发效率低的问题,提出了一种新的基于人类移动模式(HMP)的机会网络数据分发策略:选择目标地址匹配(DM)标点、目标地址到达时间(DAT)、网络跳数(NH)这三个数据作为分发策略中的关键因素,把三者的综合评判作为中继节点选取标准并将其应用于机会网络数据转发;有效地降低无用多跳数据转发造成的网络拥塞和资源...     

Achieving higher throughput in ieee 802.11 wireless local area networks with burst transmission methods

As extensions in the emerging 802.11e for quality-of-service provisioning, burst transmission and the acknowledgment aggregation are the two important operations to improve the channel efficiency of IEEE 802.11-based wireless local area networks (WLANs). However, only a few works have been done on these operations, and usually assumed the networks to be operated under saturated traffic conditions and error-free channels. In practice, the assumptions may not be valid because real-time traffic with proper rate control will not saturate the networks and the channel is generally error-prone. Thus, the authors consider two new methods resulted from these operations and analyse their performance under unsaturated and error-prone WLANs, with a Markov chain model. The results show that the new methods generally have better throughput than the conventional IEEE 802.11 medium access control (MAC) in the WLANs.     

基于混合拓扑的机械无线传感器网络多信道数据传输方法

针对机械振动无线传感器网络节点因信道带宽窄导致网络传输速率过低,在大量原始数据传输需求下实时性较差的问题,提出一种基于簇树星型混合拓扑的多信道数据传输方法。对各传感器网络节点进行树间通信干扰最小化信道分配,避免邻频干扰影响树间并行通信,在数据同步采集结束后,各节点以分配信道组建簇树星型混合拓扑网络进行数据传输;采用树间通信握手机制和树间通信优先级抢占机制解决簇树星型混合拓扑带来的树间互盲问题;将各采集节点短地址作为调度信息载入信标进行广播,各采集节点根据调度信息决定进行数据传输或者休眠,实现树内通信能耗最小化时序调度。将提出的多信道数据传输方法与载波侦听多路访问/冲突避免机制进行对比,实验结果表明该方法能有效提高机械振动无线传感器网络数据传输速率。     

Power optimised channel coding in wireless sensor networks using low-density parity-check codes

Energy consumption of low-density parity-check (LDPC) codes in different implementations is evaluated. Decoder's complexity is reduced by finite precision representation of messages, that is, quantised LDPC decoder, and replacement of function blocks with look-up tables. It is shown that the decoder's energy consumption increases exponentially with the number of quantisation bits. For the sake of low-power consumption, 3-bit magnitude and 1-sign bit representation for messages are used in the decoder. It is concluded that high-rate Gallager codes are as energy efficient as the Reed-Solomon codes, which till now have been the first choice for wireless sensor networks (WSNs). Finally, it is shown that using LDPC codes in WSNs can be justified even more by applying the idea of trading the transmitter power with the decoder energy consumption. By exploiting the trade-off inherent in iterative decoding, the network lifetime is increased up to four times with the 3-6 regular LDPC code. Hence, it is inferred that the LDPC codes are more efficient than the block and the convolutional codes.     

利用无线传感器网络实现运动声源的定位与跟踪

1引言随着无线通信和大规模集成电路的发展,无线传感器网络受到人们越来越多的关注。在无线传感器网络中,如何融合各个节点采集的音频数据实现运动声源的精确定位和跟踪,是目前的一个研究热点。     

Distributed inference in wireless sensor networks

Statistical inference is a mature research area, but distributed inference problems that arise in the context of modern wireless sensor networks (WSNs) have new and unique features that have revitalized research in this area in recent years. The goal of this paper is to introduce the readers to these novel features and to summarize recent research developments in this area. In particular, results on distributed detection, parameter estimation and tracking in WSNs will be discussed, with a special emphasis on solutions to these inference problems that take into account the communication network connecting the sensors and the resource constraints at the sensors.     

Signal compression in wireless sensor networks

Signal compression is an important tool for reducing communication costs and increasing the lifetime of wireless sensor network deployments. In this paper, we overview and classify an array of proposed compression methods, with an emphasis on illustrating the differences between the various approaches.     

Providing differentiated services in CDMA wireless networks

With much more advanced techniques employed, various applications can be supported by 3G CDMA-based wireless networks. Providing differentiated service over wireless networks has become a very important issue in the design of wireless networks. A new media access control protocol with a hierarchical scheduling algorithm to provide differentiated service for CDMA-based wireless networks is proposed. This protocol evolves from the distributed queuing random access protocol for CDMA wireless network. The proposed protocol has been designed to have an ability to accommodate integrated traffic in the networks with effective scheduling schemes. A series of simulation experiments have been carried out to evaluate the performance of the proposed protocol with the hierarchical scheduling algorithm. The results reveal that the proposed solution performs effectively in the integrated traffic composed of messages with or without time constraints and achieves proportional fairness among different types of traffic.     

Direction finding in IEEE802.11 wireless networks

A novel direction-finding method for stations of IEEE802.11 wireless local area networks is presented in this paper. The method uses a switched beam array for determining the direction of arrival of the incident electromagnetic field in a time efficient way and associates certain medium access control (MAC) layer functions with different radiation patterns of the switched antenna array, in order to determine the proper orientation of directional beams on both entities of a communication link. The application of the proposed method to an IEEE802.11 wireless network is presented and it is depicted how the method improves the network performance without requiring any modifications to the existing MAC protocol.     

基于非合作博弈功率控制的传感器网络并行传输MAC协议

针对传统的基于竞争或调度的MAC协议用于节点密集部署的无线传感器网络中,会出现较低的吞吐量和累计延迟等问题,利用节点密集部署的无线传感器网络中普遍存在的捕获效应对MAC协议性能的影响,提出了一种单信道模式下工作的并行传输的新型高效MAC协议——基于非合作博弈功率控制的并行传输MAC协议.该协议运用博弈理论中非合作不完全...     

基于QoS升降级的无线异构网动态带宽分配策略研究

利用异构无线网络环境下实时多媒体业务传输带宽可变的特点,提出一种基于服务质量(QoS)升降级的动态带宽分配策略。该策略针对系统带宽资源不足的情况,给出基于信道容量对多媒体用户进行平缓QoS升降级的方法,使系统在用户可接受的降级程度内接入更多的呼叫,进一步,为得到满意的服务等级(GoS),设置一个限制新呼叫接入的带宽阈值,并基于Markov模型给出该阈值的计算方法。与固定划分降质水平的带宽分配策略比较的结果表明,上述带宽分配策略能有效降低新呼叫阻塞率(CBP)与切换呼叫中断率(HDP),同时能明显提高带宽资源利用率。