解码转发双向无线携能全双工中继系统的能效研究

为了优化双向单中继全双工系统的能效,在中继节点引入无线携能技术,提出了一个双向无线携能全双工中继系统。该系统中继节点以功率分割方式进行能量收集,将收集的能量用于解码转发,在保证用户的服务质量需求下,将能效优化问题转化为能量消耗最小的优化问题,依据传输时隙以及各时隙信道容量需求进一步划分为两个子优化问题;然后,以能效最大化为目标,根据各时隙的信道容量求出传输功率,利用解码转发特性求出传输时间和功率分割因子,得出能效最优解。仿真表明,所提出的双向无线携能全双工中继系统的能效是单向无线携能全双工系统的1.3倍、双向全双工放大转发中继系统的2倍和双向全双工解码转发中继系统的2.6倍。      

无线Mesh网络流量自相似性研究

近年来,无线Mesh网络已成为一个倍受关注的研究领域.对无线Mesh网络流量特性的研究将有助于网络协议的研究、评估,以及网络结构的规划和建设.本文通过对无线Mesh测试网上采集的数据包进行统计分析,揭示了网络流量具有自相似的特性.同时,解释了无线Mesh网络流量自相似性是由网络中具有重尾分布特性的多个流叠加形成的,并通过仿真进一步分析了节点移动性对流量自相似性的影响.     

DSLAM传输网技术

无线Mesh网络(Wireless Mesh Network,WMN)是一种新兴的源于移动Ad Hoc网络的宽带无线接入技术.它通过网关节点接入因特网.实际应用中当网络接入业务量很大或网络规模扩大时,一个网关节点将成为网络接入性能的"瓶颈",大量转发的数据包将导致严重的拥塞.针对此问题提出一种基于移动自组网DSR协议的多网关选播路由协议MAMSR,仿真实验表明它能有效解决接入拥塞问题.     

数据业务自相似特性研究

合适的业务源模型能够在建立理论分析模型或进行系统性能仿真时,使网络系统性能评价更加准确。自相似特性是数据业务的重要特征。本文分析了自相似业务源的建模现状,深入讨论了如何将自相似模型应用于GPRS业务源建模。通过时间序列自相似特性分析工具SELFIS,对中国移动GPRS网络中从一个网关支持节点GGSN处采集的在单位时间内收到的字节数进行分析,得出GPRS数据业务具有较强自相似性的结论。     

三节点无线高斯中继信道容量分析

分析了三节点无线中继信道容量的计算,并着重分析中继节点的位置对信道容量的影响;而文献中已有工作一般在给定中继节点位置的前提下研究快速衰落、中继节点个数或天线根数等参数对信道容量的影响。根据分析结果,在不同的系统参数取值下,无线中继信道容量一共有3种可能的取值模式:随着中继节点的位置从靠近源节点到靠近目的节点,信道容量会不断减少(模式C1),或者不断增加(模式C3),或者先增加再减少(模式C2)。在确定了无线中继信道的特点后,给出了一个数值例子来验证分析的正确性。     

一种上变频自供电无线传感器电源管理电路

电线周围的电磁场能量密度低,电磁换能器采集到的能量通常无法直接驱动无线传感器正常工作.论文采用上变频技术,设计了一种自供电电源管理电路来提高能量采集效率.由于电路的输出功率与品质因数成正比,且品质因数的大小与电路谐振电容的根号值成反比,因此通过提高电路的工作频率来减小谐振电容值,可以使高品质因数的电路产生更高的输出功率,进而增加能量采集效率.实验结果表明,该电路的最大能量采集效率是传统桥式整流电路的2.1倍.当电线中通过1A、50Hz的交流电时,电源管理电路最大采集功率为780μW,能量采集效率达到48.75%.当管理电路中超级电容能量积累达到一定程度,电容放电驱动无线传感器工作.     

无线Mesh网络可用带宽估计方法的研究

提出一个适用于无线Mesh网络的可用带宽估计(MPEAB)方法.该方法根据无线Mesh网络的结构特点,利用信号在传播过程中会发生衰落、导致信号容量减小的特征,建立信道容量与发送功率和接收功率在理想通信系统中的数量关系,估计出无线Mesh网络节点信道容量,从而进一步提高可用带宽估计算法在无线Mesh网络中的精确度.NS2实验结果表明,MPEAB方法估计的结果更接近真实的可用带宽.     

无线传感器网络技术发展现状

在对无线传感器网路（WSN）产生和发展、技术成熟程度分析的基础上,文章分析了WSN组网模式、拓扑控制、媒体访问控制（MAC）和链路控制、路由与数据转发及跨层设计、时间同步技术、自定位和目标定位技术等组网关键技术和应用支撑技术方面的研究内容。基于应用中的典型实用和示范系统,文章对WSN的应用进行了分类。     

智能电网双层无线接入架构及信道仿真研究

电力通信网络的架构及无线信道特性是决定网络性能的关键因素。首先,研究基于南方电网电力无线宽带专网的双层无线接入架构,该架构中宏蜂窝与汇聚网关之间的MIMO信道的性能将直接影响到电网的稳定和运营水平。因此,对MIMO信道性能的研究就尤为重要。主要对MIMO信道的两个典型模型WINNERⅡ模型和Kronecker模型分别从信道空间相关性、信道容量、时域衰落三方面进行理论分析与对比仿真。由仿真结果得到天线数量、信噪比、天线阵列等因素对信道容量和天线相关性的影响。仿真结果说明MIMO技术能够在电网多业务承载环境下,满足系统高速率、大容量的要求。通过比较,WINNERⅡ模型与真实传播环境匹配度高,可在双层无线接入架构中得到进一步的应用。     

延长无线多跳自组织网络生存周期的方法

针对无线多跳自组织网络由于结构缺陷所造成的生存周期短的问题,提出了一种延长该网络生存周期的方法.通过在圆形区域内搜索中间节点,以2跳数据转发代替原有的1跳转发过程,在降低源节点发送功率的同时减少整个转发过程的能量损耗.公式推导验证了方法的可行性,通过MATLAB仿真对整个传输过程的节能效果进行分析,并给出了方案实施的流程图.     

Study of the Effect of the Wireless Gateway on Incoming Self-Similar Traffic

It has been well established by now that high-speed wireline traffic exhibits self-similar behavior. Due to the important consequences of traffic self-similarity in network design, several studies have assumed that wireless traffic is also self-similar and looked at its effects on network performance. However, due to factors such as power limitations and the wireless channel, it is not straightforward that wireline traffic will remain self-similar as it enters the wireless network. This paper provides an analytical study of the propagation of traffic characteristics as wireline traffic is passed to the wireless network through a gateway. The analysis takes into account buffering and repacking operations performed at the gateway, and models for wireline traffic and the wireless channel. We consider two server models, an instant transfer model, and an energy-conserving one. We show that in most cases, in response to self-similar wireline traffic the gateway will produce self-similar wireless traffic. However, when the gateway operates under an energy-conserving mode and if it has a large buffer, wireline traffic such as non-real-time variable-bit-rate traffic will result in non-self-similar wireless traffic. We also study the delays of packets passing through a gateway that is fed by self-similar traffic and show that their survival function has an asymptotically power-law tail with index smaller than 2.     

Ad hoc wireless network traffic-self-similarity and forecasting

Lots of works have been carried out to discuss the self-similarity of Ethernet and World Wide Web traffic. In this letter, we study the ad hoc wireless network traffic collected in an ad hoc network (AHN) testbed and show that the ad hoc wireless network traffic is self-similar, which validates that AHN traffic is forecastable because self-similar time-series can be forecasted. We apply a fuzzy logic system to ad hoc wireless network traffic forecasting and simulation results show that it performs much better than does an LMS adaptive filter. All these studies are very important for evaluating network capacity and determining the battery power mode based on the forecasted traffic workload     

Queue Analysis and Multiplexing of Heavy-tailed Traffic in Wireless Packet Data Networks

Recent research based on traffic measurements shows that Internet traffic flows have a fractal nature (i.e., self-similarity property), which causes an underestimation of network engineering parameters when using the conventional Poisson model. Preliminary field measurements demonstrate that packet data traffic in wireless communications also exhibits self-similarity. In this paper, we investigate the queuing behavior of self-similar traffic flows for data applications in a packet-switching single-server wireless network. The traffic is generated by an on–off source with heavy-tailed on periods and exponentially distributed off periods. We extend previous analysis of a relation among the asymptotic distribution of loss probability, traffic specifications, and transmission rate for a wireline system to a wireless system, taking into account wireless propagation channel characteristics. We also investigate the multiplexing of heavy-tailed traffic flows with a finite buffer for the downlink transmission of a wireless network. Computer simulation results demonstrate that assumptions made in the theoretical analysis are reasonable and the derived relationships are accurate.     

WiNoC中EF-ACK容错无线接口设计

无线片上网络中的无线信道面临着严重的可靠性挑战,无线路由器的容错设计对整个片上网络的传输效率有着较大的影响.本文提出一种EF-ACK容错无线接口设计,将多条确认信息配置在一个数据包内,通过无线信道传递确认信息数据包;在无线接口处设立重传数据缓冲区,以更高效的方式确认数据以及控制错误数据包的重传;另外,提出了基于网络状态的编解码控制,在网络情况较差时用BCH编码的方式提高数据的鲁棒性.实验表明,本文方案使用了较小的额外面积和功耗开销,高效地完成了对于数据的无线确认反馈,且在错误率较高时,可以保证网络中较低的网络延迟和较高的饱和吞吐量,大大提高了网络的性能.     

An uplink power control based on truncated channel inversion fordata traffic in a cellular CDMA system

A power control scheme, called truncated channel inversion, in which a mobile suspends transmission when the wireless channel is in a bad condition in order to reduce out-cell interference is examined. It is found that capacity is improved and battery power consumption is reduced as a consequence of suspending transmission, but extra queuing delay is introduced. It is shown that the extra queuing delay depends on how fast the channel characteristics change and that the truncated scheme works well, even for moderate mobile velocities     

基于WSN技术的数据采集系统的设计

基于无线传感器网络技术以智能交通管理系统为应用实例设计了一种现场数据采集系统。具体实现上,利用加速度传感器ADXL202实现对过往车辆信息的检测,使用基于ZigBee协议的XBEE-PRO无线通讯模块实现传感器数据的无线传输,以FS2410DEV V6.0作为网关控制平台,将数据分析处理后传送给PC机服务器。系统测试表明,该设计方案可行,具有功耗低、组网能力强、传输距离远、可靠性高、拓展能力强等优点。     

无线多跳网络下基于过时信道状态信息的跨层资源分配

对于无线多跳网络跨层资源分配算法的研究大多是建立在假定每个节点能获得网络中其他节点的完美的信道状态信息(CSI)的基础上。但是由于信道的时变特性和CSI的反馈延时,在动态变化较快的无线网络中,节点所获得的CSI很可能是过时或者部分过时的。基于这个前提,该文首次在动态无线多跳网络跨层资源优化分配算法中考虑了CSI这种变化的影响,并提出了一种相应的分布式联合拥塞控制和功率分配算法。仿真结果证明该算法能够极大地提高网络效用和能量效用。     

Proxy‐RED: an AQM scheme for wireless local area networks

Wireless access points (APs) act as bridges between wired and wireless networks. Since the actually available bandwidth in wireless networks is much smaller than the bandwidth in wired networks, there is a disparity in channel capacity which makes the access point a significant network congestion point in the downstream direction. A current architectural trend in wireless local area networks (WLAN) is to move functionality from APs to a centralized gateway in order to reduce cost and improve features. In this paper, we study the use of RED, a well known active queue management (AQM) scheme, and explicit congestion notification (ECN) to handle bandwidth disparity between the wired and the wireless interface of an access point. Then, we propose the Proxy‐RED scheme, as a solution for reducing the AQM overhead from the access point. Simulations‐based performance analysis indicates that the proposed Proxy‐RED scheme improves the overall performance of a network. In particular, the Proxy‐RED scheme significantly reduces packet loss rate and improves goodput for a small buffer, and minimizes delay for a large buffer size. Copyright © 2006 John Wiley & Sons, Ltd.     

Optimal Power and Rate Control for Minimal Average Delay: The Single-User Case

Contemporary wireless systems combine aspects of network theory such as scheduling, throughput, and delay as well as information theory aspects such as capacity, coding, and power control. Design of such systems requires joint optimization of both network and physical layers. In this paper, we analyze a single-user communication system composed of a transmitter preceded by a queue used for retransmissions, Gaussian block-fading channel, and a receiver. The system average delay is optimized by using combined power/rate control under average power constraints. Dynamic programming is used for calculating the optimized policies using numerical analysis as well as analytic analysis for asymptotically large buffer size. Asymptotic results are obtained for all combinations of fixed or variable power and rate controls. The most important result extends the "water-filling" result for systems with average delay constraint     

Capacity analysis of based-regular-topologies cognitive wireless mesh networks with power control

Capacity analysis is a fundamental and essential work for evaluating the performance of cognitive wireless mesh network （CWMN） which is considered a promising option for the future network. Power control is an efficient way to avoid interference and improve capacity of wireless mesh networks. In this paper, a quantitative result of the per-node average throughput capacity of CWMN with power control is deduced for the first time, which is much helpful for understanding the limitations of CWMN. Firstly, under the large-scale channel fading model and protocol interference model, a closed-form expression for the maximum channel capacity of each node with power control is presented, under the constraint that the interference tolerated by the primary users （PUs） does not exceed a threshold. And then, with the deduced channel capacity result, the per-node average throughput capacity of CWMN is derived based on two regular topologies, i.e. square topology and triangle topology. The simulation results indicate that the capacity is effectively improved with power control, and affected by topology, tolerated interference threshold, the number of cognitive users （CUs） and primary users （PUs）.