基于无线网状网络的速率自适应算法

无线网状网络不但拥有传统无线局域网技术中所具有的成本低、部署便捷的优点,同时,因其本身具有无线自组织网络的多跳结构的特点,在可扩展性和复杂环境适应性上的优势更加显著,因此,自问世以来就受到了广泛的关注。为了提高现有的无线网状网络的传输效率,同时使其对布网环境具有更强的适应性和稳定性,在无线网状网络中的SrcRR路由协议的基础上提出了一种基于动态探针队列检测的无线网状网络速率自适应算法并将其模块化实现。该算法显著改善了网络状态探测的适时性,以此为依据进行最佳通信速率选择更可靠、更准确。该算法在Sjtu-Mesh无线网状网络测试平台上进行了实现。实现结果表明,使用该速率自适应算法的无线网状网络的稳定性、可靠性和平均吞吐量都显著提高。     

无线网络中基于优先级队列延迟限定的研究

由于无线网络环境下网络节点的增加,网络延时成为一个亟待解决的问题。为了提高服务质量(QoS),提高吞吐量,文中提出了一种基于优先级的队列延迟模型,通过将每一个包预设置优先级来区分其重要性和实时性,同时将每一个AP设备中的队列根据优先级划分为3种类型,并将预设优先级的包放入其中进行传输,从而有效减少发送端的队列延迟。通过分析和仿真可以发现,与未划分优先级队列的节点网络相比,这种方案不仅使单个节点的延迟大幅减少,也使整个网络的平均延迟明显降低,网络整体性能显著提高。     

基于二进制网络编码的无线广播重传方法

为了提高无线广播网络中数据包的传输效率,提出了一种新的基于二进制网络编码的高效无线广播重传方法(WBRBNC).法基于数据包分布矩阵(PDM),在广播重传过程中使用一种新的数据包算法选取编码包,对这些丢包采用二进制网络编码方法进行编码,然后再进行广播,使一次广播重传可以使多个具有不同丢包的接收机受益.分析和仿真表明,该方法能有效保证接收节点的编码可解性,使重传次数显著减少,更接近于理论值,从而大大提高了传输效率.另外,该方法计算开销小,很适合应用在卫星广播网和无线传感器网等资源受限的系统中.     

无线Mesh网络速率自适应算法研究

自适应速率选择是影响无线Mesh网性能的关键问题.提出了一种基于动态解调门限的速率自适应选择算法,该算法通过统计传输速率进行速率选择,能够针对不同信道环境对每种调制速率所需最小信噪比门限进行自动调整.同时,采用跨层设计思想,采用路由协议广播报文作为MESH设备间传输信噪比信息的载体,从而能够根据信噪比和传输成功率信息得...     

基于无线Mesh网络技术构建无线城市

无线Mesh网络(WMN)可以和多种无线网络系统,如无线局域网(WLAN)、无线城域网(WMAN)等相结合,改善无线网络的性能,提高网络的覆盖范围.以WMN网络技术在IEEE 802系列标准中的发展为基础,提出了一种无线城市的覆盖方案,最底层网络覆盖采用WiFi+wireless Mesh技术,WiMAX网络与WiFi...     

Novel Fastest Retransmission and Rate Control Schemes for Improving TCP Performance in Wireless Ad Hoc Networks

A number of different authors have considered the problem of performance degradation of transmission control protocol (TCP) in wireless ad hoc networks. We herein show that pauses in packet transmission due to packet losses are the fundamental cause of performance degradation of TCP in wireless ad hoc networks. To minimize the duration of packet transmission pauses, we propose a fast retransmission scheme for improving TCP performance in consideration of the inter-operability of previously deployed TCPs in wireless ad hoc networks. We also propose an additional rate control scheme for TCPs to reduce the probability of packet contention. Using OPNET and NS2 simulations, we show that our proposed schemes can provide a much better performance than conventional TCPs.     

基于无线Mesh网络的干扰感知型路由判据

在无线Mesh网络路由判据的研究中,最小跳数、ETX、ETT等路由判据没有考虑到无线网络中的干扰问题,据此选出的一般不是最佳路由。因此,基于它们的路由协议会对整个无线Mesh网络的延时、丢包率、吞吐量等性能产生较大影响。干扰感知型路由判据的提出对无线Mesh网络性能的提升起到了一定的作用。     

在多天线多信道无线Mesh网络中基于利用率最大化来融合网络编码和TCP协议

A new approach, named TCP-I2 NC, is proposed to improve the interaction between network coding and TCP and to maximize the network utility in interference-free multi-radio multi-channel wireless mesh networks. It is grounded on a Network Utility Maxmization ( NUM ) formulation which can be decomposed into a rate control problem and a packet scheduling problem. The solutions to these two problems perform resource allocation among different flows. Simulations demonstrate that TCP-I2NC results in a significant throughput gain and a small delay jitter. Network resource is fairly allocated via the solution to the NUM problem and the whole system also runs stably. Moreover, TCP-I2NC is compatible with traditional TCP variants.     

一种基于跨层的无线Mesh网络路由协议

无线Mesh网络的很多技术特点和优势来自于Mesh多跳路由.因此,路由协议的研究与设计是无线Mesh网络技术的一个重要课题.由于无线Mesh网络有自身负载均衡、路由容错与网络容量等要求,因此运用跨层设计,采用更好的路由参数,使用多径路由等方法已经成为无线Mesh网络路由协议设计的重要思路.根据无线Mesh的网络特点,按照其路由协议的设计要求,分析了路由协议DSR在Mesh网络中的不足,引入跨层设计的方法,提出了采用路由质量路径帧投递率(PFDR)为路由准则,并具有负载平衡、拥塞避免的路由协议CMRP.分析和仿真结果表明,CMRP在保持Mesh网络自身优点的同时,比起DSR在网络性能上有了较大的提升,在吞吐率方面有了很大的提高,相应的时延、抖动参数均有了大幅的下降,更加适用于无线Mesh网络.     

无线Mesh网络路由协议研究

无线网状网络(WMN)的路由算法是Mesh领域的研究重点,采用何种路由协议使无线Mesh网络在需要的环境中性能达到最优,是目前WMN路由协议应用的实际问题.文中提出了设计无线网状网路由协议时需具备的特点,对目前提出WMN路由协议进行了分析研究,并比较了WMN路由协议优缺点,对WMN路由协议的选择提供了依据.     

TCP/IP Performance over 3G Wireless Links with Rate and Delay Variation

Wireless link losses result in poor TCP throughput since losses are perceived as congestion by TCP, resulting in source throttling. In order to mitigate this effect, 3G wireless link designers have augmented their system with extensive local retransmission mechanisms. In addition, in order to increase throughput, intelligent channel state based scheduling have also been introduced. While these mechanisms have reduced the impact of losses on TCP throughput and improved the channel utilization, these gains have come at the expense of increased delay and rate variability. In this paper, we comprehensively evaluate the impact of variable rate and variable delay on long-lived TCP performance. We propose a model to explain and predict TCPs throughput over a link with variable rate and/or delay. We also propose a network-based solution called Ack Regulator that mitigates the effect of variable rate and/or delay without significantly increasing the round trip time, while improving TCP performance by up to 100%.     

一种基于博弈论的无线mesh网络信道分配算法

无线mesh网络中的信道分配会极大地影响网络的性能。为了解决无线mesh网络中的信道分配问题,提出了一种基于博弈论的信道分配(GBCA)算法。该算法将网络中每一个节点模型化为一个博弈者,每个博弈者的策略为信道的分配方案,并将整个网络的吞吐量作为效用函数的目标,效用函数的物理意义则是在给定流量需求矩阵下传输的成功率。博弈者通过相互博弈来优化收益函数,以最大化网络吞吐量。并针对GBCA算法的不足,提出了一种改进算法———GBCA-TP算法。通过NS2.34仿真分析得出,GBCA算法和GBCA-TP算法在收敛性、分组丢失率和吞吐量上都要优于当前的算法。     

基于TDMA和定向天线的无线Mesh网络广播技术

传统Mesh网络实现的广播过程中存在节点之间冲突干扰、广播延时大和信道利用率不高等问题.采用TDMA接入协议与多接口的定向天线,优化了邻居发现过程和信道分配过程.在QualNet软件上进行仿真,并与其他算法进行性能对比,仿真和对比结果表明本广播过程相较于传统广播过程,减少了邻居发现时间,提高了时隙的复用率和信道利用率,...     

Joint Subchannel,Rate and Power Allocation in OFDMA-Based Cognitive Wireless Mesh Network

In this paper, the problem of resource allocation in an Orthogonal Frequency Division Multiple Access-based Cognitive Wireless Mesh Network (CWMN) is addressed. The objective is to maximize the total utilities in a CWMN, which is defined as any increasing, concave and twice differentiable function of the end-to-end flow rate, by jointly allocating each link’s rate, power and subchannels under the constraints of multiple primary users’ Interference Temperature and multiple access interference. First, a centralized resource allocation algorithm is developed based on the Column Generation approach, and shown to be optimal. So it can perform as a criterion for designing other algorithms. Secondly, considering the applicability of algorithm in distributed system, a near-optimal distributed algorithm is proposed, which allocates subchannel based on routing information at first, and then jointly allocates the resource of rate and power. Finally, the simulation results validate the centralized and distributed algorithms, and show that better performance can be achieved than the conventional algorithm.     

On the Relationship Between Transmission Rate and Network Capacity in Multi-Radio Multi-Channel Wireless Mesh Networks

This paper quantitatively investigates the relationship between physical transmission rate and network capacity in multi-radio multi-channel wireless mesh networks by using mixed-integer linear programming to formulate the joint channel assignment and routing problem. The numerical results show that the rate lower than the highest available one can improve the network capacity due to increased connectivity. It is also shown that the lower transmission rate is able to utilize abundant channels more effectively due to the higher degree of freedom in channel assignment. Finally, it is shown that joint rate, channel assignment and routing improves the network capacity further.     

基于紧密中心性的无线mesh骨干网网关部署

将定向天线和Delaunay图应用于无线mesh骨干网络的网关部署,提出了基于紧密中心性的无线mesh骨干网络网关部署算法。根据已知的mesh路由器和网关的最大流通量对网络进行划分,形成Delaunay子图,在划分的子图中根据欧几里德距离找出距离中心点最近的3个节点,形成候选网关集,在候选网关集中选择到其他节点总路径最短的节点作为网关的部署位置,将每个子图的网关位置输出。仿真结果表明,根据网关最大流通量进行合理网络划分后,算法能最小化网络的网关数量,由mesh路由器到网关的总路径长度优于随机算法。     

基于IPv6的无线Mesh网络切换技术研究

如何提高无线Mesh网络的切换效率,同时保障其服务质量一直是一个很具有挑战性的问题,它直接关系到无线Mesh网络是否能够被广泛应用。基于此,提出将IPv6技术引入到无线Mesh网络中,使得网络中的每个设备都有一个唯一的IPv6地址和响应的MAC地址,实现移动终端的快速切换,提高了无线Mesh网络的切换效率。     

基于网络利用率最大化来提高无线Mesh网络中TCP协议的传输性能

In Wireless Mesh Networks (WMNs), the performance of conventional TCP significantly deteriorates due to the unreliable wireless channel. To enhance TCP performance in WMNs, TCP/LT is proposed in this paper. It introduces fountain codes into packet reorganization in the protocol stack of mesh gateways and mesh clients. Furthermore, it is compatible with conventional TCP. Regarded as a Performance Enhancement Proxies (PEP), a mesh gateway buffers TCP packets into several blocks. It simultaneously processes them by using fountain encoders and then sends them to mesh clients. Apart from the improvement of the throughput of a unitary TCP flow, the entire network utility maximization can also be ensured by adjusting the scale of coding blocks for each TCP flow adaptively. Simulations show that TCP/LT presents high throughput gains over single TCP in lossy links of WMNs while preserving the fairness for multiple TCPs. As losses increase, the transmission delay of TCP/LT experiences a slow linear growth in contrast to the exponential growth of TCP.     

基于无线Mesh网络的物流信息传输平台设计

无线Mesh网络是一种新型的宽带无线网络结构,即一种高容量、高速率的分布式网络,它不同于传统的无线网络,可看成是WLAN和移动AdHoe网的融合,且发挥了两者的优势。无线Mesh网络逐渐进入民用商业化研究开发和应用阶段。在此基于无线Mesh网络这一热点技术日益成熟的背景,采用无线Mesh网络主要技术及拓扑结构;在需求分析的基础上,设计基于无线Mesh网络的物流信息传输平台,并应用于实际的工商业领域中。该设计获得了良好的社会效益,具有投资少、技术成熟的特点。     

基于模糊推理的认知无线Mesh网络路由算法

认知无线Mesh网络中的节点能动态接入空闲频谱,然而,频谱空穴的频繁变化将导致网络路径的破坏,使得网络性能下降.提出了基于模糊推理的认知无线Mesh网络路由算法,该算法利用模糊Petri网的推理机制计算可行路径的可靠度,最终选择可靠度最高的路径和信道.仿真结果表明,认知无线Mesh网络使用推理机制的路由算法能够增加所选路由的可靠度,减少网络路径破坏数,提高网络吞吐量.