无线Mesh网在城市轨道交通车地通信系统中的研究

无线Mesh网因组网灵活、支持范围大和移动性强等特点,使其在城市轨道交通(城轨)中具有很好的应用前景。尝试将无线Mesh网技术应用于城轨车地通信系统中,针对车地通信存在的越区切换问题,提出了一种基于车载MMS(mobile Mesh station)位置触发的越区切换方案,利用OPNET对组网方案和切换方案进行了仿真。仿真结果表明,无线Mesh组网方案性能优于传统WLAN组网方案性能,切换方案能有效降低时延并避免了假切换和乒乓切换的发生。     

基于综合判据的无线Mesh网路由协议

为用户提供高质量、高性能的通信链路是无线Mesh网路由协议所面临的重要挑战,而当前从Ad Hoc网络沿袭下来的路由协议并不能够满足无线Mesh网的性能要求.文中以OLSR协议为原型,结合跨层优化理论,为基础设施架构的无线Mesh网提出了一种新颖的、基于综合判据的路由协议.该协议通过跨层操作机制综合考虑无线链接的长度及通信效率对链接性能的影响,从而达到优化路由选择的效果.仿真结果表明,所提出的路由协议能够有效地提高网络中分组的递交率,降低端到端的延时,并且能够在一定程度上达到负载均衡的路由效果.     

无线Mesh网GPS同步技术的研究

研究了时分、空分的无线Mesh网中通信节点之间的时隙同步问题的解决方案.传统的无线Mesh解决方案中使用全向天线加异步竞争信道的模式,节点之间的干扰随着网络规模的扩大而加剧,严重影响了通信效率.同步无现Mesh网引入时分和空分的机制,使通信节点在其预先分配到的时隙和对应方向的天线上进行通信,克服了全向、异步模式中的弊端,大大提高了通信效率.研究分析了同步Mesh网较异步Mesh网点优势和特点,以及同步精度对同步Mesh网性能的重要影响.设计并实现一种基于GPS秒脉冲的时隙同步算法,并在CPLD平台上实现该算法.     

无线Mesh网络下嵌入式视频监控系统的设计

结合无线网络视频监控的新要求,深入分析了无线网状网的网状拓扑、多跳链路、动态路由协议等关键技术和发展现状,将无线自组织网络按需距离矢量路由协议（AODV）开发应用到嵌入式Linux平台上,利用TCP协议进行呼叫连接控制,并在该平台上提出了利用多个单独视频终端节点构建基于无线Mesh网络技术的视频监控网络应用方案。实验证明这种方案是可行的。     

IMS中基于LZSS的SIP信令压缩算法研究

3GPP在R5核心网引入了IMS结构，并选择会话初始协议（SIP）作为呼叫/会话的控制信令。但在无线环境下消息过长成为SIP在IMS中的应用瓶颈。在SigComp框架下，对各种压缩算法进行了比较，并根据SIP消息特点选择LZSS算法作为SIP信令压缩的基本算法。为了进一步提高SIP信令的压缩比，提出了LZSS＋Huffman的压缩算法及其实现流程，并对算法的压缩效果进行了仿真分析。     

一种SIP穿越NAT方案的设计与实现

本文从基于SIP协议的VoIP及其他IP多媒体应用系统难以穿越NAT的问题出发，提出了一种基于STUN方式的解决方案，并详细介绍了其实现过程。该方案不需要扩展相关协议，不需要对NAT设备进行改造或升级，可以工作在多级NAT串联的环境下，而且可以使外网用户主动呼叫内网用户建立连接。该方案目前已成功应用于我们开发的基于嵌入式Linuux平台的无线VoIP网关中，并可推广到其他基于SIP协议的终端上。     

基于PSO的无线Mesh网关优化部署算法

无线Mesh网关的优化部署目标是对一给定的无线Mesh网络,合理地确定网关部署的方案,在满足用户通信时延、通信带宽以及网关相关属性约束(如网关的度,簇度数)的前提下,使得网关数量最少、网关间负载均衡以及总体通信代价最小。利用粒子群算法在多目标寻优方面的优势,提出了基于粒子群的无线Mesh网关优化部署算法。对粒子的速度、速度的相关运算规则和粒子的运动方程进行了重新定义与设计,然后提出了基于网关启发式初步部署与优化的二阶段粒子群优化算法。理论分析与仿真实验表明,基于PSO的优化算法得到的网关数量不劣于其它算法得到的结果,而且在其它性能指标方面:通信代价、网关节点数量、负载均衡方面优势明显,与Recursive_DS算法的相比分别提高了38.15%,7.85%和7.3%。     

在Linux环境下SIP通信的实现

SIP(Session Initiatioan Protocol)协议是由IETF工作组于1997年7月提出的,是应用层的控制协议,能建立、调整和终止多媒体的呼叫和会话。SIP协议是基于文本方式的,即以明文方式传输。SIP消息包括请求消息、应答消息。SIP协议侧重于将IP电话作为因特网上的一个应用,并且也采用RTP作为媒体传输的协议。本文在SIP通信过程中,采用面向连接的TCP来传输SIP的交互信令,采用面向无连接的UDP协议进行实时音频流传输。本设计是在Linux操作系统下,用套接字(socket)来实现的。设计实现了SIP协议的整个通信过程。最后,提出了进一步开发的设想。     

在Linux环境下SIP通信的实现

SIP（Session Initiatioan Protocol）协议是由IETF工作组于1997年7月提出的，是应用层的控制协议，能建立、调整和终止多媒体的呼叫和会话。SIP协议是基于文本方式的，即以明文方式传输。SIP消息包括请求消息、应答消息。SIP协议侧重于将IP电话作为因特网上的一个应用，并且也采用RTP作为媒体传输的协议。本文在SIP通信过程中，采用面向连接的TCP来传输SIP的交互信令，采用面向无连接的UDP协议进行实时音频流传输。本设计是在Linux操作系统下，用套接字（socket）来实现的。设计实现了SIP协议的整个通信过程。最后，提出了进一步开发的设想。     

基于Grover搜索的无线Mesh网流量均衡路由算法

在无线Mesh网(WMN)应用中,用户通过Mesh网关接入到Internet,这种结构容易导致不同位置的Mesh路由器通过的流量不均衡,使部分路由器成为瓶颈,从而影响网络的性能和用户的服务质量(QoS)。针对这一问题,提出了一种基于Grover量子搜索算法的无线Mesh网流量均衡路由算法。算法中利用了量子计算的并行性,根据流量均衡函数模型构建了操作矩阵,通过Grover迭代获得流量均衡路径。仿真表明,算法选择的路径可以有效地平衡无线Mesh网流量,使每用户获得的最小带宽最大化,执行效率也优于同类算法。     

基于探测的多信道无线网状网机会路由算法

多信道无线网状网的性能在很大程度上依赖于信道分配和路由选择.现有的多信道无线网状网路由大多没有考虑信道之间的干扰问题,从而导致通信性能下降.针对这一问题,提出一种基于探测的多信道无线网状网机会路由(POR)算法.首先,根据干扰能量,选出最佳通信信道集来降低信道间的传榆干扰.在此基础上,采用探测方式计算路径期望传输时延,确定候选链路集并运用机会路由机制进行数据传输以最小化端到端的传输时延.实验结果表明,POR可以显著地降低平均端到端时延,提高数据包投递率,为数据传输提供实时性和可靠性保证.     

Data forwarding based on sensor device constraints in wireless multimedia sensor networks

A variety of data forwarding schemes have been proposed for wireless multimedia sensor networks where energy awareness and reliability are essential design issues. This paper proposes a data forwarding mechanism based on sensor device constraints in wireless multimedia sensor networks. A dynamic path cost function is defined considering the constraints and characteristics of wireless multimedia sensor networks. The cost function is applied to ZigBee mesh routing, and the performance of the proposed method is evaluated using a QualNet network simulator.     

A reliable QoS-aware routing scheme for neighbor area network in smart grid

A reliable bi-directional communication network is one of the key factors in smart grid (SG) to meet application requirements and improve energy efficiency. As a promising communication infrastructure, wireless mesh network (WMN) can provide high speed and cost-effect communication for SG. However, challenges remain to maintain high reliability and quality of service (QoS) when applying WMNs to SG. In this paper, we first propose a hybrid wireless mesh protocol (HWMP) based neighbor area network (NAN) QoS-aware routing scheme, named HWMP-NQ, to meet the QoS requirements by applying an integrated routing metric to route decision with effective link condition probing and queue optimization. To further improve the reliability of the proposed HWMP-NQ, we present a multi-gateway backup routing scheme along with a routing reliability correction factor to mitigate the impact of routing oscillations. Finally, we evaluate the performances of the proposed schemes on NS3 simulator. Extensive simulations demonstrate that HWMP-NQ can distinguish different applications and satisfy the QoS requirements respectively, and also improve the average packet delivery ratio and throughput with a reduced routing overhead, even with a high failure rate of mesh nodes.     

Secure and robust multipath routings for advanced metering infrastructure

A Smart Grid is the modernization of the electricity grid using communication technology with the prime goals of reducing energy consumption as well as cost increasing reliability and creating new services for all participants. It comprises key components such as the Advanced Metering Infrastructure (AMI), which includes Neighborhood area network (NAN). When multi-hopping is considered in wireless communication, especially in WiFi and ZigBee, the range of the communication can be extended to communicate with the gateway collector in AMI network. Wireless mesh AMI network may have smart meters, a NAN gateway, and fixed as well as mobile repeaters. Though many techniques have been developed to secure on-demand routing protocols in wireless multi-hop ad-hoc networks, these protocols have shortcomings. In this paper, we propose two robust and secure multipath routing protocols for wireless mesh AMI networks. We have analyzed their robustness to various attacks. The simulation results show that the proposed protocols are better than existing secure routing protocols.     

基于路由生命期的动态源路由协议

无线Ad hoc网络拓扑结构的频繁变化以及无线信道的不稳定,使得如何提高路由可靠性成为无线Ad hoc网络路由协议研究的主要目标之一.在动态源路由协议(Dynamic Source Routing,以下简称DSR)基础上提出一个新的基于路由生命期估计的Ad hoc网络路由协议,REBDSR(Route-lifetime Estimation Based Dynamic Source Routing).该协议通过对链路状态预测估计路由生命期;路由发现算法同时使用路由生命期、路由跳数作为路径选择参数;当路由上的链路进入危险期后,启动主动式路由维护机制,发送路由失效警告以保证快速路由切换.REBDSR还以路由生命期为超时值进行路由缓存管理,解决了DSR路由缓存中存在较多过时路由的问题.大量仿真实验表明:在网络中载和重载情况下,REBDSR协议的整体性能要优于DSR协议,特别是在节点运动频繁的网络中,REBDSR协议的性能优势更为明显.     

无线mesh网中基于蚁群算法的多约束QoS路由研究

针对多约束QoS路由问题的求解,现今并没有有效的近似算法,一般采用启发式算法求解。先介绍了QoS、QoS的各种参数指标以及多约束QoS路由的定义,接着通过移动Ad-hoc网和无线mesh网络的异同的比较,根据Ad-hoc网络的研究现状,分析了蚁群算法在无线mesh网络中QoS研究的可行性。     

A quality based routing protocol for wireless mesh networks

Wireless mesh networks can provide low-cost solutions for extending the reach of wireless access points by using multi-hop routing over a set of stationary wireless routers. The routing protocol for these networks may need to address quality considerations to meet the requirements of the user. In this paper, we present a quality based routing protocol for wireless mesh networks that tries to maximize the probability of successful transmissions while minimizing the end-to-end delay. The proposed routing protocol uses reactive route discoveries to collect key parameters from candidate routes to estimate the probability of success and delay of data packets transmitted over them. To achieve accurate route quality assessments, a new route quality metric is proposed that uses performance models of data packet transmissions as opposed to estimating route quality from the transmission of control packets, which have different transmission characteristics. These models are developed after careful evaluations of multi-hop wireless transmissions and validated by computer simulations. Relevant parameters that can be used to assess the route quality metric using these models are explained. Extensive performance evaluations of the proposed quality based routing protocol are presented and its benefits in comparison to some other known routing protocols are discussed.     

航空集群网络可靠性估计路由选择策略

针对未来航空集群网络中节点间通信可靠性保障问题,提出一种基于移动预测的链路可靠性估计路由选择策略。首先,使用基于地理位置的移动预测方法对邻居节点的位置进行准确预测。其次,根据预测结果对当前节点的通信范围进行分区,对不同邻居节点所在区域的链路可靠性分别估计得到相应的可靠性估计函数值。根据得到的可靠性函数值使用概率选择模型并结合跳数因子进行路由选择。最后,以优化链路状态路由协议（Optimized Link State Routing protocol,OLSR）为基础对路由选择策略细节进行描述,并仿真验证了提出的路由选择策略的有效性。实验结果表明,该策略在适用于航空集群网络的基础上,能有效提高网络中节点间通信的可靠性。     

An anonymous distributed routing protocol in mobile ad-hoc networks

This paper proposes an efficient anonymous routing protocol for mobile ad hoc networks (MANETs). This protocol considers symmetric and asymmetric links during the wireless communication of MANETs. A MANET is one type of self-organized wireless network that can be formed by several wireless devices such as laptops, tablet PCs, and smartphones. Different wireless transmission ranges of different mobile devices lead to a special communication condition called an asymmetric link. Most research on this topic focuses on providing security and anonymity for the symmetric link without considering the asymmetric link. This paper proposes a novel distributed routing protocol beyond the symmetric and asymmetric links. This protocol guarantees the security, anonymity, and high reliability of an established route by avoiding unreliable intermediate nodes. The routes generated by the proposed protocol are shorter than previous research. The proposed protocol enhances MANET performance in assuring security and anonymity.     

Hierarchical agent-based secure and reliable multicast in wireless mesh networks

We propose and analyze a hierarchical agent-based secure and reliable multicast (HASRM) algorithm for efficiently supporting secure and reliable mobile multicast in wireless mesh networks, with design considerations given to minimize the overall network cost incurred by reliable multicast packet delivery, mobility management, security key management, and group membership maintenance. HASRM dynamically maintains a group of multicast agents running on mesh routers for integrated mobility and multicast service management and leverages a hierarchical multicast structure for secure and reliable multicast data delivery. The regional service size of each multicast agent is a key design parameter. We show via model-based performance analysis and simulation validation that there exists an optimal regional service size that minimizes the overall communication cost and the optimal regional service size can be dynamically determined. We demonstrate that HASRM under optimal settings significantly outperforms traditional algorithms based on shortest-path multicast trees extended with user mobility, security, and reliability support. We also show that a variant of HASRM is superior to a recently proposed multicast algorithm for secure group communication in wireless mesh networks.