无线白组织网中VoIP性能研究

目前,VoIP技术及其业务迅速发展,在无线自组织网络中有广泛的应用,有必要对于VoIP在无线自组网中的传输进行分析研究。利用NS-2作为仿真工具对G.711编码标准下多跳无线自组织网中VoIP的传输进行仿真,使用802．11MAC层协议和AODV路由层协议。实验结果表明,无线自组织网络环境下voIP系统性能（包括丢包率、时延等）受到多跳影响。     

无线Mesh网中实时数据业务仿真与分析

无线Mesh网络是一种架构式多跳无线网络,具有结构灵活、快速部署、自组织和自愈合等优点,具有广泛的应用前景。通过采用ns-2仿真软件对基于IEEE 802.11 MAC协议和AODV路由协议的无线Mesh网中实时数据业务的数据传输进行建模与仿真,分析了Mesh网络中数据流经过的传输跳数与吞吐率的关系,以及MAC层RTS/CTS、重传次数以及MAC层和路由层相互作用对无线Mesh网中实时数据业务性能的影响,指出了提高无线Mesh网中实时数据业务性能的所需要的改进方向。     

无线Ad hoc网络机会路由的实现与仿真

在无线自组织网络中,路由协议对网络的性能起着关键性作用。然而由于无线信道的不稳定性经常造成通信中断而需重建路由,使自组织网传统路由协议的效率大大降低。提出了一种应用于无线自组织网络的机会路由协议（WAOR）,利用无线信道的广播特性和多径传输来增强链路的可靠性。采用网络仿真器NS2的仿真结果表明,WAOR的性能优于传统的动态源路由协议（DSR）和自组织网按需平面距离矢量路由协议（AODV）。     

无线自组网络的技术研究

随着通信技术的快速发展和人们对通信要求的提高,无线自组织网成为当今网络的重要研究内容。无线自组织网络由几个可移动的无线节点自组织形成的一个多跳、灵活、无中心的网络,这些特点为它在军事和民用通信领域提供了有利保证。文章首先介绍了无线自组网的特点和应用;其次对现有路由协议存在的问题进行了研究;最后针对无线自组网存在的能量消耗,多路径,多播等问题归纳出了的六种方法对系统进行优化,提高了无线自组网络的传输性能。     

基于IEEE802.11 DCF的链路预先修复AODV路由协议

基于无线自组织网络中普遍使用的底层通信协议IEEE802.11 DCF,针对广泛应用于无线自组织网络中的路由协议(AODV),提出了一种链路预先修复算法。该算法首先推算了DCF协议中的不稳定传输范围,然后通过MAC层与路由层的跨层协作,在下一跳节点移动在不稳定传输范围时就事先采取相应的路由修复措施。相对于AODV中采用节点周期性地发送HELLO消息来监测邻居节点变化的方法,该算法更为高效及时。仿真结果表明,该算法能够有效的减小端到端时延,保障了投递率。     

Ad Hoc网路由协议在常规靶场中的应用及仿真

在试验通信系统IP化改造的要求下,建设基于多跳路由协议的无线移动自组织(Ad Hoc)试验通信网是必然的选择。传统的试验通信系统多采用集中控制的点对多点星状网,而移动自组网属于网状网,采用完全不同的组网方式,其对特定试验保障通信业务的承载能力,以及路由协议的适应性目前尚没有试验数据可供参考。对自组网路由协议在试验通信中的应用进行研究,根据想定试验场景对网络性能进行仿真分析,分别仿真了4种路由协议的数据包成功递交率、平均吞吐量以及平均时延等网络性能。仿真结果表明,4种路由协议中有3种协议综合性能完全可以满足试验通信保障任务。     

短波自组织网络HFMACA协议研究

在研究无线多路访问碰撞回避协议MACAW的基础上,针对短波无线自组织网络的分布式控制、网络拓扑结构动态变化、存在隐藏终端和暴露终端等特点,对MACAW进行了适当改进,提出了短波多路访问碰撞回避协议HFMACA,详细介绍了其基本思想、运行机制,并对其网络容量、业务成功率、业务传输时延等性能进行了仿真分析,给出了网络业务量与业务成功率及传输时延之间的关系,对短波自组织网MAC协议的研究和设计具有一定的参考意义。     

一种面向会展中心的无线自组网MAC层协议的设计

文中研究了无线令牌环协议,将MAC层的WTRP协议应用于无线自组网中,采用WTRP协议优化了会展企业中心无线自组织网络.重点介绍了WTRP协议的状态机以及控制机制,模型中的节点通过令牌获得网络的使用权,而令牌在节点之间传递,并以公平和效率为原则.网络仅需要时令牌进行管理和维护,而不需要对网络中的数据进行管理,使得数据在网络中进行透明的传输,增加了网络的保密性.通过仿真验证了模型的正确性,减少了数据包在网络节点中的等待时间,使得会展企业活动越来越便捷.     

802.11MAC协议仿真性能分析

自组织网是随着无线通信技术的快速发展而出现的一种新型多跳对等网络。由于它自身的特殊性,使得媒体接入控制协议(MAC)与传统的有线局域网、无线局域网以及蜂窝网络有很大的区别。MAC协议是自组织网协议的基础,它控制着节点对无线媒体的占用,对自组织网整体性能的提高起着决定性的作用。     

无线Mesh网QoS研究

无线Mesh网由于无线链路自身的不稳定性以及多跳传输带来的隐藏/暴露终端等问题,使得提供QoS保障带来更大挑战.对Mesh网各协议层为支持QoS所做的研究进行归纳,总结分析了已有的支持Mesh网QoS的跨层设计方案.指出了无线Mesh网络提供QoS保障的进一步研究方向.     

Upper bounding service capacity in multi-hop wireless SSMA-based ad hoc networks

Upper bounds on the service carrying capacity of a multi-hop, wireless, SSMA-based ad hoc network are considered herein. The network has a single radio band for transmission and reception. Each node can transmit to, or receive from, multiple nodes simultaneously. We formulate the scheduling of transmissions and control of transmit powers as a joint, mixed-integer, nonlinear optimization problem that yields maximum return at minimum power subject to SINR constraints. We present an efficient tabu search-based heuristic algorithm to solve the optimization problem and rigorously assess the quality of the results. Through analysis and simulation, we establish upper bounds on the VoIP call carrying capacity of the network as function of various parameters. We discuss the pros and cons of using SSMA as a spectrum sharing technique in wireless ad hoc networks.     

On-Demand Multicast Routing Protocol in Multihop Wireless Mobile Networks

An ad hoc network is a dynamically reconfigurable wireless network with no fixed infrastructure or central administration. Each host is mobile and must act as a router. Routing and multicasting protocols in ad hoc networks are faced with the challenge of delivering data to destinations through multihop routes in the presence of node movements and topology changes. This paper presents the On-Demand Multicast Routing Protocol (ODMRP) for wireless mobile ad hoc networks. ODMRP is a mesh-based, rather than a conventional tree-based, multicast scheme and uses a forwarding group concept; only a subset of nodes forwards the multicast packets via scoped flooding. It applies on-demand procedures to dynamically build routes and maintain multicast group membership. ODMRP is well suited for ad hoc wireless networks with mobile hosts where bandwidth is limited, topology changes frequently, and power is constrained. We evaluate ODMRP performance with other multicast protocols proposed for ad hoc networks via extensive and detailed simulation.     

Wireless Ad Hoc Multicast Routing with Mobility Prediction

An ad hoc wireless network is an infrastructureless network composed of mobile hosts. The primary concerns in ad hoc networks are bandwidth limitations and unpredictable topology changes. Thus, efficient utilization of routing packets and immediate recovery of route breaks are critical in routing and multicasting protocols. A multicast scheme, On-Demand Multicast Routing Protocol (ODMRP), has been recently proposed for mobile ad hoc networks. ODMRP is a reactive (on-demand) protocol that delivers packets to destination(s) on a mesh topology using scoped flooding of data. We can apply a number of enhancements to improve the performance of ODMRP. In this paper, we propose a mobility prediction scheme to help select stable routes and to perform rerouting in anticipation of topology changes. We also introduce techniques to improve transmission reliability and eliminate route acquisition latency. The impact of our improvements is evaluated via simulation.     

A distributed Newton algorithm for network utility maximization in wireless ad hoc networks

The existing distributed Newton algorithm for network utility maximization cannot be directly applied into the wireless ad hoc networks, as it does not consider the wireless link capacity variation and transmission power consumption. Regarding these, a new joint network utility maximization problem is formulated to optimize the wireless ad hoc network resource utility. The distributed Newton algorithm is implemented to solve for the dual variables and Newton directions by using the local information at each session source and link, respectively. Furthermore, a new iterative method is proposed to improve the convergence rate of the existing matrix‐splitting method. Simulation results validate the efficiency and efficacy of the proposed distributed Newton algorithm for wireless ad hoc network utility maximization.     

无线自组网SIP协议可靠性机制设计

随着无线自组网的发展,无线自组网提供实时多媒体业务成为重要的应用需求。作为下一代网络NGN中提供多媒体业务的SIP协议,应用于无线自组网时（特别是网络不可用时）,会出现不提示用户、提示不及时、误振铃、资源泄漏等问题。通过深入分析发现标准SIP协议的可靠性机制还不够完善,因此设计了proceeding状态超时、180响应重复发送、实时感应、紧急巡查等新的可靠性机制,建议提高180响应的重要性并将可靠临时响应机制运用到180响应,建议有状态SIP服务器必须使用SessionTimer（会话保持）机制,由此形成了比较完善的SIP协议可靠性机制。测试结果表明,完善后的SIP协议可靠性机制有效解决了网络不可用时引起的问题,在无线自组网中具有较好的适应性。     

无人机自组网技术研究

在无人机系统中,编组和协同作战能力对提高无人机作站效能和生存能力具有重要意义。无线自组网是一种特殊结构的无线通信网络,其通信依靠节点之间的相互协作,以无线多跳方式完成,因此网络不依赖于任何固定设施,具有自组织和自管理的特性,这种特殊的组网方式使得无线自组网非常适用于无人机系统。介绍了无线自组网的原理,分析了无线自组网应用于无人机系统主要面临的关键技术:路由技术和安全问题。介绍了无线自组网的发展情况和在无人机领域的研究情况。     

无线自组织网络MAC帧传输技术研究

无线自组织网络是近年来科学研究的热点领域之一,具有很强的实际应用价值和广泛的应用前景。实现MAC帧传输是无线自组织网络要解决的关键问题之一。采用基于路由的传输方式,可以有效实现MAC帧传输。首先通过路由生成协议和路由维护协议建立起稳定的路由,然后MAC帧将源节点中的路由封装到MAC帧头作为传输路径,最后MAC帧沿路由预定的路径,以多跳中继的方式到达目的节点。     

认知无线Ad hoc网络的认知体系结构研究

对认知无线Ad hoc网络进行了阐述。对于认知无线Ad hoc网络,要考虑到无线Ad hoc网络的整体特点,来研究网络级认知结构。而由于认知无线Ad hoc网络是基于无线Ad hoc网络体系结构,同时鉴于无线Ad hoc网络本身特点,因此网络体系参数和网络本身特性参数共同被定义为认知信息,并在与跨层设计结合基础上进行节点级认知结构设计。认知信息的获取与传输方式将认知无线Ad hoc网络网络级与节点级结构有机地联合起来,使整个认知体系成为完整有机体。     

Approximate minimum-energy multicasting in wireless ad hoc networks

A wireless ad hoc network consists of mobile nodes that are equipped with energy-limited batteries. As mobile nodes are battery-operated, an important issue in such a network is to minimize the total power consumption for each operation. Multicast is one of fundamental operations in any modern telecommunication network including wireless ad hoc networks. Given a multicast request consisting of a source node and a set of destination nodes, the problem is to build a minimum-energy multicast tree for the request such that the total transmission power consumption in the tree is minimized. Since the problem in a symmetric wireless ad hoc network is NP-complete, we instead devise an approximation algorithm with provable approximation guarantee. The approximation of the solution delivered by the proposed algorithm is within a constant factor of the best-possible approximation achievable unless P = NP.