一种基于象限转发概率的地理多播协议

针对三维空间中移动自组网的地理多播问题进行了研究,为降低传输开销并提高多播成功率,提出了一种新的基于象限转发概率的地理多播协议。该协议以发送节点为原点建立笛卡尔坐标系簇,根据转发节点与目标区域的相对位置将三维空间划分为四类转发区域,并为不同区域中的转发节点指派合理的转发概率。该协议实现了方向性转发和概率转发的综合运用,既考虑了目标位置的方向性以节省传输开销,又加入了概率广播以提高成功率。通过仿真实验与协议对比,该协议能够在保证地理多播成功率的情况下,减少传输开销,具有较好的可扩展性。     

Performance evaluation of dynamic probabilistic broadcasting for flooding in mobile ad hoc networks

In mobile ad hoc networks (MANETs), flooding is a required message dissemination technique for network-wide broadcast. The conventional blind flooding algorithm causes broadcast storm problem, a high number of unnecessary packet rebroadcasts thus resulting in high contention and packet collisions. This paper proposes a new probabilistic approach that dynamically fine-tunes the rebroadcasting probability of a node for routing request packets (RREQs) according to the number of neighbour nodes. We evaluate the performance of the proposed approach for the ad hoc on demand distance vector (AODV) routing protocol and compared against the blind flooding, fixed probabilistic and adjusted probabilistic flooding [L.M.M.M. Bani-Yassein, M. Ould-Khaoua et al., Performance analysis of adjusted probabilistic broadcasting in mobile ad hoc networks, International Journal of Wireless Information Networks 13(2) (2006) 127–140; M.B. Yassein, M.O. Khaoua et al., Improving route discovery in on-demand routing protocols using local topology information in MANETs, Proceedings of the ACM international workshop on Performance Monitoring, Measurement, and Evaluation of Heterogeneous Wireless and Wired Networks, Terromolinos, Spain, ACM Press, 2006, pp. 95–99.] approaches. The simulation results show that our proposed approach demonstrates better performance than blind flooding, fixed probabilistic and adjusted flooding approaches.     

Dynamic probabilistic broadcasting in MANETs

In mobile ad hoc networks (MANETs), the efficiency of broadcasting protocol can dramatically affect the performance of the entire network. Appropriate use of a probabilistic method can reduce the number of rebroadcasting, therefore reduce the chance of contention and collision among neighboring nodes. A good probabilistic broadcast protocol can achieve higher throughput and lower energy consumption, without sacrificing the reachability or having any significant degradation. In this paper, we propose a probabilistic approach that dynamically adjusts the rebroadcasting probability as per the node distribution and node movement. This is done based on locally available information and without requiring any assistance of distance measurements or exact location determination devices. We evaluate the performance of our approach by comparing it with the AODV protocol (which is based on simple flooding) as well as a fixed probabilistic approach. Simulation results show our approach performs better than both simple flooding and fixed probabilistic schemes.     

基于局部邻居节点和链路权值的改进AODV路由协议

在节点高速移动的Ad Hoc网络环境中,广播风暴对网络性能的影响尤为重要,且网络拓扑结构的频繁变化极易导致路由中断.传统的AODV路由协议在路由发现阶段直接使用广播转发RREQ（路由请求分组）机制,容易导致广播风暴降低网络性能;同时,协议选择跳数最少的路径作为路由,没有考虑到节点的快速移动导致路由频繁失效,因此无法适应节点高速移动的网络环境.针对上面存在的问题,提出一种对AODV进行改进的协议.该协议在路由发起过程中,基于局部邻居节点数量计算动态转发概率;选择路由时,利用跨层思想,结合网络节点移动速度提出链路权值,依据链路权值选择路由路径.NS2仿真结果表明：该改进协议提高了数据包的投递率,缩短了端到端的传输时延,能够更好地适应节点高速移动的网络环境.     

节点度估计和静态博弈转发策略的Ad Hoc网络路由协议

针对Ad Hoc网络路由发现过程中广播路由请求分组导致的广播风暴问题，提出了一种基于节点度估计和静态博弈转发策略的Ad Hoc网络路由协议NGRP.NGRP考虑边界影响，采用分段函数的思想将网络场景分为中心、边和角区域，分别估算网络中节点在不同区域的节点度，避免了周期性广播Hello消息获取节点度导致的开销；NGRP路由请求分组的转发采用静态博弈转发策略，利用节点度估算参与转发路由请求分组的节点数量，将转发和不转发作为策略集合，设计效益函数，通过纳什均衡获得节点转发路由请求分组的转发概率，从而减少了路由请求分组广播过程中产生的大量的冗余、竞争和冲突，提高了路由发现过程中路由请求分组的广播效率.运用NS-2对协议的性能进行大量的仿真，结果表明：NGRP的分组投递率、路由开销、MAC层路由开销和吞吐率这4项指标明显优于AODV+FDG，AODV with Hello和AODV without Hello协议.     

Efficient Broadcasting Using Network Coding and Directional Antennas in MANETs

In this paper, we consider the issue of efficient broadcasting in mobile ad hoc networks (MANETs) using network coding and directional antennas. Network coding-based broadcasting focuses on reducing the number of transmissions each forwarding node performs in the multiple source/multiple message broadcast application, where each forwarding node combines some of the received messages for transmission. With the help of network coding, the total number of transmissions can be reduced compared to broadcasting using the same forwarding nodes without coding. We exploit the usage of directional antennas to network coding-based broadcasting to further reduce energy consumption. A node equipped with directional antennas can divide the omnidirectional transmission range into several sectors and turn some of them on for transmission. In the proposed scheme using a directional antenna, forwarding nodes selected locally only need to transmit broadcast messages, original or coded, to restricted sectors. We also study two extensions. The first extension applies network coding to both dynamic and static forwarding node selection approaches. In the second extension, we design two approaches for the single source/single message issue in the network coding-based broadcast application. Performance analysis via simulations on the proposed algorithms using a custom simulator and ns2 is presented.     

一种基于逢低买入的频谱分配机制

为解决移动自组织网络(MANET)中网络拥塞导致的网络时延增大和吞吐量下降, 提出一种基于概率的负载均衡算法, 节点利用历史负载信息映射网络负载状态, 用概率算法进行路由准入, 从而完成负载均衡。基于历史状态的负载映射有效解决了分布式独立运算中存在的负载状态判断困难等问题, 概率算法能有效克服门限准入法则存在的模糊判别问题, 同时大量减少广播包的洪泛, 节省信道资源。结合经典的按需路由协议, 设计了H&P_DSR(History and Probability Based Dynamic Source Routing)协议。仿真和理论分析一致表明, 该负载均衡算法能够准确有效的对网络负载进行均衡, H&P_DSR协议在没有增加任何信道开销的情况下显著提高了网络吞吐量, 降低了时延。     

基于模糊控制的Ad Hoc网络QoS优先调度算法

无线移动Ad Hoc网络(MANET)作为可移动分布式多跳无线网络,没有预先确定的网络拓扑或网络基础设施以及集中控制.由于移动Ad Hoc网络的动态性和资源的限制,在如此的网络中提供QoS保障是一个挑战性任务.Ad Hoc网络的分组优先级凋度算法将增进网络的性能.提出了一个基于模糊控制的Ad Hoc网络QoS优先调度算法,用于决定Ad Hoc网络中分组的优先级.利用NS2仿真软件对分组的传输率、平均端对端的延迟等做了性能分析,仿真结果表明,该方法高效、可行,可应用于Ad Hoc网络.     

VANET中一种基于概率转发的AODV路由协议

泛洪被作为实现广播通信的最简单的技术,广泛应用于车联网VANET(vehicular Ad Hoc network)路由.然而,由于VANET中节点的快速移动以及网络拓扑动态变化,简单的泛洪容易导致大量的冗余数据包,并引发广播风暴.为此,以典型的按需式距离矢量路由协议AODV (Ad Hoc on-demand distance vector)为基础,提出基于概率转发的AODV路由协议,记为AODV_P.AODV_P协议利用概率转发机制替代AODV中的泛洪.节点利用距离、密度信息计算转发概率,并依据转发概率设置计时器.计时器时间越短,成为下一跳转发节点的可能性越大.仿真结果表明,提出的AODV_P能够有效降低冗余数据包,缓解广播风暴问题.与AODV协议相比,AODV_P在传输时延、数据包传输率方面得到了有效提高.     

按需式ad hoc移动网络路由协议的研究进展

Ad hoc移动网络是一种完全由移动主机构成的网络，网络拓扑易变，带宽，能源有限是ad hoc移动网络的主要特点，针对这些特点，目前设计的ad hoc路由协议大多采用按需查找方式，该文介绍了这方面研究的最新进展，对几种典型的按需路由协议进行了说明，分析和综合比较，文中分析了目前协议存在的一些问题并提出了相应的改进方法，最后指出了下一步研究方向。     

Analysis of a Randomized Congestion Control Scheme with DSDV Routing in ad Hoc Wireless Networks

Ad hoc wireless networks are expected to play an increasingly important role in future civilian and military settings where wireless access to a wired backbone is either ineffective or impossible. However, frequent topology changes caused by node mobility make routing in ad hoc wireless networks a challenging problem. In addition, limited capabilities of mobiles require a control on node congestion due to message forwarding.  In this paper, we present a randomized version, called R-DSDV, of the known destination-sequenced distance vector (DSDV) routing protocol for ad hoc networks and analyze its capabilities for distributed congestion control. The analysis is based on a novel approach that uses Markov chains for representing the distribution of routing information over the network. Our results indicate that a probabilistic congestion control scheme based on local tuning of protocol parameters is feasible and that such a mechanism can be effective in reducing the amount of traffic routed through a node which is temporarily congested. The traffic reduction is almost linear with respect to the decrease in the R-DSDV routing table advertisement rate of the congested node. On an average, the convergence time is relatively small as compared to the transmission rates of protocol messages.     

Performance analysis of broadcast protocols in ad hoc networks based on self-pruning

Self-pruning is an effective scheme for efficient broadcasting in ad hoc wireless networks. In a self-pruning broadcast protocol, a node may not forward a broadcast packet if a certain self-pruning condition is satisfied based on the neighborhood information. In a static network with an ideal MAC layer, only a subset of nodes forward the broadcast packet and still guarantee the complete network delivery. Various protocols have been proposed with different self-pruning conditions. Recently, a generic self-pruning protocol was proposed by Wu and Dai (2003), which combines the strength of previous conditions and is more effective. In this paper, we first propose an enhanced version of the generic protocol, which is more elegant in interpreting existing protocols and has a simpler correctness proof. Then, we evaluate the performance of the family of self-pruning protocols under various network situations with ns2. The objective is to observe the efficiency and reliability of these protocols as a function of network density, congestion, and mobility, and provide a guideline of implementation in the "real world". Our performance analysis reveals that the protocol reliability is barely affected by packet collision. However, most self-pruning protocols suffer from low delivery ratio in highly mobile networks. We further explore various techniques that improve the delivery ratio and show that both high efficiency and reliability can be achieved in highly mobile networks.     

基于WMPLS的安全自组网路由协议

基于WMPLS协议体系,结合无线移动自组网的特点,同时考虑路由的安全性,本文提出了一种基于WMPLS的安全自组网路由协议SA-WMPLS.该协议不仅提高了选路的性能,简化了转发机制,而且中间节点操作简单,能够有效抵御多种攻击方式,在实际应用中将具有较大的可行性.     

AHBP: An efficient broadcast protocol for mobile Ad hoc networks

Broadcast is an important operation in many netowkr protocols.It is utilized to discover routes to unknown nodes in mobile ad hoc networks(MANETs) and is the key factor in scaling on -demand routing protocols to large networks.This paper presents the Ad Hoc Broadcast Protocol(AHBP)and its performance is discussed.In the protocol,messages,are only rebroadcast by broadcast relay gateways that constitute a connected dominating set of the network.AHBP can efficiently reduce the redundant messages which make flookding-like protocols perform badly in large dense networks.Simulations are conducted to determine the performance characteristics of the protocol.The simulation results have shown excellent reduction of broadcast redundancy with AHBP.It also contributes to a reduced level of broadcast collision and congestion.     

Efficient broadcasting in ad hoc wireless networks using directional antennas

Using directional antennas to conserve bandwidth and energy consumption in ad hoc wireless networks (or simply ad hoc networks) is becoming popular. However, applications of directional antennas for broadcasting have been limited. We propose a novel broadcast protocol called directional self-pruning (DSP) for ad hoc wireless networks using directional antennas. DSP is a nontrivial generalization of an existing localized deterministic broadcast protocol using omnidirectional antennas. Compared with its omnidirectional predecessor, DSP uses about the same number of forward nodes to relay the broadcast packet, while the number of forward directions that each forward node uses in transmission is significantly reduced. With the lower broadcast redundancy, DSP is more bandwidth and energy-efficient. DSP is based on 2-hop neighborhood information and does not rely on location or angle-of-arrival (AoA) information. Two special cases of DSP are discussed: the first one preserves shortest paths in reactive routing discoveries; the second one uses the directional reception mode to minimize broadcast redundancy. DSP is a localized protocol. Its expected number of forward nodes is O(1) times the optimal value. An extensive simulation study using both custom and ns2 simulators show that DSP significantly outperforms both omnidirectional broadcast protocols and existing directional broadcast protocols.     

Neighborhood tracking for mobile ad hoc networks

In mobile ad hoc networks (MANETs), node mobility causes network topologies to change dynamically over time, which complicates such important tasks as broadcasting and routing. In a typical efficient localized approach, each node makes forwarding decisions based on a neighborhood local view constructed simply by collecting received “Hello” messages. That kind of neighborhood local view can become outdated and inconsistent, which induces a low-coverage problem for efficient broadcasting tasks and a low-delivery ratio problem for efficient routing tasks. In this paper, we propose a neighborhood tracking scheme to guarantee the accuracy of forwarding decisions. Based on historical location information, nodes predict the positions of neighbors when making a forwarding decision, and then construct an updated and consistent neighborhood local view to help derive more precise forwarding decisions. The inaccuracy factors of our scheme are also discussed and an accessory method is provided for possible usage. Simulation results illustrate the accuracy of our proposed tracking scheme. To verify the effectiveness of our scheme, we apply it to existing efficient broadcast algorithms. Simulation results indicate that our neighborhood tracking scheme can improve the protocols coverage ratio greatly.     

一种适用于Ad hoc网络的基于概率负载均衡算法

为解决移动自组织网络(MANET)中网络拥塞导致的网络时延增大和吞吐量下降, 提出一种基于概率的负载均衡算法, 节点利用历史负载信息映射网络负载状态, 用概率算法进行路由准入, 从而完成负载均衡。基于历史状态的负载映射有效解决了分布式独立运算中存在的负载状态判断困难等问题, 概率算法能有效克服门限准入法则存在的模糊判别问题, 同时大量减少广播包的洪泛, 节省信道资源。结合经典的按需路由协议, 设计了H&P_DSR(history and probability based dynamic source routing)协议。仿真和理论分析一致表明, 该负载均衡算法能够准确有效地对网络负载进行均衡, H&P_DSR协议在没有增加任何信道开销的情况下显著提高了网络吞吐量, 降低了时延。     

一种移动自组网中简单高效的广播算法

全网范围的广播在移动自组网中有着相当广泛的应用.基于计数器的广播算法非常适合于高速移动的网络环境.在基于计数器的广播算法的基础上提出了一种简单高效的广播算法--CBB+.理论分析和大量仿真结果表明,CBB+算法相对于原基于计数器的广播算法而言,广播的达到率有着较大的提高,并且能够减少再广播分组的发送数量,降低了广播时延.     

Anonymous Geo-Forwarding in MANETs through Location Cloaking

In this paper, we address the problem of destination anonymity for applications in mobile ad hoc networks where geographic information is ready for use in both ad hoc routing and Internet services. Geographic forwarding becomes a lightweight routing protocol in favor of the scenarios. Traditionally the anonymity of an entity of interest can be achieved by hiding it among a group of other entities with similar characteristics, i.e., an anonymity set. In mobile ad hoc networks, generating and maintaining an anonymity set for any ad hoc node is challenging because of the node mobility, consequently the dynamic network topology. We propose protocols that use the destination position to generate a geographic area called {em anonymity zone (AZ)}. A packet for a destination is delivered to all the nodes in the AZ, which make up the anonymity set. The size of the anonymity set may decrease because nodes are mobile, yet the corresponding anonymity set management is simple. We design techniques to further improve node anonymity and reduce communication overhead. We use analysis and extensive simulation to study the node anonymity and routing performance, and to determine the parameters that most impact the anonymity level that can be achieved by our protocol.     

一种结合路径跳数和转发组成员数的优化组播路由协议

在深入分析ODMRP组播协议的基础上,本文提出了将传输节点分成不同类型的策略,并在此基础上提出了一种结合路径跳数和转发组成员数的组播路由协议HF-ODMRP(OptimalMulticastProtocolwithHopsandFGsbasedonODMRP).在HF-ODMRP协议中,节点根据网络已有的转发信息将自身标记为普通节点、FG(ForwardingGroup)节点的邻居或FG节点,并赋予不同的权值.在建立路由的过程中,每个节点首先计算路径上节点的累计权值和路径的总跳数,并优先选择具有两者比值最大的路径上的节点构成FG,从而使得发送者和接收者之间既可以共用更多FG节点,降低了转发组中冗余FG节点个数,又可以提高了组播协议的有效性.模拟结果验证HF-ODMRP不仅对动态拓扑具有良好的适应性,而且大大提高了组播协议的数据转发有效性和能源消耗有效性.