基于线性网络编码的无线网络信道接入机制

为了提高无线自组织网络的通信性能,针对当前网络信道接入机制存在的不足,提出一种基于线性网络编码的信道接入机制(LNC)。首先对传统网络信道接入机制的工作原理和缺陷进行分析,然后采用线性网络编码方式提高数据包传输效率,最后运用马尔科夫链模型对LNC进行数学建模,并通过仿真实验对其性能进行分析。仿真实验结果表明,相对于传统网络信道接入机制,LNC不仅提高了网络的吞吐量,降低了节点的数据包丢失率,而且提高了信道利用率。     

中小型Ad hoc网络信道接入协议研究

在介绍了Ad hoc网络的概念及特点的基础上,系统地论述了Ad hoc网络的多址接入技术,并针对基于时分多址接入的网络系统提出了一种改进的无线自组网信道接入协议--信道预约多址接入协议.该协议通过对物理信道的动态划分,将控制信道与业务信道相分离,实现了网络控制信息和业务信息的无冲突发送,改善了网络的信道利用率和传输的可靠性.     

IEEE 802．11无线自组织网络服务质量机制研究

IEEE 802．11无线自组织网络中采用随机方式接入无线信道，提供服务质量(QoS）保证难度很大。目前已提出媒体接入层机制以改进无线自组织网络服务质量。但单纯的媒体接入层服务质量机制同样具有较大局限性。本文系统分析比较了不同无线自组织网络环境下媒体接入层和网络层服务质量机制的性能，基于上述分析结果，提出一种跨层自组织网络服务质量机制。     

基于多接口状态字的VANET信道接入算法研究

为了实现多接口车载自组织网络(VANET)车辆节点合理高效的信道接入,提出了一种基于车辆节点多接口状态字的时分竞争信道接入算法。根据车辆节点的多接口状态字给出了时隙划分的方法与竞争退避机制原则,通过综合考虑竞争类技术与时分多址技术的优点,有效解决了信道公平接入的问题。通过软件仿真比较可以看出,该算法实现了信道的合理接入,减小了平均端到端时延,增加了网络平均吞吐量,显著提高了多接口VANET的网络性能。     

一种多接口多信道VANET动态信道分配算法研究

为了合理地实现多接口多信道车载自组织网络（VANET）车辆节点间通信信道的动态分配,提出了一种基于通信双方车辆节点信道切换队列的动态信道分配算法。定义了车辆节点的射频接口状态,给出了信道的性能因子以及信道切换队列的生成方法,通过综合考虑通信双方车辆节点的射频接口状态和信道切换队列,快速自主地建立通信链路,从而解决了信道公平接入和分配不合理的问题。通过软件仿真比较可以看出,该算法实现了信道的动态分配,减小了平均端到端时延,增加了网络平均吞吐量,显著提高了多接口多信道VANET的网络性能。     

基于多步信道预约机制的多址接入协议研究

无线自组织网络(Ad Hoc网络)中实时业务的传输需要网络协议提供较为可靠的服务质量保证(Qos保证),而现有多址接入协议一般未能提供较好的Qos支持。在单步信道预约思想的基础上,提出了一种基于更为可靠的多步信道预约机制的多址接入协议,其利用实时业务分组的周期性特点,对无线信道资源进行多步预约,从而保证了实时业务的可靠传输。仿真实验表明,相较于单步信道预约机制,多步信道预约机制对网络的多址接入性能有较好的改进。     

车载自组织网络中基于时分复用的异步多信道MAC协议

为解决车载自组织网络负载较重时控制信道拥塞和信道利用率低的问题,提出一种时分复用机制的异步车载自组织网多信道MAC(Media Access Control)协议-ATMP (Asynchronous TDMA-based multi-channel MAC Protocol).ATMP协议采用时分复用的异步接入机制实现节点分时段接入控制信道,减少并发接入控制信道的节点数目,降低碰撞概率;进一步,为了解决多信道协调信息丢失问题,ATMP协议使用节点协作机制来获取节点遗漏的信道协调信息,有效降低因协调信息缺失造成的数据信道服务信息碰撞概率.仿真结果表明,ATMP协议在碰撞概率、安全消息时延及控制信道吞吐量指标上优于IEEE 1609.4标准、AMCP协议和AMCMAC协议.     

基于时分复用的车载自组织网多信道MAC协议

为解决车载自组织网络负载较重时控制信道拥塞和IEEE1609.4标准中信道利用率低的问题,提出一种使用时分复用机制的VANET多信道MAC协议。协议采用节点分时段接入控制信道的机制来降低冲突概率,规定每个节点使用两部收发机来避免数据信道空闲;使用一个优化模型确定退避过程参数,以最大化饱和吞吐量。仿真结果表明该协议具备优良的吞吐量性能,能给出较低的,稳定的安全信息时延。     

基于报文监听的Ad Hoc网络双信道接入协议

首先提出了基本的报文监听协议DCMA_BPS,并对控制报文的长度和协议的特性进行了分析,又提出了信道接入协议DCMA_PSBI,通过BI控制报文来阻止隐终端发送数据报文。仿真分析表明,DCMA_PSBI是一种非常高效实用的基于报文监听的Ad Hoc网络双信道接入协议。     

自组网中一种基于显式通知的信道接入协议

提出一种基于显示通知的信道接入协议.通过采用发送CCS帧的方法通知竞争失败的节点进行适时通信,能有效降低退避节点盲目等待时间,同时也减少了隐/显接收终端造成报文冲突丢弃的概率.仿真结果表明,该协议能有效地提高自组织网络的吞吐量、公平性和业务流的稳定性能.     

An on-demand routing protocol for improving channel use efficiency in multichannel ad hoc networks

In wireless ad hoc networks, end-to-end delivery over network is a critical concern for routing protocols. The capacity of routing protocols is constrained by the intra-flow interference introduced by adjacent nodes on the same path, and inter-flow interference generated by nodes from neighboring paths. In this paper, we develop an on-demand routing protocol M-AODV-R that solves the channel assignment, reuse and routing problem jointly. The proposed channel reuse scheme and channel assignment scheme can enhance channel reuse rate. This cross-layer design approach can significantly improve the performance of multichannel ad hoc networks over existing routing protocols. Simulation results show that the proposed routing M-AODV-R can effectively increase throughput and reduce delay, as compared to AODV protocol.     

A Cross-Layer Approach to Multichannel MAC Protocol Design for Video Streaming Over Wireless Ad Hoc Networks

This paper presents a cross-layer design for a reliable video transmission over wireless ad hoc networks based on multichannel MAC protocol with TDMA. First, we conduct a study of the multichannel MAC protocol through Markov chain model. Based on this study, two novel cross-layer modules are adopted for the design of multichannel MAC protocol. First, we adopt maximum latency rate (MLR) as the channel quality metric. Unlike the traditional MAC design based on network allocation vector (NAV), MLR is implemented to provide differentiated traffic so that the channel with smaller MLR time is initiated for higher priority traffic. Second, we adopt two congestion-aware metrics, namely MAC utilization and queue length of MAC layer, to improve the congestion-aware routing protocols with AODV and DSR. These two novel modules allow the proposed MAC protocol design to achieve high performance video transmission over wireless ad hoc networks. Experimental results show that the proposed scheme outperforms the state-of-the-art schemes under multichannel environments in wireless ad hoc networks for as much as 3.6 dB in PSNR. Such significant performance enhancement confirms that the cross-layer approach is very effective for multichannel MAC protocol design.     

Ad Hoc无线网络及其路由选择协议

AdHoc无线网络是一组无线移动主机组成的一个没有任务建立好的基础调和或集中管理设备的临时网络。文中介绍了adhoc无线网络的特点和设计，并根据表驱动和按需路由两大类重点介绍了adhoc无线网络的路由选择协议。     

A scalable multimedia QoS architecture for ad hoc networks

Communication demands have grown from separate data and voice to integrated multimedia, paving the way to converging fixed, mobile and IP networks. Supporting Multimedia is a challenging task for wireless ad hoc network designers. Multimedia forms high data rate traffic with stringent Quality of Service (QoS) requirements. Wireless ad hoc networks are characterized by frequent topology changes, unreliable wireless channel, network congestion and resource contention. Providing scalable QoS is the most important challenge for multimedia delivery over ad hoc networks. We introduce here a provisioning and routing architecture for ad hoc networks which scales well while provisioning QoS. The proposed architecture is analysed using a mix of HTTP, voice and video streaming applications over 54 Mbps 802.11 g-based ad hoc networks. The architecture is simulated and compared to well-known routing protocols using the OPNET Modeller. The results show that our architecture scales well with increase in the network size, and outperforms well-known routing protocols.     

A survey of secure wireless ad hoc routing

Ad hoc networks use mobile nodes to enable communication outside wireless transmission range. Attacks on ad hoc network routing protocols disrupt network performance and reliability. The article reviews attacks on ad hoc networks and discusses current approaches for establishing cryptographic keys in ad hoc networks. We describe the state of research in secure ad hoc routing protocols and its research challenges.     

无线传感器网络路由协议的分析与比较

无线传感器网络的路由协议设计与传统的无线ad-hoc网络有很多不同,资源高度受限和结点失效频繁是其面临的两大挑战,相关技术研究已经成为无线传感器网络研究中的热点.对近年来无线传感器网络路由协议的研究成果进行归纳、分析和比较,介绍了无线传感器网络的特点以及影响其路由协议设计的关键因素.根据协议的实现特点将无线传感器网络路由协议分为5类,对每一类涉及的重要协议进行详细阐述与分析,最后对这些协议的特点进行归纳和比较,并展望了未来这一研究方向的发展趋势.     

异构无线网络中的Ad Hoc路由及QoS分析

首先分析了纯Ad Hoc网络环境下具有QoS保证的几种典型路由协议,然后阐述了异构无线网络的体系架构以及异构网络环境下的Ad Hoc路由,包括基于节点位置信息的路由分级路由、提高网络容量的多跳中继路由、实现网络负载均衡的路由,以及跨层路由协议。最后,总结了在异构网络环境下提出的基于Ad Hoc网络多跳中继路由的负载均衡策略的研究工作,分析了仿真结果。     

高能量节点驱动的按需距离矢量路由协议

无线自组织网络中的按需距离矢量路由协议(AODV)没有考虑到能量消耗的均衡性和网络生命期的问题。针对AODV的这一缺点,提出了一种高能量节点驱动的AODV协议(HN-AODV)。此协议将高能量节点驱动的策略应用于按需路由发现过程,尽量选择能量较高的节点来承担转发任务,以此来平衡网络能耗。仿真结果显示,HN-AODV在基本不降低数据传输性能的前提下,显著提高了网络生命周期。这种高能量节点驱动的方案同样可以运用在其它类似的反应式路由协议中。     

基于链路状态加权的无线Mesh网络路由协议

由于无线Mesh网络还没有统一标准,ad hoc中的路由算法并不能完全适合无线Mesh网络.在分析ad hoc中经典路由协议AODV的基础上,结合无线Mesh网络的特点,提出了一种新颖的、基于链路状态加权的路由协议.该协议利用节点的可用带宽、吞吐性能和缓冲队列的饱和度等计算路由每一跳的代价(即权重),选择从信源到信宿累计权重最小的路径作为路由.仿真结果表明,提出的路由协议在数据包转发率、平均端到端延迟和标准化路由负栽等性能上均优于AODV,是一种适合无线Mesh网络的路由协议.     

Towards estimating lifetime of ad hoc wireless networks

Ad hoc wireless networks possess highly constrained energy resources. The available energy resources should thus be used efficiently, in order to satisfy the requirements. Hence, the protocols at all the layers of the protocol stack should be energy aware and energy efficient. However, all the existing protocols are not energy aware and perform poorly in the presence of a limited power source. Even the energy aware protocols proposed for ad hoc networks do not consider all the characteristics of the underlying batteries. Hence, they fail to efficiently utilize the available energy. There also exist a few protocols, which, though battery unaware, unknowingly prove to be energy efficient. Thus, a mechanism is required to measure the efficiency of the protocols of ad hoc networks, in terms of the network lifetime. To the best of our knowledge, there has been no reported work till date for analyzing the lifetime of the ad hoc networks for various protocols.The protocols at all the layers of the protocol stack together decide the discharge of the battery source of a node. However, assuming that only the MAC protocols decide the battery performance, we focus on measuring the energy efficiency of MAC protocols. This paper primarily provides a novel generalized analytical model for estimating lifetime of ad hoc networks, in the presence of the following two kinds of MAC protocols: (i) reservation-based TDMA protocols and (ii) a specific class of CSMA protocols that try to follow a pattern, such as a round-robin scheduling, for packet transmission. Our model uses discrete-time Markov chain with probabilistic recovery to model the batteries of the ad hoc nodes. We found that our analytical model accurately estimates the lifetime of the network for various MAC protocols. We prove through analytical and simulation studies that energy awareness is crucial in deciding the performance of the MAC protocols for both homogeneous and heterogeneous ad hoc wireless networks.