一种基于跨层功率控制的Ad hoc网络路由算法*

在无线Ad Hoc网络路由协议中引入功率控制不但可以降低网络能量消耗,同时还能改善网络的吞吐量、投递率等性能,已成为当前Ad Hoc网络的一个研究热点.本文提出了一种基于跨层功率控制的按需路由算法CPC-AODV(Cross-layer Power Control Ad hoc On-demand Distance Vector).算法按需建立多个不同功率级的路由,节点选择到目的节点最小功率级的路由来传递分组,并对网络层的数据分组、路由分组和MAC层控制帧的传输采用不同功率控制策略来降低能量消耗.仿真结果表明:算法有利于降低通信能量开销,延长网络寿命,提高网络投递率及改善网络时延.     

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。     

移动自组织网络路由选择算法研究进展

移动Ad Hoc无需基础设施,可支持高动态的移动数据通信,具有广泛应用的前景。然而,其高动态特性导致互联网现有路由协议不再适用。近年来学者针对Ad Hoc网络提出了大量的路由选择算法。给出了各种路由技术分类方法,简述了Ad Hoc网络的基本路由协议和路由选择算法,进而从预测模型、能量模型、位置信息、服务质量控制和安全支持等5个角度,深入分析了当前Ad Hoc网络路由选择算法的最新研究进展。预测模型通过基于历史信息的移动预测,降低了路由选择的时间代价;能耗模型则采用适当的数学模型来描述网络能耗情况,在选路过程中实现了分组传送的能耗最小化和能量负担均衡之间的权衡;基于位置的路由选择算法根据节点的地理位置来标识目的地,从而利用该地理位置信息进行路由选择;服务质量感知的路由选择算法在本地计算中考虑带宽、延迟、能量和电池生命周期,从而在选路过程中提供了服务质量支持;安全路由选择算法则利用适合移动Ad Hoc网络的密钥、哈希链、电子签名等技术对协议交互消息进行加密来保障网络安全。最后从通信开销、计算和存储开销、路径数量、关键节点的存在性以及算法类型等方面详细对比总结了近年来提出的30余种典型路由选择算法,指出了各自的特点...     

TAP: Traffic-aware topology control in on-demand ad hoc networks

Energy efficiency is crucial to achieve satisfactory network lifetime in ad hoc networks. In order to reduce the energy consumption significantly, a node needs to turn off its transceiver. Many existing energy-saving algorithms are based on constructing a simplified routing backbone for global connectivity. In this paper some problems involved with node sleep in on-demand ad hoc networks are addressed firstly. Then we propose a distributed, cross-layer Traffic-Aware Participation (TAP) algorithm, where nodes make decisions on whether to sleep or not based on both the traffic pattern and local connectivity. Nodes get dynamic traffic characteristics as well as active neighbors within two hops via routing control and data packets periodically. We further present a lightweight algorithm to avoid network partition resulted from node sleeping. Simulation results show that, compared to current sleep-based topology control algorithms, TAP achieves better network service quality and lower delay while allowing comparable energy conservation.     

多速率移动自组网中交叉层优化的性能分析

由于严格分层的协议无法很好地适应移动自组织网络（Mobile Ad hoe Network,MANET）的动态变化,交叉层设计与优化近年来成为MANET的一个研究热点。针对802．11b标准支持的多速率通信,分别在网络层和MAC层实现了两种多速率控制方案,并通过仿真实验详细分析了这两种速率控制方案的性能。实验结果表明,在网络层引入物理层提供的多速率信息作为路由选取标准,可有效提高网络吞吐率,降低端到端延迟;同时,在MAC层使用高速率转发中继,对网络层路由进行局部优化,可以进一步改善对拓扑动态变化的适应性。     

移动自组网基于邻居变化率稳定路径选择方法

节点移动是导致移动自组织网络性能下降、限制网络规模扩展的关键因素之一.寻找稳定路径是减小节点移动影响的有效手段.现有的稳定路径寻找方法存在以下局限:需要节点具有地理位置定位的硬件功能支持,或需要信号强度上传的交叉层功能支持.为此,提出了不需要特殊硬件支持、可独立于底层协议工作、基于邻居变化率的稳定路径选择方法.以AODV(Ad hoc on-demand distance vector)按需路由协议为基础,扩展为NCR-AODV(Neighbor change ratio Ad hoc on-demand     

End-to-end support for statistical quality of service in heterogeneous mobile ad hoc networks

In heterogeneous mobile ad hoc networks (MANETs), different types of mobile devices with diverse capabilities may coexist in the same network. The heterogeneity of MANETs makes end-to-end support for quality of service (QoS) guarantees more difficult than in other types of networks, not to mention the limited bandwidth and frequent topology changes of these networks. Since QoS routing is the first step toward achieving end-to-end QoS guarantees in heterogeneous MANETs, we propose a QoS routing protocol for heterogeneous MANETs. The proposed protocol, called virtual grid architecture protocol (VGAP), uses a cross-layer approach in order to provide end-to-end statistical QoS guarantees. VGAP operates on a fixed virtual rectilinear architecture (virtual grid), which is obtained using location information obtained from global positioning system (GPS). The virtual grid consists of a few, but possibly more powerful, mobile nodes known as ClusterHeads (CHs) that are elected periodically. CHs discover multiple QoS routes on the virtual grid using an extended version of the open shortest path first (OSPF) routing protocol and an extended version of WFQ scheduling policy that takes into account the wireless channel state. Moreover, VGAP utilizes a simple power control algorithm at the physical layer that provides efficient energy savings in this heterogeneous setting. Simulation experiments show that VGAP has a good performance in terms of packet delivery ratio, end-to-end packet delay, call blocking probability, and network scalability.     

Improving hybrid ad hoc networks: The election of gateways

The selection of an appropriate and stable route that enables suitable load balancing of Internet gateways is an important issue in hybrid mobile ad hoc networks. The variables employed to perform routing must ensure that no harm is caused that might degrade other network performance metrics such as delay and packet loss. Moreover, the effect of such routing must remain affordable, such as low losses or extra signaling messages. This paper proposes a new method, Steady Load Balancing Gateway Election, based on a fuzzy logic system to achieve this objective. The fuzzy system infers a new routing metric named cost that considers several networks performance variables to select the best gateway. To solve the problem of defining the fuzzy sets, they are optimized by a genetic algorithm whose fitness function also employs fuzzy logic and is designed with four network performance metrics. The promising results confirm that ad hoc networks are characterized by great uncertainty, so that the use of Computational Intelligence methods such as fuzzy logic or genetic algorithms is highly recommended.     

Joint routing and flow rate optimization in multi-rate ad hoc networks

Typical radios in ad hoc networks can support multi-rate transmissions. However, traditional routing protocols do not use this feature well in multi-rate ad hoc networks and therefore, the network performance and resource utilization are not optimized. Some algorithms have been proposed to take advantage of the multi-rate transmission scheme, but their performance is not optimized either. In this paper, we show that a cross-layer optimization based approach can significantly improve the performance of multi-rate ad hoc networks over existing routing algorithms. For this, we consider link interference and propose joint routing and flow rate optimization for optimal performance in multi-rate ad hoc networks, i.e., a Cross-layer Optimization based Model for Multi-rate Ad hoc Networks (COMMAN). Considering the characteristics of multi-rate ad hoc networks, we design and implement a distributed heuristic of this centralized model. It is shown that the distributed heuristic algorithm can approximate the performance of COMMAN closely.     

双向路径重选的自组网负载均衡路由协议

基于跨层负载感知和双向路径重选的自纽网负载均衡路由协议（CLBLR）在路由发现阶段和路由维护阶段，将整个路径中各节点MAC层的总平均估计时延和路径总业务流负载结合起来，共同作为路由选择和路由调整的重要依据，通过双向路径重选方法实现最优路径选择和网络业务流的均衡分布和均衡传输．协议通过禁止中间节点对路由请求进行应答和阻止不必要的路由请求分组，经由重负载中间节点转发，以保证路由发现时能够利用最新负载信息，并避免了节点在重负载情况下成为新建路由的中间节点，使协议具有一定的拥塞控制功能，以间接的方式实现了请求接纳控制．上述措施使分组传输路由很好地避免了拥塞节点，减少了网络瓶颈对网络性能的影响．仿真表明，CLBLR在分组丢失率、平均端到端时延和路由附加开销等方面具有良好性能，其优良的分布式控制特征能适应自组网的动态环境．     

基于最优Path的Ad Hoc网络地理路由算法

对基于地理信息的自组网路由中的凹节点问题做了分析,并提出了一种新的解决方案——PGA算法及其改进算法.算法采用了最优Path的思想,在Path构造、基于Path的最优寻路、路由恢复等多个方面都应用了最优Path的概念,较好地解决了凹节点的问题.通过证明,该算法具有无环性,从而实现了基于局部路由信息的无状态路由,展示了算法的可扩展性和易维护性.实验表明,即使在大型网络中,算法依然可以保持很高的报文投递率、较短的路径长度、可接受的路由表大小及可控的协议带宽开销,同时该路由算法在动态环境中具有较强的鲁棒性.     

A location routing protocol based on smart antennas for ad hoc networks

Ad hoc networks are a type of mobile networks that function without any fixed infrastructure. One of the weaknesses of ad hoc networks is that route between a source and a destination is likely to break during communication. Location-based routing algorithms are promising in reducing routing overhead in ad hoc networks. Existing location-based routing algorithms employ the Global Positioning System (GPS) as their location information provider, and synchronize information network-wide. Nonetheless, these protocols have some limitations because the use of GPS is not realistic in certain circumstances. Since smart antenna is able to infer direction and ranging information between pairs of ad hoc node, the obtained local position information can be used to improve routing mechanism. This work proposes a novel Location-Enhanced On-Demand (LEOD) routing protocol which is based on smart antenna technique. The LEOD protocol utilizes local position instead of global position to discover routes and make routing decision for the ad hoc network. Theoretical computation and simulation results show that data packet loss rate decreased significantly compared to other methods well-documented in the literature. In addition, this protocol reduces the network control overheads and the power consumption. It also improves network average throughput.     

Ad Hoc网络多路径需求路由及路径熵选择算法

无线移动Ad Hoc网络是一种不依赖任何固定基础设施的移动无线多跳网络.由于其动态性和资源的限制,在Ad Hoc网络中提供多路径路由是一个重要的研究课题.描述了一种Ad Hoc网络中基于信息熵选择的稳定多路径路由算法(stability multipath on-demand routing,简称SMDR),提出了路径熵的度量参数,并利用路径熵来选择稳定的、长寿命的多路径,减少了重构路由的次数,从而在网络拓扑频繁变化的Ad Hoc网络环境中较好地提供QoS保证和提高数据传输率.仿真结果表明,SMDR协议改进了分组传输率、端到端时延和路由负载率.SMDR协议为解决动态的Ad Hoc网络多路径传输提供了一种新的有效途径.     

A cross-layer multi-hop cooperative network architecture for wireless ad hoc networks

In this paper, a novel decentralized cross-layer multi-hop cooperative network architecture is proposed and presented. This cross-layer architecture introduces a new cooperative flooding scheme and two decentralized opportunistic cooperative forwarding mechanisms based on randomized coding, and a Routing Enabled Cooperative Medium Access Control (RECOMAC) protocol that enables cooperative forwarding, while incorporating physical, medium access control (MAC) and routing layers. RECOMAC employs randomized coding to realize cooperative diversity, so that relay selection and actuation mechanisms are alleviated and the MAC costs are reduced. The coded packets are routed in the network via the proposed cooperative forwarding schemes, which opportunistically form cooperative sets within a region, not needing a prior route to be established. Essentially, in the RECOMAC architecture, the routing layer functionality is submerged into the MAC layer to provide seamless cooperative communication, while the messaging overhead to set up routes, select and actuate relays is reduced. We evaluate the performance of RECOMAC in terms of network throughput, delay and MAC and routing overhead, in comparison to the conventional architecture based on the well-known IEEE 802.11 MAC and Ad hoc On Demand Distance Vector (AODV) routing protocols. RECOMAC is shown to provide quite significant improvement by an order of magnitude difference in all investigated performance metrics, under a variety of scenarios, considering different network sizes, static and mobile scenarios and networks with multiple flows.     

一种无线Ad Hoc网络动态混淆匿名算法

无线Ad Hoc网络的特殊性决定了它要受到多种网络攻击的威胁,现有的加密和鉴别机制无法解决流量分析攻击.在比较了抗流量分析的匿名技术基础上,提出混淆技术可以满足无线Ad Hoc网络的匿名需求,但现有的混淆算法在Ad Hoc网络下却存在安全与效率的问题.提出了一种动态混淆的RM(pseudo-random mix)算法,该算法主要对混淆器的管理部分进行重新设计.RM算法根据混淆缓冲区的情况进行决策,当缓冲区未满时采用时延转发方式,缓冲区满后采用随机数转发方式,这样既保证了无线Ad Hoc节点的匿名性,同时又解决了停等算法的丢包现象.对RM算法的安全性和效率进行了分析,仿真结果与理论分析相一致,表明RM算法在无线Ad Hoc网络下具有较好的自适应性和实用价值.     

一种改善Ad Hoc网络中TCP性能的跨层方法

大量研究表明AdHoc网络中TCP的性能非常差,这主要是由于TCP的拥塞控制机制不能有效地解决由共享信道竞争造成的分组丢失问题。文中提出了一种根据TCP发射端MAC层的RTS重发次数,来自适应地调整TCP的最大窗口大小的跨层方法,以控制网络中分组的数量,减小信道竞争。仿真结果表明,该方法能够显著地提高TCP的吞吐量,并改善其稳定性。     

基于跨层设计的Ad hoc网络能量控制算法研究

为进一步适应Ad hoc网络中各种应用的需求,提高网络性能,跨层设计已成为Ad hoc网络研究的热点之一。基于跨层设计思想,研究了多种用于Ad hoc网络的能量控制算法,给出了跨层设计方法的定义,研究和讨论了两种典型的Ad hoc网络跨层设计方法。对Ad hoc网络中多种能量控制算法进行了分类、描述、分析比较和评价,在此基础上,提出了基于跨层设计的Ad hoc网络能量控制算法存在的问题和进一步的研究方向。     

基于改进萤火虫群优化的无线自组网路由算法

针对无线自组网络拓扑结构多变、网络生存时间受限及数据包分组传输效率低下等问题,借鉴萤火虫群优化算法,提出了一种改进萤火虫群优化的无线自组网络路由算法.路由算法将萤火虫优化算法中的荧光素强度更新与无线自组网络中的节点移动速度、拥塞程度、节点剩余能量、节点间距离等因素进行相互映射,同时改进萤火虫群优化算法中的搜索萤火虫、驻留萤火虫及回溯萤火虫用于完成无线自组网络中路由协议的路由发现、路由选择及路由维护等过程,整个协议无须传送大量的控制分组,即可实现无线自组网络的稳定传输.仿真实验结果表明,与AODV及基于蚁群优化的路由算法AntRouting协议相比,本文所提出的路由算法在端到端延时、分组数据传输率及网络生存时间上均有良好的性能.     

无线Ad Hoc网络能量感知地理路由协议研究进展

无线Ad Hoc网络（以下简称为Ad Hoc网络）能量感知地理路由协议深度影响网络性能,具有降低网络能量消耗、延长网络寿命等功效,受到越来越多的关注.系统阐述了Ad Hoc网络能量感知地理路由协议的研究进展.首先介绍了Ad Hoc网络地理路由,进而详细概述了能量感知地理路由协议形成的背景、度量指标、节点选择规则、研究意义及分类;然后,详细介绍了典型能量感知地理路由协议,并从多角度对其进行了归纳总结与比较;最后,阐述了能量感知地理路由协议研究存在的问题,指出了未来需要研究的内容,并在此基础上进行总结.