Ad Hoc网带预测后备路由算法研究

网络拓扑的动态变化是AdHoc网络的主要特点,也是影响通信性能的主要因素。DSR协议是一种按需式路由协议,当发现1个链路断开的时候,就要重新建立1个新的路径,在路径重建的过程中会使包丢失,并且会造成重要的吞吐量的降低。鉴此,提出一种高效的路由协议。在移动预测的机制下,该协议能够选取另外一条后备路径来实现,减少包的丢失。     

低开销的MANET网络按需路由协议

针对简单泛洪效率低的问题,提出了一个限制洪泛的高效的路由广播算法,通过Euclidean距离来限制路由发现过程中请求分组被转发的次数;研究了减少路由维护开销,并降低路由发现的频率的方法,提出了一个基于节点高度的路由修复与优化算法,该算法使用节点监听来对链路断裂的路由进行修复与优化.基于限制泛洪的高效的路由广播算法和路由修复优化算法,提出了一种新的低开销的MANET网络按需路由协议LOOR(low overhead on-demand routing).仿真结果表明,新协议增强了路由的顽健性,减少了路由跳数,降低了路由发现的频率,提高了数据分组递送率,并显著地降低了路由控制开销.     

移动Ad hoc网络中基于链路稳定性预测的按需路由协议

移动Ad hoc网络拓扑的高度动态变化是造成传统按需路由协议的路由频繁通断的主要原因,因此在传统按需路由协议的基础上进行链路稳定性预测扩展,增强路由稳定性具有十分重要的意义。该文利用分组的接收功率把节点间的相对运动划分为靠近和远离两种类型,然后在不同相对运动类型下根据节点间距离得到了的链路平均维持时间。在路由过程中,中间节点利用得到的链路平均维持时间设置请求报文的转发延迟,通过一定转发规则选择稳定性较强的链路构成路径。仿真结果表明进行链路稳定性预测扩展后的按需路由协议能够有效增强路由的稳定性,并提高网络性能。     

A highly topology adaptable ad hoc routing protocol with complementary preemptive link breaking avoidance and path shortening mechanisms

Ad-hoc on-demand distance vector routing (AODV) is a well-known routing protocol for mobile ad hoc networks. The original AODV protocol works in a semi-dynamic fashion, by establishing a route on demand and using that route until it breaks. However, to suit the changing network topology of ad hoc networks, more aggressive and adaptable routing strategies are required. A number of researches have proposed improving AODV performance by locally repairing broken links, predicting and replacing potentially vulnerable links, or shortening a link through removing redundant nodes from the transmission path. Although local repair may relieve some problems, it usually results in longer paths and thus a considerable performance drop in heavy traffic conditions. There are also issues regarding packet loss and communication delay due to route rebuilding once the link is broken. Predicting and replacing potentially vulnerable links may require special hardware, additional tables to maintain, or other extra overhead. Finally, path shortening may result in shorter and more efficient routes, but there is no guarantee that the new paths will be robust. This paper proposes integrating preemptive link breaking avoidance and path shortening mechanisms into a modified AODV protocol. However, the difficult issue lies in determining the right timing to initiate the two independent mechanisms so that the two dynamically and complementarily operating mechanisms can work together to improve the routing performance. Through numerical analysis and simulation, we have arranged a simple parameter setting for controlling the activation of each mechanism at the appropriate time. The proposed combination is a highly dynamic ad hoc routing protocol that is capable of adapting itself to the changing network topology and achieving extremely good performance in various routing performance metrics. Extensive simulations show that each of the two schemes alone improves AODV performance. More importantly, the integrated protocol performs even better in terms of data delivery rate, average delay time, and network overhead. To be more specific, in the best cases our protocol can reduce up to 82% in control overhead and 66% in delay time, while achieving 12% more in data delivery rate comparing to AODV.     

Distributed cache updating for the dynamic source routing protocol

On-demand routing protocols use route caches to make routing decisions. Due to mobility, cached routes easily become stale. To address the cache staleness issue, prior work in DSR used heuristics with ad hoc parameters to predict the lifetime of a link or a route. However, heuristics cannot accurately estimate timeouts because topology changes are unpredictable. In this paper, we propose proactively disseminating the broken link information to the nodes that have that link in their caches. We define a new cache structure called a cache table and present a distributed cache update algorithm. Each node maintains in its cache table the information necessary for cache updates. When a link failure is detected, the algorithm notifies all reachable nodes that have cached the link in a distributed manner. The algorithm does not use any ad hoc parameters, thus making route caches fully adaptive to topology changes. We show that the algorithm outperforms DSR with path caches and with Link-MaxLife, an adaptive timeout mechanism for link caches. We conclude that proactive cache updating is key to the adaptation of on-demand routing protocols to mobility.     

Performance of Multipath Routing for On-Demand Protocols in Mobile Ad Hoc Networks

Mobile ad hoc networks are characterized by multi-hop wireless links, absence of any cellular infrastructure, and frequent host mobility. Design of efficient routing protocols in such networks is a challenging issue. A class of routing protocols called on-demand protocols has recently found attention because of their low routing overhead. The on-demand protocols depend on query floods to discover routes whenever a new route is needed. Such floods take up a substantial portion of network bandwidth. We focus on a particular on-demand protocol, called Dynamic Source Routing, and show how intelligent use of multipath techniques can reduce the frequency of query floods. We develop an analytic modeling framework to determine the relative frequency of query floods for various techniques. Our modeling effort shows that while multipath routing is significantly better than single path routing, the performance advantage is small beyond a few paths and for long path lengths. It also shows that providing all intermediate nodes in the primary (shortest) route with alternative paths has a significantly better performance than providing only the source with alternate paths. We perform some simulation experiments which validate these findings.     

基于缓存旁路和本地修复的多跳网络路由重建机制

该文针对多跳网络中现有AODV和AODV-BR按需路由算法的弊端,提出了基于缓存旁路和本地修复的AODV-CL路由重建机制。该机制利用空闲时间监听无线信道中传输的所有数据包和路由控制信令,用于维护有效的邻居节点列表及本地路由缓存,有效降低了周期性HELLO消息带来的信令负担,并增加了可用路由信息。中间节点在发现断链时,尝试采用局部修复,尽量避免由源节点广播RREQ消息发现路由。根据本地路由缓存及邻居节点的路由信息,实现了快速的路由发现及修复,能有效降低路由控制信令开销及丢包率。     

SMORT: Scalable multipath on-demand routing for mobile ad hoc networks

Increasing popularity and availability of portable wireless devices, which constitute mobile ad hoc networks, calls for scalable ad hoc routing protocols. On-demand routing protocols adapt well with dynamic topologies of ad hoc networks, because of their lower control overhead and quick response to route breaks. But, as the size of the network increases, these protocols cease to perform due to large routing overhead generated while repairing route breaks. We propose a multipath on-demand routing protocol (SMORT), which reduces the routing overhead incurred in recovering from route breaks, by using secondary paths. SMORT computes fail-safe multiple paths, which provide all the intermediate nodes on the primary path with multiple routes (if exists) to destination. Exhaustive simulations using GloMoSim with large networks (2000 nodes) confirm that SMORT is scalable, and performs better even at higher mobility and traffic loads, when compared to the disjoint multipath routing protocol (DMRP) and ad hoc on-demand distance vector (AODV) routing protocol.     

Robust multi-path routing for dynamic topology in wireless sensor networks

Wireless sensor networks are being widely researched and are expected to be used in several scenarios. On the leading edge of treads, on-demand, high-reliability, and low-latency routing protocol is desirable for indoor environment applications. This article proposes a routing scheme called robust multi-path routing that establishes and uses multiple node-disjoint routes. Providing multiple routes helps to reduce the route recovery process and control the message overhead. The performance comparison of this protocol with dynamic source routing (DSR) by OPNET simulations shows that this protocol is able to achieve a remarkable improvement in the packet delivery ratio and average end-to-end delay.     

On-demand loop-free routing with link vectors

We present the on-demand link vector (OLIVE) protocol, a routing protocol for ad hoc networks based on link-state information that is free of routing loops and supports destination-based packet forwarding. Routers exchange routing information reactively for each destination in the form of complete paths, and each node creates a labeled source graph based on the paths advertised by its neighbors. A node originates a broadcast route request (RREQ) to obtain a route for a destination for which a complete path does not exist in its source graph. When the original path breaks, a node can select an alternative path based on information reported by neighbors, and a node can send a unicast RREQ to verify that the route is still active. A node that cannot find any alternate path to a destination sends route errors reliably to those neighbors that were using it as next hop to the destination. Using simulation experiments in ns2, OLIVE is shown to outperform dynamic source routing, ad hoc on-demand distance vector, optimized link-state routing protocol, and topology broadcast based on reverse-path forwarding, in terms of control overhead, throughput, and average network delay, while maintaining loop-free routing with no need for source routes.     

Reliable Distributed Local Repair Approach for Maximizing Reliability and Packet Delivery Rate in Wireless on Demand AODV Networks

The most used protocol in Mobile Ad hoc Networks (MANETs) uses the Ad hoc On-Demand Distance Vector (AODV) routing protocol for achieving dynamic, self-organizing, and on-demand multihop routing. In AODV, wireless links may be lost occasionally because the nodes on the routing path are unreachable. Such a problem causes AODV inefficient and unreliable. For solving the problem, AODV provides a local repair mechanism for an intermediate node to find an alternative route to destination when the node detects links broken. The repair mechanism uses the broadcast-type RREQ message for discovering a repair route, which results in a large number of repair control messages and requires a large amount of power consumption for sending these messages. Therefore, in this paper we propose a unicast-type distributed local repair protocol for repairing breaks expeditiously, i.e., achieving high network reliability and utilization, less the number of control messages, and less the repair delay. Furthermore, the optimal number of hops in a neighbor table is analyzed. Numerical results indicate that the proposed approach is superior to other repair approaches in terms of successful fixing rate, control message overhead, and network utilization.     

On-demand coding-aware routing in wireless Mesh networks

Network coding,which exploits the broadcast nature of wireless medium,is an effective way to improve network performance in wireless multi-hop networks,but the first practical wireless network coding system COPE cannot actively detect a route with more coding opportunities and limit the coding structure within two-hop regions.An on-demand coding-aware routing scheme(OCAR)for wireless Mesh networks is proposed to overcome the limitations specified above by actively detecting a route with more coding opportunities along the entire route rather than within two-hop regions.Utilizing more coding opportunities tends to route multiple flows 'close to each other' while avoiding interference requires routing multiple flows 'away from each other'.OCAR achieves a tradeoff by adopting RCAIA as routing metric in route discovery,which is not only coding-aware but also considers both inter and intra flow interference.Simulation results show that,compared with Ad-hoc on-demand distance vecfor routing(AODV)and AODV+COPE,OCAR can find more coding opportunities,thus effectively increase network throughput,reduce end to end delay and alleviate network congestion.     

Query Localization Techniques for On-Demand Routing Protocols in Ad Hoc Networks

Mobile ad hoc networks are characterized by multi-hop wireless links, absence of any cellular infrastructure, and frequent host mobility. Design of efficient routing protocols in such networks is a challenging issue. A class of routing protocols called on-demand protocols has recently found attention because of their low routing overhead. We propose a technique that can reduce the routing overhead even further. The on-demand protocols depend on query floods to discover routes whenever a new route is needed. Our technique utilizes prior routing histories to localize the query flood to a limited region of the network. Simulation results demonstrate excellent reduction of routing overheads with this mechanism. This also contributes to a reduced level of network congestion and better end-to-end delay performance of data packets.     

Route Maintenance in a Wireless Mobile Ad Hoc Network

A mobile ad-hoc network (MANET) is formed by a cluster of mobile hosts, without the infrastructure of base stations. To deal with the dynamic changing topology of a MANET, many routing protocols have been proposed. In this paper, we consider the route maintenance problem, which includes two parts: route deterioration and route breakage. In a MANET, a route may suddenly become broken because only one host roams away. Even if a route remains connected, it may become worse due to host mobility or a better route newly being formed in the system. Existing protocols, however, will stick with a fixed route once it is discovered, until it is expired or broken. In this paper, we show how to enhance several existing protocols with route optimization and local route recovery capability. So the routing paths can be adjusted on-the-fly while they are still being used for delivering packets and can be patched in minimum wireless bandwidth and delay while route errors occur.     

Ad hoc网络中不相关多路由源端寻路算法

路由方案是Ad hoc网络中一个热点研究领域。其中,按需路由算法由于其有效性在带宽受限的Ad hoc网络中得到比较大的发展。然而大部分的按需路由算法,建立并只使用单条路由,当前使用的路径的链路断开时,路由算法必须执行一个路由修复过程。提出了不相关多路由源端路由算法（DMSR）,建立并利用多条最大不相关路由。算法中,中间节点等待一段时间以得到多个路由请求包（RREQ）,然后在这个RREQ中,选择相关性最小的多路径,并将这些信息写入一个RREQ中,并将它广播出去。从仿真结果可以看出本文的算法提高了数据包的正确传输率和业务均衡性。     

An adaptive load-aware routing algorithm for multi-interface wireless mesh networks

In wireless mesh networks, the number of gateway nodes are limited, when the nodes access to the internet by fixed gateway node, different requirements of nodes lead to the dataflow shows heterogeneity. Many new routing metrics and algorithms existing in traditional wired networks and the Ad Hoc network, can not be directly applied to wireless mesh networks, so how to design a routing metric and algorithm which can dynamically adapt to current networks topology and dataflow changes, avoid bottleneck node, and select the most stable and least congestion link to establish a route is very important. In this paper, we presented a new dynamic adaptive channel load-aware metric (LAM) to solve the link load imbalance caused by inter-flow and inner-flow interference, designed a self-adaptive dynamic load balancing on-demand routing algorithm through extending and improving AODV routing method with the LAM, to achieve flow balance, reduce the high packet loss ratio and latency because congestion and Packet retransmission, and can increase Network Throughput.     

Proxy-assisted routing for efficient data transmission in mobile ad hoc networks

While on-demand routing protocols have been optimized to use the aid of proxy nodes by considering the possibility of long-lived partitions due to intermittent connectivity, they do not consider the chances of using a proxy for a long distance between a pair of source and destination. In this paper, we introduce a Proxy-Assisted Routing (PART) for efficient data transmission by selecting a proxy node for every path length that is longer than the predefined value between a source and destination. Whenever route errors occur between a source node and proxy node, or a proxy node and destination node, the proxy node repairs a broken route locally by redirecting a new route to the source or destination node. To reduce routing overhead, we delineate a broadcasting zone, where nodes are only allowed to broadcast request packets within the predefined zone to the proxy. Furthermore, unicast transmission is used for the proxy selection process using IP address information at the MAC layer. When we evaluate the performance metrics through simulations, PART significantly reduces the normalized routing load by almost 55% and the packet losses by almost 30%, and increases throughput almost 70% if compared to the traditional routing protocols.     

基于能量感知的Ad Hoc路由算法研究

针对移动adhoc网络终端能量资源受限对全网路由的影响,提出一种具有终端节点能量感知的路由协议(EARP,energy-awareroutingprotocol).该协议能够根据单个节点能量的使用情况以及全路径的能量消耗情况选择不同的传输路径,在路径断裂时,增加本地维护策略,有效减少了由此引起的发包重传情况,提高了路由效率.通过节点能级的设定,防止链路传输过程中由于能量耗尽而导致的路由断裂情况.经过NS2仿真实验与其他相关路由协议进行比较,结果表明在相同的实验环境下,该路由协议能够有效均衡负载,保护低能量节点,延长网络生存时间     

DOA: DSR over AODV Routing for Mobile Ad Hoc Networks

We present a lightweight hierarchical routing model, Way Point Routing (WPR), in which a number of intermediate nodes on a route are selected as waypoints and the route is divided into segments by the waypoints. Waypoints, including the source and the destination, run a high-level intersegment routing protocol, while the nodes on each segment run a low-level intrasegment routing protocol. One distinct advantage of our model is that when a node on the route moves out or fails, instead of discarding the whole original route and discovering a new route from the source to the destination, only the two waypoint nodes of the broken segment have to find a new segment. In addition, our model is lightweight because it maintains a hierarchy only for nodes on active routes. On the other hand, existing hierarchical routing protocols such as CGSR and ZRP maintain hierarchies for the entire network. We present an instantiation of WPR, where we use DSR as the intersegment routing protocol and AODV as the intrasegment routing protocol. This instantiation is termed DSR over AODV (DOA) routing protocol. Thus, DSR and AODV—two well-known on-demand routing protocols for MANETs—are combined into one hierarchical routing protocol and become two special cases of our protocol. Furthermore, we present two novel techniques for DOA: one is an efficient loop detection method and the other is a multitarget route discovery. Simulation results show that DOA scales well for large networks with more than 1,000 nodes, incurring about 60 percent-80 percent less overhead than AODV, while other metrics are better than or comparable to AODV and DSR.     

Geographical awareness hybrid routing protocol in Mobile Ad Hoc Networks

This paper proposes a geographical awareness routing protocol based on a hybrid routing protocol, the Zone Routing Protocol (ZRP), in Mobile Ad Hoc Networks (MANETs). ZRP is created from combining proactive routing protocol and on-demand routing protocol; therefore, it inherits the advantages of both these routing protocols. The long delay time of the on-demand routing protocol and the huge routing overhead of the proactive routing approach are reduced in ZRP. However, ZRP still produces a large amount of redundant routing overhead in the route discovery process, which not only wastes energy but also increases the workload of the network, while limited bandwidth is a challenge for MANETs. To mitigate routing overhead, a geographical awareness approach that is applied to limit the discovered route area in ZRP is proposed and is called the Geographical awareness ZRP (GeoZRP). Simulation results confirm that the proposed algorithm alleviates routing overhead and end-to-end delay with only a slightly decrease in the packet delivery ratio.