Wireless Ad-Hoc Network Adaptive OLSR Routing Algorithm Design And Implementation

MANET has been widely used in military communication and disaster communications, because of its characteristics of self-organizing, and self-healing. Many routing algorithms and protocols have been proposed for MANET, including on-demand routing protocol, proactive routing protocol and hybrid routing protocol. But the dynamic network topology changes in mobile, interference and other factors of the complex terrain conditions, how to adaptive choose and use the routing, guarantee end-to-end traffic demand, has been a hot research problem. In this paper, based on the OLSR routing protocol, proposed the protocol parameter adaptive adjustment mechanism and adaptive multipath routing algorithm, design and implement the proposed adaptive multipath routing algorithm based on the linux platform. The main work includes the following three aspects:First of all, as the OLSR routing rely on nodes periodic exchange of HELLO messages and TC message each other to access link state information, the fixed emmision interval may not be adapt to the dynamic changes of network topology. When the nodes move fast, topology information is expired and the routing failure is occured. When the nodes are stationary and the network topology does not change, network resource is wastely. This paper presents an adaptive mechanism for sending broadcast message. By detecting the changes of node local link set, adjust the HELLO message’s emmison interval. By detecting the change of the local MPR selector set, MPR set and t the neighbor table, adjust the TC message’s emmison interval.Secondly, because of the time-varying electromagnetic environment and link instability for Ad Hoc network, a single path can not meet the business requirements of QoS, this paper puts forward an adaptive multipath strategy based on link quality metrics, increase the end-to-end reliability in network layer. When the single path can not meet the end to end delivery, make use of multiple path redundanct transmission.When the network environment is good, the load balancing transmission involves more nodes to participate in forwarding to increase the lifetime of the network, improve the end-to-end throughput. At the same time, multipath combined with network coding to further enhance the reliability of the end to end.Finally, build Ad Hoc network and experiment on different protocol parameters, the result show that the protocol with fixed parameters cannot adapt to the changes of network topology, protocol parameters need to be adjusted adaptively by network environment. At the same time, in the linux platform, using the IO multiplexing technology developed multipath OLSR routing protocol based on OLSRd source code. Using multithread and socket achieve the multi-path transmission and multipath load balancing. Experiments show that, when the network environment is poor and the network part of the region was interference, multi-path transmission can improve the delivery rate of end to end.