Research On Wireless Mesh Network Transmission Technology Based On Network Coding

In recent years,wireless network technology is developing quickly.The emergence of wireless Mesh networks(Mesh)makes people experience the ubiquitous convenience brought by network.People can use Mesh everywhere and anytime.Mesh networks has much advantage such as mobility,no infrastructure,high autonomy,flexibility.The number of Wireless Network users is increasing year by year.With the popularity of the wireless network technology,the demanding on transmission quality of services has become higher and higher.The existing wireless Mesh network transmission technology is increasingly unable to hold the people's growing demand for services.It's an inevitable trend to improve the transmission performance of Mesh with existing technology.Network Coding Theory was proposed in 2000 by Ahlswede in the Chinese University of Hong Kong.Network Coding change the node's forwarding mode,using "Store-Encoding-Forward" instead of the traditional mode "Store-Forward".The biggest advantage of network is that it can achieve the upper limit of network capacity which is limited by max-flow-min-cut theory.Wireless channel has feature on broadcasting.It is the preferred field of network coding application.Network Coding in Wireless Mesh Networks focuses mainly on two aspects:(1)The routing algorithm which support for network coding in mesh backbone network.(2)Using network coding to ensure reliable data transmission in mesh clients network.For the above two points,this paper do the following work:First,this paper makes some introduction about the basic principles about the network coding,then do some introduction about wireless mesh network routing technology and reliability assurance technology based on it.Flowing,this paper does some analysis about classic COPE(Complete Opportunity Encoding)coding strategy and its improvement strategy,pointing out some limitations of the application of COPE.Second,for the shortcoming of COPE need wait coding opportunity passively,the paper proposes a routing algorithm named An Improved Routing Algorithm forNetwork Coding(IRANC),which can change the data flow path and combined with the idea of hop-by-hop routing.The design of it includes five parts,Perception of the local topology,data cache,encoding and decoding judgment,the data forwarding scheduling,reliable confirmation.In the process of data transmission,Nodes can take advantage of the potential forwarding node and redundant packets in the network to determine or create the appropriate topology to use network coding,improving the transmission performance.Third,to solve the question that COPE lack of data packet combination method,this paper analyzes ??'s NCWBR method.In NCWBR,the same data packet may be coded multiple times.This paper analysis the reason in Chapter 4,and improves the method.We put forward a better packet combination method.Use this combination method in retransmission,do some analysis and comparison with NCWBR and traditional method with no coding.Finally,this paper uses the NS2 simulator to simulate the IRANC/HMBRS and the COPE strategy.The result proves IRANC algorithm can increase coding opportunities.It's also proves that using HMBRS retransmission strategy with optimal combination of coding package can get more throughput and fewer retransmission time than NCWBR.