Research On Network Coding Of Ad Hoc Network Based On QoS

Ad Hoc network is a no infrastructure supporting mobile wireless network,which has self-organization,no center,rapid deployment,dynamic topology and multi-hop characteristics.These characteristics make it can be widely used in military combat readiness,disaster relief,environmental monitoring and other fields,so it has a very broad application prospects.Now,with the growing popularity of multimedia applications,a variety of audio,video,and high real-time data services based on wireless network(such as VOIP,video conferencing,etc.)has a huge development on business applications,which makes the QoS indicators important to the Ad Hoc network.Because of the broadcast nature of the wireless channel conditions can provide space for the network redundancy coding,network coding may utilize different data packets,different nodes,different wireless channel between the temporal redundancy and spatial redundancy,the different packet information is encoded together sequentially transmitted,reducing data transmission delay and increase network capacity.The transmission of multimedia application information has strict restrictions on delay,so designing a algorithm to guarantee real-time data streaming delay QoS has an important application value.Firstly,referring to random network coding in wireless ad-hoc network,a dispatch algorithm was proposed called Random Early Detction with Priority(REDP)in this paper.Based on service priority and queue state,REDP will automatically discard the packets so as to avoid the channel congestion,thus reducing average delay and the distortion rate.By using a Markov Chain model with two different flows,the mathematical expression of the packet loss rate and average delay of REDP were presented.We validated that REDP will effectively reduce average delay under the premise of the packet loss rate satisfying the Quality of Service(QoS).Extensive simulations were carried out to contrast the performance of REDP and Probabilistic Network Coding with Priority(PNCP)in network coding environment.Results showed that REDP can significantly increase the network coding chance as well as reduce the distortion rate,therefore achieve better performance while transmitting real time network traffic such as video and audio.Secondly,this paper analyzes the application of REDP algorithm in multi-node network topology with the Lyapunov model,prove that it can enable the end to end average delay of the entire system is stable and have is an upper bound,after that the delay of dynamic allocation algorithm is proposed.The algorithm can use Markov Chain predicting node congestion,dynamically allocate delay factor and adjust the delay of each node according to the delay constraint.Finally,in multi-node networks,analyze the dynamic allocation algorithm and average delay time delay assignment algorithm performance,simulation results show that dynamic delay allocation algorithm can achieve strict delay QoS guarantee of real-time data streaming.