Performance Analysis And Application Strategies Study In Broadcasting-based Wireless Network Coding System

With rapid development of mobile communication and internet network, the requirement of broadband wireless access is increasing to meet the dramatically growing demands for wireless multimedia services.The next-generation mobile communication systems(B3G/4G) provide high data-rate,support more subscribers and guarantee quality-of-service(QoS). Hence advanced technologies will be applied in the B3G/4G system to provide higher frequency efficiency within limited wireless bandwidth, among which network coding system is promising technology.Network coding theory is an important break-though in network communication and development.The core idea of network coding is that the gateway nodes in network not only focus on simple store-and-forward,but also encode the information that passes by;therefore,the coding process has enlarged the capacity and stability of entire network.Typical evolution process of novel techniques,like network coding, almost always involves from some simple application independent with other existing techniques to some joint designing mechnisms to obtain further performance advantages.Although the key steps of network coding is the coding process,the instinct benefit lies in the difference of muti-user part, specifically,through which the same network coded packets is broadcasted or multicasted to more than one receivers,different receivers can decode individual information needed using its former information possessed respectively.In one word,more than one receiver can gain after one coding transmission by the means of multicasting or broadcasting.Based on this observation,this dissertation seeks to apply the method of network coding with some existing techniques in wireless communication system,mainly focusing on research and analysis in system performance and implementation alternatives.The mainly works include: In recent years,the coding-aware routing mechanism attracts the interest of many people to further magnify the gains achieved by network coding in wireless networks.This paper aims at revealing a unifying framework for routing in the presence of the awareness of network coding,which we call "coding-aware routing".In this paper,we propose a practical routing mechanism CCAR(Complete Coding-Aware Routing) which fairly quantify the network coding gain while considering the wireless transmission conditions.In general,there are two steps that should be realized in coding-aware routing mechanism:one is finding coding opportunity in the routing discovery phase and the other one is determining the optimum path from the coding-available paths and the coding- unavailable ones.We implement the CCAR routing in wireless mesh system in C++ with extensive evaluation,and the simulation results illustrate that compared with the ones which oblivious of coding gains using,transmission efficiency can be sharply increased in the whole network and achieves 5%-20%throughput gains.The problem of intra-channel diversity in multi-channel routing can be relived efficiently using new proposed technology called "Network coding", and hence spectral efficiency can be increased.In this framework,we presented a method for computing source-destination routes and utilizing the best coding opportunities from available ones so as to maximize the throughput,which called M-CCAR(Multi-Path/channel Complete Coding-Aware Routing).In general,there are two steps that should be realized in coding-aware routing mechanism:the first one is finding the set of candidate path using a modified DSR protocol and making aware of coding opportunity in the routing discovery phase and the other one is determining the optimum path from the coding-available paths and the codingunavailable ones using the novel routing metric of WCECTT(Weighted Cumulative Coding-aware ETT).We implement the M-CCAR routing in wireless mesh system in C++ with extensive evaluation,and the simulation results illustrate that compared with the ones which oblivious of coding gains using,transmission efficiency can be sharply increased in the whole network and achieves 10%-20%throughput gains.A novel scheme joint with chase combining and network coding for broadcast flows in a multi-user system is presented.An information-theoretic performance bound is also developed to explain and predict the coding gains of the Soft combining in network coding-based Multicasting scheme using random coding bounding techniques.It is found from the simulation results that the transmission efficiency is sharply increased in the whole network especially in fairly severe fading circumstance.Research supported in part by National Basic Research Program of China(973 Program) 2007CB310604 and Project 2009CB320401,Project 60772108 and 60702048 supported by National Natural Science Foundation of China.This work has also been supported by the Doctor Fund of Beijing University of Posts and Telecommunications.