The Source And Channel Diversity Under General Channel Condition

Consider transmitting multimedia through wireless channel due to the effects, such as fading, shadowing, interference and network congestion, the quality of multimedia will decline with the channel fluctuation. Transmitting the information through parallel channels (such as multiple frequencies, time slots and antennas etc.) is a good way to combat such channel fluctuations.In this paper, we stand on the analysis from information theory, discussing the methods which code over the parallel channels to improve the availability of transmitting system by combating the channel fluctuation. And call it as diversity problem over through the paper。The main contents of this paper are as follows.1. Construct the source and channel diversity architecture modelBased on the source and channel coding theory we investigate the approaches by which information can be coded over parallel channels and then construct the models of source coding diversity in application layer and channel coding diversity in physical layer. For evaluating the performances of diversity systems we review the rate-distortion theory with high resolution as well as taking outage probability of channel into account.2. The performance of diversity schemes under on-off channelOne kind of parallel channel which experience serious congestion and corruption can be modeled as on-off channel. We take two-dimension distribution to parametrize the property of this channel and discuss the performance of diversity schemes by using outage probability and rate-distortion theory. The theoretical analysis and experiments indicated that the source diversity has better performance than channel diversity on the on-off channel with general SNR condition.3. The performance of diversity schemes under continuous state channelIt's better to model general fading channel as continuous state channel on which the outage probability is related with not only the states of channel but also the rate. Based on the mutual information model of multiply fading channel we induce theoretically the expression of distortion exponents. Taking the Rayleigh channel as example, we conclude that with general SNR and bandwidth diversity scheme can usually approach 20dB reduced from no diversity scheme for the average distortion, while the optimal channel diversity leads to lower 5dB distortion than source diversity.4. The source diversity scheme with joint channel decodingThen based on the general diversity model we consider the multiple description coding (MD) system with joint channel decoding and prove its reachable rate region through joint classical sequence theory. The theoretical analysis show that on the on-off channel the joint decoding MD system has equal performance with general multiple description coding system, while on the continuous state channel the joint decoding MD system has larger reachable rate region and so it can reconstruct the source with high resolution.The model constructed in this paper and the related conclusion would be helpful for the practical design and implementation of real communication system.