Research On Cooperative Relay Transmission Scheme In Fast Fading Channel

In recent years,the development trend of wireless mobile communication shows that cooperative relay technology is expected to be the key technology to solve the problem of large scale network coverage,high rate data transmission,improving system capacity and combating channel fading.Moreover,diversity gain can be obtained without increasing the cost of practical hardware,which can improve the reliability and effectiveness of wireless communication system and meet the needs of users.By using distributed space-time coding,full asynchronous cooperative relay diversity gain can be obtained in the asynchronous cooperative relay communication network of slow fading channel,however the node moving quickly makes the channel become fast fading channel.Therefore,it is very important to study the transmission scheme of asynchronous cooperative relay communication system in fast fading channel.This paper focuses on the cooperative relay communication system of fast fading Rayleigh channel.The work is as follows:The distributed linear convolution space time coding scheme for asynchronous cooperative communication network is studied.After analyzing the characteristics of the distributed linear convolution space time code,a construction method of delay tolerant distributed linear convolution space time code is designed,using the suboptimal receiver to decode and analyze the complexity of the decoding.It is showed that the proposed coding scheme can achieve full spatial diversity of asynchronous networks when suboptimal receivers are used.The process of the relay node to the destination node is regarded as a fast fading channel,and the distributed space time coding of asynchronous cooperative communication network in the fast fading Rayleigh channel is studied when the maximum likelihood(ML)receiver is used.Through the proof and simulation analysis,it can obtain the full asynchronous cooperative diversity gain.In addition,a number of results verify that the minimum mean square error decision feedback receiver(MMSE-DFE)can obtain the same diversity gain in fast fading Rayleigh channel like the maximum likelihood(ML)receiver.In addition,the performance of the scheme under fast fading and slow fading channels is compared by simulation,and the simulation results are analyzed and summarized.The relay selection scheme for DLC-STC cooperative relay transmission systems under fast fading channels is studied.Firstly,the scheme of amplified and forward,and decoding forward is derived in the cooperative communication model.After analyzing their respective advantages and disadvantages,an optimal multiple relay selection scheme based on a hybrid decode amplification and forward(HDAF)protocol,targeted on the design goal of minimum bit error,with the distance between the destination node and the relay node been equivalent to the path loss on the premise of not considering the small scale fading,taken signal to noise ratio(SNR)as the basis of the decision,combined with the distributed linear convolution space time code is proposed.The relationship between signal to noise ratio and bit error rate is analyzed and deduced.Finally,the simulation shows that the relay selection strategy proposed in this paper has a better bit error rate performance than the fixed relay.