Researches On Relay Cooperation Technology In Novel Wireless Communication Networks

MIMO relay technique can effectively enhance the capacity, extend the cellcoverage, and reduce blind spots, has become the hot topics in the study of wirelesscommunication. This paper mainly study of dual-hop MIMO relay systems, the maincontributions are as follows:1. In dual-hop distributed precoding MIMO relay system, in order to overcome thedrawback of high complexity of codeword selection, the codeword selection strategybased on the feedback of right singular eigenvector of each hop channel was proposedin this paper. Firstly, the dual-hop distributed precoding matrix based on the meansquare error(MSE) was given, and the random vector quantization(RVQ) codebookwas used to quantize the right singular eigenvector, finally minimum distancecriterion was utilized to select codeword. The simulation results show that when thenumber of feedback bits are same, the BER performance of the system is approximateto the existing algorithm, but the sum-rate performance of the system is slightly betterthan the existing algorithm, and computational complexity is reduced by half.2. In the single relay multi-user MIMO system, in order to overcome the inter-userinterference, a new relay processing scheme which can be used to effectivelysuppress the inter-user interference is proposed in this paper. Firstly, the relayreceives the signal by zero forcing filtering, and then transmits the signal to the usersthrough the precoding matrix. Secondly, the signal-to-leakage-noise ratio (SLNR)receiver expression is derived and the relay precoding vector is designed by using theSLNR maximization criterion, where a suboptimal relay precoding design is proposedsince it is difficult to obtain the optimal relay precoding vector. The simulation resultsshow that the new scheme is superior to the relay terminal zero-forcing precoding onthe performance of sum rate, with both perfect channel state information (CSI) andpartial CSI at the relay.3. In the multiuser multi relay system, the phase ambiguity caused by channelquantization resulted the system cannot obtain the relay array gain, in order to overcome this problem, we introduce a new strategy combining phase information (PI)and channel direction information (CDI) feedback was given. The simulation resultsshow that the new strategy can effectively solve the problem which phase ambiguitybrings, and through allocation of feedback bits, we can maximize the system capacityunder the total number of feedback bits constraint.