Collaboration Solutions In The Wireless Relay Network Transmission Technology Research

It has been proved that the wireless relay network can significantly en-hance the throughput and increase the reliability of wireless link, and can en-large the coverage and improve the robustness of the systems. Relay technol-ogy has attracted increasing attention in recent years and is has been become an important candidate technology for 3GPP LTE-Advanced. MIMO relay chan-nels,which combines the multiple antenna system and the relay,can improve the spectral efficiency of relay network. In this dissertation,we focus on the co-operative transmission technologies in MIMO relay systems.Detailed contents are listed as:1. Investigation is made upon the asynchronous cooperative transmission scheme based on interleave-division multiple access (IDMA) in the multi-user MIMO relay system with multiple relays. This system combines IDMA and delay diversity (DD),in which every user is assigned a dif-ferent interleaver and the relays forward the signal after a random delay. By using a turbo-type MIMO IDMA receiver with low complexity incor-porating with an efficient soft MIMO multi-user detector, the destination node can distinguish the signals corresponding to the same information from multiple relays and implement maximal ratio combining (MRC) to exploit diversity gain. This scheme does not need synchronous transmis-sion, has no restriction on the number of users and relays, and all the relays need no channel state information (CSI).2. Investigation is made upon the joint linear transceiver design in two-hop non-regenerative MIMO relay network. Firstly, we joint design the signal processing matrics of the source, relay and destination based on the min-imum mean square error (MMSE) criterion under the assumption of per-fect channel state information (CSI). An iterative algorithm is proposed to get the signal processing matrics. Secondly, we extend this algorithm to the system with channel estimation errors. In order to reduce the com-putational complexity of the iterative algorithm, we also propose a block-optimization method to compute the transmission matrix of the source, relay processing matrix and the receive matrix of the destination. The block-optimization method can achieve a similar performance to the it-erative algorithm with a much lower complexity, which is much more practical in realistic relay systems.3. Investigation is made upon the robust relay precoding in the downlink channel of multi-user MIMO relay system, where multiple mobile users are served by the base station (BS) simultaneously through a single relay station (RS). Assuming that there is a limited feedback link between each user and the RS, every mobile user feeds back its channel direction infor-mation (CDI) by B bits to RS in order to implement the relay precoding. Taking into account the effect of codeword mapping errors, we proposed a robust zero forcing (ZF) precoding scheme as well as a robust MMSE precoding scheme. We also analysis the signal to interference plus noise ratio (SINR) properties of the precoding schemes. Compared to the con-ventional linear precoding techniques, the proposed robust precoders can reduce the average bit error rate (BER) of the system.