| International Mobile Telecommunication-Advanced (IMT-A) needs to provide high quality of data and multimedia service. The increased requirement for high data transmission rates enables us to research and adopt novel transmission technology to make full use of the available radio resource. Multiple-Input Multiple-Output (MIMO) and relay have been recognized as the key physical layer technologies in IMT-A communication system and have attracted our attention. This paper is focused on the algorithm design and performance analysis for multi-antenna relay system. The influence of certain factors, such as antenna numbers, relay numbers, power allocation coefficients and channel fading parameters, on the system performance is investigated. The main contribution of this paper can be included as follows:(1) In traditional point-to-point MIMO systems, codebook based precoding is usually adopted in FDD duplex and the non-codebook based precoding is more suitable for TDD duplex. The former scheme induces large signaling overheads in uplink feedback channel, while the performance of latter is restricted by the codeword mismatch between base station and destination. Two novel codebook based precoding schemes for TDD system are proposed in the paper. The adaptive codebook is first proposed, which is constructed according to channel state information (CSI). By adjusting the relationship between feedback bits and codeword distance adaptively, the proposed algorithm could reduce the feedback bits effectively with little performance loss. To eliminate the precoding matrix index (PMI) feedbacks, the contribution further proposed a precoding scheme based on linear interpolation. In this scheme, the base station could achieve the CSI of downlink channel by interpolating the uplink CSI in consecutive time slots, then the precoding matrix is chosen according to the downlink CSI. The simulation results illustrate that our proposed scheme could achieve the tradeoff between performance and overheads.(2) The theoretical performance of distributive multi-user network is studied, where all nodes are equipped with single antenna. First, the network is modeled as a parallel cooperative networks. In the model, relays forward the received signal by using three transmission strategies which need different CSI. Destination combines the received signal from source and relay by using maximum ratio combining (MRC). Then, the outage probabilities of different strategies in DF relay networks over independent and non-indentical distributive (i.ni.d) Nakagami-m fading channels are derived which is then confirmed by numerical simulations. Finally, the performances of different strategies are compared and the feasibilities of these schemes are analyzed.(3) The performance of multi-antenna relay with limited feedback precoding in centralized cellular networks over Rayleigh fading channels is investigated. The exact closed-form expression of outage probability and bit error rate, and the tight upper bound of capacity are derived for the first time. A suboptimal power allocation scheme is also proposed to optimize the system performance further. Moreover, we extend the research to i.ni.d Nakagami-m fading channels and derive the outage performance of multi-antenna relay networks with antenna selection and limited feedback precoding.(4) The research on multi-antenna single-relay networks is extended to multi-antenna multi-relay networks. The theoretical performance of two multi-antenna relay selection strategies based on different CSI are analyzed and the outage performance are derived under i.ni.d Nakagami-m fading channels. The theoretical and simulated results shows that increment of relay antennas and relay numbers can both improve the system performance of relay selection based on instantaneous CSI, while the increment of relay numbers has little impact on the performance of relay selection based on statistical CSI.
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