Research On MIMO Relay Key-Technology

Traditional cellular mobile system faces the challenge of system throughput, capacity edge-coverage and communication reliability. Besides using a range of new technology such as MIMO, B3G/4G system also adopts a new net-configuration. Relay system is a promising scheme which can satisfies the next wireless network both in the sides of higher capacity and better signal coverage. The latest research shows that the point-to-point MIMO system which deploys some relay nodes to cooperate to transmit the information can improve the system throughput, especially when the channel state is terrible.Based on the model of two-hop MIMO multiple relays, the paper mainly analyzes the system performance including the capacity, the matrix by which the relays deal with the signal and relay-selecting of the relay-enhanced cellular wireless network. The main content and the research of this paper include as follows:Firstly, the paper analyzes and simulates the key-technology of the MIMO system and three-node relays system. The result shows that, the capacity of the system with M transmit antennas and N receive antennas is MN times than the capacity of the single transmit and receive antenna system. Then the paper builds a two-hop MIMO relay system model, and studies the capacity of the model. The outcome shows that when the system model uses a single source a single destination and many relay nodes, the capacity limit and the number of the relays can be expressed in terms of logarithms.Secondly, targeted on the maximal capacity the paper researches the optimal retransmit matrix with considering joint the base station and the relay stations. The optimal matrix with which the relay deal with the signal consist of three parts: the optimized receiving matrix, the best recourse assigning in relays and the optimized pre-coded matrix. With this theory the paper optimizes the matrix of relay in AF and DF scheme, and calculates the capacity with relevant power allocation. The paper then adopts a new relay progress matrix based on the channel state, which called SVD scheme, and offers the sub-optimal power allocation. The simulation shows the SVD scheme can get mare increment of capacity then the AF scheme.Thirdly, because of different gains during different relays the paper further investigations of the relay-selecting algorithms. To achieve the same target of the maximal capacity, the paper offers an algorithm based on instantaneous channel state and analyses the out probability. The analysis and the simulating prove that the number of relays selected is reducing with the increasing SNR.Lastly, the paper analyzes the partial decode-and-foreword scheme, and finds that this scheme can get more throughput than DF scheme because PDF use more relays. Also, the paper gives the relay-selecting algorithm when the system adopt PDF scheme, and results the out probability. After simulation, we prove that the PDF scheme can get more capacity than DF with the same number of relays, especially the SNR is very low.