Research On The Uplink Multi-User Distributed Precoding Technique In Cooperative Systems

The precoding technique has been widely investigated and applied in conventional multi-input-multi-output (MIMO) systems. In wireless cooperative/relay systems, the terminals cooperatively share their limited radio resource to each others, which introduces a new type of spatial diversity. In cooperative/relay systems, terminals can process the spatial signal with the help of antennas from other system nodes; thus a so-called'virtual antenna array'can be constructed to achieve high spectral efficiency and capacity. Due to the similarity between the conventional MIMO system and the cooperative/relay system, it is feasible to introduce the precoding technique into the cooperative systems for higher spectral efficiency. However, there is little research results in this area, which motivates us for further investigation into this subject.This dissertation firstly classifies the topology structure of the cooperative/relay systems according to the number of the nodes and their relationship. The research in the dissertation mainly focuses on three typical scenarios of uplink multi-user cooperative/relay systems and the corresponding distributed precoding schemes.In the uplink multi-user cooperative/relay system with single relay node, the distributed precoding scheme can be utilized at the source nodes for the first hop transmission. The second hop transmission can either be based on spatial diversity mode or spatial multiplexing mode.In the uplink multi-user cooperative/relay system with multiple relay nodes, there are mainly two transmission modes for the first hop, i.e. the broadcasting mode and the unicasting mode. In the broadcasting mode, the transmitted signal from all source nodes can be received by each relay node. Meanwhile, with distributed precoding scheme utilized between the multiple source nodes, the unicasting mode introduces the virtual pairing between source nodes and relay nodes for single data stream transmission, which effectively mitigates the interference between data streams.In the uplink multi-user cooperative/relay system without fixed relay node, cooperative transmission can be introduced between multiple source nodes. During particular phases of the transmission, each source node can receive and forward the transmitted signal of other source nodes. Extra spatial diversity gain can be obtained with this cooperative transmission scheme. The corresponding distributed precoding design is closely related to the cooperative transmission protocol.This dissertation investigates the distributed precoding schemes in three typical scenarios of the uplink multi-user cooperative/relay systems. It also gives the performance evaluation of distributed precoding schemes in comparison to other transmission schemes under Raleigh fading channels.