Research On Rate-Embedded Two-Path Differential Relay Transmission Method

Cooperative communication is one of the hotspots in wireless communication field currently. This technology alleviates the difficulties in practical application of MIMO (Multiple Input Multiple Output) technology effectively. Its essence is using a plurality of discrete antennas to build a virtual multi-antennas array in a wireless communication system, so the system can obtain spatial diversity gain. Compare with the conventional end-to-end communication, cooperative communication will reduce the transmission power of the wireless communication network, increase the transmission rate, improve the reliability of wireless communication links and enlarge transmission distance and coverage of the wireless system. In complex distributed networks, multiple nodes and antennas make the receiver hardly get the channel state information (CSI). So the scholars transfer the focus of their research to the differential transmission method. In order to ensure the successful progress of differential transmission, the message matrix should be unitary matrix. Therefore the transmission symbols must contain certain redundant information which limits the transfer rate of the system. To solve the problem, this thesis has finished the following works:(1) Explore full-rate two-path relay transmission model. The nodes of general cooperative communication model can’t send and receive data at the same time or frequency, in the second stage of the relay, source node is often idle, which leads to the waste of time. Two-path relay transmission model is composed of one source node, one destination node and two relay nodes. Source node can send new data each slot so the model is a full-rate model which can improve spectrum efficiency of the system greatly.(2) The thesis introduces cycle delay diversity technology on the basis of existing research. The technology can enhance the channel frequency selectivity and reduce the detection complexity. The level of complexity will not increase with the increase of the number of relay nodes.(3) In order to improve the transmission rate further, the thesis designs rate-embedded differential transmission scheme. FDFR (Full Diversity Full Rate) codes are embedded into conventional differential space-time coding, so the system can get well error performance and high transfer rate. The simulation results show that rate-embedded differential transmission can enhance the spectral efficiency of the system at the same performance. While at the same spectral efficiency or fading channel, rate-embedded differential transmission can improve the error performance of the system obviously.In conclusion, rate-embedded differential space-time transmission scheme researched in this thesis own high spectral efficiency and low detection complexity. It enhances the effectiveness and reliability of the communication system and has theoretical significance and practical value.