A Full-Rate Two-Way Cooperative Relay Transmission Scheme With Low Detection Complexity

In distributed wireless communication system, the two-way cooperation communication technology can achieve the transmission of data in bi-direction coded by the physical layer network coding and overcome the limitation of half-duplex communication mode, and the spectral efficiency of system is improved significantly. Therefore, the two-way cooperation communication becomes an important research field of wireless communication system in recent years. In wireless communication network, how to achieve high reliability, high speed and low detection complexity of two-way relay transmission is worth researching further. The traditional full-diversity full-rate (FDFR) space-time code based on linear complex field (LCF) coding technique not only can obtain full diversity gain, but also improve the spectral efficiency. However the receiver nodes need detect all transmission symbols of the space and time jointly and the detection complexity is too high. Space-frequency code based on the cyclic delay diversity (CDD) technique has a simple coding structure and the receiver nodes have a unified detection structure, so the detection complexity of multi-antenna transmission system can be reduced. This thesis will focus on the study of a full-rate two-way cooperative relay transmission scheme with low detection complexity by the combination of linear complex field coding and cyclic delay diversity technique. The main research contents are shown as follows:(1) On the basis of introducing space-time code and cooperation communication technology, linear complex field coding technology is researched mainly to obtain full diversity gain and achieve full rate transmission. The probability error rate of data transmission can be reduced by coding and detection of several symbols jointly, so it can be applied to the cooperation transmission of multiple relay nodes in distributed wireless communication system.(2) In multi-antenna wireless communication system based on orthogonal frequency division multiplexing (OFDM) technique, the implementation method of cyclic delay diversity technique has been researched, the principle of simplifying codes and detection complexity has been analyzed and the application combining idea of cyclic delay diversity technique has been explored.(3) On the basis of above two classical coding transmission technology, the thesis proposes a full-rate two-way cooperative relay transmission scheme with low detection complexity by combining the advantage of the above two coding schemes. The two-way relay transmission of this scheme should be completed within three time slots. In first time slot, the data of two source nodes will be coded by linear complex field coding technique and modulated by OFDM technology, and then will be transmitted to all relay nodes. In second and third time slot, two source nodes will send new data, thus full-rate two-way transmission can be achieved, and meanwhile relay nodes will amplify the received data in previous time slot by combining CDD technique, and then send the processed data to two source nodes. According to theoretical analysis and simulation, the proposed scheme can obtain full diversity gain of the system, while it can be applied to the distributed wireless cooperation communication network with different number of relays, and the detection complexity can be reduced at receiver nodes under the condition of guaranteeing probability error rate performance of system. Therefore the proposed scheme has more practical value beyond those that have only a pursuit on a single performance.