Research On Full-Rate Distributed Transmission Scheme For Multi-Antenna Cooperative Relay Networks

Multiple-input multiple-output(MIMO) techniques can achieve low power consumption, large capacity and high-rate wireless data transmissions. However, limited by the volume of mobile terminals, power, and the position of antennas, it’s difficult for MIMO techniques to use in personal mobile terminals. Cooperative relay communication technology solves this problem efficiently, and resists channel fading through spatial diversity gain, which has attracted widespread concern and attention. Half-duplex relay transmission mode for cooperative relay communication systems has been adopted in early coding method widely, and has low spectral efficiency. In recent years, documents adopted two-way cooperative relay communications to improve spectral efficiency have been published. However, there are still many defects for high-rate and better bit error rate performances transmission methods, which meet communication requirements of complex application scenario.For above problems, combined the superiority of MIMO technology, jointly coding technique, cyclic delay diversity(CDD) ways and time division forward ways, a distributed multi-antenna transmission method for cooperative relay is in-depth discussion in thesis. The mainly research contents are as follows.(1) Under the condition of both transmitters and receivers don’t know the necessary channel state information, differential coding transmission method can implement data transmission for cooperative relay communication systems, and reduce the implementation complexity of reception facilities. But there are problems of poor bit error rate performances and complicated design in existing differential coding transmission methods. Hence a distributed differential coding transmission method based on relay grouping and CDD ways for two-way cooperative relay networks is studied in thesis. The application of CDD ways in this method can simplify transmission design process and reduce complexity detections at receiver, which provides a new way of thinking for the research on distributed transmission method for multi-antenna cooperative relay networks.(2) CDD forwarding ways is extended to use at distributed transmission method for two-way multi-antenna cooperative relay networks. The symbols to be transmitted are jointly coded appropriately at two source terminals during several time slots on each sub-carrier. Each OFDM modulation symbol is cyclically delayed at each relay in time domain, and the operated signals at all relays are transmitted to both source terminals successively in time division (TD) ways at the same time. This method reduces the interferences among antennas, realize low complexity detections, and achieve good bit error performances.(3) Based on the above results, a complicated scene of there are a direct link between transmitter and receiver for one-way distributed multi-antenna communications systems is further studied, and a full-rate distributed transmission method for multi-antenna cooperative relay network is proposed. One whole data exchange and transmission process between source terminal and destination terminal mainly includes two stages. In the first stage, the symbols to be transmitted are jointly coded appropriately at source terminals during several time slots on each sub-carrier, and then broadcasted to all relay nodes and destination node respectively. In the second stage, each OFDM modulation symbol is cyclically delayed with proper cyclic delay value at each relay in time domain. In the amplification and forwarding (AF) process, the operated signals at all relays are transmitted to destination terminal successively in time division (TD) ways, and source terminals sends the next jointly coded to destination node at the same time. Simulation results verify this method can realize full-rate transmissions, obtain good bit error performances with low coding and detection complexity, and the coding process is simple.From what has been discussed above, the research on distributed transmission method for multi-antenna cooperative relay networks in this thesis provides a new way of thinking for solving the problem of low spectrum efficiency, poor bit error rate performances and high coding complexity, and there are great theoretical values and potential application prospect.