合作式無線通訊於高性能接收器演算法及架構設計

Abstract

Cooperative communications for wireless networks have gained much interest due to its ability to mitigate fading in wireless networks through achieving spatial diversity, while resolving the difficulties of installing multiple antennas on small communication terminals. In cooperative communication, relays are assigned to help a source in forwarding its information to its destination, hence forming a virtual antenna array. Hence, how to select the best relay is important and necessary since it determines the transmission quality attainable. In this thesis, we propose a predetermined relay-selection scheme and show that our predetermined relaying scheme is outage-improved. Alamouti’s space time (ST) code and Tomlinson-Harashima Precoding (THP) Equalization are efficient schemes for the purpose of combating channel fading and interference, respectively. Consequently, the availability of channel state information (CSI) at the transmitter is a primary requirement. Unfortunately, under smoothly–varying channels, the transmitter cannot acquire complete CSI inclusive of channel gains and channel variations immediately. Hence, incomplete CSI will cause Alamouti’s ST code losing the property of orthogonality so that residual interference will occurs and increase BER. In this thesis, we propose a new THP scheme in which the transmitter merely requires channel gain information for the sake of mitigating interference in smoothly-varying channels when only partial CSI (no knowledge of channel variation) is available. In VLSI implementations of the cooperative transceiver designs, we apply the proposed predetermined relay-selection scheme and the proposed THP to cooperative communication systems to appreciate the effect of the proposed transceiver design. The system model of the simulated configuration is first introduced. Then, floating point simulation is done to verify the performance of the new transceiver design. It should be noted that with the proposed schemes, cooperative transceiver designs can help to save the hardware cost in implementing the transmitter and receiver ICs.