Performance Analysis Of Space Time Frequency Block Code For Cooperative Communication Systems

Space-time-frequency block coded (STFBC) orthogonal frequency division multiplexing (OFDM) systems, where the jointly coding is applied across different OFDM tones and transmit antennas, multiple OFDM blocks in order to exploit the spatial, temporal, and frequency diversities available, can effectively decrease the performance deterioration caused by Doppler frequency and multipath delay on time-and frequency-selective fading channels. Applying STFBC-OFDM technique into cooperative communication systems can further improve the ability of combating fading. The nonlinear effects of power amplifiers(PA) can broaden the sgnal spectrum, decrease the amplitude of OFDM signals, and deteriorate the performance of OFDM systems. Therefore, this thesis investigates the error probability of STFBC-OFDM decode-and-forward (DF) cooperative communication systems and the nonlinear effects of PA on OFDM or STFBC-OFDM amplify-and-forward (AF) cooperative communication systems, respectively.Chapter1presents a brief review of Space-time-frequency codes (STFC), cooperative communication technique, and the nonlinear effects of PA on OFDM systems.Chapter2derives the exact closed-form expressions for the average symbol error rate (SER) of STFBC-OFDM systems with M-ary phase-shift keying (MPSK) and rectangular M-ary quadrature amplitude modulation (MQAM) on time-and frequency-selective Rayleigh fading channels using moment generating function (MGF) approach. Applying STFBC-OFDM technique into cooperative communication systems, the exact closed-form expressions for the average SER of STFBC-OFDM DF single relay cooperative systems, dual-hop relay systems, relay selection cooperative systems with MPSK and MQAM are derived, respectively. Numerical and simulation results show that STFBC-OFDM systems can significantly decrease the performance deterioration caused by Doppler frequency and multipath delay and that the performance of STFBC-OFDM systems obviously outperform both Space-time block coded(STBC)-OFDM systems in high time-selective channels and Space-frequency block coded(SFBC)-OFDM systems in high frequency-selective fading channels. The SER performance of single relay cooperative systems outperform dual-hop relay systems and relay selection cooperative systems under the same channel condition and antennas allocation. Increasing the number of receive antennas can improve the error performance of systems mentioned above.Chapter3investigates the nonlinear effects of PA on OFDM cooperative communication systems on Rayleigh fading channels. The exact closed-form expressions for the average bit error rate (BER) of OFDM and STFBC-OFDM AF dual-hop relay cooperative systems with MPSK and MQAM are derived, respectively. Numerical results show that the nonlinearity of PA deteriorate the error performance of systems mentioned above and that the adjustment of the power back-offs factors in the source and relay nodes can effectively decrease the deterioration and be close to the performance of linear PA’s.Chapter4finishes the paper with concluding remarks.