A Study On The Performance Of High Rate Full Diversity Space-time-frequency Codes On Broadband MIMO Fading Channels

Space-time-frequency (STF) code can achieve the spatial, temporal, and frequency diversities offered by multiple-input multiple-output (MIMO)-orthogonal frequency diversion multiplexing (OFDM) systems. The STF codes can combat multipath impairment and improve spectral efficiency and link reliability of wireless communications systems. This thesis is devoted to investigate the performance of space-frequency codes or high-rate full-diversity STF codes on broadband MIMO fading channels, which is focus on the error performance of STF with variety coding configurations, STF decoding algorithm, and iterative clipping and filtering algorithm using in STF-OFDM systems.Chapter1presents a brief review of STF coding scheme, STF decoding algorithm and peak to average power ratio (PAPR) reduction algorithm in OFDM systems.Chapter2presents a novel space-frequency blocks coding (SFBC)-OFDM system with unequal modulations. The closed-form expressions for the average symbol error rate (SER) or average bit error rate (BER) of SFBC-OFDM systems with unequal modulation and cross M-ary quadrature-amplitude modulation (MQAM) are derived. Numerical and simulation results show that the theoretical analyses are accurate.Chapter3studies the sphere decoding (SD) algorithms based on the modified minimum mean square error (MMSE) solution for initial radius selection. The SD algorithms is used in full-rate full-diversity SFBC coding, full-rate full-diversity space-time-frequency block coding (STFBC) and high-rate full-diversity layered STFBC-OFDM systems over spatially correlation fading channels. Simulation results show that the SD algorithms based on modified MMSE method for initial radius guarantees the performance of SD algorithms and significantly reduce the computational complexity of the SD algorithms. The correlation of spatial of fading channels can deteriorate the average SER performance of STF-OFDM systems.Chapter4describes the nonlinear model of high power amplifier (HPA), and investigates the effect of HPA nonlinear distortion on the performance of STF-OFDM systems. The iterative clipping and filtering algorithm is studied in STF-OFDM systems. Simulation results show that the HPA nonlinearity deteriorates the average SER performance of STF-OFDM systems. Iterative clipping and filtering algorithm can effectively improve the detrimental effect of nonlinear HPA on STF-OFDM systems.Chapter5finishes the thesis with concluding remarks.