A PAPR Reduction for STBC MIMO-OFDM Systems in 4G Wireless Communications using PTS Scheme

Orthogonal Frequency Division Multiplexing (OFDM) is of great interest for researchers and research laboratories all over the world. OFDM is widely used in contemporary communication systems for its good robustness in multipath environment, and its high spectral efficiency. The capacity of wireless system can be increased dramatically by employing Multiple Input Multiple Output, (MIMO) antennas. The combination of MIMO and OFDM system is found to be very beneficial. A major drawback of OFDM-MIMO System is its high Peak to Average Power Ratio (PAPR) Reduction. The peak power of a signal is a critical design factor for band limited communication systems, and it is necessary to reduce it as much as possible. Many PAPR reduction techniques have been used to reduce PAPR. Partial transmit sequence (PTS) is one of the most well-known peak-to-average power ratio (PAPR) reduction techniques proposed for MIMO-OFDM systems. However the computational complexity of traditional PTS method is tremendous. In this paper a new partial transmit sequence (PTS) technique, based on C-A-PTS technique, for two antennas STBC MIMO-OFDM system, is proposed which can achieve better PAPR performance at much less complexity. The main idea behind this is to separate the input data vector, generated by Alamouti algorithm, into real and imaginary parts and separately multiplied with phase factors. The optimum weighting coefficient of antenna two can be directly obtained by appropriating mapping from that of antenna one which leads further to reducing complexity computation. Simulation results show that the proposed approach can reduce computationally complexity and achieve a better PAPR reduction and bit error rate performances compared to C-A-PTS.