In the modern world, wireless communications have been developed very rapidly and demand for multimedia services is growing day by day. Higher bandwidth over wireless network is requirement of communication systems. These systems are implemented using multi carrier frequencies for providing higher data transmission rate and mobility of user and these systems are implemented with use of MIMO OFDM (Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing) technique. The MIMO OFDM have limitations of high PAPR and carrier frequency offset sensitivity. Integration of STBC with MIMO OFDM over frequency selective channel is implemented to improve further PAPR performance. In this frequency selective channel is converted to several flat fading channels thereby eliminating ISI. This technique STBC MIMO-OFDM has high Peak-to-Average Power Ratio (PAPR) also. To achieve better performance this PAPR also has to be reduced. In this paper, variation of different parameters like number of subcarriers, OFDM symbols and its effect on PAPR has been presented. Simulation Results show that reduction of PAPR is possible with increase in phase factor with four transmitting antennas.

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OFDM MIMO STBC modified PTS ISI QPSK phase factor.