A method to reduce the peak power with signal space expansion (ESPAR) for OFDM system

OFDM (orthogonal frequency division multiplexing) is an effective technique for high data rate wireless transmission. However, the OFDM system has a problem with the peak to average power ratio (PAPR) being very high. A high PAPR can cause severe distortion when transmitted through a nonlinear device. Therefore, because extreme power amplifier specification is required, high power consumption and large hardware is required. We propose a new method called ESPAR (Expansion of the signal Space for Peak to Average ratio Reduction) in order to reduce the peak power. ESPAR expands the signal space by modulating some subcarriers and not modulating the other subcarriers. The proposed system selects the symbol patterns with low signal power in the expanded signal space and transforms data sequences to the pattern. We evaluate the characteristics of the proposed system by computer simulation and show the advantage of ESPAR.