Optimized LDPC Code Concatenated with Trellis Shaping for PAPR Reduction in SISO-OFDM Systems

Different techniques have been used for the peak-to-average power ratio (PAPR) reduction of orthogonal frequency division multiplexing (OFDM) systems. Among these, trellis shaping provides state of the art performance in terms of PAPR reduction as well as mean power reduction with moderate computational complexity. Therefore, this manuscript addresses the effect of using shaping codes with higher trellis depths for PAPR reduction of the OFDM systems. Using shaping codes of higher depths improve the PAPR reduction as well as bit error rate (BER) of the system. Moreover, we concatenate an optimized low-density parity-check (LDPC) code with Trellis shaping to further improve the performance of the OFDM system in terms of BER. For the LDPC code, the variable node degree distribution is optimized based on the error probabilities of the individual bits inside a quadrature amplitude modulation (QAM) constellation taking into consideration the error probabilities of the shaping codes used. Simulation results show that the proposed technique has better PAPR reduction as well as better BER as compared to the already existing systems using Trellis shaping with a shaping code of 4 states concatenated with an optimized LDPC code.