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RESEARCH PRODUCT

Reducing the peak and average power for OFDM systems using QAM by constellation shaping

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In this paper, we present a shell mapping scheme to reduce the peak and average power of orthogonal frequency division multiplexing (OFDM) signals using quadrature amplitude modulation (QAM) by constellation shaping. Our approach can be considered as an extension of the shell mapping technique introduced originally in the V.34 recommendation of ITU-T. The shell mapping method uses multiple cost functions, each having the OFDM block length N as a parameter. The cost functions are presented in closed form for any N. The main advantage of the proposed scheme is that the peak and average power can be reduced without sacrificing the data rate, and no side information is needed at the receive side. We apply our constellation shaping technique to OFDM systems with N equal to 16, 32 and 128 subcarriers. The results show that the peak and average power decrease with increasing values of N. This advantage is partly offset by a slightly higher system complexity. Copyright © 2009 John Wiley & Sons, Ltd.