JOINT CONSTELLATION EXTENSION AND TONE RESERVATION FOR PAPR REDUCTION IN ADAPTIVE OFDM SYSTEMS

One major drawback of Orthogonal Frequency Division Multiplexing (OFDM) is the large peak-to-average power-ratio (PAPR), which significantly degrades the power efficiency. In order to prevent non-linear distortions the PAPR needs to be minimized to guarantee a linear dynamic range of the high power amplifier. Therefore, various reduction algorithms have been proposed. However, they do not include link adaptation requirements. Previous results show that bit and power loading algorithms in adaptive OFDM systems fail to meet the target error rate requirements if large time-domain peaks occur. Hence, in this paper a joint utilization of extended constellation alphabets of active subcarriers and tone reservation for peak power reduction in adaptive OFDM systems is derived. The resulting linear programming (LP) problem can be efficiently solved and the solution is lossless in terms of throughput. Furthermore, a suboptimal algorithm, which achieves great PAPR reduction with lower complexity, is proposed while link adaptation is employed.