Nonlinearity Reduction by Tone Reservation with Null Subcarriers for WiMAX System

Abstract

This paper proposes an effective tone reservation method with null subcarriers (TRNS) to reduce the peak to average power ratio (PAPR) for so-called WiMAX system. The TRNS method utilizes a part of null subcarriers in guard band to reduce the PAPR, which satisfies the spectrum mask regulation and avoids bandwidth sacrifice. Furthermore, this paper analyzes the properties of order statistics of orthogonal frequency division multiplexing (OFDM) signals. A type of low complexity TRNS method (LC-TRNS) is proposed to solve problems of the TRNS method, including high complexity and the performance degradation under low predefined threshold. Finally, a joint nonlinearity reduction scheme by predistortion and TRNS method is proposed. Not only the nonlinear distortion in the WiMAX system is reduced, but also the good tradeoff between power efficiency and system performance is achieved. Both analytical and simulation results demonstrate that those proposed methods are effective in terms of spectrum mask regulation, total degradation, complementary cumulative probability function versus PAPR threshold, and bit error rate in presence of nonlinear distortion.