Peak and Average Power Reduction of OFDM Signals Based on Trellis Shaping with Controllable Region Expansion

Trellis shaping (TS) is an efficient and flexible signal controlling technique based on the trellis structure at the transmitter. It can be used for reducing both average power and peak-to-average power ratio (PAPR) of orthogonal frequency-division multiplexing (OFDM) signals. Most studies in the framework of TS have focused on the simple sign-bit shaping, which controls the signal transition with only a single controlling bit per quadrature amplitude modulation (QAM) symbol (or subcarrier). In this paper, we attempt to increase the number of the controlling bits so as to improve the PAPR reduction capability of OFDM signals. The resulting approach, which we refer to as a controllable region expansion, is a novel extension of the conventional TS where the number of the controlling bits per QAM is increased without imposing additional complexity. Through the investigation based on extensive computer simulations using a nonlinear power amplifier (PA) model, it is shown that the proposed extended TS can achieve a better trade-off compared to the conventional sign-bit TS in terms of PAPR reduction capability, PA efficiency, and resulting bit error rate (BER) performance.