Peak-to-average power reduction for OFDM system using a multiple-constellation ACE method

Abstract

Orthogonal frequency division multiplexing (OFDM) has become a popular technology for modern communication systems as it offers the advantages of high data rate transmission and robustness against the frequency selective fading channel. However, the high peak-to-average power ratio (PAPR) of the transmitted signal causes problems for power amplifier design and the power efficiency of the transmitter. Thus, research in the area of PAPR reduction has been receiving a lot of attention.

A multiple-constellation Active Constellation Extension (ACE) for PAPR reduction in an OFDM-based system is proposed in this thesis. Conventional ACE uses a fixed modulation scheme (i.e. PSK or QAM) over all sub-carriers. The proposed method adopts simplified adaptive modulation according to the quality of the sub-channels The multiple-constellation ACE is able to significantly reduce PAPR as the conventional ACE is able to do Moreover due to the use of multiple constellations, the proposed method makes use of the frequency selectivity to improve transmission rate by employing higher level linear modulation for sub channels with higher Signal-to-Noise Ratio (SNR). As a result, the proposed method offers a trade-off between data throughput, Bit Error Rate (BER) performance and PAPR reduction.