Combining block-coded modulation codes and improved constellation extended schemes to reduce peak-to-average power ratio in orthogonal frequency-division multiplexing systems

Abstract

Orthogonal frequency-division multiplexing (OFDM) has been recommended as the standard for numerous wireless transmission systems. However, OFDM still has deficiencies that must be improved, such as a high peak-to-average power ratio (PAPR) occurring in the transmission signal. A constellation extended scheme (CES) is one technology for reducing high PAPR. The PAPR performance of the CES is directly correlated to the amount of candidate signals, high PAPR in OFDM systems will be significantly reduced as the candidate signals increase. However, because calculating the PAPR values of candidate signals requires more inverse fast Fourier transform operations, the CES hardware circuit is difficult to achieve. Therefore this study combines the CES, partial transmit sequences (PTSs) and block-coded modulation (BCM) codes to propose a BCM–CES–PTS technology, which simultaneously improves the high computation of the CES, the necessary side information delivered in PTS and the lack of error correction capabilities in the transmitted signal itself, applying this to a 16-QAM modulation OFDM system. In addition, this study proposes two structures of the CES by arranging the extended constellation points in symmetrical and asymmetrical forms, called S-BCM–CES–PTS and AS-BCM–CES–PTS, respectively. The generator matrices of the two structures were proposed to simplify the division of the circuit into sub-blocks.