An evaluation of modified μ-Law companding to reduce the PAPR of OFDM systems

High peak-to-average power ratio (PAPR) is a common problem in OFDM transmissions. This paper investigates the influence and effects of various mu-Law companding parameters to assist in reducing the high values of PAPR. Results for modified mu-Law companding, where the use of a further new companding profile parameter PR (peak ratio) is applied, are presented. Simulation studies of PAPR, bit-error-rate (BER) and power spectral density (PSD) are investigated as a function of mu and PR. It is shown that modified mu-Law companding significantly reduces PAPR, though marginally larger (0.5 dB) than normal mu-Law companding, and significantly improves BER to levels better than mu-Law companding. The spectral splatter due to companding is also evaluated and noted that the larger the companding profile, mu, the larger will be the sideband splatter. The results allow an optimum companding profile based on the use of both mu and PR to be chosen in relation to acceptable or desired PAPR and BER requirements. A brief evaluation of companding and selected mapping (SLM) in terms of PAPR reduction and BER is also presented. (C) 2009 Elsevier GmbH. All rights reserved.