Peak to Average Power Reduction (PAPR) in OFDM (Using MATLAB Software)

Orthogonal Frequency Division Multiplexing (OFDM) spread spectrum technique distributes the data over a large number of carriers that are spaced orthogonally apart at precise frequencies i.e, sub-carriers are able to carry information without interference, which prevents the demodulators from seeing frequencies other than their own. The benefits of OFDM are high spectral efficiency, robustness to channel fading, immunity to impulse interference, capability of handling very strong multi-path and frequency selective fading without having to provide powerful channel equalization. Multi-carrier modulation systems such as OFDM have very high Peak to Average power ratio (PAPR); i.e. they exhibit very high peaks whose power is very large compared to mean power. The different subcarriers may all line up in phase at some instants in time and therefore produce a large peak equal to the sum of the amplitudes of the individual subcarriers. However, with large number of subcarriers, the magnitude of samples of OFDM symbols is approximately Rayleigh distributed and the large peaks occur with extremely low probability. In this paper different techniques for reducing PAPR, such as Partial Transmit Sequence (PTS), Suboptimal PTS, Repeated Clipping and Frequency Domain Filtering techniques and a new technique based on the combination of PTS and Clipping techniques, that gives more reduction in PAPR than PTS technique and less in-band distortion compared to clipping technique, making this technique adaptive for the implementation of low-PAPR OFDM system, are analyzed and simulated in MATLAB.