ABSTRACT

Orthogonal Frequency Division Multiplexing (OFDM) suffers the effect of Peak to Average Power Ratio (PAPR) that reduces the strength or power of radio frequency (RF) signal at the transmitter and which also pushes the performance of transmitter amplifier into distortion. In order to minimize the effect of PAPR in OFDM, this paper proposed a system that precodes the OFDM signal using Walsh-Hadamard Transform (WHT) and Log function companding algorithm. Simulations were conducted in MATLAB environment while varying the number of subcarriers, N = 16, 64, 128, 256. simulation results indicated original OFDM revealed high PAPR in transmitted signal for the different number of subcarriers (N) such that for N =16, 64, 128, and 256, resulting in 7.964dB, 8.885 dB, 9.548 dB, and 9.961 dB respectively. With the introduction of WHT-Log companding scheme, the PAPR of OFDM signal was significantly reduced to 4.775 dB, 4.285 dB, 4.517 dB, and 4.602 dB by a percentage improvement of 40%, 51.8%, 52.7%, and 57.8% for N = 16, 64, 128, and 256 respectively. As a result, from the simulation results, the proposed system can be said to have largely reduced PAPR in OFDM system using a scheme with significant computational complexity.

Keywords: - Log companding, OFDM system , PAPR, WHT