Reduction of Peak to Average Power Ratio in OFDM System Using Discrete Cosine Transform Technique

Abstract

 Orthogonal frequency division multiplexing (OFDM) is a form of multi-carrier modulation technique with high spectral efficiency, robustness to channel fading and immunity to impulse interference. Recently, it is being used for both wireless and wired high data rate communications. Despite of its many advantages, OFDM has a main drawback, namely high Peak to Average Power Ratio (PAPR).High PAPR causes saturation in power amplifiers, and leads to inter-modulation products among the sub carriers and disturbing out of band energy. Therefore, it is desirable to reduce the PAPR. In this paper we used Inverse Discrete Cosine Transform (IDCT) technique in the transmitter side to reduce PAPR problem. The use of this technique in the output of Inverse Fast Fourier Transform (IFFT) stage gave good results toward reduction PAPR. The receiver side includes Discrete Cosine Transform to achieve correct detection. Computer simulation tests have been applied on IEEE 802.11a standard as OFDM practical system with the proposed method .The results exhibit the ability of such techniques to reduce the PAPR with no major effect on the system performance as compared with the conventional OFDM technique