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


Orthogonal frequency division multiplexing (OFDM) is a form of multi-carriermodulation technique with high spectral efficiency, robustness to channel fading andimmunity to impulse interference. Recently, it is being used for both wireless and wired highdata 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 poweramplifiers, and leads to inter-modulation products among the sub carriers and disturbing outof band energy. Therefore, it is desirable to reduce the PAPR. In this paper we used InverseDiscrete 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 gavegood results toward reduction PAPR. The receiver side includes Discrete Cosine Transform toachieve correct detection. Computer simulation tests have been applied on IEEE 802.11astandard as OFDM practical system with the proposed method .The results exhibit the abilityof such techniques to reduce the PAPR with no major effect on the system performance ascompared with the conventional OFDM technique.