Reduction of Peak to Average Power Ratio (PAPR) in Orthogonal Frequency Division Multiplexing (OFDM): A Novel Approach Based on Clipping and Amplification

Reduction of Peak to Average Power Ratio (PAPR) in Orthogonal Frequency Division Multiplexing (OFDM) is investigated here. Clipping can be performed in two ways- one is to clip the complex envelopes of OFDM signal and the other is to clip the Inphase (I-signal) and Quadrature phase (Q-signal) independently. The detailed investigation concerning the PAPR reduction and Complementary Cumulative Distribution Function (CCDF) of both the techniques is made. A novel approach based on clipping and amplification is introduced as a mean for reducing PAPR in OFDM signal. Our Proposed scheme combines the effect of clipping the peak signals and amplifying the signals that have low amplitude of OFDM signal, hence the name Clipping and Amplification method. The method is then simulated and detailed comparisons in terms of PAPR reduction with other methods are made. Comparison among different M-array modulation techniques is made to draw the conclusion for the best suited modulation technique for OFDM in terms of PAPR reduction. Finally, relations among PAPR, threshold of clipping, threshold of amplification and CCDF are established. Results show that our proposed approach gives better performance than clipping method at the expense of increased CCDF.

I. Introduction

Orthogonal frequency division multiplexing (OFDM) is a multicarrier modulation scheme that has been an attraction of all eyes, because of its high spectral efficiency, high data rates, and combating radio impairments and above all with the event of increase in Very Large Scale Integration (VLSI) technology and Digital Signal Processing (DSP), the implementation has become much more cost effective and simpler. Its use in wireless communication has attracted considerable attention in the recent years and is recognized as an excellent method for high speed wireless communication. With the event of increasing speed, facility, spectrum efficiency, multimedia facilities, system performance, Grade of Service (GOS), probability of bit error, signal to noise ratio (SNR) and many more factors, the modulation technique employing single carrier scheme is rapidly replaced by Multi Carrier Modulation (MCM) scheme. OFDM provides flexibilities in data link layer, physical layer and other link layers that make it an ideal candidate for Fourth Generation (4G) wireless communication system [2]. Speed is the most important factor that is limited by the efficient use of bandwidth. The Fourth Generation (4G) mobile system employing OFDM modulation technique enables high speed communication up to Mega bits per second (Mbps).