Improvement of PAPR and BER in OFDM Using Combination of SLM and Clipping Techniques

Orthogonal Frequency Division Multiplexing (OFDM) is high speed data transmission scheme. It has got various advantages like easy and efficient in dealing with multi-path, robust against narrow-band interference, supports various modulation schemes and perfect for MIMO etc. In spite of having various advantages it has got one major drawback of high Peak to Average Power Ratio (PAPR). One of the common technique for reducing the PAPR is Clipping, in this method a threshold value of the amplitude is set and any sub-carrier having amplitude more than that value is clipped. Advantage of clipping is that PAPR reduction is obtained without any redundancy and no side information is needed to transmit. Another technique is Selective Mapping (SLM), where M number of random phase sequences are multiplied with the actual data to be transmitted and out of M stream one stream is selected which have less PAPR, in SLM Bit Error Rate (BER) is improved compared to Clipping and SLM both. In this paper clipping and SLM both are combined to improve PAPR as well as BER. Simulation results show that PAPR and BER both are improved for combination as compared to clipping and SLM.