An Improved SLM Technique For PAPR Reduction In OFDM Systems

Orthogonal Frequency Division Multiplexing (OFDM) is widely used as a standard modulation for various high data rate wireless communication systems. It is worked by converting high data rate streams into a number of parallel low data rate streams. OFDM has many advantages over single carrier modulation systems. Some of these advantages are robustness to frequency fading channels, high transmission bit rate and high spectral efficiency. However, OFDM has its drawbacks. One of the main problems is high Peak-to-Average Power Ratio (PAPR), which brings disadvantage likes an increased complexity of system. Several techniques have been proposed in order to reduce PAPR. Hence, this paper presents Discrete Cosine Transform (DCT) precoded Selected Mapping (SLM) technique that is implemented to reduce PAPR of OFDM system. Simulation results show that implementation of DCT precoded SLM technique can reduce PAPR to about 1.55dB for 512 subcarriers and four selective data blocks at clipping probability of 10 -3 . From the simulation results, as number of subcarriers increases, PAPR value also increases. The PAPR reduction effect is improved with the increasing number of selective data blocks. Besides, the number of selective data blocks should also be chosen carefully as it affects the computational complexity of OFDM system.