The Impact of OFDM-IM System Parameters on the Performance of the SLM PAPR Reduction Technique

Abstract

Orthogonal Frequency Division Multiplexing with Index Modulation (OFDM-IM) is an effective communication technology that utilizes subcarrier indices to transmit information in addition to the information traditionally modulated on active subcarriers. However, OFDM-IM suffers from high peak-to-average power ratio (PAPR), which can result in signal distortion and hence system performance degradation. One of the techniques used to alleviate the PAPR in OFDM-IM is the selected mapping (SLM) technique. The effectiveness of the SLM PAPR reduction technique is affected by OFDM-IM system parameters, such as the number of subcarriers and subcarrier activation ratio. This paper explores the impact of these OFDM-IM system parameters on the PAPR reduction performance of the SLM technique with different phase sequence settings.

The obtained results provide an overview of the collective effect of both OFDM-IM and SLM parameters in different operation cases. The findings show that the amount of PAPR reduction is mainly affected by the number of subcarriers, and less affected by the subcarrier activation ratio. That is a greater PAPR reduction of up to 4.2 dB is achievable with relatively smaller number of subcarriers. The results show the limited effect of more complex phase vectors, hence suggesting simpler SLM parameter setting alternatives to achieve a target PAPR reduction performance. Finally, the results show the improvement in Bit Error Rate (BER) performance of OFDM-IM system employing the SLM with carefully selected PAPR reduction parameters.