Receiver Design for Dual-Mode Index Modulation Aided OFDM

Nowadays, variants of Spatial Modulation (SM) are studied by a lot of researchers in order to increase Spectral Efficiency (SE) more. One of the important variants of SM is known as Orthogonal Frequency Division Multiplexing Index Modulation (OFDM-IM). In OFDM-IM, selection of active subcarriers is based on the idea of the selection of active antennas in the SM. Then, to take OFDM-IM a step further in terms of SE, Dual Mode OFDM-IM (DM-OFDM-IM) has been proposed that activates entire subcarriers unlike that of OFDM-IM. However, in all these studies same assumption is made, i.e., channel is perfectly known at the receiver. However, this assumption is not accurate for practical applications. For this reason, the presented simulation results and theoretical analysis without channel estimation cannot represent the real system performance. In this study, a pilot symbol aided channel estimation for DM-OFDM-IM scheme is considered. We investigate the effect on Bit Error Rate (BER) performance of five different interpolation techniques. The simulation results illustrate that, interpolation techniques perform similiar BER performance for low and moderate Signal-to-Noise Ratio (SNR) range. However, at the high SNR values (SNR> 30 dB), Low-Pass and SPLINE interpolation techniques give the highest performance among all considered techniques.