On the performance of OFDM Index Modulation over Nakagami fading channels

Recently, Orthogonal Frequency Division Multiplexing with Index Modulation (OFDM-IM) has been introduced as a novel multi-carrier system to carry additional information bits compared to conventional OFDM. In this paper, we provide a closed-form expression of an OFDM-IM system for M-ary signal constellations such as M - QAM and M - PSK modulation schemes over a Nakagami-m fading channel. Simulation results illustrate that OFDM-IM improves system performance in high data-rate transmission over conventional OFDM under various Nakagami fading factor m.

I. Introduction

There is a high demand to meet the significant increase in the high data-rates transmission in communication systems, therefore multi-carrier transmission scheme has become the most popular and dominant modulation technique in the major communication infrastructure [1]. Orthogonal frequency division multiplexing (OFDM) scheme is utilized extensively in high speed wireless communication system, due to its immunity and robustness against multi-path fading and interference [2]. OFDM with index modulation (OFDM-IM) offers considerable utilization of OFDM sub-carrier indices to carry additional information besides that carried by the constellation symbol of each sub-carrier [2]. Therefore, OFDM-IM increases the transmission spectral efficiency and improves the bit error rate (BER) performance for signals with high signal-to-noise ratio (SNR) compared to conventional OFDM. In OFDM-IM, data bits are carried by two entities, namely the subcarrier indices and the combined digital modulation constellations [3], [4]. The special design of OFDM-IM makes it more capable of constructing energy-efficient transmit-signals, yielding a higher achievable rate [2]. OFDM-IM turns frequency selectivity into a benefit, thus enhancing the system performance in fading channels. The performance of OFDM-IM under Rayleigh fading channel is investigated in [4].