Performance Comparison of OFDM and OFDM-IM for 6G Wireless Networks

Abstract

This paper presents a comparative performance analysis of conventional coded orthogonal frequency-division multiplexing (OFDM) and multiple-input multiple-output (MIMO) OFDM with index modulation (OFDM-IM) as candidate waveforms for future sixth-generation (6G) wireless communication systems. A Rayleigh fading channel model is considered, employing convolutional channel coding, M-QAM modulation ($M \in\{4,16,32,64\}$), and minimum mean-square error (MMSE) equalization under identical bandwidth and transmit power constraints. Unlike classical OFDM, OFDM-IM activates only a subset of subcarriers within each subblock, enabling additional information transmission through subcarrier indices while reducing average interference and spectral leakage. Simulation results demonstrate that OFDM-IM consistently outperforms conventional OFDM by achieving notable signal-to-noise ratio (SNR) gains at practical bit error rate (BER) levels, along with significantly improved energy efficiency and reduced out-of-band (OOB) emissions across all considered modulation orders. These performance advantages highlight the strong potential of OFDM-IM as an energy-efficient and spectrally compact waveform for emerging 6G applications, including ultra-reliable low-latency communications, massive machine-type communications, and spectrum-constrained Internet-of-Things uplink scenarios.