Index Modulation Techniques for Next-Generation Wireless Networks

TLDR

Index modulation (IM) is a communication technique that encodes data in the indices of system components such as antennas, subcarriers, or RF mirrors, and has attracted growing interest in recent years. This paper aims to comprehensively review the basic principles, emerging variants, and recent advances of IM for next‑generation wireless networks, and to outline future research directions. The authors analyze three IM forms—spatial modulation, channel modulation using parasitic RF mirrors, and OFDM‑IM—examining their principles, recent developments, and potential for low‑complexity, spectrum‑ and energy‑efficient applications.

Abstract

What is index modulation (IM)? This is an interesting question that we have started to hear more and more frequently over the past few years. The aim of this paper is to answer this question in a comprehensive manner by covering not only the basic principles and emerging variants of IM, but also reviewing the most recent as well as promising advances in this field toward the application scenarios foreseen in next-generation wireless networks. More specifically, we investigate three forms of IM: spatial modulation, channel modulation and orthogonal frequency division multiplexing (OFDM) with IM, which consider the transmit antennas of a multiple-input multiple-output system, the radio frequency mirrors (parasitic elements) mounted at a transmit antenna and the subcarriers of an OFDM system for IM techniques, respectively. We present the up-to-date advances in these three promising frontiers and discuss possible future research directions for IM-based schemes toward low-complexity, spectrum- and energy-efficient next-generation wireless networks.