Introduction

Abstract

The deployment of the fifth generation (5G) cellular networks is accelerating across the world. 5G is expected to deliver multi-Gbps peak rates with ultra-low latency and ultra-high reliability. As an indispensable complement to cellular networks, wireless local area networks (WLANs) will still coexist with 5G networks. With a surging demand for high data rate communications, new WLAN standards have been developed, such as IEEE 802.11ax that is popularly known as Wi-Fi 6. A high data rate is required by not only wireless networks but also wire communications like asymmetric digital subscriber line. To meet the requirement of high data rates, these standards use multi-carrier communications, and in most cases, orthogonal frequency division multiplexing (OFDM). However, with the rapid development of information and communication technology (ICT) industries, the unprecedented surge of mobile data traffic requires future wireless networks to support both high spectral efficiency (SE) and energy efficiency. The current OFDM systems may not be able to cope with the challenges. Recently, index modulation has emerged as a competitive performance-enhancing technique for OFDM communications systems. In this chapter, first, we briefly review OFDM and identify the key challenges. Then, we introduce the concept of index modulation, mainly focusing on the realizations based on the OFDM framework. Finally, the organization of this monograph is given at the end of this chapter.