Unprecedented levels of spectral and energy efficiency are expected from next-generation wireless networks to achieve ubiquitous communications between anybody, anything, and anytime. In order to reach the challenging objectives of next-generation wireless networks, the researchers have envisioned novel physical layer (PHY) concepts such as massive multiple-input multipleoutput (MIMO) systems and non-orthogonal multi-carrier communications. However, wireless communication and signal processing communities are still working relentlessly to come up with new and more effective PHY solutions towards next-generation wireless networks. There has been a growing interest on index modulation (IM) techniques over the past few years. IM, in which the indices of the building blocks of the considered communications systems are used to convey additional information bits, is a novel digital modulation scheme with high spectral and energy efficiency. IM schemes may have remarkable potential and impact to shape 5G and beyond radio access technologies due to their inherently available advantages over conventional systems. Since the initial skepticism of both academia and industry on the potential and applicability of IM technologies has now gone away, we strongly believe that IM is not another simple digital modulation alternative, but rather can be a game-changing communication paradigm whose time has come!

Motivated by these observations, this Special Issue in IEEE J-STSP aims to capture the stateof-the-art advances in IM concepts and to collect the latest advances on the signal processing aspects of IM techniques. The topics of interest include, but are not limited to the following:

Topics of interest in this special issue include (but are not limited to):