Index Modulation for 6G Communications

Over the past decades there has been a tremendous increases in data throughput and the number of connected nodes, with recent studies foreboding these increases in next generation networks. These tremendous increases will undoubtedly result in increasingly stringent requirements of spectral efficiency and energy efficiency. In recent years, index modulation has attracted researchers' attention as a means of meeting these two requirements. Different from conventional amplitude-phase modulation schemes, index modulation employs one or more index domain(s) in addition to the classic amplitude-phase constellation diagram. Therefore, index modulation offers a means to form a higher-dimensional modulation scheme, which considerably enhances the spectral efficiency under proper system configurations. By index modulation, only a subset of transmit antennas/orthogonal subcarriers/time slots will be activated to form a unique activation pattern. Consequently, the index of activation pattern can be used to modulate extra bit stream, in addition to the bit stream modulated by data constellation symbols. As a young-born paradigm, there are still a large number of open research questions awaiting solutions and further research activities are of high importance to finally promote index modulation to the practical stage. Apart from theoretical research, the concerns of practical implementation need to be addressed. In light of the aforementioned advantages of applying index modulation for 6G communications, as well as the remaining research problems, we propose this Research Topic to attract original and high-quality publications addressing the theoretical and practical issues related to index modulation.

All types of manuscripts accepted for submission to Frontiers in Communications and Networks are welcome, including Original Research, Systematic Review, Methods, Technology Report, and so on (details can be found at https://www.frontiersin.org/journals/communications-and-networks#article-types). The particular topics of interest include but are not limited to the following:

• Artificial intelligence and learning techniques assisted index modulation
• Massive MIMO and reconfigurable intelligent surface (RIS) assisted index modulation
• Index modulation in millimeter-wave, terahertz and optical wireless communications
• Index modulation for underwater optical/acoustic communications
• Distance-aware and space-frequency-correlated index modulation
• Index modulation with high mobility
• Physical security and secrecy related issues of index modulation
• Index modulation in multi-user and cooperative relay networks
• Performance analysis for index modulation based communication systems
• Resource allocation and optimization for index modulation based communication systems
• Detection and transceiver designs for index modulation
• Index modulation aided interference mitigation techniques
• Pilot designs and channel estimation techniques for index modulation
• Network architecture designs for index modulation
• Signal processing techniques for index modulation
• Novel index modulation bit-to-pattern mapping relation designs
• Index modulation aided non-orthogonal multiple access, energy harvesting, and cognitive radio schemes
• Emerging applications of index modulation
• Implementation challenges and future research directions of index modulation