Generalized Space-Frequency Index Modulation: Low-Complexity Encoding and Detection

This paper is concerned with an attractive multiantenna multi-carrier modulation scheme, termed as generalized space-frequency index modulation (GSFIM), which is a promising modulation scheme for next generation wireless systems. GSFIM uses both spatial domain and frequency domain to encode bits through indexing. In GSFIM, information bits are mapped through antenna indexing in the spatial domain, subcarrier indexing in the frequency domain, and M-ary modulation. GSFIM can offer higher rates using fewer transmit radio frequency (RF) chains and better performance compared to conventional MIMO-OFDM. In this paper, we address the problem of low-complexity encoding and detection of large-dimensional GSFIM signals. The proposed encoding procedure exploits the low complexity computation of combinadics in combinatorial number system. This allows 'on-the-fly' computation of GSFIM encoding maps. For detecting GSFIM signals, we propose a low complexity detection algorithm based on a multi-stage message passing approach. The proposed low complexity encoding/detection algorithms allow practical implementation of large-dimension GSFIM systems.