CIAMA: A new multiple access scheme

This paper studies advanced multi-access techniques to support a high volume of concurrent access demanded in future wireless networks. Sparse code multiple access (SCMA), as a code-domain Non-Orthogonal Multiple Access (NOMA), serves multiple users simultaneously by frequency-domain coding. Blind Interference Alignment on the other hand applies time-domain coding to accommodate multiple users. Unlike beamforming, both of them need no CSIT, which saves the control cost of channel information feedback and highly simplifies the implementation of multiple access. To achieve even higher multiplexing gain and diversity order, we propose a new multiple access framework, which makes use of both time and frequency coding by combining SCMA and BIA, and is named as SparseCode-and-BIA-based multiple access (CIAMA). Then we analyze two decoding schemes, the two-stage decoding scheme consisting of zero-forcing and Message Passing Algorithm (MPA), and the Joint Message Passing Algorithm (JMPA) enhanced by constructing a virtual factor graph. Simulation results indicate that although the two-stage decoding performance is inferior to both BIA and SCMA, it has low decoding complexity. On the other hand, the JMPA decoding scheme achieves the same diversity gain as STBC-based SCMA while gaining even higher multiplexing gain, which makes the CIAMA with JMPA decoding scheme an attractive MA scheme in future wireless communication networks.