Non-Orthogonal Multiple Access With Sequence Block Compressed Sensing Multiuser Detection for 5G

Compressed sensing-based multiuser detection (CSMUD) is a promising candidate to enable grant-free non-orthogonal multiple access for massive machine-type communication in the fifth-generation (5G) wireless communication system. Exploiting the sporadic node activity of the massive machine-type communication, CSMUD recovers the signal from far fewer linear measurements than the number of users, thereby facilitating massive connectivity. However, with the increase in the number of sensor nodes, the errors in the activity detection also increase. In this paper, we propose sequence block-based compressed sensing multiuser detection (SB-CSMUD), which enhances the activity detection by using block of multiple spreading sequences as signature of the node. It is demonstrated both empirically and theoretically that the SB-CSMUD scheme besides improving the detection error rate also increases the spectrum efficiency. Simulation results show that for the same least square estimation error rate (LSER), SB-CSMUD not only reduces the bandwidth by 10% but also reduces the bit error rate by more than 1.5 order of magnitude at signal-to-noise ratio (SNR) of 15 dB. The bandwidth can even be reduced by 25%-30% at SNR > 20 dB for achieving the same detection error rate at the cost of LSER. Furthermore, owing to the diversity in the spreading, the proposed scheme provides a more homogeneous performance for all the nodes. In addition, the computational complexity of the SB-CSMUD is the same as that of CSMUD at the only expense of the memory requirement for hosting the block sequence at the node.