A novel compressed sensing-based non-orthogonal multiple access scheme for massive MTC in 5G systems

The main challenges for massive machine type communication in 5G system are to support random access for massive users and to control signaling overhead and data processing complexity. To address these challenges, we propose a novel compressed sensing (CS)-based non-orthogonal multiple access (NOMA) scheme, called CS-NOMA, which introduces low coherence spreading (LCS) signatures to enable joint activity and data detection without requiring the activity information of users in advance. We present a sufficient condition for the construction of the LCS signatures to ensure that a CS-based multi-user detection (CS-MUD) can be effectively deployed in base station. Furthermore, we study the CS-NOMA scheme with imperfect channel state information (CSI) and present a bound for the performance of the CS-NOMA scheme. Simulation results show that the proposed scheme achieves a relatively high system overload (up to 4) when the active users are relatively sparse with an activity ratio of 1%, which implies that the CS-NOMA scheme can significantly improve the spectral efficiency, avoid the control signaling overhead, and reduce the transmission latency.