A group-based M2M multiple access scheme in massive MIMO MU-SCMA cellular networks

Machine-to-machine (M2M) communications is regarded as the keystone of Internet of things (IoT) since it enables ubiquitous data exchange among devices without any artificial intervention. Cellular system is expected to play a significant role in successfully implementing the M2M communications for its ready-to-use infrastructure. However, there still exist many challenges, such as co-channel interferences to existing mobile users, congestions and limited battery capacity of M2M devices. In this paper, in order to realize M2M communication over cellular system, we propose a power- and spectrum-efficient massive-code-space-multiplex (massive-CSM) access scheme, in which quasi-orthogonal massive MIMO channels are utilized as resource blocks in the framework of SCMA. In the proposed scheme, group headers gather data from M2M devices by D2D links and communicate with eNB. Additionally, D2D-link power consumption optimization and transmit layers allocation algorithm are provided to minimize power consumption of codewords distribution among group headers. By applying random matrix theory, we also drive an uplink asymptotic equivalent (AE) of signal to interference plus noise ratio (SINR) of the system as the number of eNB antennas approach infinity. Simulation results show that the proposed multiplex access scheme improves the uplink capacity several times than traditional scheme and our algorithm achieves better results with less time complexity.