Joint control of random access and dynamic uplink resource dimensioning for massive MTC in 5G NR based on SCMA

The massive machine-type communication (mMTC) usage scenario, also known as the massive Internet of Things (mIoT), involves a huge number of MTC devices having high requirements on increased battery lifetime, which autonomously transfer small amounts of data with relaxed delay requirements, without human intervention. The current cellular network is unsuitable for this scenario, due to the limited uplink resources allocated to the physical random access channel (PRACH) and to the physical uplink shared channel (PUSCH). With this in mind, in this article, we propose a new framework, customized for massive MTC services, that includes a joint control of the dynamic resource allocation between the PRACH and the PUSCH, and a new random access (RA) procedure based on an adaptive access class barring (ACB) scheme that appropriately spreads RA reattempts in time. In addition, to further increase the transmission efficiency, we adopt the sparse code multiple access (SCMA) technique for PUSCH resources, because SCMA results as the most promising nonorthogonal multiple access (NOMA) technique to support massive MTC connectivity with small-size data. The simulation results show that the proposed control framework significantly improves the number of succeeded communications in comparison with the other proposals available in the literature. Furthermore, an energy consumption model is introduced to show the considerable energy saving achieved by the MTC devices which adopt our joint control scheme.