Analysis of Contention-Based SCMA in mMTC Networks

Massive Machine Type Communication (mMTC) is one of the three new applications of fifth-generation (5G) networks. Users in mMTC applications have different patterns of transmission and requirements than traditional LTE applications; they are massively deployed and transmit small packets of data sporadically. Grant-based access scheme is inefficient to satisfy the mMTC requirements; therefore, grant-free contention-based access (CBA) is appointed as a promising solution to this problem. In this paper, we analyze the performance of contention-based sparse code multiple access (SCMA) concerning the probability of success of transmission and the area spectral efficiency. We derive closed-form expressions for both performance metrics and validate them with numerical simulations. Furthermore, we compare the results with an OFDMA contention-based approach.