NOMA-Based Random Access in mMTC XL-MIMO

Abstract

In machine-type communication (MTC), massive access attempts are generated and the massive MIMO is the key technology to support this demand. To support massive MTC (mMTC), the recent extra-large scale massive multiple-input multiple-output (XL-MIMO) architecture has been seen as a promising technology for providing very high-data rates in high-user density scenarios. Therefore, the large dimension is of the same order as the distances to the user equipment (UE) causing spatial nonstationarities and visibility regions (VRs) to occur across the huge XL array extension. We investigate the random access (RA) problem in crowded XL-MIMO scenarios; the proposed grant-based random access (GB-RA) protocol combining the advantage of non-orthogonal multiple access (NOMA) and strongest user collision resolutions in extra-large arrays (SUCRe-XL) named NOVR-XL can allow access of multiple colliding users in the same XL subarray (SA) selecting the same pilot sequence. The proposed NOVR-XL GB-RA protocol is able to provide a reduction in the number of attempts to access the network, while improving the average sum-rate, as the number of SA increases.