Joint Signature Estimation and Angular Domain Channel Reuse based Random Access for Massive Connectivity

Recently, massive multiple-input multiple-output (mMIMO) aided random access (RA) aroused much research interest in the area of massive machine-type communications (mMTC). Nevertheless, the performance of RA is still constrained by the limited availability of orthogonal preambles and channel resources. To overcome this limitation, we propose to consider the angle-of-arrival (AOA) and time-of-arrival (TOA) information of the transmitted preambles as additional signatures of an active user. To facilitate this signature assignment, a joint signature estimation (JSE) method with effectively suppressed complexity is proposed. Additionally, to enhance the availability of channel resources, we design an angular domain channel reuse (ADCR) scheme that leverages the estimated AOA signature to improve uplink channel efficiency. By applying the JSE and ADCR to a grant-based RA (GBRA) scenario, we demonstrate that our proposed scheme effectively addresses the preamble limitation problem and contributes new channel reuse to the spatial domain, thereby improving RA performance.