A Novel Grant-Based Pilot Access Scheme for Crowded Massive MIMO Systems

We propose a novel grant-based pilot access scheme to tackle the pilot collision in crowded massive multiple-input multiple-output (MIMO) systems. The proposed scheme divides the cell into several annuluses. Then, weaker user equipments (UEs) in each annulus, judged by a decision rule in a strongest-user collision resolution (SUCRe) scheme, send their reselected or allocated idle pilots to a base station (BS). We call this scheme enhanced SUCRe combined idle pilots access (E-SUCR-IPA). We analyze the number of successful UEs and the successful access probability of one UE with respect to its distance to the BS for the E-SUCR-IPA scheme. Numerical results show that the E-SUCR-IPA scheme significantly increases the number of successful UEs while ensuring fairness among UEs compared to baselines.