  Extra-large massive multiple-input multiple-output (XL-MIMO) systems is a new
concept, where spatial non-stationarities allow activate a high number of user
equipments (UEs). This paper focuses on a grant-based random access (RA)
approach in the novel XL-MIMO channel scenarios. Modifications in the classical
Strongest User Collision Resolution (SUCRe) protocol have been aggregated to
explore the visibility regions (VRs) overlapping in XL-MIMO. The proposed
grant-based RA protocol takes advantage of this new degree of freedom for
improving the number of access attempts and accepted UEs. As a result, the
proposed grant-based protocol for XL-MIMO systems is capable of reducing
latency in the pilot allocation step.
