When a wireless user equipment (UE) device is first powered up or when it tries to recover from loss of coverage, it is typically required to search for its last registered Public Land Mobile Network (RPLMN) in every supported radio access technology and frequency bands associated therewith before attempting to register on another PLMN. The issue for operators is that when a UE device loses coverage from its home PLMN, it may have to perform a full band scan (FBS) of all supported bands before possibly selecting a National Roaming Partner (NRP). Today, such a full scan already takes a fairly long time in a dense or complex radio environment, which will be further exacerbated when additional frequency bands are introduced and more access technologies are integrated.
In addition, it is important to note that in most scenarios a full band scan can give rise to inefficient utilization of radio resources. Relatedly, the time to perform a full scan may be so long that the radio environment may have changed significantly between the time when the scan was started and the time the UE device decides to select a new PLMN. As a result, by the time the UE decides to select a new network, another high priority network may have appeared again.