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LAU Reject Cause: Location Area Not Allowed

location area update mobile communication network gsm plmn

In this scenario, the network sends a message to the mobile station (MS) indicating a Location Area Update (LAU) reject with the cause “Location Area Not Allowed.”

Image alt: LAU Reject-Location Area Not Allowed

This cause is transmitted to the MS when it’s restricted region-wise, as illustrated in the figure above. The graphic shows a geographical area where an MS is restricted from service.

As shown, the upper part of North America is restricted for the MS. Consequently, the MS will not receive service from any Public Land Mobile Network (PLMN) within that region. Based on the mobile station’s (MS) subscription details, the network determines this restriction and returns this cause, rejecting the LAU request.

Notably, this cause is only sent by the Home PLMN (HPLMN) to the MS. Upon receiving this cause, the MS enters a limited service mode. The MS will also not search for any PLMNs while in this mode.

Let’s consider an example. Suppose the operator “Verizon” provides service, and a subscriber is permitted to access the network service in the region marked in green but restricted in the region above (as shown in the image). When the mobile subscriber enters the restricted region where service isn’t available, the network will send the reject cause “Location Area (LA) not allowed” to the MS.