Enhanced Handling on Forbidden PLMN List

Abstract

A method of enhanced handling of a Forbidden Public Land Mobile Network (PLMN) list is proposed. When a UE tries to attach to a PLMN and receives an ATTACH Reject message having no integrity protection, it could be transmitted from a network entity trying to block the PLMN for providing service. Therefore, by introducing a temporary forbidden PLMN list and a timer T3247, UE can avoid adding the PLMN ID to the Forbidden PLMN list and avoid being blocked for network access. Instead, UE is only temporary refrained from selecting the PLMN ID and is able to retry for the network access after T3247 expiry. The temporary list together with T3247 mechanism thus gives UE more opportunity to try with the same PLMN ID at a different time and/or a different UE location, where the malicious blocking is no longer available.

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