LTE : Why does UE maintain various lists ?

Question

UE maintains lists for "Forbidden tracking areas", "Forbidden PLMN's", "Equivalent PLMNs" etc.
why these elements required and what would be the impact on system or UE, if it does not maintain such lists ?

Answer 1

Hi,

i.e. lack of forbidden Tracking Area would result in spike of Rejected/Failed TAU procedures.
From my experience, when I/we went life with LTE in UK quite small number of subs was generating thousands of TAUs each 5-10 minutes. Imagine you have to troubleshoot it where part of Rej TAUs are because subscriber is not allowed in this TAC/TAI.

PLMN is.. basically the same.
Maybe more with regards to roaming agreements. If operators have not agree on how they will be treating each subscribers, then PLMN of one OpCo is blocked by other, and the first one by the second one.
There is no spike in HO/TAU failures.

Cant tell anything about equivalent PLMN. I'm guessing, by the name, it's when there is an agreement on roaming between two or more OpCos. If this is true then there is no issue in TAU/HO.