Why in LTE, TAU is needed in connected mode while LAU is not needed in legacy 2G/3G in connected mode?

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The whole purpose of TA is to know where the UE is situated so that it can be pagged. In connected mode, the eNB and MME already know which cell the UE is connected to so why TAU is neeeded in connected mode? Note that location area update is not required in 2G/3G in connected mode. In legacy 2G/3G, LAU only happens after the call is released so why in LTE the TAU is needed in connected mode?

posted Jul 18, 2017 by anonymous

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