Fast Dormancy in LTE

[hagoel]

Is LTE support Fast Dormancy
what is the message the UE sent to go idle in LTE ?

[wolverine]

There is no fast dormancy concept in LTE. LTE uses DRX (and DTX) in connected mode therefore the UE can go into a battery saving mode whilst still being connected (similar to CPC in WCDMA UMTS). Of course the control of the DRX timers is still down to the operator so in theory you could still have an operator who uses values that are detrimental to the UE battery life.