cellular-networklte4g

How EnB will inform to UE about incoming call in RRC connected state in LTE?


Generally if UE is in RRC Idle state, ENB will inform to UE via paging message about CS domain i.e incoming call.

My doubt is in LTE, when UE is in RRC Connected State, how network will notify to UE about incoming MT call ? In which Information element or message ?

Any help will be appreciated !!


Solution

  • There's a NAS message called "CS Service Notification". Assuming the UE is "RRC Connected" and assuming it has a established NAS connection, that's what the MME uses to notify the UE. That leads the UE to reply with the "Extended Service Request" message, and then what follows is pretty similar to what would happen if the UE was being paged.