Mobility Management

Mobility Management:

Mobility Management

–MME – IDLE Mobility and Handovers

–S-GW – LTE and 3GPP user plane mobility

–P-GW – Mobility for non 3GPP interworking

•Mobility Management states

–EMM-DEREGISTERED - The UE is not reachable by a MME

–EMM-REGISTERED - The UE location is known and UE has at least one PDN connection

–ECM-IDLE - No NAS signaling connection between UE and network

–ECM-CONNECTED – Signaling connection between the UE and the MME

•Mobility Management Procedures

–IDLE mobility – TAU inside of LTE

–Handover – X2 and S1 handover for different scenarios

           Intersystem Mobility – For Idle mobility TAU/RAU 

 

LTE Tracking Area:

Tracking area (TA) is similar to Location/routing area in 2G/3G

Tracking Area Identity = MCC (Mobile Country Code), MNC (Mobile Network Code) and TAC (Tracking Area Code)

When UE is in Idle, MME knows UE location with Tracking Area accuracy

Handover Procedure:

•X2 handover (X2 interface between eNodeBs)

–UE Moves from eNodeB to eNodeB using X2

–MME is not changed S-GW can be changed

–eNodeBs makes preparation – MME update GW for downlink

•S1 handover

–The S1-based handover procedure is used when the X2-based handover cannot be used.

–No X2 interface or MME change

–MME handle handover signalling and update S-GW

•Inter RAT handover

–Relocation used in UTRAN

–PS handover used in GERAN

Mobility Comparison between 3G & LTE: