Cisco Cisco ASR 5700
Mobility Management Entity Overview
Features and Functionality - Base Software ▀
MME Administration Guide, StarOS Release 18 ▄
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Interworking with SGSNs
This feature enables an integrated EPC core network to anchor calls from multi-mode access terminals and supports
seamless mobility on call hand-offs between an LTE or GERAN/UTRAN access network. This provides a valuable
function to enable LTE operators to generate incremental revenue from inbound roaming agreements with 2G/3G
roaming partners.
seamless mobility on call hand-offs between an LTE or GERAN/UTRAN access network. This provides a valuable
function to enable LTE operators to generate incremental revenue from inbound roaming agreements with 2G/3G
roaming partners.
In order to support inter-RAT hand-offs for dual-mode access terminals between LTE and 2G/3G networks with 3GPP
Pre-Release 8 SGSN's, the MME will support combined hard handover and SRNS relocation procedures via the GTPv1
Gn/Gp reference interface. In preparation for the handover, the MME sends a Forward Relocation Request to the SGSN
and includes subscriber identity and context information including IMSI, Mobility Management context and PDP
context. The PDP context includes the GGSN address for the user plane and the uplink Tunnel Endpoint ID. These
addresses are equivalent to the PDN GW address. The MME maps the EPS bearer parameters to the PDP contexts.
Pre-Release 8 SGSN's, the MME will support combined hard handover and SRNS relocation procedures via the GTPv1
Gn/Gp reference interface. In preparation for the handover, the MME sends a Forward Relocation Request to the SGSN
and includes subscriber identity and context information including IMSI, Mobility Management context and PDP
context. The PDP context includes the GGSN address for the user plane and the uplink Tunnel Endpoint ID. These
addresses are equivalent to the PDN GW address. The MME maps the EPS bearer parameters to the PDP contexts.
After sending the forward relocation signaling to the target SGSN, the MME deletes the EPS bearer resources by
sending a Delete Bearer Request to the S-GW with a Cause code that instructs the S-GW not to initiate delete
procedures toward the P-GW.
sending a Delete Bearer Request to the S-GW with a Cause code that instructs the S-GW not to initiate delete
procedures toward the P-GW.
When a mobile subscriber roams from an EUTRAN to GERAN/UTRAN access network it must also send a Routing
Area Update (RAU) to register its location with the target network. The target SGSN sends a Context Request to the
MME with P-TMSI to get the Mobility Management contexts and PDP contexts for the subscriber session. The SGSN
uses the Globally Unique Temporary ID (GUTI) from the MME to identify the P-TMSI/RAI.
Area Update (RAU) to register its location with the target network. The target SGSN sends a Context Request to the
MME with P-TMSI to get the Mobility Management contexts and PDP contexts for the subscriber session. The SGSN
uses the Globally Unique Temporary ID (GUTI) from the MME to identify the P-TMSI/RAI.
Handover Support for S4-SGSNs
The S3 interface facilitates user mobility between an MME and an S4-SGSN providing for the transfer of the UE
context between the two. It is a GTPv2 control plane interface that supports the following handover types:
context between the two. It is a GTPv2 control plane interface that supports the following handover types:
E-UTRAN-to-UTRAN and E-UTRAN-to-GERAN (MME-to-R8 SGSN) handover through:
Routing Area Update (RAU) based MME-R8 SGSN relocation where the RAU could be a result of UE
movement.
Attach at an RNC connected to a R8 SGSN
S1 handover/SRNS relocation based MME-R8 SGSN relocation
UTRAN-to-E-UTRAN and GERAN-to-E-UTRAN (R8 SGSN-to-MME) handover through:
Tracking Area Update (TAU) based R8 SGSN-MME relocation where the TAU could be a result of UE
movement.
Attach at an eNodeB connected to an MME.
SRNS relocation/S1 handover based R8 SGSN-MME relocation.
All handover types support handing over multiple bearers and multiple PDNs from the MME to a R8 SGSN and vice
versa.
versa.
The S3 interface also supports the following features:
Monitor Protocol and Monitor Subscriber
Subscriber Session Trace
IPv4 and IPv6: for peer SGSN selection, the preference is given to IPv6 addresses. IPv4 addresses are ignored if
IPv6 addresses are present.
Operator Policy for SGSN selection