The SRNS relocation feature facilitates connected mode inter-RAT handovers between UTRAN (3G) networks or between UTRAN and EUTRAN (LTE) networks. The advantage of this feature is that the radio bearer establishment occurs before the actual handover at the target.
The Gn/Gp SGSN and S4-SGSN support inter- and intra-SGSN SRNS relocation to enable:
- Handovers of an MS from one RNC to another RNC
- Handovers of an MS from one RNC to an eNodeb
The S4-SGSN supports the optional setup of indirect data forwarding tunnels (IDFT) between the eNodeB and the RNC via the SGW during connected mode handovers. This allows the S4-SGSN to support connected mode handovers between the UTRAN and E-UTRAN networks across the S3 interface. IDFT is not supported on the SGSN across the Gn interface.
The SRNS Relocation feature is included with the base SGSN license. It does not require an additional feature license.
Relationships to Other Features
This section describes how the SRNS Relocation feature relates to other SGSN features.
- For an SGSN operating via the Gn/Gp interfaces, a 3G service (sgsn-service) must be configured and enabled before SRNS Relocation can be configured.
- For an S4-SGSN, both a 3G service (sgsn-service) and S4-SGSN support (egtp-service) must be configured before SRNS Relocation can be configured.
- If operators are using non-standard LAC ranges, then a network-global-mme-id-mgmt-db must be configured and associated with the sgsn-service.
For detailed instructions on configuring the above, refer to the appropriate chapters in this guide.