S3 Interface

S3 - This is a control interface between the MME and 2G/3G SGSNs. The interface is based on Gn/GTP-C (SGSN-SGSN), possibly with some new functionality to support signalling free idle mode mobility between E-UTRAN and UTRAN/GERAN.

S3 will not support packet forwarding; instead this will be supported on the S4 interface.

S3 is a many-to-many interface and is backwards compatible with the Gn interface.

The S3 interface will be similar to the S10 interface between MMEs which will be used for intra-LTE mobility between two MME pool areas.

LTE S3 Interface