The scope of this document covers support for an evolved access terminal (UE as known in this specification) using the eHRPD air interface and the S101 tunnel to access the core network architecture defined in 3GPP TS 23.401 [24] and TS 23.402 [25] . This specification covers:

- An interface between the HRPD Serving Gateway (HSGW) and the Packet Data Network Gateway (P-GW, also known as PDN GW) and procedures for that interface.

- An interface between the UE and the HSGW and procedures for that interface.

- An interface between the HSGW and the PCRF and procedures for that interface.

- An interface between the HSGW and the AAA and procedures for that interface.

- Internal functions and responsibilities of the HSGW.

- Interfaces between HSGWs to support inter-HSGW handoff procedures.

- An interface from the S-GW to the HSGW to support data forwarding during handoff from E-UTRAN to eHRPD.

- Interfaces between the HSGW and the eAN/ePCF.