You can deploy the SBC on the Access Edge and Peering Edge in an IMS/VoLTE network. On the Access Edge, the functional roles include: P-CSCF (IMS-AGW), E-CSCF, ATCF (ATGW) and EATF. On the Peering Edge the functional roles include: IBCF (TrGW).
Refer to Configuring SBC as Access SBC with External P-CSCF for details.