VoLTE SBC — SIP to the mobile network

There are three reasons to put mobile radio into a telephone installation, and none of them is the mobile network itself. The first is a site that has no usable fixed line: a construction container, a wind farm substation, a shop in a building where the copper was never replaced. The second is failover — the SIP trunk is fine until the fibre is cut, and then every call has to go somewhere. The third is cost: calls into mobile networks are often cheaper from a SIM in the same network than through the fixed-line provider.

The VoLTE SBC covers all three from the same box. Two, four or six LTE ports carry voice and SMS, and the hybrid models add ISDN or analogue interfaces in the same housing, so the mobile path and the fixed-line path meet in one device with one dialplan instead of two boxes and a routing puzzle between them.

It is the successor to the GSM gateway and remains backward compatible: 2G and 3G still work, so an existing installation can be replaced without rewriting its plan. What improves is the voice path — VoLTE sets up calls faster and sounds better than a call over the 2G network.

On the SIP side it is a full eSBC. Two network ports, topology hiding, DoS protection, header rewriting and codec conversion, with transparent and transcoded sessions licensed exactly as on the modular line. Calls between the mobile or PSTN interfaces and SIP do not consume a session licence; only SIP-to-SIP traffic does.