Circuit Switched FallBack

Mitel's VoLTE Interworking Function (IWF) solution provides a means of supporting new technologies while removing the risk, cost and time to market disadvantages associated with legacy core network upgrades.

Mitel's VoLTE Interworking Function (IWF) solution provides a means of supporting new technologies while removing the risk, cost and time to market disadvantages associated with legacy core network upgrades.  With Mitel's VoLTE IWF, LTE operators can preserve lucrative voice and SMS revenues, assure global roaming and interoperability, and get to market rapidly. The IWF supports CSFB and SR-VCC that can be deployed independently, in sequence, or simultaneously.

An operator who is looking for CSFB as interim solution and SRVCC as final solution for VoLTE, can deploy CSFB IWF first and later perform a software upgrade to enable SRVCC IWF functionality, avoiding the need for any MSC upgrades for CSFB or SRVCC.

CSFB (CSFB IWF)

Circuit Switch Fall Back or CSFB IWF delivers voice and SMS to CSFB-enabled LTE devices without requiring MSC upgrades.  Circuit Switch Fall Back (CSFB) advocates the use of existing circuit switch (CS) core infrastructure for voice & SMS services and a 3GPP-defined IMS-based solution for providing multimedia services in LTE networks.

Mitel's VoLTE IWF facilitates the rapid deployment of LTE with CSFB by eliminating the need for MSC upgrades thereby reducing operational complexities in deploying LTE voice and SMS services. Investment is based on a common platform for future evolution to converged voice and messaging applications including IMS-based VoLTE. This is a strategic investment in 4G rather than the tactical 3G upgrade approach required by incumbent MSC vendors.

The VoLTE IWF for CSFB is a centralized solution with standard interfaces.

VoLTE IWF for SR-VCC (SR-VCC IWF)

The second is Single Radio Voice Call Continuity (SR-VCC) IWF to support mobility across IMS and CS Core, again eliminating the need for MSC upgrades. SRVCC provides the ability to transition a voice call from the VoIP/IMS packet domain to the legacy circuit domain.

Mitel’s Interworking function, enabling SR-VCC in LTE networks, doesn’t require upgrades to legacy MSCs. The solution introduces SR-VCC IWF bridging CS core and EPC core by front ending the legacy MSCs in the operator network. The solution is agnostic of actual transfer of user sessions being controlled by SCC-AS or by ATCF in the network. The SRVCC IWF is a pure signaling solution reusing existing bearer capabilities of the network.

Platform

The CSFB IWF and SRVCC IWF share the same hardware and software platform,