VoLTE and VoWi-Fi

VoLTE and VoWi-Fi picking up quickly.

Voice over LTE (VoLTE) and Voice over Wi-Fi (VoWi-Fi) are taking center stage for service providers to deliver HD quality voice and multimedia services. The number of commercial VoLTE and VoWi-Fi deployments is rapidly increasing. Launching VoLTE and VoWi-Fi services require mobile operators to not only deploy the IP multimedia subsystem (IMS), but to also integrate it with the policy and charging rules function (PCRF).

Requirement for PCRF binding

In networks with multiple PCRF’s deployed, it has to be ensured that all Diameter sessions established over the Gx, Rx and S9 reference points for a specific IP-CAN session use the same PCRF instance. This session correlation capability is often referred to as “session binding” or “PCRF binding”. For example, sessions created over Gx for LTE users may be routed to a specific PCRF based on the subscriber identifier – IMSI. When another session is created over Rx – for a VoLTE voice call, for example – this session is identified by the assigned IP address. To ensure that session requests are routed to the correct PCRF, the relationship between the subscriber identifier, the assigned IP address and the chosen PCRF instance has to be maintained for the duration of the IP-CAN session.

Geo-redundancy for call continuity

Moreover, session binding requires geo-redundant implementation, with session-binding data synchronization across sites, supporting Gx/Rx session continuity for local and geo-redundant failovers. In the event of a failure, the call should continue with the session and metering state preserved – all completely seamless to the user.

Traditional PCRF and Diameter router solutions provide limited capabilities for geo-redundant session binding and intelligent load sharing.

Full support for PCRF binding with VoLTE and VoWi-Fi

Nomios Netherlands is fully equipped to support PCRF binding for VoLTE and VoWi-Fi. On the platform, session binding (“stickiness”) can be applied for PCRF or any Diameter device that requires binding. Through the graphical user interface of the Nomios Netherlands solution, users can configure AVP(s), for which Nomios Netherlands guarantees that the same peer connection will be selected during the session. This applies to all Diameter applications so that all Diameter traffic for a given subscriber session goes to the same PCRF instance. Association of incoming messages to a session can be based on various Diameter parameters or combinations of parameters, such as:

  • APN
  • IP Address

Nomios Netherlands supports the relevant functions and Diameter applications for PCRF binding for VoLTE and VoWi-Fi, including Gx, Rx, Sh, S6b, S9, SWm, SWx and Cx. Geo-redundant session binding is provided by using the on-board (high-available) session store with cross-site data replication. The session store is multi-node aware, using a distributed storage model. In case of a node or site failure, the established session is processed by the redundant (other) node or site without any interruption.

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