Integrating an OCS Platform to Facilitate 4G to 3G Roaming
With DIAMETER signalling becoming the key interface for next generation networks and increasingly being driven by the growth of LTE, IoT, autonomous vehicles and VoLTE, it is crucial that operators are able to seamlessly communicate with subscribers as they traverse between legacy networks and IMS.
As a mobile operator deploys a state-of-the-art online charging system (OCS) in their 4G network, the platform needs to overcome inter-op challenges with subscribers as they roam into 3G networks.
An OCS platform typically supports a range of interface technologies – XML, HTML, JSON, DIAMETER etc. The charging functions in 3G networks are handled over the legacy SS7 CAMEL protocol. Furthermore in some 3G networks pre-pay subscribers are dynamically credit checked by the network over Unstructured Supplementary Service Data (USSD), a legacy protocol commonly used for billing, location based services, mobile money and menu based information services.
To deliver end-to-end 3G <-> 4G Roaming you need to provide both CAMEL to DIAMETER and DIAMETER to USSD functionality.
In order to manage the flexibility of DIAMETER and the forecasted volumes of signalling data the industry has developed a set of standard DIAMETER based network products. Included in this product set is the Inter-Working Function (IWF) which provides 3GPP specified DIAMETER to SS7 CAMEL, MAP and RADIUS interworking and is obviously the primary product interface to the OCS.
At Squire Technologies our SVI_IWF product is tightly integrated with our Telephony Application Server (SVI_TAS) which provides a set of flexible API’s to allow for the rapid deployment of new interfaces, in this instance used to provide USSD to DIAMETER. The operator then went one step further and delivered a separate USSD application. They decided the interface to the OCS would optimally be performed over HTTP. It was a straightforward task to manipulate the HTTP API on the SVI_TAS to deliver this extended functionality.
The IWF is deployed and embedded in a pair of DIAMETER Routing Agent’s (DRA’s) that provide resiliency through redundancy, load sharing and balancing via sophisticated on-board routing.
Full support for session binding insures correct online credit control is being performed when multiple simultaneous services are being billed for a single subscriber.
This solution provides both flexibility and scalability for the operator. As network demand increases new instances of the OCS platform can be launched and configured to point its DIAMETER interface at the pair of DRA’s which will automatically route messages to and from the appropriate OCS. This model allows for ease of deployment in a cloud based NFV network allowing OCS resources to be easily deployed or removed as network demand dictates.