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Testing EPC for precise LTE/4G billing structures

Posted: 21 Dec 2012 ?? ?Print Version ?Bookmark and Share

Keywords:LTE? offline charging systems? evolved packet core?

Offline Charging System (OFCS): The OFCS allows for the collection of network resource charging information concurrently with that resource usage. The OFCS enables the aggregation and correlation of the charging information from multiple sources and delivers it to a Billing System.

Components of validating the EPC
Measurements are essential to assessing the quality and performance of the EPC. They must be rich, flexible, visual, complete, and represent an accurate real-time view of the network or device being tested. Service providers must remember a few key areas in their test and validation methodology, in order to get the insight they will need to optimise performance and accuracy:

???Quality of Service (QoS). The quality of service, expressed in jitter, latency, packets dropped, and other measurements, is a key performance indicator in an all-IP network. QoS testing measures the degradation of a guaranteed bit rate flow, such as a voice call, when a sudden data surge occurs. QoS imbalances should be measured on a per service data flow, per-subscriber, and node level basis using triple-play and video-rich traffic.
???Quality of Experience (QoE). QoE tests validate the perceived quality of a voice or video stream. Based on well-established standards, QoE tests are essential to assess the overall quality of the network from the user's view, and they are especially effective as end-to-end measurements conducted between mobile equipment and the edge of the IP core network.
???Deep Packet Inspection (DPI). DPI is a cornerstone capability of the PDN-GW since QoS enforcement is performed by inspecting and regulating ingress and egress traffic. Using DPI to simulate PDN behaviour and to observe and report traffic violations, the EPC can certify service level agreements (SLAs). Triple play and video-rich traffic is essential for testing node functions that enforce QoS, such as DPI.
???Subscriber behaviour. Subscriber modelling emulates the mix, volume, and variability of mobile user communities. It is only by using rich traffic profiles, including video, file transfer, instant messaging, email, torrents, etc., that the EPC core network can be fully battle-tested.
???Charging. LTE charging occurs mostly in the PDN-GW and SGW. Interfaces have been defined for offline and online charging. A crucial EPC charging test involves checks and balances between the generated traffic trigger events and the measured charging events.
By creating a high number of subscribers and their behaviour, and stepping through a sequence of events that trigger charging data records (CDR), operators can successfully validate the EPC billing system. These events can include establishment of dedicated bearers for VoLTE services or a conversational video session, roaming, access to a specific external network (APN), and many other events. In fact, there are dozens of events that a particular operator may choose to monetize, each of which can trigger CDRs to be generated by the S-GW or P-GW and sent on to the OCS or OFCS. By comparing the emulated event counts to the records in the OCF/OFCS the accuracy of the charging system can be determined.

Closing the loop C Preparing for LTE billing
The deployment of LTE wireless networks and the required interoperability with legacy technologies creates new levels of network complexity. Fortunately, through a full EPC evaluation using test tools for all mobile network elements from layer 2-7, service providers can meet the high demands of LTE while simultaneously generating revenue. The ability to decipher an average text message user versus the avid YouTube video watcher will not only allow service providers to create a realistic billing model, but also charge according to usage. Deep insight into their networks will equip service providers with the necessary information to tackle these new LTE infrastructures head on.

About the author
Joseph Zeto, serves as a senior market development manager within Ixia's marketing organisation. He has over 17 years of experience in wireless and IP networking, both from the engineering and marketing sides. Joe has extensive knowledge and a global prospective of the networking market and the test and measurement industry. Prior to joining Ixia, Joe was Director of Product Marketing at Spirent Communications running Enterprise Switching, Storage Networking, and Wireless Infrastructure product lines. Joe holds a Juris Doctorate from Loyola Law School, Los Angeles, CA.

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