The IMS Forum today announced preliminary results of its fourth Plugfest for testing interoperability of IP Multimedia System applications and services, with a focus on bringing operations and billing systems into the fray.

Full results of the interoperability testing won’t be made available for another several weeks, but representatives pointed to progress made during this week’s testing. Among the advances: scaling up the test network to two, fairly large-scale test networks; successfully completing IMS-based calls spanning multiple vendor gear and customer devices; and integrating in BSS platforms, including live charging/billing systems from HP and Amdocs.

IMS advocates often tout the importance of new service enablement as a key driver for IMS. Integrating and testing billing components, then, ensures that such services can be accurately tracked and charged for.

“We’re finally getting to a larger deployment-style network that we’re testing her in the lab,” said Lincoln Lavoiem, vice chair of IMS Forum Interoperability Testing. By bringing in billing interfaces for the first time, he added, the tests were able to focus on ensuring that “operators can generate revenue from new and existing services moving to IMS.”

Panelists said that in addition to managing standard billing in an IMS environment, the BSS testing with IMS today will help operators down the line implement more exotic billing mechanisms – such as targeted advertising or pay-per-use – that will be used to support IMS-delivered multimedia services.

Above all, tackling BSS is in focus with the IMS Forum’s goal to promote new service revenues – rather than cost savings – as the key driver of IMS migrations.

“Demonstrating the fact that there are key apps with the potential to generate new revenue is extremely important for IMS,” said Vikram Saksena, CTO of Sonus Networks.

While the latest Plugfest demonstrates significant progress on the IMS interoperability front, key challenges remain, Saksena said. In particular, carriers need help determining successful strategies for inching into IMS rather than taking a greenfield approach as well best practices for managing complex multi-vendor IMS environments, Saksena said.

Speaking of next steps, the IMS Forum has begun preliminary discussion on the focus areas for Plugfest 5. While no firm decisions have been made, likely areas of interest included integrating cable TV applications into IMS. Also on tap: a return to IMS’s roots as a wireless platform, via a focus on advanced mobile technologies like GSM4, LTE, wifi and wimax, said Manuel Vexler, chair of the technical working group for the IMS Forum.

Companies participating in IMS Forum Plugfest 4 included

HP, Amdocs, Acision, Mu Security, NextPoint Networks, Sonus Networks, Tekelec, Aricent, Empirix, Startent, Radvision, Mavenir Systems, Shenick Network, Alpha Networks and Data Connection.