VoLTE could cause a storm, KPN warns

KPN, the incumbent Dutch operator, told the audience at LTE World Summit about the networking battles it has had in bringing VoLTE services, and roaming, to market. Revealing the results of some live network trials, the operator warned of the effect or influence VoLTE could have on traffic in the signalling network.

Wendy Ooms, who’s a senior architect of voice and mobile signalling at KPN, said operators can expect a boom in signalling traffic when VoLTE becomes a reality.

“On various interfaces you’ll be seeing at least a two-fold growth in signalling traffic, because of VoLTE, and its need to have multiple bearers of voice and video per call,” she said. “All of this traffic will be doubled again on the Diameter Routing Agent.”

Ooms then explained the environment in which the operator trialled its VoLTE services.

“We ran a pilot with 100 participants, both international and external customers, who received a VoLTE-ready phone, to trial VoLTE on our live network, which covers 98.2% of population,” she said. “We mainly focussed on the voice aspect of VoLTE, with limited use of ViLTE [Video over LTE]. Customers used a shared IMS mobile and fixed infrastructure, and we utilised DRA in all diameter interfaces.”

Finally, Ooms warned the audience that even slightly altering IMS registration times could cause an SIP storm, and identified wifi as a potential solution.

“SIP signalling can have a massive effect of the load on the mobile network if you’re not doing it right,” she said. “During our trial, someone changed the IMS registration time from 50 minutes to 5 minutes, and the load generated absolutely exploded. SIP registration storms can occur on mobile when users lose their connection, and multiple users come flooding back when the service becomes available again. Wifi could be a solution to integrate with VoLTE if one user is somewhere 4G doesn’t reach.”