The most challenging aspect of introducing Voice over LTE services (VoLTE) will be deciding how and whether to transition individual legacy voice services to the new domain, according to Michel Lenoir, programme manager for LTE at Vodafone Netherlands. The move to VoLTE gives operators a chance to reassess their voice services portfolio but the range of options open to them is wide and operators must be clear about which services they want to keep and how best to maintain them, Lenoir told Telecoms.com.

“With all the IN-based vocie services in our core network we need to decide what we’re going to do with them,” he said. “Do we port them into an IMS domain and, if so, how? Do we secure interworking with the circuit switched domain and the new IMS domain?  There are all sorts of options and, for me, this is the most challenging discussion that we have.”

Some services may be wound down but others are “so key to the user experience”, Lenoir said, that they have to be maintained. Some can be ported across to VoLTE while for others the service logic might remain in the legacy network requiring Vodafone to “try to build a proxy” for them.

Vodafone Netherlands is working with specialist software provider OpenCloud on this issue and OpenCloud’s head of marketing Mark Windle told Telecoms.com that gaps in the LTE standard mean that operators will have to find their own route through these interoperability issues.

“There are parts within the standards for VoLTE relating to how IMS networks and legacy networks interoperate where the standard effectively says ‘we don’t know how to do this, it will be done by some unspecified magic in the service layer’,” said Windle. “Operators have to find a way of doing that themselves and best practice will hopefully emerge.”

While the solution will be technical the service decisions will be made by marketing departments, Lenoir said. “We as technical people will say what it will cost but it will be marketing who decides,” he said.

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