NEC has been asked by Japanese network operator Softbank Mobile to provide an IMS-based network to support its femtocell service, for full commercial deployment in January 2009.
The deployment will mark the first time femtocells have been deployed using the IP Multimedia Subsystem (IMS) from end to end, despite the two technologies naturally fitting together to provide seamless roaming between macro and micro networks.
IMS has been a long time coming, despite the majority of the industry recognising an inevitable evolution of telephony. IMS uses SIP (Session Initiation Protocol) to negotiate connections between communicating parties, including reservation of bandwidth over intervening hops and notification of the billing system. Importantly, IMS is carrier-technology-neutral - an IMS call can take place over a cellular network, an ADSL connection, or a happy combination of the two with seamless roaming.
Femtocells are tiny in-home base stations - 3G in this instance - that allow a normal mobile phone to connect to the cellular network over the punter's broadband connection within the home, using frequencies owned by the network operator.
Originally IMS was considered impossible without IPv6 - the next-generation internet routing system that is also widely considered an inevitable evolution, but hasn't arrived quite as quickly as hoped. Various bodges have allowed IMS deployment over IPv4 while we're waiting.
Softbank Mobile has been testing the technologies since June, and will be running more trials during the rest of 2008. The system will be ready for punters to start signing up next year. ®