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The Unlicensed Mobile Access (UMA) specifications are being developed by a group of 13 infrastructure providers, handset makers and network operators - Alcatel, AT&T Wireless, BT, Cingular Wireless, Ericsson, Kineto Wireless, Motorola, Nokia, Nortel Networks, O2, Rogers Wireless, Siemens, Sony Ericsson and T-Mobile USA. The group hopes to attract other members, with Vodafone a notable absentee so far, as is Swisscom, o?ne of the most advanced cellcos in offering integrated dual-network services.

The aim is to have the specifications adopted by the main standards bodies in the field, the 3GPP and IEEE, in time for dual-mode handsets and PDAs becoming generally available. In phase o?ne, the group will develop and maintain the specs itself, but is already working with the 3GPP o?n a more formal standard.

With UMA technology, subscribers receive a consistent set of mobile voice and data services as they transition between access networks. Solutions based o?n the UMA platform support hand-off of active mobile voice calls and data sessions between networks, without interruption of service. Although details are sketchy at this point, the UMA says its technology enables seamless connections by ?tunneling GSM/GPRS protocols through a broadband IP network and an unlicensed radio link?.

The initiative shows that, however reluctant some cellcos have been to embrace Wi-Fi and the potential erosion of GPRS/3G revenues, there is now a critical mass of operators that realize multiple networks are the way of the future. Wireline and full service carriers such as BT and France Telecom are also moving rapidly towards converged next generation networks and services that support cellular, wired telephony, Wi-Fi and Bluetooth.

It is likely that Motorola will be a major contributor to the standard. It has already said that it plans to submit its voice over WLAN platform, co-developed with Proxim and Avaya, to a standards body and also, of course, has huge cellular experience o?n the handset and infrastructure side. It was the second vendor after Nokia to announce a dual-node handset earlier this year, and plans to incorporate cellular hand-off into its enterprise VoWLAN architecture next year.

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