Key Words: UMA, Unlicensed Mobile Access, GSM, GPRS, Bluetooth, 802.11, Wi-Fi, Telecommunications, Wireless, and Mobile.

Unlicensed Mobile Access, UMA, is the technology that makes it possible to provide access to GSM and GPRS mobile services over unlicensed spectrum technologies, like Bluetooth and 802.11. This means that subscribers can roam and handover seamlessly between private unlicensed wireless networks, GSM networks, local area networks, and the public switched telephone network (PSTN) using the same dual-mode mobile phone. UMA will allow mobile phone service providers to provide a higher quality and lower cost service by creating transparent transitions between networks. Many of today’s leading wireless companies have adopted a set of open specifications in order to promote UMA technology and secure its place in the future of telecommunications.

UMA technology was founded by a number of leading operators and vendors, called The UMA Consortium, and has been in development since January 2004. The list of participants, include British Telecom, Cingular, Motorola, Nokia, and T-Mobile US, who are active in the testing and further development of UMA Technology. These companies first published the UMA Technology specifications on September 2nd 2004 in hopes of attracting interest in what they were doing. They then passed on the specifications to the 3rd Generation Partnership Project (3GPP) and were approved on April 8th 2005. Since then the participating companies have been testing and further developing UMA technology for future integration.

The objective to developing UMA technology has always been to develop and publish an open set of technical specifications designed to extend mobile voice and data services over the unlicensed spectrum, and encourage those specifications to be adopted on a large scale. Once the UMA standard has been established wireless companies can focus their research and development on fixed mobile convergence (FMC) to fully integrate and connect the mobile world to fixed line infrastructure. While FMC is a new and powerful technology, UMA remains the cornerstone of future wireless innovations.

The following steps describe how UMA works in greater detail. When a mobile subscriber moves within range of an unlicensed wireless network with a UMA-enabled, dual-mode headset they are allowed to connect. Once connected the headset uses a UMA Network Controller (UNC) through the broadband IP access network and is authenticated and authorized for accessing GSM voice and GPRS data services by using the unlicensed wireless network. Once approved, the subscriber’s present location information stored in the core network is refreshed, and from then on all mobile voice and data traffic is sent to the handset through the Unlicensed Mobile Access Network (UMAN) instead of a cellular radio access network (RAN).

Roaming is a general wireless term that means the extending of connectivity service in an unregistered foreign location and has frustrated many wireless users for years; however, a UMA-enabled subscriber can move outside the range of the unlicensed wireless network to which they are connected. The subscriber never notices that the handset and UNC facilitate roaming back to the licensed outdoor network and this means good things for those subscribers who are UMA-enabled. Those same UMA-enabled subscribers can handover active GSM voice calls or GPRS data sessions seamlessly between access networks of an unlicensed wireless network. These are two important reasons among many why UMA technology is important.

UMA can co-exist with technologies already in place like Wi-Fi and Bluetooth, but acts independently of this underlying spectrum. This means that UMA is transparent to existing CPE devices such as access points, routers, and modems. This is important in today’s world, in which innumerable devices vie for the same airspace. UMA technology also provides the same mobile identity on both unlicensed wireless networks and Cellular RAN. Going the other direction, Monica Paolini of Senza Fili (which means without wires in Italian) is one of the world's leading independent experts on UMA technology. Paolini published an article in Telecommunications Magazine on Feb 1, 2006 titled, “Unlicensed Mobile Access: A License to Print Money?” in which she wrote about the large amount of money to be made by providing UMA in direct competition with Voice over IP and fixed-line providers which she predicts will become a fading trend by 2010.

This new technology offers an alternative way to access GSM and GPRS core network services using IP-based broadband connections, which will give the companies who adopt this technology quite a unique edge on their competitors. The companies’ subscribers will be able to take advantage of a more seamless experience with the use of UMA Network Controllers to provide secure transport of GSM/GPRS signaling over IP. UMA technology provides a cost benefit and enhanced feature set by making improved voice quality and in-building coverage available while offloading traffic from higher cost GSM radio networks that are currently in place.

UMA technology will also change the future of how wireless telecommunication is achieved for the better. The existing GSM cell radius in a residential location is about 7.77 square miles, an area which can cover over 12,000 homes on quarter acre plots. However, taking into account the poor in-building penetration provided by older GSM technology up to 70% of those homes may suffer from poor coverage and service. By using a UMA-enabled dual-mode phone that offloads traffic to localized Wi-Fi networks it is possible to gain back any lost coverage due to inadequate in-building penetration. Once outside the call is handed off to a local cellular network seamlessly. This is just one situation in which UMA technology can be a benefit to both wireless companies and their subscribers.

UMA technology in the not so distant future looks to reduce costs of networks by transferring traffic to less expensive existing broadband infrastructure whilst improving the quality of services for in-building calls. This means new revenue sources for operators as well as more features and quality of service for subscribers. UMA has come a long way since 2004, from drawing board to the publication of UMA specifications in 2005 and further as a potential means to achieve fixed mobile convergence. Look for UMA to become another standard of innovative future of wireless telecommunication.