Unlicensed Mobile Access (UMA) was initially developed by an industry group consisting mainly of operators searching for new ways to expand and improve mobile access. They wanted the standard to offer the advantages of converged services, leveraging wired/WLAN access in-building, to save cost and reduce churn. There was a great desire in this early work to develop a solution that would be cost-effective and would not have to rely on waiting for a full QoS-based Voice-over-IP (VoIP) solution to be widely available throughout the industry. The solution was to “tunnel” GSM voice over a broadband connection using either Bluetooth or Wi-Fi as the access interface.
Today, UMA is a global standard developed by the 3rd Generation Partnership Project (3GPP) in Release 6. UMA provides subscriber access to mobile wireless circuit, packet and IMS-based services over devices using IP-based networks, such as DSL, cable and Wi-Fi. UMA solutions promote seamless handovers, high levels of service transparency, and a relatively low-impact way of deploying converged services in a 2G or 3G network with the cost benefits of unlicensed spectrum and Internet backhaul. UMA also specifies seamless handovers between 2G and 3G GSM-HSPA radios and unlicensed access. Both UMA and the complementary IP Multimedia Subsystem (IMS) architecture, are key elements in the transition to the Fixed-Mobile Convergence (FMC) of wireless devices.
T-Mobile USA was one of the first operators to deploy a UMA solution with its T-Mobile Hotspot@Home service which enables its customers to seamlessly transfer from a mobile cellular call to their fixed home Wi-Fi networks. Rogers in Canada offers Talkspot as its UMA offering to customers while Cincinnati Bell provides its Home Run service. Although North American operators are among the primary facilitators of UMA, there are commercial UMA services in Europe as well.
A special dual-mode cellular/Wi-Fi handset equipped with WLAN or Bluetooth as well as the UMA protocol UMA device is required to allow subscribers to seamlessly roam and handover between cellular and Wi-Fi networks. There are numerous leading manufacturers who provide UMA terminals. Femtocells may also be used to deliver UMA services.