UMA is the 3rd Generation Partnership Project (3GPP) global standard for subscriber access to mobile circuit, packet and IMS-based services over any IP-based access network, including the Internet. With UMA, mobile operators can now leverage the cost and performance advantages of IP access technologies (DSL, Cable, Wi-Fi...) to deliver high-quality, low-cost mobile voice and data services in the locations where subscribers spend most of their time - the home and office.

To enable access to the mobile service core via IP-based networks, the UMA standard defines a new core network element (the UMA Network Controller (UNC)) and associated protocols that provide for the secure transport of mobile signaling and user plane traffic over IP. The UNC interfaces into the core network via existing 3GPP specified interfaces.

Fundamentally, UMA provides a standard, scalable, secure IP interface into the core service network of mobile operators. By deploying a UMA Network Controller (UNC), mobile operators can extend all existing and future circuit, packet and IMS-based services over any IP-based access network, including the Internet. While initially developed to enable dual-mode cellular/Wi-Fi handset services, the UMA standard can be leveraged to deliver a number of compelling new fixed-mobile convergence services.

UMA-enabled Dual-Mode Wi-Fi Handsets: By far the most well-known UMA service is dual-mode cellular/Wi-Fi handsets (DMH), which enables operators to provide high-performance, low-cost mobile services to subscribers when in range of a home, office or public Wi-Fi network. With a UMA-enabled dual-mode Wi-Fi handset, subscribers can automatically roam and handover between cellular and Wi-Fi access, receiving a consistent set of services as they transition between networks.

UMA-enabled Femtocells: UMA-enabled femtocells represent a growing UMA service opportunity. The wireless industry has been searching for low-cost licensed indoor coverage solutions since the beginning of mobile networks. Unfortunately, the bulk of this opportunity (i.e. residential environments) has been beyond the addressable market for cost and operational reasons. To be successful, a residential licensed access point (i.e. femtocell) deployment must include low-cost femtocells (under €150), a reasonable approach for managing RF interference, and a standard, scalable, IP-based approach for core network integration.

UMA provides standard, secure, scaleable, and cost effective IP-based access into core mobile service networks. It can be directly leveraged to address the core network integration challenge. There are several UMA-based femtocell trials currently underway, and UMA-enabled femtocells are available today.

UMA-enabled Terminal Adaptors: The market for broadband telephony service has increased dramatically over the last few years. At the end of 2007, Vonage Holdings alone had more than 2 million subscribers paying between $15 and $25 per month for a telephone service delivered over existing broadband access connections. Now, with UMA-enabled terminal adaptors, mobile operators can also participate in this large and growing service opportunity. A UMA-based fixed line VoIP service is the ideal approach for mobile operators looking to increase fixed-to-mobile substitution by directly capturing in-home fixed minutes of use.

UMA-enabled terminal adaptors enable mobile operators to leverage an existing R99 or R4 core network to deliver a standard analog telephone service over broadband access networks (a.k.a. broadband telephony). As far as subscribers are concerned, the service behaves as a standard analog fixed telephone line. The service is delivered in a manner similar to other fixed line VoIP services, where a simple device (in this case the UMA-enabled terminal adaptor) is connected to the subscriber's existing broadband service.

There are commercial UMA-based fixed line VoIP services today as well as UMA-enabled terminal adaptors.

UMA-enabled Softmobiles: Connecting laptops to broadband access at hotels and Wi-Fi hot spots has become a standard part of everyday life, particularly for international business travelers. In addition, many travelers are beginning to utilize laptops and broadband connections for the purpose of voice communications. Rather than using mobile phones to make calls and pay significant roaming fees, they are turning to PC-based soft-phones and VoIP services when making international calls. This represents a significant threat and opportunity for mobile operators.

Fortunately, thanks to UMA, mobile operators will soon be able to leverage their existing UNC deployments to also provide soft-phone (or soft-mobile) services (also known as 'the Skype Killer'). To use a UMA-enabled softmobile service, a subscriber would simply place a USB memory stick with an embedded SIM into a USB port on their laptop. The UMA-enabled softmobile client would automatically launch and connect over IP to the home mobile service provider. From that point on, the subscriber would be able to make and receive mobile calls as if he or she was in their home calling area. The service would function in a similar manner to soft-phone clients provided by VoIP providers such as Vonage.