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UMA / GAN Tutorial

An overview or tutorial about the basics of UMA - Unlicensed Mobile Access and GAN - Generic Access Network providing fixed-mobile convergence between cellular and unlicensed spectrum technologies such as 802.11 Wi-Fi and Bluetooth.

UMA or Unlicensed Mobile Access, along with GAN or Generic Access Network are a new technology that will probably become one of the major drivers in cellular mobile communications. The new technology allows convergence between mobile and fixed line communications systems, providing the possibility for users to have just one number and one phone for the telecommunications requirements.

UMA / GAN promises to offer new opportunities to users, mobile operators and manufacturers alike. Thus UMA could be one of the major drivers for the mobile telecommunications industry in the near future providing revenue from new sources as well as providing an upgrade path for existing users.

Drivers for UMA fixed-mobile convergence

The level of mobile use has grown rapidly around the globe. Particularly in western countries where users have access to both fixed and mobile services there has been a growing desire to use just one phone for all their services. With access to wireless connectivity rising from the increased use of DSL lines to the home as well as wireless coverage in work place and in wi-fi hotspots there is the possibility of using a variety of short range wireless connectivity, and chiefly 802.11.

An additional factor is that IMS and VoIP services are now becoming far more widespread and this raises the possibility of using a single user interface and connecting the phone either over the cellular network, or by using wireless connectivity through Wi-fi access points - the system choosing the optimum service.

With users providing a definite push to generate the technology for this fixed-mobile convergence, UMA is bound to be a growing technology.


There are two terms associated with the convergence technology namely UMA - unlicensed mobile access and GAN - generic access network. Both are virtually the same, and indeed the phones that are being marketed are being described as UMA phones.

UMA was the first term to be used. The UMA Industry Forum was founded by a dozen leading cellular companies. However to ensure that there was standardisation - a key element required for the success of UMA, the work was introduced into 3GPP under the GSM EDGE Radio Access Network (GERAN) group. The standard was ratified in April 2006 as TS43.318 release 6 and this included the term GAN - Generic Access Network.

Although GAN is the term that is used within GERAN to describe the technology, it is not seen as much outside the 3GPP environs. Instead the term UMA has been used for much of the marketing of these products. However in essence both terms, GAN and UMA can be used to describe the technology.

Introducing UMA / GAN to a network

The introduction of UMA / GAN by a network operator is relatively low cost and straightforward. While GSM and UMTS require relatively expensive and complicated backhaul circuits as well as costly base stations, the addition of UMA only requires the users to additionally utilise their existing broadband connections.

This means that the network operator only needs to introduce one major element to the network. This is the UMA Network Controller or UNC. This can be considered as being much like a Base Station Controller (BSC) but for the UMA functionality. One side of the UNC is connected to the Internet giving connectivity for the WLAN access points, and the other side of the UNC uses a standard A interface for the circuit-switched communications through to the mobile services switching centre (MSC) and a Gb interface for the packet switched connectivity through to the serving GPRS support node (SGSN).

Although UMA and GAN are effectively the same, in GAN parlance slightly different terms are used. GAN refers to the UNC as the GAN Controller (GANC).

By using the UNC or GANC, it means that when a device hands over from a GSM to a WLAN, it appears to the core network as just a different base station.

Further reading
UMA / GAN Conformance testing

By Ian Poole

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