Generic Access Network
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The Generic Access Network (GAN) was formerly known as Unlicensed Mobile Access (UMA), until it was adopted by the 3GPP in April 2005.
It describes a telecommunication system allowing seamless roaming and handover between local area networks and wide area networks using the same dual-mode mobile phone. Unfortunately the term GAN remains little known outside the 3GPP community, and the term UMA continues to be used in preference as a marketing term.
The local network could be based on private unlicensed spectrum technologies like Bluetooth or 802.11. The wide network is alternatively GSM/GPRS or UMTS mobile services.
It lets mobile operators deliver voice, data and IMS/SIP (IP Multimedia Subsystem/Session Initiation Protocol) type applications to mobile phones on local networks. Its ultimate goal is the convergence of mobile, fixed and Internet telephony (Fixed Mobile Convergence).
On the cellular network, the mobile handset is communicating over the air with a base station, through a base station controller, to servers in the core network of the carrier. Under the GAN system, when the handset detects a LAN, it establishes a secure IP connection through a gateway to a server called a GAN Controller (GANC) on the carrier's network. The GANC translates the signals coming from the handset to make it appear to be coming from another base station. Thus, when a mobile moves from a GSM to a Wifi network, it appears to the core network as if it is simply on a different base station.
GAN was developed as UMA by the Unlicensed Mobile Access Consortium (UMAC) and is now part of the 3rd Generation Partnership Project (3GPP) specifications TS 43.318 and TS 44.318.
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[edit] Modes of Operation
A typical UMA/GAN handset will have four modes of operation:
- GERAN-only: In this mode, only cellular networks are used.
- GERAN-preferred: Cellular networks are used if available. Otherwise, the Wifi radio is used.
- GAN-preferred: Use a Wifi connection if an access point is in range. Otherwise, use the cellular network.
- GAN-only: Use only the Wifi connection.
In all cases, the handset will scan for GSM cells when it first turns on, so it can determine its location area. This allows the carrier to route the call to the nearest GANC, set the correct rate plan, and comply with existing roaming agreements.
[edit] Advantages
For carriers:
- Instead of erecting expensive base stations to cover every nook and cranny of a neighbourhood, GAN allows carriers to add coverage using low cost Wi-Fi access points. When at home, subscribers will have perfect coverage.
- In addition, GAN relieves congestion on the GSM or UMTS spectrum by removing common types of calls and routing them to the operator via the relatively low cost Internet
- GAN makes sense for network operators that also offer internet services. Operators can leverage sales of one to promote the other, enjoying the ability to bill both to each customer.
- Some other operators also run networks of 802.11 hotspots, such as T-Mobile. They will be able to leverage these hotspots to create more capacity and better coverage in many populous areas.
- The subscriber, not the network, will pay directly for much of the costs associated with the service. They will pay for a connection to the Internet, effectively paying the expensive part of the cost of routing calls from their location.
For subscribers:
- Subscribers also benefit in not having to rely upon their operator's ability to roll out towers and coverage, allowing them to fix some types of coverage blackspot themselves (such as in the home or office.)
- The presumably cheaper rates for Wi-Fi use, coupled with better coverage at home, will make it more affordable and practical to use cellphones instead of land lines. It is more convenient to use a single number, a single handset, and a single phone directory for all calls.
[edit] Disadvantages
- Handsets must support Wi-Fi network access which requires additional space, power and complexity and may affect the size, weight and battery performance of the phone.
- GAN is an extension of the cellular network over Wi-Fi and connects to the carrier's servers. Carriers may charge for this service. If so, subscribers may wonder why they are being charged for data that is going over their own internet connections which they provide at their own expense.
- GAN is designed around connecting directly to an existing 2/2.5G GSM network. As such it is only suitable for network operators who have an existing GSM network. For operators such as '3' in the UK this is not the case. To address the issue a development which may eventually be referred to as EGAN kicks off in January 2007.[1]
[edit] Service Deployments
On September 25, 2006 Orange announced their “unik” service ( “unique ” in the UK). The announcement, the largest to date, covers more than 60m of Orange’s mobile subscribers in the UK, France, Poland, Spain and the Netherlands.
In the second week of September, 2006, Telecom Italia quietly posted a UMA-based service called “Unico” on their web site.
On August 28, 2006, TeliaSonera was the first to launch a Wi-Fi based UMA service called “Home Free”.
The first service launch was British Telecom with BT Fusion in the fall of 2005. The service is based on technology which is pre-3GPP GAN standard. Initially, BT Fusion used UMA over Bluetooth with phones from Motorola; since Jan 2007, it uses UMA over Wi-Fi with phones from Nokia, Motorola and Samsung and is branded as a "Wi-Fi mobile service".
[edit] UMA pilots
Various manufacturers and networks have been trialing the GAN/UMA across the world.
Nokia started its first public Unlicensed Mobile Access pilot over Wireless LAN in the city of Oulu during July 2006. The live trial will last at least two months and is being conducted under real life surroundings and conditions. Fifty families from the city of Oulu will be trying and testing the functionalities of this new technology with the help of a brand new Nokia 6136 mobile device.[2]
T-Mobile recently launched a "public trial", starting in Seattle, in October 2006.[3]
[edit] Similar Technologies
GAN/UMA is not the first system to allow the use of unlicensed spectrum to connect handsets to a GSM network. The GIP/IWP standard for DECT provides similar functionality, though requires a more direct connection to the GSM network from the base station. While dual-mode DECT/GSM phones have appeared, these have generally been functionally cordless phones with a GSM handset built-in (or vice versa, depending on your point of view), rather than phones implementing DECT/GIP, due to the lack of suitable infrastructure to hook DECT base-stations supporting GIP to GSM networks on an ad-hoc basis.[4]
GAN/UMA's ability to use the Internet to provide the "last mile" connection back to the GSM network solves the major issue that DECT/GIP has faced. Had GIP emerged as a practical standard, the low power usage of DECT technology when idle would have been an advantage compared to GAN.
There is nothing preventing an operator from deploying micro- and pico-cells that use towers that connect with the home network over the Internet. Ericsson has announced[5] a so-called "Femto-cell" system that does precisely that, broadcasting a "real" GSM or UMTS signal, bypassing the need for special handsets that require 802.11 technology. In theory, such systems are more universal, and again require lower power than 802.11, but their legality will vary depending on the jurisdiction, and will require the cooperation of the operator.
[edit] Devices
[edit] References
- ^ [1], [2]
- ^ Nokia 6136 Press Release
- ^ T-Mobile USA UMA Pilot PR page (warning: Flash heavy)
- ^ DECT Web DECT/GSM DUAL MODE and the advent of the ONEPHONE SERVICE
- ^ Ericsson launches world's smallest GSM radio base station for home coverage - Ericsson Press Release, 2007-FEB-09
[edit] See also
[edit] External links
- 3GPP GAN Specification 43.318, 3GPP GAN Specification 44.318
- UMA
- UMA Today — contains also a list of available GAN handset
- UMA / GAN overview — with an onsite link to page on UMA / GAN conformance testing
- 3GPP
- Free download of 3GPP standards available at
