GENERIC ACCESS NETWORK

The 'Generic Access Network' (GAN), also known as 'Unlicensed Mobile Access' (UMA), is a telecommunication system allowing seamless roaming and handover between local area networks and wide area networks using a dual-mode mobile phone. It lets mobile operators deliver voice, data and IP Multimedia Subsystem/Session Initiation Protocol (IMS/SIP) type applications to mobile phones. Its ultimate goal is the convergence of mobile, fixed and Internet telephony (Fixed Mobile Convergence).
The local network may be based on private unlicensed spectrum technologies like Bluetooth or 802.11, while the wide network is alternatively GSM/GPRS or UMTS mobile services. On the cellular network, the mobile handset communicates 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.
The system was initially called UMA and then renamed to GAN. It was developed by a group of operator and vendor companies. The initial specifications were published on 2nd September 2004. The companies then contributed the specifications to the 3rd Generation Partnership Project (3GPP) as part of 3GPP work item "Generic Access to A/Gb interfaces". On 8th April 2005, 3GPP approved specifications for Generic Access to A/Gb interfaces for 3GPP Release 6.
[ftp://ftp.3gpp.org/Specs/archive/43_series/43.318/ TS 43.318] and [ftp://ftp.3gpp.org/Specs/archive/44_series/44.318/ TS 44.318], and renamed the system to GAN. But the term ''GAN'' is little known outside the 3GPP community, and the term ''UMA'' is more common in marketing.

Contents

Modes of operation

Advantages

Disadvantages

Service deployments

UMA pilots

Similar technologies

Devices

References

See also

External links

Modes of operation

A typical UMA/GAN handset will have four modes of operation:

★ GERAN-only: uses only cellular networks

★ GERAN-preferred: uses cellular networks if available, otherwise the Wifi radio

★ GAN-preferred: uses a Wifi connection if an access point is in range, otherwise the cellular network

★ GAN-only: uses only the Wifi connection
In all cases, the handset scans for GSM cells when it first turns on, to 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.

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 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, and can 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.

★ Subscribers, not the network, pay directly for much of the costs associated with the service. They pay for a connection to the Internet, effectively paying the expensive part of the cost of routing calls from their location.
For subscribers:

★ Subscribers do not rely on 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 cheaper rates for Wi-Fi use, coupled with better coverage at home, make it more affordable and practical to use cellphones instead of land lines.

★ GAN is currently the only commercial technology available that combines GSM and Wi-Fi into a service that uses a single number, a single handset, single set of services and a single phone directory for all calls.

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.

★ Compared to completely free Wi-Fi VoIP services such as Skype, the fact that GAN is an extension of the cellular network and connects to the carrier's servers practically means that carriers will charge for this service in one way or another.

★ 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 called EGAN is under way in 3GPP.^[1]

Service deployments

The first service launch was British Telecom with BT Fusion in the autumn 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".
On August 28, 2006, TeliaSonera was the first to launch a Wi-Fi based UMA service called “Home Free”.
In the second week of September 2006, Telecom Italia quietly posted a UMA-based service called “Unica” on its web site.
On September 25, 2006 Orange announced its “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.
On June 6th 2007 Finnish virtual operator Saunalahti announced plans to publish UMA services on week 24 with the Nokia 6136 UMA phone. Announcement in finnish
The first UMA deployment in the United States was announced by Cincinnati Bell on June 18, 2007. The service called CB Home Run allows users to seamlessly transfer from the Cincinnati Bell cellular network to a home wireless network or Cincinnati Bell's WiFi HotSpots. This was followed shortly by T-Mobile on June 27, 2007. T-Mobile's service, called ''T-Mobile HotSpot@Home'', allows users to seamlessly transfer from the T-Mobile cellular network to a home wireless network or T-Mobile HotSpot.

UMA pilots

Various manufacturers and networks have been trialing the GAN/UMA across the world.
Nokia started its first public UMA pilot study over Wireless LAN in the city of Oulu in July 2006. The live trial was to last at least two months and be conducted under real life surroundings and conditions by fifty families, with new Nokia 6136 mobile devices.^[2]
T-Mobile launched "HotSpot@Home" in 2007^[3]
Cincinnati Bell Wireless launched "CB Home Run" in 2007.
^[4]

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, but 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.^[5]
GAN/UMA's ability to use the Internet to provide the "last mile" connection 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^[6] 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.

Devices

★ Motorola - A910

★ Nokia - 6136, 6086

★ Samsung - P200, T709

★ Sagem - my419X

★ Samsung - Samsung T409^[7]

References

1. [1], [2]
2. Nokia 6136 Press Release
3. http://www.t-mobile.com/company/PressReleases_Article.aspx?assetName=Prs_Prs_20070627&title=T-Mobile%20Introduces%20Unlimited%20Calling%20Over%20Wi-Fi%20With%20the%20National%20Launch%20of%20T-Mobile%20HotSpot%20@Home
4. [3]
5. DECT Web DECT/GSM DUAL MODE and the advent of the ONEPHONE SERVICE
6. Ericsson launches world's smallest GSM radio base station for home coverage - Ericsson Press Release, 2007-FEB-09
7. http://www.t-mobile.com/shop/phones/Detail.aspx?device=93369e8f-a580-49b2-93bd-88fcd1321b85

See also

★ IEEE 802.21

★ IEEE 802.11r

★ IEEE 802.11u

External links

★ 3GPP GAN Specification 43.318, 3GPP GAN Specification 44.318

★ UMA Today — contains also a list of available GAN handset

★ 3GPP

★ Free download of 3GPP standards available at

★
★ 3GPP Specifications Home Page

★
★ ETSI GSM UMTS 3GPP Numbering Cross Reference

★ Dafocus UMA/GAN Protocols encoder/decoder