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SEMINAR REPORT ON GENERIC ACCESS NETWORK (GAN)
1. ABSTRACT
Generic Access Network (GAN) is a telecommunication system which extends mobile services voice, data and IP Multimedia Subsystem/Session Initiation Protocol (IMS/SIP) applications over IP access networks.
This report will attempt to discuss the details of the GAN, its evolution, its services, architecture, and other implications.

By:
Karan Kukreja
109/B.Tech(CSE)/ASET/2005

2. INTRODUCTION
The Generic Access Network (GAN) is an evolving wireless communications system in which mobile phone sets function seamlessly between local area networks (LANs) and wide-area networks (WANs). Using GAN technology, a cell phone subscriber can communicate by voice, data and multimedia. As GAN technology is implemented, cellular telephone subscribers can expect improved coverage, the ability to use a single phone set for all their voice communications and perhaps cheaper rates with a single bill for Internet and voice communications.
Main application of this GAN/UMA is the Dual-mode Handset service.
3. THEORETICAL DESCRIPTION
3.1 How does this dual-mode service work
With dual-mode services(GSM and Wi-fi), subscribers make calls from outside the home as they would ordinarily, using the GSM radio network at the standard tariff rate. But inside the home, the call travels over the subscriberâ„¢s wireless broadband connection, so the operator can enjoy a similar economic structure as VoIP-over-broadband provider.

3.2 Basic requirements for using GAN services
To offer GAN dual-mode services, mobile operators need handsets, network controllers,
call control, the security to protect the mobile operator voice network from
Internet-based threats, and wireless access points for their subscribers.
3.3 Participating companies and vendors of the GAN
Alcatel
British Telecom
Cingular
Ericsson
Kineto Wireless
Motorola
Nokia
Nortel Networks
O2
Research in Motion
Rogers Wireless
Siemens
Sony Ericsson
T-Mobile US
3.4 A note on the history of the GAN (also called as the UMA)

In September 2004, the participating companies published the initial UMA specifications and formally introduced them to the 3rd Generation Partnership Project (3GPP) standards body.
In April 2005, an unprecedented eight months later, the UMA specifications were incorporated into the 3GPP release 6 specifications. While referred to as "Generic Access Network" or GAN, within the 3GPP specifications.
In mid 2006, mobile operators around the world began announcing their intention to deploy dual-mode handset (DMH)-based UMA services.
Throughout 2007, there were constant announcement of new UMA-enabled dual-mode phones to support the commercial service offers.
In early 2008, the first commercial UMA-based fixed line VoIP service appeared as well as the first UMA-enabled softmobile client.
4. TECHNICAL DETAILS
4.1 GAN functional architecture:

As seen in the figure the GAN functional architecture consists of 5 basic components :
4.1.1. GANC(GAN Controller)
4.1.2. Security gateway
4.1.3. Authentication, Authorization and Accounting (AAA) infrastructure
4.1.4. Dual mode handset
4.1.5. Standard Wi-fi access point
4.1.1.GANC :
The GANC provides dual-mode handsets with alternative access
to GSM voice and GPRS data services.
For voice traffic, the GANC integrates directly into an operator Mobile Switching Center (MSC) through the A interface.
For data traffic, the GANC integrates directly into an operator serving GPRS support node (SGSN) through the Gb interface.
4.1.2. Security gateway :
The introduction of a GAN solution into an operator network raises numerous security implications and vulnerabilities inherent in an
IP-based architecture. The security gateway provides two important security roles in the GAN:
Secure authentication (through Extensible Authentication Protocol“SIM [EAP-SIM] or EAP“Authentication and Key Agreement [EAP-AKA]) of mobile subscribers
Termination of secure tunnels (through IP Security [IPSec]) with InternetKey Exchange Version 2 [IKEv2]) from the handset.
4.1.3. Authentication, authorization, and accounting (AAA) infrastructure:
The AAA infrastructure interacts with numerous elements in the GAN architecture, including:
Security gateway : The AAA infrastructure interacts directly with the security gateway to validate mobile credentials during IPSec tunnel establishment. This includes the use of EAP mechanisms for SIM-based authentication using either EAP-SIM or EAP-AKA.
HLR: The AAA infrastructure includes a MAP Gateway function for communication to the operator HLR using the SS7 transport protocol. During authentication, the AAA infrastructure is responsible for converting RADIUS authentication messages from the security gateway into SS7 MAP Invoke messages to the HLR. This allows the existing HLR to verify a user on the GAN using the IMSI/triplets sequence that is standard for GSM/GPRS authentication.
4.1.4. Dual-mode handset:
The dual-mode handset allows an end user to connect to either a public GSM radio network or a private Wi-Fi or Bluetooth radio network and maintain the same service capabilities.
4.1.5. Standard Wi-Fi access point:
A standard Wi-Fi access point (or hotspot) is used to provide Wi-Fi access to a dual-mode handset. This Wi-Fi access point may be enhanced with specific Quality of Service (QoS) and security mechanisms, such
as rate-limiting for uplink traffic, Call Admission Control to
limit the number of dual-mode handsets that may associate with it, 802.1x encryption, etc.
4.2 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 802.11 radio.
GAN-preferred: uses a 802.11 connection if an access point is in range, otherwise the cellular network.
GAN-only: uses only the 802.11 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.
5. ADVANTAGES
For the 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 802.11 access points. When at home, subscribers have very good 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 the 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 802.11 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 802.11 into a service that uses a single number, a single handset, single set of services and a single phone directory for all calls.
6.DISADVANTAGES
Handsets must support 802.11 network access which requires additional space, power and complexity and may affect the size, weight and battery performance of the phone.Increasingly, consumers take advantage of unlimited or otherwise high-volume data tariffs to make VoIP calls via SIP, as with Skype.
GAN will mean that this type of usage is more likely to be charged on a per-minute or unit basis as with voice calls, which may increase the cost of mobile calls made over IP.
7. GAN/UMA BEYOND THE DUAL MODE
While UMA is nearly always associated with dual-mode GSM/Wi-Fi services, it is actually a Ëœgenericâ„¢ access network technology. It provides a generic method for extending the services and applications in an operatorâ„¢s mobile core (voice, data, IMS) over IP and the public internet.GAN defines a secure, managed connection from the mobile core (GANC) to different devices/access points over IP.
7.1 Femtocells:
Femtocells are small cellular base stations, typically designed for small household or business environment. The GAN standard is currently used to provide a secure, managed, standardized interface from a femtocell to the mobile core network.
7.2 Analog Terminal Adaptor:
Recently T-Mobile announced a commercial trial of a fixed line VoIP service. Similar to Vonage, consumers can port their fixed phone number to T-Mobile, then T-Mobile associates that number with an ATA (analog terminal adaptor). The consumer plugs the ATA into their home broadband network and begins receiving calls to the fixed number over the IP access network. Linksys developed a UMA-enabled ATA specifically for this application.
7.3 Softmobile :
Consumers have started to use telephony interfaces on their PCs. Applications like Skype offer a low cost, convenient way to access telephony services while traveling. Now mobile operators can offer a similar service with a UMA-enabled softmobile client. Developed by Vitendo, the client provides a mirror interface to a subscriberâ„¢s existing mobile service. For the mobile operator, services can now be extended to a PC/laptop, and they can give consumers another way to use their mobile service.
8. SIMILAR TECHNOLOGY
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. 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. Several companies have developed so-called Femtocell systems that do 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.
9. CONCLUSION
GAN dual-mode services to the home give mobile operators the opportunity for a significant competitive advantage by accelerating fixed-mobile substitution, increasing penetration, and reducing turnover. The GAN architecture provides an essential prerequisite for dual-mode services”protecting the mobile operator™s voice network from threats originating from the Internet. Because the security infrastructure that is
used to offer dual-mode services can be reused for other services, including IMS, the investment in the GAN solution provides a competitive advantage for tomorrowâ„¢s service as well as todayâ„¢s.
10.REFERENCES
1. GAN participating companies page link http://umatechnologyparticipants/index.htm
2. UMA overview http://umatodayumaOverview.php
3. A Brief History of UMA http://umatodaybriefHistory.php
4. 3GPP OVERVIEW
http://3gppAbout/about.htm
5.Definitions
http://searchmobilecomputing.techtargets...07,00.htmL
6.All about protocols
http://voxeoproducts/voip-home.jsp
7. GSM, TDMA - CDMA, Wireless LAN
http://whitepapers.techrepublic.comabstract.aspxdocid=268373
8.http://whitepapers.techrepublic.comthankyou.aspxauthId=ikq5icupT4KI8U8Gu92k KgRMRbkImtNEM82eO7wUxjdLDvUjT/ypXW8oj8PB4ZB4&&promo=100511&docid=268373&view=268373&load=1
9.GAN and its working http://en.wikipediawiki/Generic_Access_N...chnologies
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