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).

The Generic Access Network (GAN) is a developing wireless communications system that allows mobile phones to effortlessly switch between LANs and wide-area networks (WANs). A cell phone subscriber can communicate via voice, data, and multimedia across large-scale cellular and small-scale Wi-Fi systems using GAN technology. All system handoffs should, in theory, take place without disrupting the communication session.

Subscribers of cellular telephones should expect better coverage, the opportunity to utilise a single phone for all voice calls, and possibly lower pricing with a single bill for Internet and voice communications when GAN technology is adopted. However, phone set technology for GAN use has two modes, both of which must be available at all times. This necessitates the presence of two transceivers in every phone set at all times, one for traditional cellular service and the other for Wi-Fi. The battery is put under more current demand as a result of this.

Cellular device users use a general access network (GAN) to connect and interact with different types of communication devices in telecommunication systems. GAN protocols were developed primarily for wireless communication systems, allowing mobile phones to effortlessly perform functions between wireless local area networks (WLANs) and wide area networks (WANs) without interfering with the communication session. Voice, data, IP multimedia subsystem, and Session Initiation Protocol (SIP) applications are all possible with modern GAN technology.

Initially, the 3rd Generation Partnership Project backed a GAN interface specification developed by a group of suppliers and operators. The LAN is typically built on unlicensed proprietary technology like as 802.11, which lets a mobile device to communicate with a base station over the air via a base station controller. The Global System for Mobile Communications, generic packet radio service, and the Universal Mobile Telecommunications System are all popular WAN services.

GAN technology’s main feature is a dual-mode handset service that allows mobile phone subscribers to smoothly switch between wireless LANs and WANs. This improved feature of seamless roaming allows customers to communicate with people all around the world using their cell devices at a cheaper cost.

The adoption of GAN technology is driving structural changes in cell phones. GAN currently has two separate accessible modes, requiring each phone to have two transceivers. The first is for traditional cellular service, while the second is for advanced applications such as Wi-Fi.

GAN has various drawbacks in addition to its benefits. GAN subscriber services are susceptible to interference since UMA uses various frequencies. Cellular devices that use multiple LAN and WAN signals via GAN are quite expensive and limit the talk and standby duration of the mobile device.

The Generic Access Network’s capability has been improved in recent years to enable connection possibilities other than audio connectivity. Data and multimedia broadcasts are now supported by the network. Many people who use their mobile gadgets extensively during the workday have found this to be beneficial. It is now feasible to attend and communicate in a web conference using a handheld device, with the same convenience as attending an audio conference call, thanks to these developments using a Generic Access Network.

The increased switching and routing components that enable for connectivity are part of the Generic Access Network’s brilliance. Seamless roaming, which allows a user to connect to a network and make a connection, is now so efficient that a user can connect with people all over the world as easily as making a normal phone call. Receiving and sending multimedia is similar in that the process is no more difficult for the end user than downloading and viewing a file on a desktop computer.

Unlicensed Mobile Access, or UMA, was the name of the Generic Access Network prior to 2005. However, when the role expanded to include connections that allowed for the sharing of more sorts of data, it became clear that a new name for this type of telecommunications system was required. Today’s technology, which is linked to the Generic Access Network, is transforming the structure of cell phones. One significant distinction is the requirement for two transceivers in each device, one for traditional audio and the other for Wi-Fi and more sophisticated applications.

What is the operation of this dual-mode service?

Subscribers who use dual-mode services (GSM and Wi-Fi) make calls from outside the home as they normally would, utilising the GSM radio network at the ordinary tariff rate. However, within the home, the call is routed over the subscriber’s wireless broadband connection, allowing the operator to operate in a similar manner to a VoIP-over-broadband provider.

The initial UMA specifications were produced in September 2004 by the participating firms and formally introduced to the 3rd Generation Partnership Project (3GPP) standards organisation.

The UMA requirements were adopted into the 3GPP release 6 specifications in April 2005, an unusual eight months later. Within the 3GPP specifications, it is referred to as “Generic Access Network” or GAN.

Mobile operators all around the world began declaring their plans to implement UMA services based on dual-mode handsets (DMH) in mid-2006.

Throughout 2007, new UMA-enabled dual-mode phones were constantly announced to facilitate commercial service offers.

The first commercial UMA-based fixed line VoIP service, as well as the first UMA-enabled softmobile client, debuted in early 2008.

The functional architecture of the GAN

The GANC allows dual-mode handsets to use GSM voice and GPRS data services simultaneously.

The GANC integrates directly into an operator’s Mobile Switching Center (MSC) for voice traffic via the A interface.

Through the Gb interface, the GANC integrates directly into an operator providing GPRS support node (SGSN) for data traffic.

The introduction of a GAN solution into an operator network brings with it a slew of security concerns and vulnerabilities that come with an IP-based architecture. In the GAN, the security gateway serves two critical security functions:

Mobile subscribers’ secure authentication (through Extensible Authentication Protocol–SIM [EAP-SIM] or EAP–Authentication and Key Agreement [EAP-AKA])

Secure tunnels (through IP Security [IPSec]) using InternetKey Exchange Version 2 [IKEv2] are terminated from the device.

GAN/UMA isn’t the first system that allow devices to connect to a GSM network using unlicensed frequency. Similar capability is provided by the GIP/IWP DECT standard, although it necessitates a more direct connection to the GSM network from the base station. Due to the lack of suitable infrastructure to connect DECT base-stations supporting GIP to GSM networks on an ad-hoc basis, dual-mode DECT/GSM phones have primarily 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.

The ability of GAN/UMA to leverage the Internet to offer the “last mile” link to the GSM network addresses a fundamental problem for DECT/GIP. When compared to GAN, DECT technology’s reduced power usage when idle would have been an advantage if GIP had been a viable standard. Nothing prevents an operator from establishing micro- and pico-cells that connect to the home network via the Internet via towers. Several businesses have developed so-called Femtocell systems that do exactly that, transmitting a “genuine” GSM or UMTS signal without the requirement for special 802.11 phones. In principle, such systems are more general and require less power than 802.11, but their legality varies by jurisdiction and will necessitate the operator’s participation.

Operational modes

The GAN standard for Release 6 allowed for a 2G (A/Gb) connection from the GANC to the mobile core network (MSC/GSN). All commercial GAN dual-mode handset deployments use a 2G connection today[when?] and all GAN enabled devices are dual-mode 2G/Wi-Fi. However, the standard stipulated that multimode handset operation be supported. As a result, the standard includes compatibility for 3G/2G/Wi-Fi handsets. In the second half of 2008, the first 3G/UMA devices were announced.

There are four modes of operation on a standard UMA/GAN handset:

  • Only cellular networks are used in GERAN.
  • If cellular networks are available, GERAN is chosen; otherwise, the 802.11 radio is used.
  • If an access point is within range, GAN-preferred uses an 802.11 connection; otherwise, the cellular network is used.
  • GAN-only: just uses the 802.11 network.

When the handset initially powers on, it scans for GSM cells to establish its local area. This enables the carrier to route the call to the nearest GANC, apply the appropriate tariff plan, and adhere to current roaming agreements.

The GAN specification was updated at the end of 2007 to include 3G (Iu) interfaces from the GANC to the mobile core network (MSC/GSN). This native 3G interface can be used to supply 3G femtocell services as well as dual-mode handsets. These additional capabilities are described in the GAN release 8 documentation.


For carriers:

  • GAN lets carriers to extend service using low-cost 802.11 access points rather of installing expensive base stations to fill dead zones.
  • Subscribers who are at home enjoy excellent coverage.
  • Furthermore, GAN reduces congestion on the GSM or UMTS airwaves by eliminating typical types of calls and redirecting them to the operator over the relatively low-cost Internet.
  • For network operators who also provide Internet services, GAN makes sense. Operators can use one’s sales to promote the other, and each consumer can be charged for both.
  • T-Mobile is one of the operators that runs 802.11 hotspot networks. They can use these hotspots to increase capacity and improve coverage in densely populated areas.
  • The provider of the Internet and Wi-Fi connection pays for a connection to the Internet, effectively paying for the expensive part of routing calls from the subscriber. Carriers, on the other hand, rarely pass on these savings to customers who utilise Wi-Fi for calls in the form of decreased prices.

For Subscribers :

  • Subscribers do not rely on their operator’s capacity to deploy towers and coverage, allowing them to repair various sorts of coverage dead zones (such as at home or at work) on their own.
  • The lower costs for 802.11 use, along with better coverage at home, make using cellphones instead of land lines more inexpensive and practical.
  • When roaming outside of a carrier’s network, IP over 802.11 eliminates pricey roaming charges.
  • GAN is the only commercial technology that integrates GSM and 802.11 into a service that employs a single number, a single handset, a single set of services, and a single phone directory for all calls[citation needed].
  • GAN can seamlessly transition between IP and cellular coverage; calls made using third-party VOIP and a data phone, on the other hand, are dropped upon exiting high-volume data coverage.


  • To use the service, subscribers must upgrade to devices that support Wi-Fi/UMA.
  • When the handset switches from Wi-Fi to regular wireless service or vice versa (due to the handset moving out of or back into the Wi-Fi range), calls may be more likely to disconnect. Depending on whose handset is utilised, the degree to which this is a problem may vary.
  • The UMA may use a frequency that is more susceptible to certain types of interference.
  • Before any benefits may be realised, some preparation may be necessary to supply connection parameters (such as authentication details). This may take some time for subscribers and will necessitate further support. Support fees may extend beyond the wireless phone company: network administrators may be called to assist a user in entering suitable phone settings (that the network administrator may know little about).
  • Due to the additional circuitry/components required to handle various signals (both UMA/Wi-Fi and the type of signal used by the provider’s towers), phones that support multiple signals may be more expensive, particularly to manufacture.
  • This makes advantage of the network resources that provide the Wi-Fi signal (and any indirect network that is then utilised when that network is used). The available bandwidth has been depleted. Some types of network traffic (such as DNS and IPsec-encrypted) must be allowed by the network, therefore deciding to support this may impose some security (firewall) rule requirements.
  • The WiFi module must be activated in order to use GAN/UMA on a mobile device. When compared to disabling GAN/UMA, this drains the battery faster and reduces both talk and standby time (and in turn WiFi).
  • UMA does not operate with E911 that is cellular-based and uses GPS/Assisted GPS. Typically, the subscriber registers a fixed primary address with the carrier via mobile settings, a carrier-provided app, or a carrier-provided website.
  • There are no assurances of QoS. Due to the fact that the Internet (and, by extension, most home networks) uses a best-effort delivery approach, network congestion can affect call quality. Gaming, high-definition video, and peer-to-peer file sharing compete for available bandwidth, which is usually a problem for the subscriber’s home network. Some network equipment can deal with this by setting QoS for VoIP protocols, however this is complicated by the fact that most UMA operates over IPsec over UDP, rendering the underlying protocols (IMS/SIP) invisible to the network. Handsets can alleviate this by assigning IPsec traffic to a different WMM class (such as AC VO) internally.


Mobile operators can gain a considerable competitive advantage by accelerating fixed-mobile substitution, increasing penetration, and lowering turnover with GAN dual-mode services to the house. The Cisco GAN architecture is a necessary pre-requisite for dual-mode services, which safeguard the mobile operator’s voice network against Internet-based attacks. The Cisco GAN solution provides a competitive advantage for tomorrow’s services as well as today’s since the security infrastructure utilised to support dual-mode services can be employed for future services, including IMS.

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