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Chapter 5 GENERIC ACCESS NETWORK TOWARD FIXED–MOBILE CONVERGENCE Unlicensed Mobile Access (UMA) is different from other technologies that deliver voice and data over IP/Wi-Fi. Offering a completely seamless service to the end user as he moves between the macro Global System for Mobile (GSM) access network and Generic Access Network (GAN). GAN is part of 3GPP R6 standards. Section 5.1 TRENDS IN THE INDUSTRY 5.1 TRENDS IN THE INDUSTRY UMA allows operators to deliver GSM/General Packet Radio Service (GPRS) services over a fixed broadband network to a dual-mode Wi-Fi handset in a completely seamless manner. Mobile and broadband networks also show drawbacks: Difficult for the normal GSM network to provide good enough coverage using limited, licensed spectrum. Section 5.2 STANDARDIZATION 5.2 STANDARDIZATION How to deliver a GSM service over an IP connection? How to spread out GSM coverage into homes without investing in spectrum licenses and expensive and work-intensive base station installations? The user has the same number and same service when roaming between public radio access and Wi-Fi network The specifications have since been adopted by 3GPP. Section 5.3 GAN OVERVIEW 5.3 GAN OVERVIEW 本圖取自"Technologies for Home Networking". Edited by Sudhir Dixit and Ramjee Prasad, published by John Wiley, 2008. 5.3 GAN OVERVIEW Moving between these three access networks, should: Remain connected to the same mobile core network Enjoy the same services; be reachable on the same number, and so forth Experience no break in service when moving between a GAN coverage area and, for example, GERAN 5.3 GAN OVERVIEW 本圖取自"Technologies for Home Networking". Edited by Sudhir Dixit and Ramjee Prasad, published by John Wiley, 2008. 5.3.1 Security Based on the security mechanisms defined for the 3GPP Interworking WLAN IP Access scenario. IKEv2 , EAP/SIM, EAP-AKA All defined in Internet Engineering Task Force (IETF) specifications. 5.3.2 “Discovery” and “Registration” Used to allocate the best possible GANC for the handset in the current location. Discovery: Used between the handset and the Provisioning GANC, which is the initial point-of-contact in the GAN. Provisioning GANC is to allow access to the GAN and allocate a Default GANC to each mobile station (MS), which is main point-to-contact for handset in GAN. 5.3.2 “Discovery” and “Registration” Handset tries to access GAN from a new location, it will initiate Registration to the Default GANC. When registration is accepted, the Serving GANC returns the “GAN System Information” to the handset. Serving GANC connect to the Mobile-services Switching Center (MSC) , support handovers between the GAN and the macronetwork. 5.3.3 Rove In and Rove Out Used in the GAN standard for roaming between the WLAN coverage and GERAN/UTRAN. Rove in means the handset starts communicating actively using the protocols in the Up interface and these protocols start serving the upper layers in the Handset. Rove out means the handset stops communicating using the protocols in the Up interface and the relevant GERAN/UTRAN protocols are used instead and serve also the upper layers in the Handset. 5.3.4 Transparent Access to Services in the Mobile Core Network The Up interface protocols provide transparent support for services in the mobile core network. This is achieved by tunneling all the upper-layer messages, like mobility management, SMS, call control…etc Over the Up interface and then interworking these to the existing mechanisms in the A and Gb interfaces. 5.3.5 GPRS Support in GAN The Up interface also supports transport of GPRS control signaling and user plane traffic using specific procedures. Allow the network to support a very large number of handsets. No need to keep handset-specific data in the GPRS part of GANC for idle handsets. 5.3.6 Location Services Handset indicates to the GANC the current camped GERAN or UTRAN cell. Handset includes the MAC address of the WLAN AP being used, and the GANC can use an external database to map these to an exact geographic location of the AP. 5.3.7 Emergency Services Placed over GERAN/UTRAN or over GAN. Over GERAN/UTRAN: existing location determination services are used Over GAN: Location determination mechanisms are used to guide the core network in routing to the right Public Safety Answering Point (PSAP) 5.3.8 GAN Protocol Architecture Generic Access Circuit Switched Resources (GA-CSR) Mobility management (MM) Base Station System Application Part (BSSAP) Message Transfer Part (MTP) Signaling Connection Control Part (SCCP) Direct Transfer Application Part (DTAP) 5.3.8 GAN Protocol Architecture 本圖取自"Technologies for Home Networking". Edited by Sudhir Dixit and Ramjee Prasad, published by John Wiley, 2008. 5.3.9 Bluetooth or Wi-Fi? Particularly with Wi-Fi equipped handsets There seems to be consensus that Wi-Fi will prevail. GAN is an opportunity to offer a voice service over local WLAN networks with good coverage while ensuring that the traffic remains controlled in their core networks. Section 5.4 BENEFITS WITH THE GAN TECHNOLOGY 5.4 BENEFITS WITH THE GAN TECHNOLOGY No radio license is required, because GAN operates in the license-free spectrum. No radio planning is required. Current license-free technologies such as Bluetooth and IEEE 802.11 are “self-planning.” Range is limited compared with the macro technologies of GERAN and UTRAN. Typically, one can expect 20–30 m indoors and up to 100 m outdoors or larger indoor spaces. 5.4 BENEFITS WITH THE GAN TECHNOLOGY GAN utilizes WLAN access points that are either already in place or set up for the purpose. These are typically around the 50–100 USD price point, or even lower. GAN uses IP as its bearer service; It may be delivered over DSL, cable, Ethernet, or other networks already in place to homes and offices. 5.4.1 Operators Deploy mobile voice services over the broadband networks that are now becoming broadly deployed. With GAN, a converged end-user offering can be constructed that both leverages mobile telephony and broadband. 5.4.2 End User If typical market mechanisms prevail, some of these benefits will be passed on to the end user. With GAN, the end user experience remains the same in the WLAN domain as in the wide area radio domain. End user has one phone with one number independently of access method and location The end user experiences functionality transparency (same services independently of network) and seamless mobility between the two domains with roaming and handover in both directions. 5.4.3 Terminal Availability Standardization is a key element while introducing new protocols into the handsets as this guarantees interoperability between the handsets and the infrastructure. Terminal and network vendors have taken an active part in the 3GPP GAN standardization process. The standard minimizes the impact on the terminal and leverages on already existing implementations in the handsets. Section 5.5 PRACTICAL EXPERIENCES 5.5 PRACTICAL EXPERIENCES Setting up the service, plugging in the access point, registering the handset, and so forth, are usually straightforward, a “plug and play” experience. Coverage, even with early pre-UMA handsets with low-power Bluetooth radio,is sufficient for residential uses and comparable with normal cordless phones. Service and user experience is indistinguishable from what is found via the macronetwork, except for battery life, which with some early implementations was significantly lower with UMA enabled. Section 5.6 IMPACT ON NETWORKS AND PROCESSES 5.6 IMPACT ON NETWORKS AND PROCESSES Operators will probably need to change certain configuration data in order to facilitate. (e.g., Handover between GAN and GERAN.) The key components of the GAN itself need to be installed (e.g., the GANC, the security gateway, etc) GANC is largely going to appear as “just another BSC”. This impact is probably going to be modest compared with the work involved in launching a completely new type of service. Section 5.7 DISCUSSION 5.7 DISCUSSION Voice over WLAN” protocols do not deliver the same transparency, as they rely on the user being served by a different core network when in “WLAN-mode.” On the business side, GAN offers many compelling features: Allows broadband operators to combat “fixed-tomobile substitution” by offering a full-spec mobile service to their customer base. Section 5.8 EVOLUTION OF GAN 5.8 EVOLUTION OF GAN IMS is a core network evolution that will offer current voice and data services, as well as new combinations of these, through different access networks. IMS is an evolution of the core and service layers, whereas UMA is an evolution of the mobile access network. Evolution to 3G is another topic often discussed in relation to GAN. Section 5.9 CONCLUSIONS 5.9 CONCLUSIONS GAN is backed by a number of dominant handset and system providers on the market. This technology is proved to work and the protocols are standardized, there are no technical barriers for success.