3G and Its Interworking with WLAN

This chapter presents an overview of the 3G networks and standards as wellas interworking and handover mechanisms between the IEEE 802.11WLAN and UMTS. A detailed description of WLAN is given in Chapter 4.The Third Generation Partnership Project (3GPP) has already specifiedthe Release ‘99 (R99) standards, which are focused on asynchronous transfermode (ATM) as the backbone network. The recent developments are focusingon all IP-based networks to be standardized for the Release 2000 (R00)of 3GPP. The all-IP network is evolving from packet-switched mobile corenetwork of R99.With the forecast of over 1 billion mobile users estimated by the endof 2002, packet-based multimedia services, including IP telephony, areexpected to account for more than 50% of all wireless traffic. There is amomentum in the industry to evolve the current infrastructure, networkservices, and the end-user applications toward an end-to-end IP solutioncapable of supporting quality of service (QoS) meeting the needs of the dominantdata traffic. At present there are three types of 2G networks: GSM [1,2], IS-95, and PDC.There are several 2.5G data transport standards, which are being implementedby many operators. Decisions are based on user demand, spectrum availability, equipment and spectrum license costs, backward compatibility,and assessment of which will be the dominant 3G worldwide standard.In the future, mobile access to the Internet will be a collection of differentwireless services, often with overlapping areas of coverage. No one technologyor service can provide ubiquitous coverage, and it will be necessary fora mobile terminal to employ various points of attachment to maintain connectivityto the network at all times. The most attractive solution for suchconsideration is to utilize high-bandwidth data networks such as IEEE802.11a/b WLAN whenever they are available and switch to an overlay publicnetwork such as UMTS with lower bandwidth when there is no WLAN coverage.Think of a scenario whereby users may wish to be connected to WLANfor low cost and high bandwidth in the home, airport, hotel, or shopping mallbut will also want to connect to cellular technologies�"for example, GPRS orUMTS�"from the same terminal. In particular, the users in this scenariorequire support for vertical handover (handover between heterogeneous technologies)between WLAN and UMTS.This chapter describes five possible network-layer-level architecturesfor interworking and handover between WLAN and UMTS without makingany major changes to existing networks and technologies, especially at thelower layers such as MAC and PHY layers [3, 4]. This will ensure that existingnetworks will continue to function as before without requiring currentusers to change to the new approach. The implementation involves incorporatingnew entities like emulators and protocols that operate at the networkor higher layers to enable interworking and intertechnology roaming thatwill be transparent to the mobile user to the extent possible.Evolution toward 3G is described in Section 2.2. Section 2.3 gives thefull details of 3G and its releases (R99 and R00). The 3G-deployment scenariosare discussed in Section 2.4. Section 2.5 presents the 3G impact onthe existing network. Section 2.6 describes the general approach to an interconnectionphilosophy and the essential aspects of making interconnectionbetween IEEE 802.11 WLAN and UMTS. Strategy and consequencesbehind the five approaches are described in Sections 2.7 through 2.11. Handoverissues have been discussed in Sections 2.12 and 2.13. Finally, Section2.14 presents the conclusions and future directions.