Wireless LAN Access Technology

During the last decade mobile communication networks follow the evolution of fixed networks in order to provide moving subscribers with all the services and applications of fixed subscribers. This however is unfeasible due to restrictions and limitations imposed by the hostile radio channel. The global system mobile (GSM) network, known as 2G technology (Mouly & Pautet, 1992), is adequate in meeting voice communication speeds of a typical subscriber since it offers limited communication capabilities (< 9.6 kb/s). The ideal mobile network would be able to provide moving subscribers with continuous access to every possible voice or data network, leading to the realization of a “mobile office.” The result of this effort (although somewhat restrictive in terms of realizable bit rates) was another evolution in mobile networks, the general packet radio service (GPRS) network (usually referred to as 2.5G), with available data rates of approximately 40 kb/s up to 100 kb/s. The universal mobile telecommunication system (UMTS) (usually referred to as the third-generation cellular network or 3G), with competitive rates of 300 kb/s and a future possible upgrade up to 2 Mb/s, is the realization of a new generation of telecommunications technology for a world in which personal services will be based on a combination of fixed and mobile services to form a seamless end-to-end service for the subscriber. Its realization at least requires provision of a unified presentation of services to the end user, mobile technology that supports a very broad mix of communication services and applications, and finally on-demand flexible bandwidth allocation reaching 2Mb/s per subscriber. Moreover the exploitation of pure (not tunneled) Internet protocol (IP) interconnection of network elements between each other for data exchange and operation and maintenance purposes should be available, along with the provision of flexible end-to-end all-IP connectivity in terms of user information. 3.5G and 4G (Esmailzadeh, Nakagawa, & Jones, 2003) systems are already under investigation. Aiming to “context-aware personalized ubiquitous multimedia services” (Houssos et al., 2003), 3.5G systems promise rates of up to 10Mb/s (3GPP Release 5), while with the use of greater bandwidth, these rates may raise even more in 4G (Esmailzadeh et al., 2003). On the other hand, the last five years a standardization effort has started for the integration of Wireless local area network (WLAN) in order to support higher bit rates in hotspots or business and factory environments, with a cell radius on the order of 100m. In any case, 4G and WLAN technology are going to be based on an IP backbone between access points (APs) and access controllers or routers and the Internet. Mobile IPv4 and IPv6 are already under investigation (Lach, Janneteau, & Petrescu, 2003) to provide user mobility support for context-type services.