etwork planning. As the data traffic will be higher in quantity and quality, delay study will constitute an important part of the planning process. KEY TECHNOLOGIES FOR FOURTH-GENERATION NETWORKS Real Time Protocol UDP/TCP IP (ver6) Data Link Layer Physical Layer Figure 10.4 Protocol structure in an All-IP network The major change in the transmission network is the use of All-IP for the flow of traffic. Third-generation transmission networks use an ATM (asynchronous transfer mode) layer for the flow of traffic, while an All-IP network will not have an ATM layer (see Figure 10.4). The major impact of this on transmission network dimensioning is reduced overheads. Overheads in the data link layer will depend on the media. The IP (version 6) layer takes over from ATM layer in these networks. 10.2.3 Wireless Local-area Networks Performance A wireless local-area network (WLAN) is a flexible data communication system, being an alternate to existing wired LANs. This technology removes the hassel of taking wires and cables to and from equipment in an office environment. The Institute of Electrical & Electronic Engineers developed the standards for WLAN, specified in IEEE 802.11. The initial standards specified an operating frequency band of 2.4 GHz and a theoretical data rate of up to 11 Mbps. Subsequent issues of the standards have increased the capacity of the WLAN to 54 Mbps, in the same frequency band. What is the expected role of WLANs in fourth-generation networks? It is expected that WLANs will complement the existing 3G and All-IP 4G networks in high-density area networks by providing similar services at an even higher bandwidth (compared with mature 3G and 4G radio networks). The technology is considered to be best suited to low-usage mobile users who want high data rates in an indoor setting. This also means that the mobile equipment should have the flexibility to choose the access technology at any given time, depending on the environment. Network Planning for a WLAN Network planning is expected to focus mainl