 and control functions that are achieved using LWAPP are summarised in Table 3-4. Although the initial draft specification for LWAPP expired in March 2004, a new IETF working group called Control and Provisioning of Wireless Access Points (CAPWAP) was formed, with most working group members continuing to recommend LWAPP over alternatives such as Secure Light Access Point Protocol (SLAPP), Wireless LAN Control Protocol (WICOP) and CAPWAP Tunnelling Protocol (CTP). It seems likely that LWAPP will be the basis of an eventual CAPWAP protocol. Chapter Three Wireless LAN Arrays The so-called "3rd generation" architecture for WLAN deployment uses a device called an access point array, which is the LAN equivalent of the sectorised WMAN base station illustrated in Figure 3-7. A single access point array incorporates a wireless LAN controller together with 4, 8 or 16 access points, which may combine both 802.11a and 802.11b/g radio interfaces. A typical example uses 4 access points for 802.11a/g coverage, employing 180° sector antennas offset by 90°, and 12 access points for 802.11a covering, with 60° sector antennas offset by 30°, as illustrated in Figure 3-12. This type of device, with 16 access points operating 802.11a and g networks at an individual headline data rate of 54 Mbps, offers a total wireless LAN capacity of 864 Mbps. The increased gain of the sector antennas also means that the operating range of an access point array can be double or more the range of a single access point with an omnidirectional antenna. For high capacity coverage over a larger operating area, multiple access point arrays, controlled by a second tier of WLAN controllers would Combined beam pattern for 12 sector antennas, each 60° beamwidth, with 30° offset between adjacent antennas Combined beam pattern for 4 sector antennas, each 180° beam width, 90° offset between adjacent antennas Figure 3-12: Antenna Configuration in a 16-sector Access Point Array Wireless Network Physical Architecture Access point array coverage area; x 802.11g + 4 X