ommencing physical installation. A variety of simulation programs, often based on the AT&T Wireless model and more recently the Stanford University Interim (SUI) models, can be found online that can assist in the survey process (see the Section "Wireless MAN Resources by Standard, p. 369". These tools can be used to provide an initial coverage estimate, but they should be used with caution as the performance of the network will be largely determined by local environmental conditions that can only be properly accounted for by on-site physical and RF surveys. The results of the physical and RF surveys will provide essential input to network planning, determining the best network equipment specification and configuration to avoid potential sources of interference as well as line- of-sight obstacles, while allowing for other specific local conditions. As discussed below, antenna selection is perhaps the most important element in equipment planning, and the suitability of the selected base station and subscriber antennas will be a key factor in determining the ultimate performance of the network. This selection will be based in part on the site survey results. Physical Site Survey Considerations A physical site survey will check the visual line-of-sight from various points in the target area to the potential base station locations. Fresnel zone clearance (see the Section "Fresnel Zone Theory, p. 113") should also be considered as well as the direct line-of-sight (Figure 13-1). The survey should consider local topography, possible obstructions such as tall buildings, and the proximity to locations such as airports where radar may be a potential cause of interference (this will be checked in the RF survey). Implementing Wireless MANs Business district; LOS Existing towers poor between buildings Fresnel zone problems around business district Low ground elevation; poor LOS from east and west Leafy suburbs; seasonal foliage cover Figure 13-1: A Physical Site-Survey Map for a MAN Installation At the subscriber set-up stage,