With wired networks, planning the installation of cabling is fairly straightforward. You can survey the site and look for routes where installers can run the cable. You can measure the distances and quickly determine whether cable runs are possible. If some users are too far away from the network, you can design a remote networking solution or extend the length of the cable by using repeaters. When the design is complete, installers can run the cables, and the cable plant will most likely support the transmission of data as planned.
A radio-based wireless LAN installation is not as predictable. It is difficult, if not impossible, to design the wireless system by merely inspecting the facility. Predicting the way in which the contour of the building will affect the propagation of radio waves is difficult. Omnidirectional antennas propagate radio waves in all directions if nothing gets in the way. Walls, ceilings, and other obstacles attenuate the signals more in one direction than the other, and even cause some waves to change their paths of transmission. Even the opening of a bathroom door can change the propagation pattern. These events cause the actual radiation pattern to distort, taking on a jagged appearance.
To avoid installation problems, an organization should perform propagation tests to assess the coverage of the network. Neglecting to do so may leave some of the users outside of the propagation area of wireless servers and access points. Propagation tests give you the information necessary to plan wired connections between access points, allowing coverage over applicable areas.