pment specifications and location. Capital Equipment Selection and Location Having completed both physical and RF site surveys, and established potential base station locations to serve the target area, a link budget can be calculated for typical and extreme subscriber locations within the target operating area. This will establish the transmitter power and antenna gain requirements at each base station as well as the CPE antenna gain required to achieve the desired system performance, taking account of any regulatory limitations (such as EIRP) on the type of equipment that can be used. Four key elements need to be considered in selecting and locating capital equipment; Base station transmitter/receiver Base station antenna Implementing Wireless MANs Base station antenna location Customer premises equipment. Selection of a Base Station Transmitter/Receiver The base station transmitter/receiver (Figure 13-3) is key to achieving maximum effective coverage of the target area. Besides transmitter power and receiver sensitivity, quality and reliability are the factors which will determine overall system performance and, by keeping maintenance and downtime to a minimum, will also reduce operating costs and assure subscriber satisfaction. Base Station Antenna Selection Base station antennas come in many shapes and sizes but in most wireless MAN applications omnidirectional coverage will be required. This may be achieved with either omnidirectional or multiple sector antennas (Figure 13-4). Directional antennas may also be required, for example to extend a MAN using a point-to-point bridge. In general, within local regulatory limitations, it is preferable to provide the maximum possible antenna gain at the base station, since, for a given link budget, this allows a reduction in the specification and cost of CPE. Installing higher cost antennas at a few base stations is clearly preferred Figure 13-3: A Base Station Transmitter (Courtesy of Aperto Networks Inc.) Chapter Thirteen Figure 13-4: A Base Station Sector Antenna A