00 million sets and growing. We provide a brief review of cordless telephone set technology below. Other examples are those governed by IEEE 802.11 series of specifications, 802.15 and 802.16, which have been described earlier. The European-developed GSM, although listed as cellular, may also be included under the PCS umbrella. It not only is widely used in Europe, Africa, and Asia, but also is beginning to have deep penetration in North America. 18.8.2 Narrowband Microcell Propagation at PCS Distances The microcells discussed here have a radial range of < 1 km. One phenomenon is the Fresnel break point, which is illustrated in Figure 18.17. This figure illustrates that signal 18.8 PERSONAL COMMUNICATIONS SERVICES (PCS) Receive signal strength n1 = 1.3; sd1 = 2.1 n2 = 3.2; sd2 =0.70 Distance from transmitter (m) Freq. = 800. MHz, Tx height = 13.4 m, Rx height = 1.6 m Figure 18.17 Signal variation on a line-of-sight path in a rural environment. (From Ref. 17, Figure 3.) level varies with distance R as A/R", where R is the distance to the receiver. For distances greater than 1 km, n is typically 3.5 to 4. The parameter A describes the effects of environmental features in a highly averaged manner (Ref. 17). Typical PCS radio paths can be of an LOS nature, particularly near the fixed transmitter where n = 2. Such paths may be down the street from the transmitter. The other types of paths are shadowed paths. One type of shadowed path is found in highly urbanized set- tings, where the signal may be reflected off high-rise buildings (see Figure 18.4). Another is found in more suburban areas, where buildings are often just two stories high. When a signal at 800 MHz is plotted versus R on a logarithmic scale, as in Figure 18.17, there are distinctly different slopes before and after the Fresnel break point. We call the break distance (from the transmit antenna) RB. This is the point for which the Fresnel ellipse about the direct ray just touches the ground. Such a model is illustrated in Figure 18.18. The distance RB is a