 that says half the capacity is gone at such and such a cell size. There is some distance, some radio signal path, where a single voice call will use the entire capacity of a cell sector because it takes the full power of the transmitter, even with antenna gain and processing gain, to produce a signal that surpasses the thermal noise of the receiver. Clearly, we do not want to operate our CDMA system in this mode often. Radio signal path gains vary considerably, so it is not enough that most subscribers are in good coverage areas. If a wireless telephone system is going to compete in the marketplace on the basis of superior service, then it must have very few areas of poor radio performance. Those weak regions are the areas that will lose calls first when the system gets busy. The subscriber will be making a perfectly ordinary cellular phone call with perfectly good signal, but when somebody else starts a data session, the first sub- scriber's call gets noisy for a few seconds and then is dropped. Or a few calls from a weak zone use up the entire CDMA capacity, and a large community of subscribers near the base station is blocked. We recommend making sure that the coverage picture is good enough that events such as these seldom happen. The bad news is that poor radio signal paths erode CDMA capacity. The worse news is that these weak radio areas are typically three- and four-cell zones with pilot pollu- tion adding to the capacity problem. The radio coverage maps described in Sec. 47.9 and the pilot-pollution maps described in Sec. 48.5 are invaluable aids in engineering a system to avoid these circumstances that consume capacity. The bottom line in CDMA cell coverage is that high-demand areas should have high radio signal path gain. It is not so important to make good radio paths better, but it is terribly important to make bad radio paths good. Once we have good enough signal to climb onto the steep part of the curves in Figs. 28.1 and 28.2, we are operating in a high-efficiency CDMA mode. Making a good radio p