y warning of impending overload in a CDMA system is power levels: high trans- mit power in either direction, too many power-up messages for the reverse link, or more signal than noise at the base station receiver. In a small-cell, high-density area, these symptoms may not appear until the base station is very close to saturation. Therefore, planning ahead is essential. We can use the planning models described Chap. 48 to estimate how much traffic each sector is supporting and how close it is to its maximum. The planning tools take into account such factors as the effects of terrain on propagation, intercell and intracell interference, and pilot pollution. We have to use some judgment because the computer program may not know the usage patterns and the mix of services of our subscribers. In a growing system, we can use earlier experience to calibrate our computer predic- tions. As our system has been growing, we have been adding cells, and we know how much traffic the old cells could handle before they ran out of capacity. That traffic level Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Adding Cells to a CDMA System Increasing Capacity is going to be a good estimate for how much traffic the current cells can handle. If our own system has been consistently worse or better than the computer prediction, then it may be that we have a tougher or easier subscriber community. Perhaps we have more bursty data users or fewer multimedia messages than we assumed in the com- puter models. Adding base stations means adding backhaul. A new base station needs its own transport back to its mobile switching center (MSC). This will be discussed in Sec. 44.1, but we should keep in mind that available cheap transport is an important component in selecting new base station locations for growth, just as it was in initial system base station placement. 42.2 Cell 