 that we have not exceeded the capacity of the packet pipe. In fact, if the pipe is close to ca- pacity, we should plan to upgrade it on the same visit to the base station. Although new base stations are expensive, the entire principle of cellular telephony is that we can grow our system by adding cells. Let us turn our attention to adding new base stations and new cells in the next chapter. Downloaded from Digital Engineering Library @ McGraw-Hil (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. Source: CDMA CAPACITY AND QUALITY OPTIMIZATION Chapter Adding Cells to a CDMA System We grow cellular networks by adding cells and, in doing so, increase capacity and rev- enue. If we plan carefully, the new cells arrive before customer complaints about block- ing or poor call quality but not before they are needed. Base stations are expensive, so adding cells too soon decreases net revenue. In addition to adding cells at the right time, we want to add the right type of cell at the right place and engineer the network with the new cell for minimal intercell interference. 42.1 Determining When to Add Cells Ultimately, a cellular telephone system grows by adding cells. We can use more power- ful amplifiers and higher-gain antennas, we can use all the code division multiple ac- cess (CDMA) carriers that are available, and we can add sectors, but there is a point where a base station is carrying as much traffic and earning as much money as it can. If we want to increase the traffic and revenue of a system, then we have to use more base stations. Once we have our base stations set up for their maximum load, we need to know when to add more of them. A cell-splitting criterion we do not want to use is waiting until we have high blocking and subscriber complaints. Good planning is the art of staying ahead of trouble rather than waiting for it to happen and then reacting to it. As we discussed in Chap. 41, the primar