. It reduces customer complaints and loss of customers to our competitors. Careful planning and implementation also reduces the need for frequent, rushed, poorly planned, expensive upgrades followed by high main- tenance costs. 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. Source: CDMA CAPACITY AND QUALITY OPTIMIZATION Chapter Adding Transport As our cellular network grows, we need to add transport capacity, both in backhaul and in the connections from the MSC to other network components and other networks. In addition, we may be able to reduce network costs by reorganizing the configuration of the backhaul network periodically. 44.1 Adding Backhaul The normal way a telephone system grows is by adding capacity through the use of big- ger pipes. As more telephone users served by a local exchange office make more calls, the telephone company adds more trunks between that local exchange office and other local exchange offices and interexchange carriers. When a business expands its local telephone network, it upgrades its private branch exchange (PBX) and adds capacity by adding trunks to the existing links to the public switched telephone network (PSTN). Cellular growth is different because of the limiting nature of the air-interface capac- ity. Capacity is added to a cellular system by adding cells. This means that a wireless system grows by adding base stations, and the backhaul network grows by adding more transport pipes rather than by making the existing pipes bigger. The backhaul re- quirement for a base station can be no more than the maximum capacity of the air in- terface for all the sectors using all the code division multiple access (CDMA) carriers. Sometimes a backhaul pipe from one base station gets bigger. When a cell gets more CDMA carriers or more sectors, its base station requires more transport to the mobile switching center