ry.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Basic Wireless Telephony Basic Wireless Telephony zoning permit increases the cost of a base station and also delays its construction. Dur- ing the delay, customers in that area are doubly irritated: As cellular customers, they are experiencing poor service, and as residents, they are experiencing a vendor trying to reduce the quality of their neighborhood. The same people who clamor for cellular telephone service are not at all anxious for their neighborhoods to have a skyward spire prickly with radio antennas at the top. Having more capacity in one base station is more economical than having multiple base stations because it aggregates transmission and reception for more users into one building. In addition, a base station also aggregates telephone trunking from the base station to the rest of the wireless system. This is a serious economy because getting any kind of digital link from one place to another is usually a much bigger problem than adding more capacity once a link is already in place. The paging and access channels are also aggregated at the cell level. While radio frames, antennas, cables, and trunks cost money, their costs are usually relatively small compared with the costs of the building, tower, power supply, telephone access, and zoning issues required for each base station. 5.2.2 Sectors and antenna faces Cells are usually divided into sectors. As discussed in Sec. 4.1, omnidirectional, three- sector, and six-sector cells are the sector plans that make sense for conventional reuse systems (FDMA and TDMA). Other sector plans can make sense in CDMA systems, where the primary sources of interference are other calls in the same cell. The cell sector is formed by having an antenna face at the base stations. Three an- tenna faces give some cellular towers their distinctive triangular platforms. The face contains directional antennas, both transmitting and receiving