d from one small radio tower. Having many small cells allows for reuse of frequencies and results in greater call capacity than a single radio service area with the same number of channels. The model of a cellular transmission structure with managed interference is the ba- sis of all cellular systems, including the original analog systems, Europe's time division multiple access (TDMA)-based Global System for Mobility (GSM) and the latest code division multiple access (CDMA) technologies used for Personal Communication Ser- vices (PCS) and universal mobile telephony system (UMTS). 5.1 The Wireless Signal Path We follow the links in the chain of a wireless telephone call from the portable (or ve- hicular) telephone through the radio path and the wireless telephone system to wher- ever the call is connected. We will start with the full story from a user terminal to a regular landline telephone. Figure 5.1 shows us the chain from wireless to landline telephone through the radio link, the base station, the base station to mobile switching center (MSC) pipe, the MSC, another pipe, the public switched telephone network (PSTN), and the local loop. After describing this chain in detail, we will consider the differences when the call is from one wireless telephone to another. 5.1.1 Wireless to landline The user terminal is a complete two-way radio, as described back in Chap. 3. The user terminal can detect the presence of a wireless telephone environment through its pag- ing and access channels. It synchronizes itself to the system and makes itself known to the system by registering itself. This tells the system that there is a user terminal in a 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. Basic Wireless Telephony Key Radio Concepts Radio Local Trunk Trunk Mobile Switching Station Landline Center Telephone Cellular Telephone Figure 5.1 The wireles