to broadcast its own identity clearly enough for the user terminal to synchronize itself to the access channel, to identify the system, and to respond in a narrow time window SO that the system can detect the response. The user terminal registers with the wireless telephone network by sending a mes- sage on the signaling channel. The registration message identifies the user terminal to the serving system. The user terminal registers when it is powered on and recognizes the wireless system paging channel. The user terminal registers again when it recog- 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. Telephony Engineering Concepts Telephony Engineering Concepts nizes a new wireless telephone system. The user terminal may move to another cell and detect another base station's paging channel, but it only reregisters when it detects a different system identification. A user terminal also will reregister after a specific period of time. There is a timing cycle dictated by the system and communicated on the paging channel. When the ap- propriate time interval has passed, the user terminal registers again. We call this au- tonomous registration. If we did not have some kind of autonomous registration, then the wireless system would have to keep registrations current for a long time. A user ter- minal might leave the service area or be powered off, and it has no way of knowing that this will happen. As a result, the system cannot rely on the user terminal notifying the system that it is no longer connected and available to receive calls. Autonomous regis- tration allows the system to drop a phone's registration if it fails to reregister at the specified interval. In this way, the system's record of registered phones is reasonably close to the reality at any given moment. The registration timeout cycle is a parameter that affects both the currency of