Site home page
Get alerts when Linktionary is updated
Book updates and addendums
Get info about the Encyclopedia of Networking and Telecommunicatons, 3rd edition (2001)
Download the electronic version of the Encyclopedia of Networking, 2nd edition (1996). It's free!
Contribute to this site
Electronic licensing info
Spread Spectrum Signaling
Note: Many topics at this site are reduced versions of the text in "The Encyclopedia of Networking and Telecommunications." Search results will not be as extensive as a search of the book's CD-ROM.
Wireless mobile communications and wireless LANs can use a variety of schemes to transmit analog or digital information between base stations and users. One method is to transmit at a specific frequency, much like a radio station transmits at a frequency that you dial on your radio. For example, the AMPS mobile cellular telephone system operates in the 824-MHz to 894-MHz frequency range. This range is divided into a pool of 832 full-duplex channel pairs (one sends, one receives). Calls are made over the channels.
The only problem with this scheme is that anyone with an appropriate radio receiver can listen in on a target frequency. The other problem is that the frequency occupies a narrow band that is susceptible to interference, either accidental or malicious. Spread spectrum is a technique of spreading a signal out over a very wide bandwidth, often over 200 times the bandwidth of the original signal.
Spread spectrum technology was first used in World War II as a way to provide jamproof radio communication for guided torpedoes. A spread spectrum transmitter spreads the signals out over a wide frequency range using one of the following techniques:
CDMA (Code Division Multiple Access) is a digital cellular standard that uses wideband spread spectrum techniques for signal transmission. CDMA is employed in cellular phone systems and has become the top choice for new high-bandwidth 3G (third-generation) phones because of its spectral efficiency. CDMA is also used in wired systems such as shared cable access networks so that the shared spectrum is used more efficiently.
Copyright (c) 2001 Tom Sheldon and Big Sur Multimedia.