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CDMA (Code Division Multiple Access)

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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.

CDMA is an access technology and air interface for wireless digital cellular systems and other communication systems. CDMA was originally developed by Qualcomm, although the underlying technology has been around since the 1940. Qualcomm now holds the patents for CDMA and is greatly benefitting as it becomes the wireless access technology of choice around the world.

CDMA uses wideband spread spectrum techniques for signal transmission, as opposed to narrowband channel techniques used in conventional analog systems. CDMA's use in mobile communications systems is covered under the topic "Wireless Mobile Communications."

CDMA was approved as a digital multiple access technique for cellular telephony by the TIA (Telecommunications Industry Association) in 1993. It is also called "IS-95." The CDMA Development Group uses the trademarked named cdmaOne to describe a full IS-95 system with ANSI-41 switch interconnections and other standards. While CDMA has traditionally been a wireless technology, CableLabs recently adopted S-CDMA (Synchronous CDMA) as developed by Terayon for use in cable data network modems. S-CDMA synchronizes signals so that the signal do not create mutually generated interference. This reduces noise and allows more efficient use of the available spectrum.

This topic continues in "The Encyclopedia of Networking and Telecommunications" with a discussion of the following:

  • Comparison to traditional cellular systems
  • CDMA's spread spectrum technology
  • Security and privacy issues
  • Qualcomm's HDR (High Data Rate) technology
  • Evolution to third-generation and fourth-generation cellular systems

An industry consortium called CDMA Development Group (CDG) develops products and services for CDMA and works to promote its adoption around the world. The CDG is composed of telecommunication service providers and manufacturers who are pushing for interoperability standards among related equipment vendors. Refer to the related entries page for links.

Refer to "Wireless Mobile Communications" for more information.

Copyright (c) 2001 Tom Sheldon and Big Sur Multimedia.
All rights reserved under Pan American and International copyright conventions.