Code Division Multiplexing

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What Does Code Division Multiplexing Mean?

Code division multiplexing (CDM) is a networking technique in which multiple data signals are combined for simultaneous transmission over a common frequency band.

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When CDM is used to allow multiple users to share a single communications channel, the technology is called code division multiple access (CDMA).

Techopedia Explains Code Division Multiplexing

CDMA uses spread spectrum, a technology that was developed in World War II to prevent enemies from intercepting and jamming transmissions. In spread spectrum, a data signal is sent over a range of frequencies in an assigned frequency spectrum.

A pseudo-random spreading code is used to multiplex the base signal. Multiplexing with a spreading code increases the bandwidth required for the signal, spreading it out over the available spectrum. The receiving device is aware of the spreading code and uses it to demultiplex the signal.

CDMA provides a certain amount of built-in security, as the transmissions of multiple users are mixed together within the frequency spectrum. The spreading code is required to decode a specific transmission.

Different variations of CDM and CDMA are used in 2G and subsequent generations of cellphone technology.

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Margaret Rouse
Senior Editor
Margaret Rouse
Senior Editor

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.