By: Christine Martz
Meaning of CDMA - "Code Division Multiple Access",
is a digital wireless transmission technology that allows for a large amount of
users to share access to a single radio channel.
CDMA is most broadly used by the protocol IS-95, also known by it's "brand" name
cdmaOne, as a cellular phone technology. CDMA is a form of multiplexing,
allowing numerous signals to occupy a single transmission channel.
It uses a spread spectrum approach for digitally transmitting data or voice
over radio frequencies. Sounds are digitized and then the information is broken
into data packets that are encoded with a unique identification code. All of the
packets are sent over a spread range of radio frequencies. The cell phone or data
device on the other end receives all of the data packets, reassembles those packets
with the correct code for your conversation or connection, and then converts the
broken bits of data into useful sound and information. This allows innumerable amounts
of calls to occur simultaneously and a bigger amount of traffic for a finite number of available
frequencies than analog or the other digital standards. Not only does CDMA's spread spectrum
technology ensure that there will be no interference, it also makes the signals
difficult to detect and jam. For this reason the military uses CDMA transmission
for secure phone calls.
Qualcomm developed the IS-95 standard. CDMA systems have been
in commercial operation since 1995.
“…Code
Division Multiple Access (CDMA) technology, pioneered by QUALCOMM, provides
excellent voice capacity and data capability for mobile and fixed wireless
networks. Because of its advantages, CDMA serves as the foundation for 3G
services worldwide. CDMA works by converting speech into digital information,
which is then transmitted as a radio signal over a wireless network. Using a
unique code to distinguish each different call, CDMA enables many more people
to share the airwaves at the same time - without static, cross-talk or
interference.” [Qualcomm]
“…Voice
calls and data connections are each assigned codes, not specific frequency
channels - hence the term "Code-Division Multiple Access." The device on the
receiving end knows the proper code, and automatically filters out any data
that isn't stamped with it. This method frees a lot of space on the network
that otherwise wouldn't be available, and it adds security." [Nokia]
“…Generically (as a multiplexing scheme), code division
multiple access (CDMA) is any use of any form of spread spectrum by multiple
transmitters to send to the same receiver on the same frequency channel at
the same time without harmful interference.” [National Semiconductor]
“…CDMA
is a protocol used in wireless communications. The technique is a form
of multiplexing, which allows for nurerous signals to occupy a single
transmission channel to better exploit available bandwidth.” [Yang Xianzu - Chairam of
China Unicom LTD.]
“…CDMA
or Code Division Multiple Access, is an advanced technology that permits
high-volume communications in a small area, with limited interference from
other traffic. It was originally designed for military communications
applications in rear areas.” [U.S. State Department]
