CDMA Facts
- CDMA drops fewer calls and generally has better reception and stronger signals. CDMA has the best noise immunity, is the least susceptible to multipath (fading), and can talk to more than one cell at a time so that cell-to-cell handovers (a critical cause of dropped calls) are a soft exchange and not a hard switch
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- CDMA 2000 EV-DO
- Code division multiple access (CDMA) is a form of multiplexing and a
method of multiple access to a physical medium
such as a radio channel,
where different users use the medium at the same time thanks to using
different code sequences. By contrast, time division multiple access divides
access by time, while frequency-division multiple access divides it by
frequency. CDMA is a form of "spread-spectrum" signaling, since the
modulated coded signal has a much higher bandwidth than the data being
communicated.
An analogy to the problem of multiple access is a room (channel) in which
people wish to communicate with each other. To avoid confusion, people could
take turns speaking (time division), speak at different pitches (frequency
division), or speak in different directions (spatial division). In CDMA,
they would speak different languages. People speaking the same language can
understand each other, but not other people. Similarly, in radio CDMA, each
group of users is given a shared code. Many codes occupy the same channel,
but only users associated with a particular code can understand each other.
CDMA also refers to digital cellular telephony systems that use this
multiple access scheme, such as those pioneered by QUALCOMM, and W-CDMA by
the International Telecommunication Union (ITU).
CDMA has been used in many communications and navigation systems, including
the Global Positioning System and in the OmniTRACS satellite system for
transportation logistics.
