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Code Division Multiple
Access (CDMA) is a digital air interface
standard, claiming eight to fifteen times the
capacity of traditional analog cellular
systems. It employs a commercial adaptation of
a military spread-spectrum technology. Based
on spread spectrum theory, it gives
essentially the same services and qualities as
wireline service. The primary difference is
that access to the local exchange carrier (LEC)
is provided via a wireless phone.
Though CDMA?s application in cellular
telephony is relatively new, it is not a new
technology. CDMA has been used in many
military applications, such as:
Anti-jamming (because of the spread signal, it
is difficult to jam or interfere with a CDMA
signal). Ranging (measuring the distance of
the transmission to know when it will be
received). Secure communications (the spread
spectrum signal is very hard to detect).
CDMA is a spread spectrum technology, which
means that it spreads the information
contained in a particular signal of interest
over a much greater bandwidth than the
original signal. With CDMA, unique digital
codes, rather than separate RF frequencies or
channels, are used to differentiate
subscribers. |
