CDMA
is a form of Direct Sequence Spread
Spectrum communications. In general,
Spread Spectrum communications is
distinguished by three key elements:
1.
The signal occupies a bandwidth much
greater than that which is necessary
to send the information. This results
in many benefits, such as immunity
to interference and jamming and multi-user
access, which we’ll discuss
later on.
2.
The bandwidth is spread by means of
a code which is independent of the
data. The independence of the code
distinguishes this from standard modulation
schemes in which the data modulation
will always spread the spectrum somewhat.
3.
The receiver synchronizes to the code
to recover the data. The use of an
independent code and synchronous reception
allows multiple users to access the
same frequency band at the same time.
The
CDMA air interface can be used in
both 2G and 3G networks. CDMA allows
for international roaming as it is
compatible with other cellular technologies.
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