Code-Division
Multiple Access,better
known as CDMA is a digital cellular
technology that uses spread-spectrum
. It refers to any of several protocols
used in so-called second-generation
(2G) and third-generation (3G) wireless
communications. Essentially, CDMA
is a form of multiplexing, which allows
numerous signals to occupy a single
transmission channel, optimizing the
use of available bandwidth. The technology
is used in ultra-high-frequency (UHF)
cellular telephone systems in the
800-MHz and 1.9-GHz bands.
CDMA was first used
by British army allies during World
War II to foil German attempts at
jamming transmissions. The allies
decided to transmit over several frequencies,
instead of one, making it difficult
for the Germans to pick up the complete
signal. Later, Qualcomm claimed patents
on the technology and became the first
to commercialize
In this technology
specific frequency is not assigned
to each user. Instead, every channel
uses the full available spectrum.
Individual conversations are encoded
with a pseudo-random digital sequence.
CDMA
is better than other mobile technologies
available as it provides better capacity
for voice and data communications,
allowing more subscribers to connect
at any given time.
The
original CDMA standard, also known
as CDMA One and still common in cellular
telephones in the U.S., offers a transmission
speed of only up to 14.4 Kbps in its
single channel form and up to 115
Kbps in an eight-channel form. CDMA2000
and wideband CDMA deliver data many
times faster. |
