Planet WML-3565 User Manual page 34

short-duration impulse noise. Direct-sequence spread-spectrum (DSSS) generates a redundant
bit pattern for each bit to be transmitted. This bit pattern is called a chip (or chipping code). The
longer the chip is, the greater the probability that the original data can be recovered. Even if one
or more bits in the chip are damaged during transmission, statistical techniques embedded in the
radio can recover the original data without-the need for retransmission. To an unintended
receiver, DSSS appears as low power wideband noise and is rejected (ignored) by most
narrowband receivers.
14. What is Spread Spectrum
Spread Spectrum technology is a wideband radio frequency technique developed by the military
for use in reliable, secure, mission-critical communication systems. It is designed to trade off
bandwidth efficiency for reliability, integrity, and security. In other words, more bandwidth is
consumed than in the case of narrowband transmission, but the trade off produces a signal that
is, in effect, louder and thus easier to detect, provided that the receiver knows the parameters of
the spread-spectrum signal being broadcast. If a receiver is not tuned to the right frequency, a
spread –spectrum signal looks like background noise. There are two main alternatives, Direct
Sequence Spread Spectrum (DSSS) and Frequency Hopping Spread Spectrum (FHSS).
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