Planet WML-3565 Инструкция по эксплуатации онлайн [34/34] 65751

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).