Table des Matières
Publicité
Les langues disponibles
Les langues disponibles
members
of
wireless network?
What
is
Spectrum?
What is DSSS? What is
FHSS? And what are
their differences?
Would the information
the
Refer to the game's user guide for more
information.
Spread
Spread Spectrum technology is a wideband radio
frequency technique developed by the military for
use
communications 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).
Frequency-Hopping Spread-Spectrum (FHSS) uses
a narrowband carrier that changes frequency in a
pattern that is known to both transmitter and
receiver. Properly synchronized, the net effect is to
maintain
unintended receiver, FHSS appears to be 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, 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
receiver, DSSS appears as low power wideband
noise
narrowband receivers.
WLAN features two-fold protection in security. On
in
reliable,
a
single
logical
for
retransmission.
and
is
rejected
36
secure,
mission-critical
channel.
To
an
unintended
(ignored)
by
To
an
most
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