Planet Technology WL-U357v2 - Manual (Page 31)

new generation and has been incorporated into the newly-approved security
standard 802.11i. It supports 128, 192 and 256-bit encryption key length and
adopts Rijndael algorithm. It is widely believed it is impossible to crack
AES.
What is DSSS? What is FHSS? And what are their differences?
Frequency-hopping spread-spectrum (FHSS) uses a narrowband carrier that
changes frequency in a pattern that is known to both transmitters and
receivers. Properly synchronized, the net effect is to maintain a single logical
channel. To an 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 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.
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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