Sparklan WUBR-502GN, Руководство пользователя

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User’s Manual 60
11. Would the information be intercepted while transmitting on air?
WLAN features two-fold protection in security. On the hardware side, as with Direct
Sequence Spread Spectrum technology, it has the inherent security feature of scrambling.
On the software side, WLAN series offer the encryption function (WEP) to enhance security
and Access Control. Users can set it up depending upon their needs.
12. 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 transmitter and receiver. 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.
13. 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).
14. What is WMM?
Wi-Fi Multimedia (WMM), a group of features for wireless networks that improve the user
experience for audio, video and voice applications. WMM is based on a subset of the IEEE
802.11e WLAN QoS draft standard. WMM adds prioritized capabilities to Wi-Fi networks
and optimizes their performance when multiple concurring applications, each with different