Linksys WAP54GPE - Wireless-G Exterior Access Point User Manual page 53

Wireless-G Exterior Access Point
What is the ISM band?
The FCC and their counterparts outside of the U.S. have set aside bandwidth for unlicensed use in the ISM
(Industrial, Scientific and Medical) band. Spectrum in the vicinity of 2.4 GHz, in particular, is being made
available worldwide. This presents a truly revolutionary opportunity to place convenient high speed wireless
capabilities in the hands of users around the globe.
What is Spread Spectrum?
Spread Spectrum technology is a wideband radio frequency technique developed by the military for use in
reliable, secure, mission-critical 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).
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, 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.
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, the WLAN
series offers a variety of wireless security methods to enhance security and access control. Users can set it up
depending upon their needs.
Can Linksys wireless products support file and printer sharing?
Linksys wireless products perform the same function as LAN products. Therefore, Linksys wireless products
can work with NetWare, Windows NT/2000, or other LAN operating systems to support printer or file
sharing.
What is WEP?
Appendix A: Troubleshooting
46
Frequently Asked Questions