Linksys WUSBF54G User Manual page 25

Appendix A
What is infrastructure mode?
When a wireless network is set to infrastructure mode,
the wireless network is configured to communicate with a
wired network through a wireless access point.
What is roaming?
Roaming is the ability of a PC to communicate continuously
while moving freely throughout an area greater than that
covered by a single access point. Before using the roaming
function, the workstation must make sure that it is the
same channel number with the access point of dedicated
coverage area.
To achieve true seamless connectivity, the wireless
LAN must incorporate a number of different functions.
Each node and access point, for example, must always
acknowledge receipt of each message. Each node must
maintain contact with the wireless network even when
not actually transmitting data. Achieving these functions
simultaneously requires a dynamic RF networking
technology that links access points and nodes. In such
a system, the user's end node undertakes a search for
the best possible access to the system. First, it evaluates
such factors as signal strength and quality, as well as the
message load currently being carried by each access
point and the distance of each access point to the wired
backbone. Based on that information, the node next
selects the right access point and registers its address.
Communications between end node and host computer
can then be transmitted up and down the backbone.
As the user moves on, the end node's RF transmitter regularly
checks the system to determine whether it is in touch with
the original access point or whether it should seek a new
one. When a node no longer receives acknowledgment
from its original access point, it undertakes a new search.
Upon finding a new access point, it then re-registers, and
the communication process continues.
What is 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
Wireless-G USB Network Adapter with Wi-Fi Finder
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?
The Adapter 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 Adapter offers the
encryption function (WEP) to enhance security and access
control.
What is WEP?
WEP is Wired Equivalent Privacy, a data privacy mechanism
based on a 64-bit or 128-bit shared key algorithm, as
described in the IEEE 802.11 standard.
Troubleshooting
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