Appendix B: Glossary
802.11b -
The 802.11b standard specifies a wireless product networking at 11 Mbps using
direct-sequence spread-spectrum (DSSS) technology and operating in the unlicensed radio
spectrum at 2.4GHz, and WEP encryption for security. 802.11b networks are also referred to
as Wi-Fi networks.
802.11g
-
specification for wireless networking at 54 Mbps using direct-sequence spread-
spectrum (DSSS) technology, using OFDM modulation and operating in the unlicensed radio
spectrum at 2.4GHz, and backward compatibility with IEEE 802.11b devices, and WEP
encryption for security.
Ad-hoc Network -
An ad-hoc network is a group of computers, each with a Wireless N USB
Adapter, connected as an independent 802.11 wireless LAN. Ad-hoc wireless computers
operate on a peer-to-peer basis, communicating directly with each other without the use of
an access point. Ad-hoc mode is also referred to as an Independent Basic Service Set
(IBSS) or as peer-to-peer mode, and is useful at a departmental scale or SOHO operation.
DSSS
(
D
irect-
S
equence
S
pread
S
pectrum)
-
DSSS generates a redundant bit pattern for all
data transmitted. This bit pattern is called a chip (or chipping code). Even if one or more bits
in the chip are damaged during transmission, statistical techniques embedded in the
receiver can recover the original data without the need of retransmission. To an unintended
receiver, DSSS appears as low power wideband noise and is rejected (ignored) by most
narrowband receivers. However, to an intended receiver (i.e. another wireless LAN
endpoint), the DSSS signal is recognized as the only valid signal, and interference is
inherently rejected (ignored).
FHSS
(
F
requency
H
opping
S
pread
S
pectrum)
-
FHSS continuously changes (hops) the
carrier frequency of a conventional carrier several times per second according to a pseudo-
random set of channels. Because a fixed frequency is not used, and only the transmitter and
receiver know the hop patterns, interception of FHSS is extremely difficult.
Infrastructure Network -
An infrastructure network is a group of computers or other
devices, each with a Wireless N USB Adapter, connected as an 802.11 wireless LAN. In
infrastructure mode, the wireless devices communicate with each other and to a wired
network by first going through an access point. An infrastructure wireless network connected
to a wired network is referred to as a Basic Service Set (BSS). A set of two or more BSS in a
single network is referred to as an Extended Service Set (ESS). Infrastructure mode is
useful at a corporation scale, or when it is necessary to connect the wired and wireless
networks.
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
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