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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.
