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G
The 802.11b standard specifies wireless product networking at 11 Mbps
IEEE 802.11
B
using direct-sequence spread-spectrum (DSSS) technology and operating
in the unlicensed radio spectrum at 2.4 GHz. It supports WEP encryption
for security. All 802.11 networks are also referred to as Wi-Fi networks.
The specification for wireless networking at 54 Mbps using direct-sequence
IEEE 802.11
G
spread-spectrum (DSSS) technology, using OFDM modulation and
operating in the unlicensed radio spectrum at 2.4 GHz. Includes backward
compatibility with IEEE 802.11b devices and WEP encryption for security.
An ad hoc network is a group of computers, each with a wireless adapter,
A
N
D HOC
ETWORK
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 generates a redundant bit pattern for all data transmitted. This bit
DSSS (D
-
IRECT
pattern is called a chip (or chipping code). Even if one or more bits in the
S
S
EQUENCE
PREAD
chip are damaged during transmission, statistical techniques embedded in
S
)
PECTRUM
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 (that is, another wireless LAN endpoint),
the DSSS signal is recognized as the only valid signal, and interference is
inherently rejected (ignored).
FHSS continuously changes (hops) the carrier frequency of a conventional
FHSS (F
REQUENCY
carrier several times per second according to a pseudo-random set of
H
S
OPPING
PREAD
channels. Because a fixed frequency is not used, and only the transmitter
S
)
PECTRUM
and receiver know the hop patterns, interception of FHSS is extremely
difficult.
LOSSARY
– 40 –
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