Syngress - Eleventh Hour Network+ Exam N10-004 Study Guide (11 ...

60 CHAPTER 4 Wireless Networking
Table 4.1
(Continued)
802.11 Standard Details
Uses a modulation technique known as orthogonal
frequency division multiplexing (OFDM).
To be 802.11a compliant, devices are only required to
support data rates of 6, 12, and 24 Mbps – the standard
does not require the use of other data rates.
802.11a is not backward compatible with 802.11 b because
of the use of a different frequency band and the use of
OFDM at the physical layer.
802.11a and 802.11b devices can be easily colocated
because their frequencies will not interfere with each other.
IEEE 802.11g
IEEE 802.11n
Defines networks that use the ISM 2.4 GHz bands.
Supports data transmission rates up to 54 Mbps.
Backward compatibility with 802.11b.
To achieve the higher rates of transmission, 802.11g devices
use OFDM in contrast to QPSK, which is used by 802.11b
devices as a modulation technique.
802.11g devices are able to automatically switch to QPSK
to communicate with 802.11b devices.
To provide both higher data rates (up to 300 Mbps) in the
ISM 2.4 GHz bands and the 5 GHz U-NII band, 802.11n was
introduced.
It is backward compatible with 802.11b/g.
To achieve the higher rates of transmission, 802.11n
devices use multiple input/multiple output (MIMO) to take
advantage of multiple antennas.
EXAM WARNING
You need to be familiar with the 802.11 standards, the speeds, operation, and so on, for
the Network+ exam.
Ad Hoc and Infrastructure Network Configuration
The 802.11 standard provides for two modes for wireless clients to communicate:
ad hoc and infrastructure. The ad-hoc mode is geared for a network of stations
within communication range of each other and is created spontaneously between
the network participants. In infrastructure mode, access points (APs) provide
more permanent structure for the network. An infrastructure consists of one or
more APs as well as a wired network behind the APs that tie the wireless network
to the rest of the network infrastructure.