Note
Chapter 4 Wireless Technology
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the 802.11standards are given a “Wi-Fi compliant” seal, which means any
device bearing the Wi-Fi seal is compatible with any other device bearing the
seal, Figure 4-18. This process led to competing yet compatible standards by
both organizations. As a result, users are able to mix and match components
from various manufacturers. There are many proprietary devices and software
products on the market that may not be fully compatible with other devices.
802.11g
The IEEE 802.11g standard followed the 802.11a and 802.11b standards. 802.11g
operates in the 802.11b frequency range of 2.4 GHz. This makes it downward
compatible with 802.11b devices. When communicating with 802.11b devices, the
maximum data rate is reduced to 11 Mbps. The maximum throughput for the
802.11g standard is 54 Mbps, but the maximum distance is typically much shorter
than an 802.11b device. An 802.11g device can use the lower data rates of 48 Mbps,
36 Mbps, 28 Mbps, 24 Mbps, 12 Mbps, 11 Mbps, 9 Mbps, 6 Mbps, 5.5 Mbps, 2 Mbps,
and 1 Mbps. Since 802.11g is assigned to the same frequency range as 802.11b, it is
susceptible to the same sources of radio interference.
802.11g and 802.11b devices are not compatible with 802.11a devices because
they use different frequencies. It must be noted that while the standards are
different, there are devices on the market that can communicate with any of the
mentioned wireless standards. In other words, there are wireless devices that can
communicate with 802.11a, 802.11b, and 802.11g devices.
802.11n
The 802.11n standard operates at 5 GHz and is backward compatible
with the 2.4-GHz frequency range. In 2009, the Wi-Fi Alliance organization
ratifi ed (approved) a standard based on a draft version of 802.11n. However,
manufacturers developed 802.11n wireless network devices before the 802.11n
classifi cation was ratifi ed in an effort to offer superior wireless devices. Therefore,
these devices may not exactly match the 802.11n ratifi ed standard.
There cannot be a defi nitive range for individual IEEE wireless standards, only
approximations. Range is determined by radio wave power expressed in watts. There are
many electronic factors that affect radio wave ranges.
Figure 4-18.
Wireless PCMCIA
adapter card with the
Wi-Fi compliant seal.
(3Com Corporation)
Wi-Fi compliant seal