Asus PCI-G31 User Manual

Page 33

PCI-G31 WLAN Card User Manual

ASUS WLAN Card

Compared with 802.11g:

802.11a is a standard for access points and radio

NICs that is ahead of 802.11g in the market by about six months. 802.11a operates

in the 5GHz frequency band with twelve separate non-overlapping channels. As

a result, you can have up to twelve access points set to different channels in the

same area without them interfering with each other. This makes access point

channel assignment much easier and significantly increases the throughput the

wireless LAN can deliver within a given area. In addition, RF interference is much

less likely because of the less-crowded 5GHz band.

IEEE 802.11b (11Mbits/sec)

In 1997, the Institute of Electrical and Electronics Engineers (IEEE) adopted the

802.11 standard for wireless devices operating in the 2.4 GHz frequency band.

This standard includes provisions for three radio technologies: direct sequence

spread spectrum, frequency hopping spread spectrum, and infrared. Devices that

comply with the 802.11 standard operate at a data rate of either 1 or 2 Mbps.
In 1999, the IEEE created the 802.11b standard. 802.11b is essentially identical

to the 802.11 standard except 802.11b provides for data rates of up to 11Mbps for

direct sequence spread spectrum devices. Under 802.11b, direct sequence devices

can operate at 11Mbps, 5.5Mbps, 2Mbps, or 1Mbps. This provides interoperability

with existing 802.11 direct sequence devices that operate only at 2Mbps.
Direct sequence spread spectrum devices spread a radio signal over a range of

frequencies. The IEEE 802.11b specification allocates the 2.4GHz frequency band

into 14 overlapping operating Channels. Each Channel corresponds to a different

set of frequencies.

IEEE 802.11g

802.11g is a new extension to 802.11b (used in majority of wireless LANs today)

that broadens 802.11b’s data rates to 54 Mbps within the 2.4 GHz band using

OFDM (orthogonal frequency division multiplexing) technology. 802.11g allows

backward compatibility with 802.11b devices but only at 11 Mbps or lower,

depending on the range and presence of obstructions.

Infrastructure

A wireless network centered about an access point. In this environment, the access

point not only provides communication with the wired network but also mediates

wireless network traffic in the immediate neighborhood.

The 802.11a standard gains some of its performance from the higher frequencies

at which it operates. The laws of information theory tie frequency, radiated power

and distance together in an inverse relationship. Thus, moving up to the 5GHz

spectrum from 2.4GHz will lead to shorter distances, given the same radiated

power and encoding scheme.