Asus WL-320gE - Manual (Page 54)

5.
Appendix
5 ASUS 802.11g Access Point
Chapter 5 - Appendix
and Electronic Engineers (IEEE). Most wired networks conform to 802.3, the
specification for CSMA/CD based Ethernet networks or 802.5, the specification for
token ring networks. 802.11 defines the standard for wireless LANs encompassing
three incompatible (non-interoperable) technologies: Frequency Hopping Spread
Spectrum (FHSS), Direct Sequence Spread Spectrum (DSSS), and Infrared.
802.11 specifies a carrier sense media access control and physical layer
specifications for 1 and 2 Mbps wireless LANs.
IEEE 802.11a (5Mbits/sec)
Compared with 802.11b: The 802.11b standard was designed to operate in
the 2.4-GHz ISM (Industrial, Scientific and Medical) band using direct-sequence
spread-spectrum technology. The 802.11a standard, on the other hand, was
designed to operate in the more recently allocated 5-GHz UNII (Unlicensed
National Information Infrastructure) band. And unlike 802.11b, the 802.11a
standard departs from the traditional spread-spectrum technology, instead using
a frequency division multiplexing scheme that’s intended to be friendlier to office
environments.
The 802.11a standard, which supports data rates of up to 54 Mbps, is the Fast
Ethernet analog to 802.11b, which supports data rates of up to 11 Mbps. Like
Ethernet and Fast Ethernet, 802.11b and 802.11a use an identical MAC (Media
Access Control). However, while Fast Ethernet uses the same physical-layer
encoding scheme as Ethernet (only faster), 802.11a uses an entirely different
encoding scheme, called OFDM (orthogonal frequency division multiplexing).
The 802.11b spectrum is plagued by saturation from wireless phones, microwave
ovens and other emerging wireless technologies, such as Bluetooth. In contrast,
802.11a spectrum is relatively free of interference.
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 5-GHz
spectrum from 2.4 GHz will lead to shorter distances, given the same radiated
power and encoding scheme.
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 5 GHz 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.