Asus USB-N66 - Manual (Page 24)

USB-N66 WLAN Adapter User Manual
2 ASUS WLAN adapter
IEEE
The Institute of Electrical and Electronics Engineers. The IEEE sets standards for
networking, including Ethernet LANs. IEEE standards ensure interoperability
between systems of the same type.
IEEE 802.11
IEEE 802.xx is a set of specifications for LANs from the Institute of Electrical
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 (54Mbits/sec)
Compared with 802.11b: The 802.11b standard was designed to operate in
the 2.4GHz ISM (Industrial, Scientific and Medical) band using direct-sequence
spreadspectrum 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 5GHz spectrum from 2.4GHz will lead to shorter distances, given the
same radiated power and encoding scheme.