Wednesday, April 27, 2011

IEEE Wireless Standards

The first attempt at a wireless standard was the HomeRF protocol, which did not catch on because of its slow (1.6 Mbps) speed. It was replaced by the 802.11 standard, which ran at 1 or 2 Mbps. Because of its limited speed, it is also history. In 1999, the IEEE added the “a” and “b” refinements. Products conforming to the 802.11a standard operate at speeds of up to 54 Mbps on a very short-wave frequency of 5 billion cycles per second, or 5 gigahertz, abbreviated GHz. Its speed advantage is offset by its shorter range, which is typically 50 to 200 meters. Unlike the more popular b standard, it uses a modulation scheme with the hefty name of Orthogonal Frequency Division Multiplexing (OFDM) that makes possible data speeds as high as 54 Mbps and cuts down on cross-channel and reflected-signal interference. More commonly, communication takes place at 6, 12, or 24 Mbps. Today the most widely followed standard by far is known as IEEE 802.11b. It moves data at a top speed of 11 Mb ps in the 2.4 GHz frequency band. It is more prone to interference than 802.11a, but the lower frequency gives it a longer range, estimated at between 75 to 300 meters.

The g standard is compatible with the b standard and operate on the same 2.4 GHz frequencies.
But it's faster at 54 Mbps and less vulnerable to radio noise. Its greater capacity makes it a promising
media for wireless streaming video. As often happens with a burgeoning technology, as soon as the Committee handed down the standard, it began amending it. Other additions are in the IEEE pipe:
-802.11d and h will accommodate European regulations governing
radio devices.
802.11e is due in January 2003. It adds quality of service (QoS)
802.11f will add protocols that enable data sharing between disparate
systems in 2003.
802.11i addresses security holes in the present standards.
The Wireless Next Generation (WNG) specification seeks to combine
all the above into one universal standard.
Ultrawideband (UWB) was granted a limited license in February
2002 for use in the 3.1 GHz and 10.6 GHz bands, but only indoors
or in handheld peer-to-peer applications for now.

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