B-B1-0390-3
Wu Cheok Sam
Assignment 2
EBIS304 – 001
What is 802.11?
The 802.11 standards are a group of evolving specifications defined by the Institute of
Electrical and Electronic Engineers (IEEE).
Commonly referred to as Wi-Fi the 802.11standards define a through the air interface
between a wireless client and a base station access point or between
two or more wireless clients. There are many other standards defined by the IEEE, such as
the 802.3 Ethernet standards. Let me introduce several types of 802.11 standards:
802.11a
Ratification of 802.11a took place in 1999. The 802.11a standard uses the 5 GHz spectrum
and has a maximum theoretical 54 Mbps data rate. Like in 802.11g, as signal strength
weakens due to increased distance, attenuation (signal loss) through obstacles or high noise
in the frequency band, the data rate automatically adjusts to lower rates(54/48/36/24/12/9/6
Mbps) to maintain the connection.
The 5 GHz spectrum has higher attenuation (more signal loss) than lower frequencies,
such as 2.4 GHz used in 802.11b/g standards. Penetrating walls provides poorer
performancethan with 2.4 GHz. Products with 802.11a are typically found in larger
corporate networks or with wireless Internet service providers in outdoor backbone
networks.
802.11b
In 1995, the Federal Communications Commission had allocated several bands
of wireless spectrum for use without a license. The FCC stipulated that the use
of spread spectrum technology would be required in any devices. In 1990, the
IEEE began exploring a standard. In 1997 the 802.11 standard was ratified and is now
obsolete. Then in July 1999 the 802.11b standard was ratified. The 802.11 standard
provides a maximum theoretical 11 Megabits per second (Mbps) data rate in the 2.4 GHz
Industrial, Scientific and Medical (ISM) band.
802.11g
In 2003, the IEEE ratified the 802.11g standard with a maximum theoretical data rate of
54 megabits per second (Mbps) in the 2.4 GHz ISM band. As signal
strength weakens due to increased distance, attenuation (signal loss) through
obstacles or high noise in the frequency band, the data rate automatically
adjusts to lower rates (54/48/36/24/12/9/6 Mbps) to maintain the connection.
When both 802.11b and 802.11g clients are connected to an 802.11g router, the 802.11g
clients will have a lower data rate. Many routers provide the option of
allowing mixed 802.11b/g clients or they may be set to either 802.11b or
802.11g clients only. To illustrate 54 Mbps, if you have DSL or cable modem
service, the data rate offered typically falls from 768 Kbps (less than 1 Mbps) to 6 Mbps.
