- The IEEE wireless LAN standard
is:
- 802.11
A.k.a.: Wi-fi
- Different variants of the
standards are
differentiated with a
letter
Example:
- 802.11a
- 802.11b
- 802.11g
- 802.11n
- 802.11ac
- And so on... they keep changing the standard (higher speed)....
- The 802.11 protocols are
the most commonly used
home/office wireless networks today:
- History:
- 802.11a: (1999):
- operates in the 5 GHz band with a maximum net data rate of 54 Mbit/s
- Not popular.... (equipment was expensive)
- Does not inter-operate with 802.11b
- 802.11b: (1999)
- operates in the 2.4 GHz band with a maximum net data rate of 11 Mbit/s
- Very popular (maybe because equipment was cheap :))
(BTW, microwave ovens operates in the 2,4 GHz range !!!)
- 802.11g: (2003)
- operates in the 2.4 GHz band
with a maximum net data rate of 54 Mbit/s
- It is fully backwards compatible with 802.11b.
- operates in the 2.4 GHz band
with a maximum net data rate of 54 Mbit/s
- 802.11n: (2009)
- Not really a new standard....
- Is an amendmentment to the existing 802.11 standards....
- maximum data rate of 600 Mbit/s !!!
Most important amendment:
- MIMO (Multiple Input, Multiple Output -- multiple antennas)
- More wireless standards
are still being proposed....
MIMO: multiple input, multiple output
- MIMO
Signal Processing
uses multiple antennas
that
send and receive data at the
same time
to improve signal coherence.
- This technique increase the transmission rate significantly.
This is not a Electrical Engineering class...
If you want to know more about MIMO, see: click here
- 802.11a: (1999):
- An 802.11 Lan is
subdivided into cells
- Each cell uses
a different transmission
frequency !!!
- Signals of
different frequency
do not
interfere
with each other
(E.g.: radio stations on different frequencies FM 90.1 and FM 94.9 can transmit simultaneously)
- Signals of
different frequency
do not
interfere
with each other
- Each cell is called a
Basic Service Set (BSS)
- A BSS is
serviced by
an Access Point (AP)
(a.k.a. a
base station)
Example:
- A BSS is
serviced by
an Access Point (AP)
(a.k.a. a
base station)
- Most 802.11 networks consist
of multiple APs
- The Access Points are
interconnected together using a
"backbone"
network.
- The backbone network is usually an Ethernet network
Example:
The backbone network is called:
- The distribution system in 802.11 literature
The entire interconnected wireless LAN is called:
- a Extended Service Set (ESS)
- The Access Points are
interconnected together using a
"backbone"
network.