13th Lecture - Networking - Wireless Lans

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[size=5][b]IEEE 802.11b[/b][/size] was ratified in 1999. It operates in the 2.4-GHz ISM band that is available worldwide. The standard
specifies one RF transmission: direct sequence spread spectrum (DSSS). It provides four data
rates up to 11 Mbps: 1, 2, 5.5, and 11 Mbps.

The 802.11b standard is the most commonly deployed WLAN standard.

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[img]http://i55.tinypic.com/2daej9s.png[/img]


There are 11 channels available in the United States. However, only three of these channels are
nonoverlapping.

In the ETSI domains, there are 13 available channels, but again there are only three
nonoverlapping channels.

[img]http://i51.tinypic.com/2nqy4k1.png[/img]


An access point on channel 1 does not share frequencies with an access point on channel 6
because the channels do not have any common frequencies.


Three access points in the same cell on three
nonoverlapping channels (for example, 1, 6, and 11) provide an aggregated data rate for the cell
of 33 Mbps (3 x 11Mbps), with an aggregated throughput of about 16 Mbps (half of the
aggregate).



If the same three access points shared the same channel, the aggregate data rate would still be
11 Mbps, but the aggregated throughput would be closer to 6 Mbps.

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AP Coverage:

[img]http://i52.tinypic.com/25rcehk.png[/img]


WLAN clients have the ability to shift data rates while moving. This technique allows the same
client operating at 11 Mbps to shift to 5.5 Mbps, 2 Mbps, and finally still communicate in the
outside ring at 1 Mbps.

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The[b][size=5] 802.11a[/size][/b] standard was ratified at the same time as 802.11b. Provides up to a 54-Mbps data rate.

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The [b][size=5]802.11g[/size][/b] WLAN standard was ratified in June 2003. The aim was to provide higher data
rates than the 802.11b standard. By using the 2.4-GHz band, backward compatibility was
possible with existing 802.11b WLANs.

The 802.11g standard uses the same three nonoverlapping channels: 1, 6, and 11. The 802.11g standard provides full backward compatibility with 802.11b. 802.11g

Problems with 802.11g:

[img]http://i53.tinypic.com/25qvfw1.png[/img]

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[size=5][b]802.11 Standards Comparison: [/b][/size]

[img]http://i53.tinypic.com/2lifpmp.png[/img]

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[size=5][b]Range comparison :[/b][/size]

[img]http://i51.tinypic.com/ojnp68.png[/img]

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[size=5][b]WLAN Security : [/b][/size]

[img]http://i54.tinypic.com/apfkg8.png[/img]

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[size=5][b]How does a client associated with Access Points :[/b][/size]


[img]http://i51.tinypic.com/2rr1gxw.png[/img]

[ding]

endi vayya nee istamunapudu chepthunav classes

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[quote name='shakkku' timestamp='1319502409' post='3027735']
endi vayya nee istamunapudu chepthunav classes
[/quote]

[img]http://pictures.picasion.com/pic16/0673580f85eefed43e8e56d194bcf370.gif[/img]

[ToughGuy]

[quote name='shakkku' timestamp='1319502409' post='3027735']
endi vayya nee istamunapudu chepthunav classes
[/quote]

chepthe cheppinchukovali ..no questions --pokiri

[img]http://www.gifsoup.com/view6/2540027/maddy-o.gif[/img]

[ding]

wireless vlan support???????/
layer 2 & 3 roaming guinchi seppu

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[quote name='shakkku' timestamp='1319503280' post='3027794']
wireless vlan support???????/
layer 2 & 3 roaming guinchi seppu
[/quote]