802.11n standard bandwidth.

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Nov 12th, 2009
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I am reading things about the 802.11n standard, but I have some things that I do not understand very well.

So, can someone tell me what the maximum bandwidth in the 802.11n standard is?

That bandwidth is dependent, if I used a 20MHz or 40Mhz channel?

What is the role and how that as to do with the bandwidth?

The maximum bandwidth that I can have is 300MHz or can be more, for example, 400MHz or even more?

The 802.11b/a/g standards, the transmissions of data are wall made in half-duplex.

In 802.11n standard, the transmissions of data are wall made in full-duplex? Is MIMO something to do with this?

Thanks in advance,

Rui Capao

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Peter Nugent Fri, 11/13/2009 - 08:53
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First point you are getting your MHz and Mbps muddled but no worries

Max bandwidth for 802.11n is 600Mbps this is with 4 spacial streams using 64QAM and a guard interval of 400nS and 40MHz channels (channel bonding)

Thats the absolute maximum in the standard however I am not aware of anyone doing that at the presentr time.

Cisco maximum is 150Mbps on 2.4GHz and 300Mbps on 5.0GHz. This is because its at least impractical to channel bond 2.4GHz due to channel interference but you can on 5.0GHZ.

Each data rate is given an MCS (modulation coding scheme)index value.

The data rate can vary also by the guard interval which has two options of 800 or 400ns. If we take Cisco max of MCS 15 the vlues are

20MHz channel 800ns GI 130Mbps

20Mhz channel 400ns GI 144Mbps

40MHz channel 800ns GI 270Mbps

40Mhz channel 400ns GI 300Mbps

Smaller guard interval more bandwidth. Also if you double the channel width you get slightly more throughput than simply doubling the data rate as the bit where the two channels join is used more efficiently.

802.11n is not full duples its just alot more efficient than 802.11a/b/g its still a collision domain that uses csma/ca.


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