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WirelessRudy
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MCS values explained?

Wed Jun 20, 2012 1:31 pm

I know, all the information can be distilled by searching and reading on the internet.
But wouldn't it be nice if MT would produce a guideline in the wireless faq. on the setting of these in real environment.

Like when it is advised to go for configured rate setting or just to use the default (= all) setting.

And when configured rate settings are used to fine tune/tweak the link, which values would be preferable used when?

All the MCS values represent different coding schemes on how the radio's transport data over the air. But which coding scheme performs best under what circumstance is still not clear to me.
I usually play a bit with setting until I get a reasonable or good result. But maybe I can do better if I would only have some more information on the characteristics.

Now there will be obviously guys around that have plenty of time to test and test and test and test to see which coding schemes works best in certain link situation.
But many of us will not have that time and even if they have, why invent the wheel when its already known by someone else?

So, which mcs works best under deploring weather conditions like rain, snow etc.
Which works best in very long links.
Which are best in NLOS situations.
Which have best characteristics when it comes to penetrate through walls or trees etc.

Would it make a difference for each mcs value if the link is single, dual or even triple chain?
And what about the channel width?

Which values perform better under heavy noise conditions etc.
Would the type of antenna have any impact on specific values? Would some mcs value perform better on a dish or a mesh?
How important is a good noise separation between both chains of the antenna and would it make a difference on which mcs is used?

By now there must be enough knowledge gathered by many and I think MT should also be ready to share more of the secrets about the mcs values with us simple users..

I think it be in the interest of everybody if we can get the best out or our links.
Please share your knowledge....
Show your appreciation of this post by giving me Karma! Thanks.

Rudy R. Puister

WISP operator based on MT routerboard & ROS.
 
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macsrwe
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Re: MCS values explained?

Fri Jun 22, 2012 10:50 am

I'm not an expert on this subject, but I approach the problem by examining the datasheet for the transmitting and receiving radios. Each data sheet gives transmitter power at a given MCS level, and receive sensitivity for a given MCS level. If your signal strength on the link falls below this requirement, then this MCS level is not going to work for you. I set my radios to use nothing higher than the MCS level that gives an acceptable fade margin of 15dB to the signal I get in good conditions.
 
Tbird
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Re: MCS values explained?

Sat Jun 23, 2012 6:13 pm

http://mcsindex.com/

What you can achieve on the modulation and coding scheme depends on the specific link vs. the TX/RX specifications on your RF and antennas. In my opinion it's not possible to give an general recommendation for what settings to use. Would be nice if automatic functions worked perfectly.

Tb
 
wolfeyes
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Re: MCS values explained?

Tue Jul 31, 2012 10:44 am

I know, all the information can be distilled by searching and reading on the internet.
But wouldn't it be nice if MT would produce a guideline in the wireless faq. on the setting of these in real environment.

Like when it is advised to go for configured rate setting or just to use the default (= all) setting.

And when configured rate settings are used to fine tune/tweak the link, which values would be preferable used when?

All the MCS values represent different coding schemes on how the radio's transport data over the air. But which coding scheme performs best under what circumstance is still not clear to me.
I usually play a bit with setting until I get a reasonable or good result. But maybe I can do better if I would only have some more information on the characteristics.

Now there will be obviously guys around that have plenty of time to test and test and test and test to see which coding schemes works best in certain link situation.
But many of us will not have that time and even if they have, why invent the wheel when its already known by someone else?

So, which mcs works best under deploring weather conditions like rain, snow etc.
Which works best in very long links.
Which are best in NLOS situations.
Which have best characteristics when it comes to penetrate through walls or trees etc.

Would it make a difference for each mcs value if the link is single, dual or even triple chain?
And what about the channel width?

Which values perform better under heavy noise conditions etc.
Would the type of antenna have any impact on specific values? Would some mcs value perform better on a dish or a mesh?
How important is a good noise separation between both chains of the antenna and would it make a difference on which mcs is used?

By now there must be enough knowledge gathered by many and I think MT should also be ready to share more of the secrets about the mcs values with us simple users..

I think it be in the interest of everybody if we can get the best out or our links.
Please share your knowledge....
+1
 
0ldman
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Re: MCS values explained?

Wed Aug 01, 2012 5:45 pm

What I've seen it is fairly comparable to 802.11A/G, though I am not using the higher dual chain speeds.
 
WirelessRudy
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Re: MCS values explained?

Thu Aug 02, 2012 2:08 am

What I've seen it is fairly comparable to 802.11A/G, though I am not using the higher dual chain speeds.
?
MCS values are different coding schemes used by 'n' protocol working radios. Imho it's completely different than what the normal connection rates are of legacy radios. The latter work with one coding scheme only.

But maybe I misunderstand you, please explain what you mean with "fairly comparable to 802.11A7G"?
Show your appreciation of this post by giving me Karma! Thanks.

Rudy R. Puister

WISP operator based on MT routerboard & ROS.
 
0ldman
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Re: MCS values explained?

Thu Aug 02, 2012 7:23 pm

The lowest 802.11n speed is 6.5mbps BPSK 1/2 coding rate.

The lowest 802.11a/g speed is 6mbps BPSK 1/2 coding rate.

Jump to about 19.5mbps QPSK 3/4 and compare to 18mbps QPSK 3/4.

58.5mbps 64-QAM 3/4 = 54mbps 64QAM 3/4.

65mbps 64-QAM 5/6 encoding.

It is essentially a 1/1 comparison through the speeds. 802.11n has slightly lower overhead, which I don't know why.

This isn't even mentioning the short guard interval.

The encoding rates of N vs A/G vs AC, they're all essentially the same aside from the top end and additional streams. 802.11n is an evolutionary growth of A/G and AC is a growth of N.

AC is essentially the same as N with wider channels and more streams. We won't see the full benefit of AC any more than we do the 600mbps promised with N.

I think I'm going to try to make an encoding + streams + extension channel chart based on the encoding method, a cheat sheet. 18mbps = 19.5mbps = 39mbps @ dual chain = 68mbps @ dual chain + extension.
 
0ldman
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Re: MCS values explained?

Thu Aug 02, 2012 7:52 pm

Quick chart.

I'll add 802.11b and long vs short interval, but this is what I've done quickly.
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