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Belyivulk
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N in a PtmP Enviroment - my observations

Sun Apr 03, 2011 12:22 am

Hey All,

I just wanted to share / query other peoples results with N in a PtMP enviroment.

In these tests we were running ROS 5.0, Single chain, 20mhz channel, SXT's running ROS 5.0 as clients, in nstream with 8 clients to the Omni. Total EiRP is around 800mW, furthest client is 4km.

So - under N, running MCS 5 we achieve approx 31mbit REAL TCP throughput running a Btest from an SXT to a PPC router in our core. Under this example the client has a signal of -59/-60 - i imagine we were maxing out the CPU on the SXT.

Also under N we have another SXT running with a signal of -74/-80 (not great), running the same Btest to the same PPC router, MCS 5 wont stay connected, when locked into MCS 4 - we get under 10mbits, MCS 3 we get 15mbits, but it is very unstable and CCQ's are jumpy. I didnt try going to any lower rates

When we lock this SXT into A rates - 24mbit/mode we get 16mbit/sec very stable with good CCQ's.

So i am wondering if other people have seen similar results - where clients with very strong signals get great throughput under N, but clients with less great signals get substantially worse throughput - which then is much better under A rates.

Anyone?
 
WirelessRudy
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Re: N in a PtmP Enviroment - my observations

Sun Apr 03, 2011 1:17 am

In the many post I have been reading about the usage of ´n´ (and it did count for my own two backhauls as well) is that ´n´ needs at least -60 or better signal to perform.
Don't ask me why but when my links were -70 (which is usually still good enough for ´a´ to get high data rates) my ´n´ link was crap. Only after I put the high power ´n´ cards in same board with same antenna and my signal came near -60's suddenly ´n´ started to work as expected.
my 2 pennies for it....
 
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Belyivulk
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Re: N in a PtmP Enviroment - my observations

Sun Apr 03, 2011 1:20 am

That definately reflects our experience :) I guess the higher modulation rates of N need a cleaner received signal?
 
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warwick09
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Re: N in a PtmP Enviroment - my observations

Sun Apr 03, 2011 3:04 am

To Wirelessudy and Belyivulk

what are your corresponding noise floor levels? ( have you used sub 5ghz frequencies ? )

.... I'm thinking of switching most of my network over to the n-draft (single Chain) to ensure future competitiveness. However it still seems to be a "etchy" work in progress.
 
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Belyivulk
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Re: N in a PtmP Enviroment - my observations

Sun Apr 03, 2011 3:12 am

Hi Warwick

Our noise floor on the links above is reported as -120db (very quiet up here)

On another AP we run 4.16 with NV2 package so we can use N rates on 10mhz channels - there are 40 clients connected, nearly all of them A only, but we have two or three SXT's connected to this site, they are able to achieve at best 11mbits on N rates - but this is on a 10mhz channel shared with 40 other A clients, using Nstream.

So this works well for us - but all our SXT's clients have signals of around -60 to -75, A clients are as high as -82 and many km's out (upto 20km's away)

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