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CarulloS
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Some 802.11n Questions I'd like answers on...

Thu Jul 30, 2009 12:43 am

I may have missed answers in the forum somewhere but after reading through most of what I could find I am still left with some questions...

1) If I were to purchase some new N minipci cards to use what would you all recommend (those who have had a chance to spend some time on testing them)

2) Can a N card (R52N) work exactly the same as a standard card like the R52(H) cards? Is there any compelling reason not to only buy R52N cards instead of R52 or R52H? R52N power specs show same as R52H...

3) It appears that you can use a single antenna with the multi-channel mimo cards by setting the chains = 1 in wireless settings is this correct? Looks like there was a chains 1 or 1 & 2 and then channel options 20Mhz and above or below setting for using 40 total Mhz... So, with only 1 chain and 20Mhz or 40Mhz you can use only one standard single polarized antenna?

4) Last, I notice on a post that the available freq options for 5N and 5A were different. If we have extra channel license is this compatible with the 5N settings... It doesn't appear so but I would like some clarification.

Thanks for your time in answering these questions, I felt they were relevant enough to put in one post because finding info about the mimo cards and operations has been challenging.

Scott
 
CarulloS
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Re: Some 802.11n Questions I'd like answers on...

Fri Jul 31, 2009 5:20 am

I have another question to add to the N list...

If I use new N cards for backhaul link that will replace existing link using 5Ghz R52 with Bridge-StationWDS settings then what is the speed limitation with N and WDS that I read about? I understand there is a limitation but I'm wondering exactly what that limit is speed-wise using WDS and N?

Assuming there is a big difference between the transfer rates with and without WDS then I understand in my scenario EOIP tunnel would be used to work around WDS issue. Are there an other side effects of using EOIP tunnel or will it behave just like WDS link does without it? Just looking for potential gotchas before implementation. Thanks.

Scott
 
uldis
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Re: Some 802.11n Questions I'd like answers on...

Fri Jul 31, 2009 2:37 pm

Another option if you don't like the EOIP you can use MPLS. Here is an example how to configure it.
http://wiki.mikrotik.com/wiki/Transpare ... using_MPLS
 
CarulloS
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Re: Some 802.11n Questions I'd like answers on...

Fri Jul 31, 2009 4:04 pm

I'm not opposed to anything, I'd just like some answers to my questions please.

Thanks,
Scott
 
WirelessRudy
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Re: Some 802.11n Questions I'd like answers on...

Fri Aug 14, 2009 2:55 am

CarulloS,

Did you already found some answers to your questions through other sources? This tread hasn't produced any yet...... :(
 
CarulloS
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Re: Some 802.11n Questions I'd like answers on...

Fri Aug 14, 2009 3:16 am

No I have not had my questions answered. I do have some gear that I have been testing / learning with so I am making progress but getting simple answers to questions seems hard to come by when it should be easy and painless :) Especially on a vendors forum...

Scott
 
uldis
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Re: Some 802.11n Questions I'd like answers on...

Fri Aug 14, 2009 1:32 pm

most of the questions are already answered in the other N topics.

R52N card works on the same frequencies like R52 or R52H.
You can also use one chain and one antenna for the N card and connect to A/B/G/N networks. And using that one chain you can also use 2 20mhz channels (extension channel). Note that N card doesn't support turbo mode.
about WDS and N cards, you will not be also to use all the N features and that means that you will not be able to get the max throughput, but you can always use EOIP or even better MPLS (look on the wiki for more info on the MPLS, there is an example).
 
itatwork
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Re: Some 802.11n Questions I'd like answers on...

Mon Aug 17, 2009 5:28 am

I'm sure I read somewhere on these forums that using 1 antenna on an N card would damage it...
So we can actually run one antenna and single chain N to get results similar to the Ubiquiti Bullet M series?
 
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Re: Some 802.11n Questions I'd like answers on...

Mon Aug 17, 2009 5:59 am

What 802.11n features are lost in WDS mode, and how much performance is lost due to those lost features ?
 
CarulloS
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Re: Some 802.11n Questions I'd like answers on...

Mon Aug 17, 2009 6:31 am

Write off WDS and N its slower than not using N so there is no point. Either use WDS and B/G/A or use N without WDS. After testing it I can tell you they don't mix.

Scott
 
CarulloS
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Re: Some 802.11n Questions I'd like answers on...

Mon Aug 17, 2009 6:32 am

I should have mentioned... Just use EOIP or another alternative to WDS with N, does the exact same thing functionally and works perfect.

Scott
 
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Re: Some 802.11n Questions I'd like answers on...

Mon Aug 17, 2009 11:24 am

Can anyone tell me if when a/b/g is used with 52N card, which connector represents ant-a and which ant-b.
I seem not to see any difference either one or the other enabled in ROS (in console, the option in winbox doesn't exist anymore!!! ros4b4)

On short (test) distances I even don't see enough difference between using chain1 or 2 for one particular connector in ´n´ mode, to be 100% sure which connector I should connect to antenna to align.
Can MT give a decisive answer please...
 
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Re: Some 802.11n Questions I'd like answers on...

Mon Aug 17, 2009 2:05 pm

antena-a and antenna-b option isn't used for the N cards.
For the N cards you should use Chain 0 and/or Chain 1.
 
WirelessRudy
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Re: Some 802.11n Questions I'd like answers on...

Mon Aug 17, 2009 5:45 pm

OK, Uldis. thanks for that

What is now the best setting in ´N´ mode:

Have both station and AP all four boxes ticket 'on' (Thus chain 0 and 1 both Rx and Tx 'on'?
Or is it better to have them cross enabled?

Thus AP Tx-chain0=on and Rx-chain0=off and Tx-chain1=off and Rx-chain1=on while on the station it is just the opposite?

You probably think I can determine myself but I am afraid I have an issue with one of the chains on one of the boards it looks like.

I can only keep station connected by always leave Rx-chain0=on with same power setting. If I switch that one off I have to increase the dBm on the station at least 3 figures to get it back. But then the signal is -30dBm, so a lesser power setting should also reach the other end....
So please some clearance (that is useful to other readers too) so I can go on determine if, and where, I have an issue. So far best result I have seen on my link (with mpls tunnel) is 20Mb tcp traffic.
 
uldis
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Re: Some 802.11n Questions I'd like answers on...

Tue Aug 18, 2009 1:05 pm

if you have both antennas connected then it is better to have both chains enabled for receive and transmit.
Better leave the default power - do not use higher output power as that might damage the wireless card.
Try to use UDP Bandwidth test as the RouterBoards can't generate so much TCP by the selves.
 
WirelessRudy
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Re: Some 802.11n Questions I'd like answers on...

Tue Aug 18, 2009 9:34 pm

if you have both antennas connected then it is better to have both chains enabled for receive and transmit.
Thanks for this clarification.
Better leave the default power - do not use higher output power as that might damage the wireless card.
I am testing with 23dBm dual disk antenna's that are in my garden 10 mtrs apart. I had the cards both set to 1dBm power and still getting -24, -26dBm readings. After this chain0 is disabled I have to tune the power up to 3dBm to get it back on the other end.... when it then is back the power reads -30dBm.
So the issue would rather be the cards don' t work well at minimal output instead of high outputs....

Try to use UDP Bandwidth test as the RouterBoards can't generate so much TCP by the selves.
udp is getting up to 100Mb. But I ran download tests from a laptop to a Pc connected to the both routers and also did do an ordinary big file transfer. Best speed still 20-24Mb....
 
CarulloS
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Re: Some 802.11n Questions I'd like answers on...

Tue Aug 18, 2009 10:45 pm

I'll make an educated guess as far as the power goes with the N cards...

With one chain (antenna) output at say 9db - add another chain with equal output you end up with 12db (not 19db)

Anytime you double your power you get 3db more gain / output.

I believe that's why you can only get the max power out of the N cards by using both chains otherwise you end up 3db less with only one chain. At least that's my take on it :)

Scott
 
dalejoyce
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Re: Some 802.11n Questions I'd like answers on...

Fri Aug 21, 2009 2:05 am

WirelessRudy - Did you fix the problem with low throughput when testing with PC-to-PC? I am experiencing the same problem. When testing between 2 x Routerboards using BandwidthTest i get 63mb/s TCP with 100% CPU usage. When testing with PC-to-PC i only get 20mb/s-30mb/s

Cheers
 
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Re: Some 802.11n Questions I'd like answers on...

Fri Aug 21, 2009 12:08 pm

signal levels of -30dBm is very very high, and as far as i know low throughput is caused by interference you are causing yourself with signal being too high. Thus higher degradation when transmit/receive alternates more frequently, like in normal TCP traffic transfer when every packet (window size) send have its ACK packet sent back.
 
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Re: Some 802.11n Questions I'd like answers on...

Sun Aug 23, 2009 2:09 am

Delajoyce:

I had a real life link setup and came across yet other problems with ´n´ protocol. Have changed cards now for normal one because needed the link to work as temp. replacement of failing backhaul.
This weekend totally occupied with complete overhaul of two towers, one because the emergency ´n´ link didn´t work immediate and the old backhaul antenna died. To replace that ordered a very expensive elevated work platform and thus arranged to have to two towers overhauled because it makes the ´bleeding´ (money) at least a bit economical........

Hope everything to be back in working order with a normal backhaul and parrallel new dual pol antenna's with new ´n´ cards for testing and later definate assignment.

Keep you guys informed on the proceedings this week.... :)
 
CarulloS
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Re: Some 802.11n Questions I'd like answers on...

Sun Aug 23, 2009 10:13 pm

I am attempting to use MPLS / VPLS tunnel instead of EoIP to test preformance / throughput. I have never done anything with mpls or vpls and cannot seem to even find it in the winbox or terminal interfaces on the RB411 boards I'm testing with. Is this a licensing problem (level 3) or am I just missing it or is there some other file for 4.0b4 I need to download and add to packages? I search forum and was unable to find this answer...

Thanks
 
WirelessRudy
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Re: Some 802.11n Questions I'd like answers on...

Sun Aug 23, 2009 11:50 pm

The mpls/vpls comes with a separate package.

In the ros3.x it is a ´test´ package: http://www.mikrotik.com/download.html

Download it and install it.

In ROS4.x it is in the packages list.
 
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Re: Some 802.11n Questions I'd like answers on...

Thu Oct 22, 2009 12:52 am

What types of spacing are people using when they connect 2 antennas to an R52N card?

Also has anyone tried using 2 sectors to one R52N card?

-Zatara

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