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Creating stable PTP connection in Noisy 2.4 GHz environment

Posted: Mon Oct 28, 2013 6:08 pm
by thasser
Hey Guys,

So here is my problem:
I have two RB911 boards connected to 2.4 GHz itelite antennas. My signal strength is around -33/-32 dBm between the two antennas (~0.5 km apart) plus a 90+% CCQ RX/TX, so there is a very good signal. I am using RouterOS 6.4, nv2, 20 MHz wide channels, with Adaptive noise Immunity on AP and Client mode on both radios (seemed to help for a bit), and have both radios added in the connect/access lists. With the set-up we currently have, I am losing an unacceptable amount of ping to the client PTP radio. I have tried about 4 different frequencies right now and am starting to run out of options. The CONNECTION RELIABILITY is HIGHEST priority, with BANDWIDTH being the LOWEST.

I was considering trying to connect using either 10 MHz or 5 MHz wide channels, as I have exhausted (from my POV, this is where you guys come in to play!) almost all other known possibilities. Is there anything else someone could suggest trying or something I have looked over in the wiki or forum that addresses the best way to communicate PTP in a noisy, 2.4GHz environment?

P.S. I understand that 2.4 is saturated in most places, and I knew this going in. I have confidence that there is a good, reliable solution Mikrotik has given that this is a common issue.

Thank you in advance,
- Big Tim

Re: Creating stable PTP connection in Noisy 2.4 GHz environm

Posted: Tue Oct 29, 2013 5:09 pm
by wirelesswaves
You may have a problem because the received signal is just too high. ( both ends)

add 18 dB attenuation to both sides of the link.

Wireless>>Advanced>AntennaGain

put 18 in that field, do both ends.

Then ping from tools menu and report back to forum.. Check distance

Go to registration page, right click... add distance to display columns and make sure that the distance setting (dynamic) hasnt gone to some crazy figure like 50kms.

Adding 18dB in the antenna cloumn will force the radio card to adjust its power to be within regulatory domain.

Alternatively go to card-rates.... make fixed... set all to 2dBm (instead of default)

Re: Creating stable PTP connection in Noisy 2.4 GHz environm

Posted: Tue Oct 29, 2013 5:20 pm
by thasser
wirelesswaves,

Thanks for the suggestion, I think you may be correct, the signal is very, very strong (see attached). I will try what you suggested. And report back. For now here are my results with the PTP @ 5 mhz channel bandwidth.

Re: Creating stable PTP connection in Noisy 2.4 GHz environm

Posted: Tue Oct 29, 2013 7:09 pm
by thasser
Per wirelesswaves request, here are my new signal results. We will see how long we can keep constant communication. Summary: Back to 10 MHz (5 MHz throughput maxed out at about 4/5 Mbps, true throughput via bandwidth test-tcp one way). Changed antenna power setting to 18 dBi. See attached.

Re: Creating stable PTP connection in Noisy 2.4 GHz environm

Posted: Tue Oct 29, 2013 7:25 pm
by wirelesswaves
Hi,, thanks for the karma increase.

Swop back to 20Mhz channel... Use Japan and 2484 (just as a temporary solution)

Ditch nv2 until link is stable.

Try 80211

Advanced settings. Fiddle with CPE only!!

HW retries = 10
HW protection mode = rts/cts
HW protection threshold = 512

ANI = ap+client

All else default.

Do not change anything on AP or BRidge.

reduce signal to -50 -60

I cant see NV2 working well for you, if your evironment is noisy. Your SNR is already high, reducing bandwidth wont help in your case.. Might actually cause a problem, since other 3rd party equipment might not read your beacon or be aware of your channel usage.


Is this just a ptp link... If it is then maybe you could do away with NV2 and try the settings suggested.. IMO... NV2 may not be the right choice in a crowded band like that.

Dont forget that when you are using nv2, that your pings may not be a true reflection of what is really going on. ( unless the link is loaded)

I have always found that pings which appear to have latency can be somewhat misleading when using NV2 on an unloaded link.

You may be able to keep the latency down by using Nstreme, since you have plenty of SNR spare. Might be more reliable than a TDMA mode in a band that is already full.

Re: Creating stable PTP connection in Noisy 2.4 GHz environm

Posted: Tue Oct 29, 2013 8:14 pm
by thasser
I am still losing some ping here. I do have only a PTP where my receiver is on top of our temporary office receiving from another radio about 500 meters away. I will try your suggestions one step at a time. I especially like the offset freq. since this is a temporary office as well. Thanks for your suggestions once again, wirelesswaves!

Re: Creating stable PTP connection in Noisy 2.4 GHz environm

Posted: Tue Oct 29, 2013 8:38 pm
by thasser
Went ahead and switched to 802.11 and saw all of the advanced options appear, so I went ahead and set them as well. We are now hovering around -60 dB and back on a 20 MHz channel. I will let you know how the connection holds up. The implementation here has never been done, especially in this environment. I forgot to mention, in addition to all the noise, I am on the gulf coast (90+% humidity expected daily) so I have humidity, early morning fog, salt water, etc. We will see how it goes!

Re: Creating stable PTP connection in Noisy 2.4 GHz environm

Posted: Tue Oct 29, 2013 8:41 pm
by thasser
And lastly:

Re: Creating stable PTP connection in Noisy 2.4 GHz environm

Posted: Wed Oct 30, 2013 8:07 am
by wirelesswaves
ok.. all seems ok..

I use preamble "long" at both ends.

If you get the ocassional drop, then enter 2484 in the cpe scan list and make sure that 80211 is set for mode at both ends.

I avoid using "any" or "nv2,nstream,80211" as it causes longer time for reconnect.

I have some cpe's that disconnect several times a day, but the reconnects are so fast that even phone calls are not broken!.

The reason why I would steer clear of 5Mhz or 10Mhz is that I have seen Ubnt gear simply unable to detect the presence of MT gear, when the MT is on 5Mhz spacings..

Sl