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Problem. Solving 30km 11N wireless link issues.

Posted: Fri May 21, 2010 12:41 am
by chainsawman

We are setting a new link using 802.11N.
The calculations performed prior to implantation in the link indicated that it would be completed smoothly, as you can see in the picture attached:


After the installation is complete, the signal strength obtained was about what had been calculated, however, the TX-QCC was not good quality.
The traffic is only about 11~13Mb.
I tested various ways of setting up and none of them succeeded. :(




Below is the configuration of the wireless card:
/interface wireless
set 0 ack-timeout=dynamic adaptive-noise-immunity=ap-and-client-mode \
    allow-sharedkey=no antenna-gain=0 area="" arp=enabled band=5ghz-onlyn \
    basic-rates-a/g=6Mbps comment="" compression=no country=brazil \
    default-ap-tx-limit=0 default-authentication=yes default-client-tx-limit=\
    0 default-forwarding=no dfs-mode=none disable-running-check=no disabled=\
    no disconnect-timeout=3s frame-lifetime=0 frequency=5680 frequency-mode=\
    regulatory-domain frequency-offset=0 hide-ssid=no ht-ampdu-priorities=0,1 \
    ht-amsdu-limit=8192 ht-amsdu-threshold=8192 ht-basic-mcs=\
    mcs-0,mcs-1,mcs-2,mcs-3,mcs-4,mcs-5,mcs-6,mcs-7 ht-extension-channel=\
    below-control ht-guard-interval=any ht-rxchains=0,1 ht-supported-mcs="mcs-\
    12,mcs-13,mcs-14,mcs-15" ht-txchains=0,1 hw-fragmentation-threshold=\
    disabled hw-protection-mode=none hw-protection-threshold=0 hw-retries=15 \
    l2mtu=2290 mac-address=xx:xx:xx:xx:xx:xx max-station-count=2007 mode=\
    bridge mtu=1500 name=wlan1 on-fail-retry-time=100ms periodic-calibration=\
    default periodic-calibration-interval=60 preamble-mode=both \
    proprietary-extensions=post-2.9.25 radio-name=FORTALEZA rate-set=default \
    scan-list=default security-profile=default ssid=VSP-DST-CPG-I \
    station-bridge-clone-mac=00:00:00:00:00:00 supported-rates-a/g=\
    6Mbps,9Mbps,12Mbps,18Mbps,24Mbps tx-power=25 tx-power-mode=card-rates \
    update-stats-interval=disabled wds-cost-range=50-150 wds-default-bridge=\
    none wds-default-cost=100 wds-ignore-ssid=no wds-mode=static wmm-support=\

/interface wireless nstreme
set wlan1 comment="" disable-csma=yes enable-nstreme=yes enable-polling=yes \
    framer-limit=3200 framer-policy=best-fit

/interface wireless wds
add arp=enabled comment="" disabled=no l2mtu=2290 master-interface=wlan1 mtu=\
    1500 name=CHAPADA wds-address=yy:yy:yy:yy:yy:yy

This is the antenna used at both ends, it is an antenna 32dbi dual polarization:

Can anyone point me where would be the configuration error, or any hint that may solve the problem?

Thank you.

Edit: Yes, this post is based on changeip post.

Re: Problem. Solving 30km 11N wireless link issues.

Posted: Fri May 21, 2010 1:32 am
by jcem
I've done the following with both a and n links....

For a- link I disable lower Rates - That way the link wont change from Rates 6,9,18.... and only changes between 18 and 36 the CCQ goes 2-3 times

For n-link I disable higher HT MCS t and lower HT MCS - you have to test what works for your link until the CCQ becomes stable at 90-99%

I'm not sure if this is the correct way, but I more than doubled the TP and it's been stable for 6m now in versions 4.5-4.9


Re: Problem. Solving 30km 11N wireless link issues.

Posted: Fri May 21, 2010 2:23 pm
by chainsawman
I believe that just changing the data rates will not solve the problem, because even the 11A is not working properly.

Before performing the modification of antennas and cards, we had 29dbi antennas with XR5 cards and link worked perfectly, reaching 20Mbps tx and rx in 5ghz-turbo.

Re: Problem. Solving 30km 11N wireless link issues.

Posted: Fri May 21, 2010 5:21 pm
by 0ldman
Did you set it to 5GHz, not 5GHz A/N?

I have found (testing on the ground) that A is much more reliable than A/N in less than ideal situations. R52HN in A/N was kind of spotty with an AP a few feet away one channel below, but A was solid.

I am sincerely hoping this helps, because I am doing a link about the same distance soon (suppose to be today if my climber will show up).

Re: Problem. Solving 30km 11N wireless link issues.

Posted: Fri May 21, 2010 7:31 pm
by jcem
The pictures I posted are actually from two different AP's

- when setting an -n you can "fool" the system by setting f.e. disable Rate 54
and f.e. HT MCS 0-6. It will then "jump" to HT-20,40 without having to be able
to connect reliable to Rate 54.

- you can play around with this after the link is up. If it is P2P you only have to change
AP. But if there are multiple stations then you have to comprise the AP
and finetune the station.

This works for me...

Good Luck with your new Link!

Re: Problem. Solving 30km 11N wireless link issues.

Posted: Sat May 22, 2010 1:34 am
by chainsawman
Since yesterday I'm testing this new link, but without success.

We are using cables LMR-400, 1.5 m long.
This is just a PtP link.

I tried to set:
5ghz, 5ghz-an, 5ghz-only;
various combinations of HT-MCS;
11A data rates disabled / enabled (enabled is better);
ht-txchains=0,1 ht-rxchains=0,1;
ht-txchains=0 ht-rxchains=0 (0,0 is better);
ht-txchains=1 ht-rxchains=1;
RouterOS version 4.6 or 4.9 (no difference);
Nstreme disabled, nstreme enabled (enabled is better);
Several different channels, including those who do not show anything in the spectral signal-scan.
With or without WDS (no difference);
The antenna was aligned in chains 0 and 1, first one, then another;
Tx-power=14, Tx-power=17, Tx-power=25, Tx-power=default;
Tx-power-mode=default, Tx-power-mode=card-rates, Tx-power-mode=all-rates-fixed;
adaptive-noise=ap-and-client-mode or none;
Periodic-cabration=enabled or disabled;
Disable-csma=yes or no.

None of these settings has improved the connection. CCQ is ranging between 8~30%.
The bandwidth is only 12Mb in only one direction, 6~8Mb in both directions. :?

I returned the antenna 29dbi with XR5 cards that gave me the old 25Mbps in both directions.
This antenna is not pointed at the same location, but in a location 4km farther. Perhaps we are experiencing interference on the tower that was tested, I will draw conclusions pointing to the same tower that the link is currently running. But only next week.
Next week I will resume testing.

If someone can give me an idea, I appreciate it.

Re: Problem. Solving 30km 11N wireless link issues.

Posted: Sun May 23, 2010 3:47 pm
by Letni
Can you run the spectrum analyzer to see if there is noise on both sides?


Re: Problem. Solving 30km 11N wireless link issues.

Posted: Mon May 24, 2010 12:08 am
by lukkes
set the ACK to 408 in both sides... please tell me if this helps you.. I'm almost sure that this is your problem...