06-13-2018 06:31 AM
I am having a problem with the link between two PowerBeam M2 400 airMax Bridges. When the units start up, I get great throughput and no lost packets. After running from several hours to a few days, they start slowing down with increased latency and lost packets. Restarting either the system configured as an access point or the system configured as a station fixes the problem for a few hours or days again, and then the problem repeats.
The other thing that will fix the problem temporarily is to download the support info from the Access Point side. As with rebooting this fixes the problem for a while before it returns. However this only works if the support info is downloaded from the Access Point side and does not work when the support info is downloaded from the Station side.
Both the Access Point and the station are running version 6.1.7 (XW) of the software, but this problem also existed on all previous versions of the software that we have tried. At first, I thought that the slowness was caused by external interference, but the fact that I can temporarily fix the problem just by downloading the support info from the Access Point side has me scratching my head.
Configuration/status information on the units is as follows:
Channel Width: 20 MHz
Frequency: 2447 (no extension channel)
Output Power: 26 dBm
Max Tx Rate: MCS 15, 130/144.4
Distance: 0.4 miles (Auto Adjust)
Aggregation: 32 Frames, 50,000 Bytes
Tx Combined Signal Strength: -55 dBm
Rx Combined Signal Strength: -55 dBm
airMax Quality: 80% - 90%
airMax Capacity: 60% - 80%
Does anybody have any idea what could be causing my problem?
06-13-2018 08:18 AM
How obstructed is the path?
When changing settings on a radio, the link may come up at a higher air rate, but slowly lower its modulation because of interference and/or wireless retries.
What do the tx/rx rates look like on the station when it is slow?
Have you tried other frequencies?
06-13-2018 10:00 AM
> How obstructed is the path?
The path has a few trees about 100 feet from to the Station side. We cut down some other trees in the path last summer and saw no improvement in performance. We have other 2.4 GHz Ubiquiti equipment (NanoStation M2) going through more obstructions than this without any problems.
>When changing settings on a radio, the link may come up at a higher air rate, but slowly
>lower its modulation because of interference and/or wireless retries.
>What do the tx/rx rates look like on the station when it is slow?
The Max TX rate on both sides is set to auto and is currently running between 130 and 144.4 from the Access Point side and between 52 and 117 from the Station side. The link has not been heavily used recently and has traffic primarily from the Station to the Access Point. From the Station to the Access Point is a constant 1 Mbps to 4 Mbps of traffic and from the Access Point to the Station is about 100 Kbps of traffic.
I will check the rates when the system slows down again and post them here. This should be within a day. When the system is good, I can ping for hours with zero packet loss until it goes bad and then I lose about 1 in 10 pings at which point it will not improve until I do something like download the support info from the Access Point side.
>Have you tried other frequencies?
We have tried different frequencies and channel widths, all with the same problem.
06-14-2018 06:06 AM
Our link went slow again last night. I haven’t done anything to fix it yet. I took a look at the status and it looks about the same as when the link was working properly. The TX/RX rates are about the same (between 130 and 144.4 from the Access Point side and between 52 and 117 from the Station side). Negotiated rates show up with signal strength for MCS13, MCS14, and MCS15 and sometimes MCS12. This is the same as when the link was running fine.
Product: PowerBeam M2 400
Connection Time: 2 days 21:31:25
RX Signal: -57 dBm
TX Signal: -60 dBm
Noise Floor: -87 dBm
Distance: 0.3 miles (0.5 km)
TX Power: 26 dBm
TX/RX Rate: 104 Mbps / 144.444 Mbps
TX/RX Bit Rate: 616.89 kbps / 19.26 kbps
TX/RX Packets: 37836984 / 18024516
TX/RX Packet Rate, pps: 33 / 15
Bytes Transmitted:57060204948 (57.06 GBytes)
Bytes Received: 1010550599 (1.01 GBytes)
Negotiated Rate Last Signal, dBm
Signal strength is around 56 dBm at each end. AirMax Quality is between 80% and 90% and airMax Capacity is running between 60% and 80%. This is all the same whether link is functioning properly or there is slowness. Is there anything else that I should look at before fixing the link before downloading the support info?
06-14-2018 01:59 PM
>Have you done a spectrum scan at both ends of the link?
Here is the Spectrum Analyzer screen from the Access Point side.
It will probably be a few days before I can get a bucket truck to get to the Station side to run the Spectrum Analyzer.
We have most recently been trying channels between 4 and 8 with a 20 MHz bandwidth.
06-15-2018 09:18 AM
@ClaremontNH Could you send the Support Info file from both units after seeing this? Please send to firstname.lastname@example.org and include a reference to this thread.
06-20-2018 08:17 AM
James, the support files have been sent to your email address.
I did a little more investigation to help identify what is going on. Since aggregation was enabled on both the Access Point side and the Station side of the bridge link, I thought that after a PowerBeam was operational for a while that there may have been an issue that caused a PowerBeam to wait a long time to fill an aggregated frame before sending it, so I tried turning off aggregation on both end of the link. After turning off aggregation, the problem doesn’t appear to occur. Previously aggregation was set to 32 frames and 50,000 bytes (defaults when I setup the PowerBeams). Does this make sense? For now, I will leave aggregation disabled.