Radar Issue

[Fazza]

Our PTP Bridge briefly went down (it's a Deliberant APC Mach 5 V2) and in the logs it says it was Radar was detected, as soon as it stopped detecting Radar connectivity resumed.

 

Not sure what Radar is when it comes to wireless, but clearly it doesnt like it! Can anyone shed any light on this and what we can do to stop it from happening again?

 

Thanks.

 

[Linfit]

My understanding is that some of the 5GHz radio channels can potentially interfere with Weather Radar from overflying aircraft. We have a Cisco controller and ours detects radar quite often (we get a lot of aircraft overflying coming in to Manchester) and when it does it shuts those channels down. I think that if its a problem you can stop your controller from using those channels. I haven't gone into it in any detail as it does not cause major problems for us. I'm sure someone who knows more about these things will be along shortly......

[mjk]

It probably means it found an RF interference source and classified it as "radar", which, conceivably is a source of interference.

If it is happening frequently you'll need to find the source of the interference or move to a different frequency (perhaps a laser PtP link ?)

[Fazza]

Thanks for that!

 

I've sent out an email explaining that and Unidentified Flying Object has caused their outage and asked that people be on the lookout for such things the next time it happens.

[roadhouse1387]

Its exactly what you previous poster said. Its part of the offcom rules which state that because some of the 5ghz specturm allocated to outdoor bridging is shared with some types of radar (actually, some military radar) they get the priority i its use.

 

It used to be the case that tx power on these frequencies was limited to a couple of hundred watts but not so long ago, that was raised to maximum of 1w for 5ghz band B, which is probably what your bridge is using. A condition of this was the implementation of TPC and DFS, Transmit Power Control and Dynamic Frequency Selection. The first is designed to automatically reduce tx power in order to use only that strength which is required to maintain the link. The second, and the source of your issues, is designed to listen specifically for allocated users of that spectrum such as radar, and move frequency when its detected. This can lead to drop outs because A, the process isnt seamless, and B, the rules also state that the radio must wait for bit before transmitting again to make sure the interference has gone.

 

remember using the 5ghz is license free for wifi use on bands A and B (you need one for band C), but you (we actually) are really just squatting on it because it is already allocated to these other uses. The theory is, as long as wifi license free use is limited in tx power and frequency, then it can be safely shared. even if we are treat as the poor relation in the partnership.

 

If your problem is that it goes off and stays off for quite some time, it may be that your bridge has been set to use a specific frequency rather than a selection so it has no where to run when radar is detected. Check you bridge config out and see what it says.

 

HTH

Cheers