PMP450 3.65GHz Low Beacon % Issue

Quick question, what does it mean when I have an SM that reports that it's only getting like between 9%-15% beacons? The majority of the SM's  on this APreport 100%, and a couple report 80-90% beacons. The AP is 13.2 firmware along with all clients, 3.65GHz, using a 20MHz channel width, and all the other clients have really good throughput and modulation.

The SM in question is about 2.3 miles away, and is recieving a signal at -62dBm with an SnR of 12dBm and fluctuating modulation of between 4x and 2x MIMO-B. The AP is seeing the SM @ -65dBm, SnR of 21dBm and a modulation of 1x MIMO-A. When I do an RF link test, I get horrible throughput at 4.8mbps DL 44% effeciency, and 247kbps UL 65% effeciency, and it says transmitter at 1X MIMO-A. It also has a ton of re-regs.

At first I thought maybe  the client was too close to the tower, but we have clients that are les s then 2 miles away that are working great, and we have clients that are 10 miles away working great as well.

Pretty stumpted here... I think I'm going to swap out the radio and try a new one when I get a chance.

The Beacon % value is a measurement over a 16 second period and is basically showing you the percentage of beacons the SM received from the AP.  If you are seeing a low percentage then we'd expect a link test to also be poor which sounds like what you are experiencing.  When you look at the AP Eval page does the SM see any other AP's?  Have you tried running a spectrum analysis at the SM?  With the AP powered on it will show the RF from the AP so best case would be to run the spectrum scan while the AP is off but we'd understand if its not possible to do this if the AP is in production.  

I'd suggest a remote spectrum scan and then checking to see if there are any reflections at the SM.  What type of roof is the SM installed on?  Is it on the edge of the roof or shooting across the entire roof top?  Is the path going over any bodies of water?  Can you attach a google earth image showing the path?

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We ended removing the reflector dish and just using the bare SM...  we went from 15% beacons to 95% becaons and RF link tests now 30mbpsDL, and 5mbpsUL. We did some tests and if we were to reposition the SM higher up on the house, it would increase the link quality even further. It's fine for now. We had another link with poor beacon % (70%) @ 13 miles and we repositioned/realigned the dish, and now it's at 92% beacons and has much higher RF link test, and re-regs have stoped.

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Eric - Can you share with the community what steps you went through in order to re-position / re-align the dish?  We have heard numerous reports from other customers that dish alignment is a bit tricky, so any tips or tricks on alignment could help others in this situation.

Do you typically use the alignment screen on the GUI, the alignment tone, or other tools to help?



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On the path you removed the dish from was it non line of site (NLOS) or near line of site (nLOS)?

It's a strange problem when you have a good signal strength and a low beacon %. Symptoms include strong signal to the SM, but poor signal and modulation back to the AP. Clients experience re-regs often and poor throughput.

We've only had two cases of this so far (coincidentally both on 3.65GHz, and both on the same sector) and in both instances we ended up re-aligning the SM's and focused more on trying to increase the beacon % and less on the signal. To align, the field tech on the roof typically uses a netbook connected via WiFi to the customers network on the inside of the house to view the signal and beacon % on the SM home page. Web page auto update on the SM is set to 1 second.

In both cases after we re-aligned, the reported signal at the SM was slightly lower, but the beacon % was much higher, with RF link tests producing much higher throughput, and the AP reporting a higher signal and higher modulation with no more re-reg's.

Both connections are clear/perfect LOS to the tower.

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