Good SNR, baad throughput

Hi all.

I've been having an issue the last while that I just can't seem to get sorted out.

We are using RF Elements symmetrical horn antennae with ePMP 2000 radios. Recently I had throughput for all clients on one access point drop drastically on the downlink side. I thought it's just noise on the frequency, but after doing many SA scans and frequency changes I cannot seem to get throughput any better.

All SMs have a SNR of at least 30 on both sides, with modulation rates between 9-12 for most clients. Wireless link tests give results of between 1 and 7 Mb/s downlink and between 5 and 25 uplink. These results are fairly consistent throughout frequencies.

The AP and most SMs are on firmware 4.4.3, with one Elevate unit.

I've had to push the unit slightly beyond EIRP limits just to attempt a temporary solution, better SNR seems to help a little when pushing the power up but surely 30db SNR should provide better results?

Any suggestions will be appreciated.


SnR levels aren't the same as CINR... so you could very well be getting sporadic interference and not seeing it reflected in SnR levels. I'd run a few ACS scans with the min/max timers set to the max, and watch out for a better channel to try out. Looks like you're using sync, which is good... you might be able to use back to back frequency reuse which will give you more channel options.

ALSO... any reason why you're using 50/50 TDD split, and 2.5ms, and a long GI? Unless you have very specific reasons for using these settings, most WISP's should typically be using 75/25, 5ms, and short GI for best performance.


Hi PresConnect - if you submit a screen shot of your MONITOR -> PERFORMANCE screen, that might help the community give you some insight. :) 

Hi Eric!
Thank you for the reply, I appreciate your input.

To start with your questions, I used the 50/50 split as far as possible to increase the client upload speeds(we sell symmetrical packages with best effort upload speeds), but I've switched to 75/25 this past week due to the performance issues we were having. I've migrated all the APs on our network to 75/25 to keep the sync happy.

I use the 2.5ms and long GI specifically for noise mitigation, I've read that this will provide a more stable link with less jitter and lower latency, especially since some of the links on the network cross water.

I'm quite frustrated with the performance at the moment although I understand there might be interference/noise. We are doing everything in our power to mitigate self-interference and using the horns to cut out interference from other WISPs in the area, and even keep our installations within 2.5km due to the high noise.

Is there anything else I can try for noise mitigation in your experience?

Using 2.5ms isn't going to help or hurt with noise. I'd use 5ms to squeeze more throughput out of the link. If you're not sync'd with your neighbors/competitors and/or you're not using back to back freqency reuse, along with horns provide excellent front to back ratios and zero side lobe bleed....  it might make sense to use flexible frame mode. This will give you the lowest latency/jitter and better download/upload rates depending on the majority direction of traffic.