Understanding SM retransmission in cnMaestro

Products ePMP
1

I would like to understand how to interpret the re-transmission information, specific questions:

  1. Is the SM recording only Uplink retransmissions? (see image below).
  2. In cnMaestro I can see both uplink and download re-transmissions, Can you please confirm that downlink means from AP to SM, and uplink means from SM to AP? Correct, I confirmed it, see reference below.
  3. From the images below, it seems that I have re-transmission in the downlink, What could be causing it?

Here the chart from cnMaestro:

image
image1503Ă—660 73.9 KB

Here the chart from the SM web interface:

image
image1539Ă—546 68.5 KB

References:

image
image739Ă—76 29 KB

2
  1. Is the SM recording only Uplink retransmissions? (see image below).

It’s recording both uplink and downlink retransmissions. If you mouse over the graph it will tell you exactly what % each is.

  1. In cnMaestro I can see both uplink and download re-transmissions, Can you please confirm that downlink means from AP to SM, and uplink means from SM to AP?

Downlink and uplink %'s are shown from the perspective of the radio you click on.

  1. From the images below, it seems that I have re-transmission in the downlink, What could be causing it?

Re-transmissions can be caused by interference (either from self or external), poor or rapidly changing modulation, or high frame utilization.

Go through your SM’s and look for ones that are showing high re-transmissions and try to improve their RSSI/SnR/modulation.

Make sure that your AP’s are sync’d properly, and that you’re using at least a 10MHz or greater guard band between AP’s on adjacent frequencies.

Make sure your AP’s “Subscriber Module Target Receive Level” is set to -60.

Try using a different channel and/or channel width (probably smaller) on the AP and see if that improves your re-transmission rate.

2 Likes
3

Thanks for your feedback, @Eric_Ozrelic, that is what I’m going to do next, for each poor SM, I will improve those parameters, I will start improving the height of the SM over the ceil which I have seen makes a huge difference.

4

The most notable source of high retransmissions is dual band routers, but we have also seen cheap weather stations and other wireless devices that do not care what else is on that frequency. Video baby monitors tend to be the worst offenders.