WiFi Signal Strength Graphs

WiFi generally works well, but sometimes it does not and I’d like to know why: Is the signal weak? Is the noise floor increasing? To measure that, get the data and collect and make nice graphs out of it!

Gather data

Mikrotik SXT Lite5

You need a method to get raw data out of your wireless device (Mikrotik SXT Lite5). In my case:

  • Create an account on the SXT to log in (via ssh key, see here)
  • A script to gather the data (I use telegraf with the InfluxDB line protocol). The REST API of RouterOS 6.x is unfortunately not yet usable.
#!/bin/bash
set -euo pipefail

# gather_one(router,interface)
function gather_one {
  ssh -i ~/.ssh/id_sxt17 telegraf@$1 "/interface wireless monitor $2 once" | tr -d '\r' >/tmp/f1
  radio_name=$(awk '/^ *radio-name:/{print $2}' /tmp/f1)
  if [[ -z "$radio_name" ]] ; then
    radio_name=$2
  fi

  tx=$(awk '/^ *tx-ccq:/{print $2/100}' /tmp/f1)
  rx=$(awk '/^ *rx-ccq:/{print $2/100}' /tmp/f1)
  tx_overall=$(awk '/^ *overall-tx-ccq:/{print $2/100}' /tmp/f1)
  nf=$(awk '/^ *noise-floor:/{print $2/1}' /tmp/f1)
  sn=$(awk '/^ *signal-to-noise:/{print $2/1}' /tmp/f1)

  if [[ ! -z "$rx" ]] ; then echo "signal,host=$1,radio=$radio_name rx=$rx" ; fi
  if [[ ! -z "$tx" ]] ; then
    echo "signal,host=$1,radio=$radio_name tx=$tx"
  else
    echo "signal,host=$1,radio=$radio_name tx_overall=$tx_overall"
  fi

  if [[ ! -z "$sn" ]] ; then echo "signal,host=$1,radio=$radio_name sn=$sn" ; fi
  if [[ ! -z "$nf" ]] ; then echo "signal,host=$1,radio=$radio_name nf=$nf" ; fi
}


gather_one sxt17.lan wlan1-gateway
gather_one router.lan wlan1
gather_one router.lan wlan2
  • telegraf.conf needs to run the above script and feed the data into InfluxDB:
[[inputs.exec]]
  commands = ["/home/harald/bin/wlan-influxdb.sh"]
  timeout = "10s"
  data_format = "influx"

Create a new panel in Grafana:

Top left panel definition

And here the resulting graphs:

Signal Strength, Noise Floor and Signal Quality

Note that the various hardware variations don’t always show the same raw data about the wireless interfaces. E.g. my router does not show the signal strength, only the noise floor.

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