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License: Free

WiFi Signal Strength Probe

Overview

The WiFi Signal Strength probe monitors wireless network connectivity quality by measuring signal strength and link quality. It automatically detects WiFi connections and collects metrics about signal level, SSID, and access point information.

Quick Start

# probes.d/10-wifi_signal_strength.yaml — each file under probes.d/ is a YAML array of probes
- name: wifi_signal_strength
  type: wifi_signal_strength

That is the whole configuration. The probe reads no parameters and collects every 60 seconds; the cadence is fixed in the code and a params block, interval included, is ignored.

Key Metrics

Metric Description Unit Platform
wifi_signal_strength Signal level dBm Windows, Linux
wifi_quality Link quality % Linux only

On Linux the signal level is the one iwconfig reports, or, where iwconfig is not installed, the one iw reports; the link quality then follows iwconfig's own scale, (dBm + 110) out of 70. On Windows netsh reports a percentage, which the probe converts to dBm with the usual approximation (dBm = percentage / 2 - 100), so 100% reads as -50 dBm and 60% as -70 dBm.

Platform Support

  • Windows - Uses netsh wlan show interfaces (signal percentage, converted to dBm)
  • Linux - Uses iwconfig when present (package wireless-tools), otherwise iw, which current distributions install by default (Debian 13 and Raspberry Pi OS included). iw lives in /usr/sbin; the probe finds it there even when the service account's PATH does not include it.
  • macOS - Not supported
  • BSD - Not supported

Auto-enable: Probe only starts if WiFi is actively connected.

Configuration Parameters

This probe reads no parameters. It collects every 60 seconds, a cadence fixed in the code.

The probe collects every 60 seconds. There is no way to change that cadence, and no other setting: it detects the WiFi connection by itself and starts only when one is up.

Signal Strength Interpretation

The metric is in dBm on both platforms, so one scale applies everywhere.

Range Quality Description
-30 to -50 dBm Excellent Maximum performance
-51 to -60 dBm Good Reliable connection
-61 to -70 dBm Fair Minor issues
-71 to -80 dBm Poor Slow speeds
-81 to -90 dBm Very Poor Barely connected
< -90 dBm Unusable No connection

On Windows the value is derived from the netsh percentage, so it never goes above -50 dBm: a full-strength connection reads -50 dBm, and the "Poor" band starts where netsh shows about 60%.

Tags

Each metric includes these tags:

Tag Description Example
ssid WiFi network name "CompanyWiFi"
bssid Access point MAC address "00:11:22:33:44:55"

Monitoring Integration

PRTG

# strategies.d/00-http.yaml
http:
  endpoints: ["prtg"]

Access: http://localhost:8080/api/{key}/prtg/metrics

PRTG Channels: - WiFi Signal Strength (dBm) - WiFi Quality (%) - Linux only

Nagios

# strategies.d/00-http.yaml
http:
  endpoints: ["nagios"]

The signal level is reported in dBm, the link quality in percent (Linux only).

Use Cases

1. WiFi Performance Monitoring

Objective: Track WiFi connection quality over time

Metrics: wifi_signal_strength, wifi_quality

Alert: Signal below -70 dBm

Benefits: - Identify coverage dead zones - Detect access point issues - Monitor roaming behavior - Track interference patterns

2. Remote Worker Connectivity

Objective: Monitor home office WiFi quality

Configuration: the quick start above; the 60-second cadence cannot be tightened.

Alert Rules: - Signal below -75 dBm: warning (ask the user to move closer) - Signal below -85 dBm: critical (connectivity issues)

3. Mobile Device Monitoring

Objective: Track WiFi stability on laptops/tablets

Metrics: Signal strength + packet loss (Gateway probe)

Combined Setup: 

# probes.d/00-host.yaml
- name: wifi_signal_strength
  type: wifi_signal_strength
- name: ping_gateway
  type: ping_gateway

4. Access Point Performance

Objective: Compare signal strength across multiple access points

Metrics: Signal strength by BSSID tag

Analysis: - Group by BSSID to compare APs - Identify weak access points - Optimize AP placement

Troubleshooting

Probe Not Starting

Symptom: Probe doesn't collect metrics

Cause: No active WiFi connection detected

Diagnosis: 

# Windows
netsh wlan show interfaces

# Linux
iwconfig

Solution: Connect to WiFi network first

Windows: "Error checking WiFi connection"

Symptom: Probe fails on Windows

Possible Causes: 1. WiFi adapter disabled 2. No WiFi hardware 3. Permission issues

Solutions: 

# Enable WiFi adapter
netsh interface set interface "WiFi" enabled

# Check adapter status
netsh wlan show interfaces

Linux: "Command not found: iwconfig"

Symptom: Probe fails on Linux

Cause: wireless-tools package not installed

Solution: 

# Debian/Ubuntu
sudo apt-get install wireless-tools

# RHEL/CentOS
sudo yum install wireless-tools

# Arch Linux
sudo pacman -S wireless_tools

Linux: Alternative with nmcli

Without iwconfig, the probe can still detect that WiFi is up through nmcli, but it cannot read the signal level: install wireless-tools for the metrics.

# Check WiFi status
nmcli radio wifi

# Enable WiFi
nmcli radio wifi on

No Signal Strength Data

Symptom: Probe runs but returns no metrics

Windows: 

# Check netsh output manually
netsh wlan show interfaces
# Look for "Signal" line

Linux: 

# Check iwconfig output
iwconfig
# Look for "Signal level=" line

Unstable Signal Readings

Symptom: Signal fluctuates rapidly

Possible Causes: 1. WiFi interference (microwaves, Bluetooth) 2. Moving laptop/device 3. Multiple access points with same SSID 4. Distance from access point

Solutions: - Move closer to access point - Switch to 5GHz band (less interference) - Use wired connection for stability - Check for interfering devices

Alert Thresholds

Metric Warning Critical Action
Signal Strength <-70 dBm <-80 dBm Move closer to AP
Link Quality (Linux) <60% <40% Check interference

Performance

  • CPU: <0.1% (command execution overhead)
  • Memory: ~5MB
  • Network: None (local command execution)
  • Collection Time: ~100-500ms per collection, every 60 seconds

Best Practices

Combined Monitoring

For complete connectivity monitoring, combine with:

  1. Gateway Ping - Network latency and packet loss
  2. Network Probe - Interface traffic and errors
  3. WebApp Ping - Internet connectivity

Example Configuration: 

# probes.d/00-host.yaml
- name: wifi_signal_strength
  type: wifi_signal_strength
- name: ping_gateway
  type: ping_gateway
- name: ping_webapp
  type: ping_webapp
  params:
    url: "https://www.google.com"

Dashboard Design

Essential Panels: 1. Signal Strength Gauge - Current signal level 2. Signal Timeline - Trend over time 3. SSID Table - Connected networks 4. Quality vs Strength - Correlation chart (Linux)

Metric reference

Every metric this probe can emit. Metric is the OpenTelemetry name the OTLP, Prometheus and Zabbix outputs derive theirs from. Name is what a Nagios check and the API metrics= filter match. PRTG channel is the label PRTG shows, placeholders filled from the series' tags.

Metric Name PRTG channel Unit Description
senhub.system.network.wifi.signal_strength.dbm wifi_signal_strength WiFi Signal Strength dBm WiFi signal strength in dBm (higher = stronger, typical range -30 to -90)
senhub.system.network.wifi.quality_ratio wifi_quality WiFi Signal Quality % WiFi signal quality as a percentage (0-100)