III. Wireless LAN

VigorAP Interference Monitor Usage

VigorAP 710
VigorAP 800
VigorAP 802
VigorAP 810
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Channel Planning
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DrayTek's Interference Monitor feature tests signal quality through the VigorAP's web interface, with a visual representation and statistics to determine whether wireless channels are free for potential use, or would be able to transmit wireless signals effectively. This aids with the setup and troubleshooting of wireless networks, both locally and working remotely from the access point.

The Interference Monitor can scan all channels at once to visualise the channel usage and possible interference on all channels in a wireless band, then recommend which channel to use for the best signal quality at the time of scanning.

Interference Monitor visualises channel usage in two ways:

  • Channel Utilisation - IEEE 802.11 wireless ethernet packets detected on the channel
  • Channel Energy - Energy levels detected on that frequency band, which can include both wireless transmissions and other, non 802.11 sources of energy on that frequency band

Applicable Products:

  • VigorAP 710
  • VigorAP 810
  • VigorAP 900
  • VigorAP 902
  • VigorAP 903
  • VigorAP 910C

The Interference Monitor can be found in the [Diagnostics] > [Interference Monitor] menu:

There are two sections available in the Interference Monitor:

Current Channel

Displays details of the currently active wireless channel on the selected band, with a graph displaying the history of the Channel Utilisation & Channel Energy results.

This can be useful for troubleshooting wireless issues

All Channels

Displays Energy and Utilisation for all channels on the selected 2.4GHz or 5Ghz Band.

This can be useful for determining the clearest wireless channel in the VigorAP's current location

Current Channel

Interference Monitor - Current Channel

The Current Channel tab of Interference Monitor shows details of the currently active wireless channel for the selected Band, with a usage graph and statistics of that wireless channel displayed below. This can be set to contuously monitor by selecting the "Auto-Refresh" option.

Channel Information Table
Wireless interface that Interference Monitor will display information for. This option is available on Dual-Band (2.4GHz & 5GHz) VigorAP access points.
Currently active wireless channel on the selected Band.
TX Power
Power output specified for the wireless interface as selected in [Wireless LAN] > [Advanced Setting].
Country Code
Wireless region that the wireless interface operates in.
802.11 wireless modes supported / allowed by the wireless interface.
Specified Channel Bandwidth of the wireless interface.

Channel Status Table
Channel Utilisation

Detected 802.11 wireless signals (WiFi pre-amble) either from the VigorAP or other 802.11 WiFi devices.
0% - Channel idle, 100% - Channel fully utilised.

Indicates how frequently the wireless channel is in use either by the VigorAP, its wireless clients, or other nearby wireless access points.

Channel Energy

Wireless energy detected on that frequency band, both from 802.11 WiFi signals and other sources.
0% - no energy detected on this Channel, 100% - high energy detected on this Channel.

The energy indicated is that of its own wireless radio, wireless clients and nearby wireless access points.
Wireless clients that are further from the VigorAP may require more transmission power which can cause the Channel Energy value to be higher than the Channel Utilisation value.
It can be used to determine possible interference by comparing its value plotted on the graph alongside the Channel Utilisation. If the Channel Energy increases and decreases with the Channel Utilisation, as it does in the graph above, only normal 802.11 traffic is detected.
If the graph's Channel Energy line does not move in-line with the Channel Utilisation, it could be indicative of possible interference from something transmitting on the frequency that isn't an 802.11 wireless network.


A counter value displaying the number of times during one second that the Clear Channel Assessment has determined the channel is in use.
0 - Channel has been assessed to be free for use.

If the channel is in use at the time of sampling, it increases the FalseCCA count. This can be indicative of either wireless interference or a busy wireless channel, which can reduce wireless throughput and increase latency.

TX Fail

Number of failed WiFi packet transmissions. 0 - no packets have failed to transmit.

Failed transmissions will cause packet loss and significantly reduce wireless throughput.

TX Retry OK

Number of WiFi packets that failed an error check, then succeeded after retransmission.
0 - no packets have required retransmission to be sent successfully.

When packets need to be retransmitted, this increases the time spent sending that packet. High Retry counts will significantly increase latency / delays for wireless clients and may reduce wireless throughput.

This value will typically show some retries, which is normal given the nature of wireless network. If this value is frequently high, the wireless channel or network may be too busy.

Primary Channel Busy

Usage of the primary wireless channel (specified in Wireless LAN > General Setup).
0% - Channel is idle, 100% - Channel is fully utilised.

Secondary Channel Busy

Usage of the secondary wireless channel (specified in Wireless LAN > General Setup).
0% - Channel is idle, 100% - Channel is fully utilised.

Channel Status Graph

The graph displays the Channel Utilisation and Channel Energy values over the selected time period (X axis), with the graph scaling to fit the percentage values defined on the left (Y axis).

Select a different 5 minute time period to view wireless usage on that channel over the last 30 minutes:

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