Interference Scan (also known as Interference Management (IM) Scan) is an end-to-end, Controller-coordinated scan that aims at performing real-time measurements of interference affecting a specific interfered link (referred to as the victim link). The Controller filters the network topology to identify potential interfering links (known as aggressor links).
The Controller then issues batches of scan requests to the filtered aggressor nodes or sectors. These requests are transmitted using the antenna beams and transmit power intended for their data links. Meanwhile, the victim receiver listens for these scan requests (transmissions). The extent to which the victim receiver detects these scan requests determines the level of interference exerted by the aggressor links on the victim receiver.
Output of Interference Scan
Using the cnMaestro UI, you can run the Interference Scan tool. The scan results show the victim link and its corresponding receiver MAC address (which serves as a unique identifier for the network devices).
It also provides a list of aggressor links along with their corresponding Signal-to-Noise Ratio (SNR) values relative to the victim receiver. SNR indicates the measurement of a signal strength compared to background noise, with higher values indicating better signal quality.
Impact on link performance
The interference from aggressor links impacts the maximum data rate that the victim link can achieve, determined by the Modulation and Coding Scheme (MCS). For instance, achieving MCS9 requires an SNR of at least 10 dB. However, if interference from an aggressor link reduces the SNR to 6 dB, the victim link will be limited to MCS4 or lower, resulting in slower data rates.
If the SNR is less than 0 dB, the interference is minimal and the aggressor links are unlikely to impact the victim link’s performance.
Running the Interference Scan tool in cnMaestro
You can run the Interference Scan tool using the Map page in cnMaestro UI only.
Note: cnMaestro 5.2.0 and later versions support the UI controls for running the Interference Scan X feature (tool).
To run the Interference Scan tool, complete the following steps:
- Log in to the cnMaestro UI and navigate to the Map > Networks page.
- Select a cnWave network and click on the link for which you want to run the interference Scan tool. The Details section on the right side of the Map page displays the selected link information. For example, there is a Backup-POP_V5K linked to V5K-DN2 in the figure below.
- Click the icon next to the link name and select Interference Scan X from the drop-down list. For example, Interference Scan is used for the link highlighted between Backup-POP_V5K linked to V5K-DN2 in the figure
below.
When Interference Scan X is selected, the Interference Scan section appears with the victim node names on the right side of the Map page (as shown in the figure below).
- Select the required victim node and click Start.
The Interference Scan tool detects neighboring interfering links with wireless settings that may affect your network. The Interference Scan tool can be executed on any of the victim nodes. In the figure below, Interference Scan is executed on the first victim node Backup-POP_V5K. If no aggressor is found, a message appears stating that no interference found.
When you run the Interference Scan test on the second victim node (for example, V5K-DN2), the aggressor (if any) details are displayed as shown in the figure below. In this case, Backup-POP_V5K to V5K-DN2 uses channel 1 and V5K-DN2 to V5K-DN1 uses channel 1. The SNR values need to be analysed.
Note: The cnMaestro UI displays both a map view and a list view of the victim-aggressor relationship.The map is color-coded to show the severity of interference. The lower the SNR from aggressor links, the greater the interference on the victim link.
5. View the scan result for the selected victim node and take appropriate actions.