Summary:
How to analyze a link disconnection or drop on the PTP 670/650 link? This article describes the use of the diagnostic plotter and spectrum expert to verify link drops and fluctuations.
Cause:
How to confirm the link drop issue with the diagnostic plotter and spectrum expert.
Solution:
To check if the link is dropping we must check the below information:
- Radio and wireless link uptime.
- Receive level of the link.
- Vector error of the link.
- Link loss of the link.
- Interference level of the link.
On the radio’s System Status page, we can view the radio’s wireless link uptime (elapsed time indicator), receive power, link loss, and vector error. The latest values are shown in the 4th column.
We can check RF values in the diagnostic plotter as well. The diagnostic plotter will have the RF values for 31 days. It is available in graphical and csv format.
- Vector error --- System >> Diagnostic plotter
Vector error compares the received signals In-phase / Quadrature (IQ) modulation characteristics to an ideal signal to determine the composite error vector magnitude. The expected range for vector error is approximately -2 dB to -33 dB. Values between -35 dB and -30 dB are considered good values. To get a stable link the vector error graph should be a straight line.
- Receive power --- System >> Diagnostic Plotter
Receive power and vector error should be a straight line to get a good stable link.
If the receive power is fluctuating then it can be due to loss of signal, weather conditions, alignment, etc.
- Link loss --- System >> Diagnostic Plotter
The link loss is the total attenuation of the wireless signal between the two point-to-point units.
LINKPlanner importance to analyze the link performance
We have to verify the current values with the predicted values in LINKPlanner (LP).
It is always recommended to plan the link in LINKPlanner so that we can compare the predicted values with the current values to evaluate the performance of the link.
- The LP project file should be updated with the most accurate antenna height of the devices.
- The LP predicted receive power should be matching with the current link receive levels.
- The LP will show the allowed variations as well.
- Ensure that the link availability is near the recommended five nines (99.999%).
- The LP will show the performance of the link in each modualtion level with the link availability. This will help us to understand the most stable modulation level the link can attain.
PTP 670 Spectrum Expert
To check the interference of the link we have to check the spectrum expert tab (System >>> Spectrum Expert) of the link. This page is used to view and configure spectrum usage.
The Spectrum Expert page displays the following plots:
- The Local Receive Spectrum (local radio), and the Peer Receive Spectrum (remote radio).
Graphical explanation of the spectrum management page:
Performance review of the link with interference
- If the link has interference there will be link fluctuation.
- Verify the vector error and receive level graph on the diagnostic plotter.
- If the vector error is fluctuating and receive level is constant or steady, then it will be due to interference.
- We have to add the interference level of the link into the LINKPlanner project file.
- LP will automatically update the link availability when the interference is added.
If there are multiple PTP 670 device, then we have to use the PTP sync device to reduce the self-interference. You can try different bands available as per your local regulatory requirements and check for improvements in the interference level.
The complete bandwidth ( Channel BW configured) should be interference-free to have a stable link.
The centre frequency (green color / active channel) and the wireless spectrum occupied by the active channel should be interference free.