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03.21.2025
Cellular SCADA Communications Troubleshooting
The pervasiveness of Cellular Data Communications has prompted its use in many SCADA, Remote Monitoring, Data Logging, and Video Surveillance applications.
There are instances where the deployed cellular communications is unreliable or has become unreliable. This can be caused by equipment failure, lack of cellular network coverage, changes in cellular network coverage, or weather related RF path challenges.
When the site or sites are at remote locations that are difficult to access and the application is mission critical it is necessary to follow the proper troubleshooting procedures to ensure that the cellular communications problem is promptly resolved.
The following steps are recommended to repair unreliable cellular communications systems:
- Cellular Path Study
- Onsite Cellular Path Test
Utilize Cellular Tower Location Apps and RF Path Coverage Software to determine expected cellular signal levels prior to site visit. This is done to understand the terrain and optimal antenna pointing and minimum required antenna heights.
Onsite Cellular Signal Testing
Onsite Cellular Signal testing is performed to verify signal reliabilty for proposed deployments or to troubleshoot communication problems at existing sites.
The following steps are performed during onsite cellular signal testing. Note that spare/test equipment (modem, jumper, lightning arresters, antenna) must be be brought for troubleshooting in event of finding a equipment failure.
Measure Received Cellular Signal with a Cell Phone, Cell Phone Signal App, and/or Cellular Signal Analyzer. A Cellular Signal Analyzer is preferred as it has external antennae connection.
Verify Cellular Signal Strength with the Existing Cellular Modem System using its Modem Diagnostics.
Test the VSWR of Antenna, Cable, Lightning Arrester using an Antenna Analyser to insure there is no problem with the antenna system.
Test Antenna Pointing & Height. Use a pipe mast if elevated antenna height is required.
Test System Fade Margin With Variable RF Attennuator after cellular signal signal is optimized. It is recommended that you have 15 to 20 dB of fade margin.
Use Ping Test on cell modem to determine end to end commuications reliability.
Test with Alternate Cellular Modems. Existing cellular modem may be defective or they may not support current 4G / 5G technology.
Test Alternative Antennae systems including YAGI and/or Diversity Antennaes.
Test Coverage with Alternatve Carriers or Dual Carriers / Dual SIM.
Test Backup Satellite Communications Path (Starlink, BGAN, Iridium) if cellular communication coverage at site is found to be unreliable.