FIELD SERVICE BULLETIN

GPS Synchronization

Document Number FSB9079
Revision 000v002
Download the PDF version Application Global
Effective Date January 2, 2020
Expiry Date N/A
BULLETIN TYPE SEVERITY RECOMMENDATION
  Warranty Service   High – Perform immediately
X Informational X Medium – Perform at next scheduled maintenance
  Customer Specific   Low – Perform when system exhibits symptoms

Download the PDF version

SUBJECT: Loss of GPS Synchronization

MODEL / SYSTEM AFFECTED:    uGPS receiver running firmware version AXN_5.1.1 
                                                        cnPulse receiver running firmware version AXN_5.1.1
                                                        ePMP1000/2000/3000 Access Points with integrated GPS running firmware AXN_5.1.1

REASON FOR BULLETINThis bulletin addresses a GPS synchronization issue that started around 13:00 CST on 12/31/2019.
This Field Service Bulletin address the recovery procedures and root cause of the issue.

SYMPTOM:
Customers are reporting a loss of GPS Sync when:

  1. Using a uGPS receiver connected to a CMM5 Injector via the UGPS port.
  2. Using a uGPS receiver directly attached to an Access Point’s AUX port.
  3. When using the internal GPS on a PMP450 or ePMP Access Points.

The loss of sync is causing radios with “AutoSync + Free Run” Enabled and “Free Run Before GPS Sync” Disabled to stop transmitting following a reboot. Radios configured for “AutoSync” only will cease to transmit immediately after sync is lost.

Radios that have “AutoSync + Free Run” Enabled might experience interference from neighboring APs due to the loss of sync.

CURRENT STATUS OF INVESTIGATION: The issue was cause by the GLONASS System Days Since Leap Year rollover that happens on every Leap Year at 00:00 Moscow Time. The GPS Chipset did not handle this rollover properly in firmware AXN_5.1.1 and it affects both UGPS and cnPulse devices with a GPS chip running this firmware. By now, it may have self-recovered, but if anything is lingering, a power cycle of the GPS device is required. This can be done via the AP if it is powered by the AP otherwise it will have to be done manually.

RESOLUTION:

  • The current fix for a uGPS receiver connected to a CMM5 injector via the UGPS port is to either power cycle the CMM5 injector or unplug the uGPS receiver from the UGPS port and plug it back in again.
  • For Access Points that have directly attached or internal GPS receivers, power cycling the Access Point will reset the internal GPS receiver.
  • For units that have uGPS receivers is powered via an external POE or PSU then the uGPS will need to be power cycled by removing power to the POE/PSU.

If you encounter an issue please open a support ticket with the Cambium Support team at the following URL: https://support.cambiumnetworks.com

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