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02 April 2019

GPS week roll-over issue during epoch restart

02 April 2019

The Global Positioning System (GPS) uses a 10-bit counter to keep track of the current week number and date. It corresponds to 1024 weeks counting since 00:00:00 UTC January 6, 1980, which was week 0.

The 10-bit counter only hold 1024 weeks and will therefore roll over approximately every 19.7 years since launch of the GPS system, this occurred the first time year 1999 and is due to happen in 2019 again when the counter return to 0 from 1023 and the GPS epoch ends.

The next GPS epoch rollover will be at 23:59:42 UTC April 6, 2019.
Telit HE910 series 3G/HSPA+ modules with embedded GPS tracker will be affected at this date.

Location data and time reports will remain correct while the date and week number will be affected e.g. in the NMEA sentence $GPRMC and if AT commands to acquire these details are available in the product.

For the Qualcomm MDM9x15 series (4G/LTE Cat 3) and MDM6200 (3G/HSPA+) series chipsets there is a offset used, so the GPS week roll over will occur 1054+1023 weeks since launch of the GPS, and more precisely in beginning of November 2019 (UTC 23:59:42 November 2, 2019)

LTE Cat 3 modules based on Qualcomm MDM9x15 series chipsets:
Sierra Wireless EM73- / MC73- series
Telit LE910 series (only LTE Cat 3 series with GPS embedded)
Simcom SIM7100 series
Huawei ME909U series
ZTE ZM8620 V2 series

3G/HSPA+ modules based on Qualcomm MDM6200 series chipsets:
Huawei EM820W / MU609 series
Telit DE910 series
Simcom SIM5320 series

Please see the related technical documents bellow on proposed solutions and fixes for Telit and Sierra Wireless.
Additional information from Huawei and Simcom will follow regarding their corresponding products

Cellular modules with GPS tracker that are NOT affected by the 2019 GPS week roll-over issue:
Telit LM960
Telit LM940 and LN94* series
Telit LE910C1/LE910C4 series
Huawei ME906s series
Simcom SIM7500 / SIM7600 series
Simcom SIM7500 -h / SIM7600 -h series
ZTE GosunZn WeLink ME3630 series

Should you have questions or concerns regarding the GPS week roll-over issue, don't hesitate to contact us.

This archive contains the Sierra Wireless EM/MC73 Series GPS 2019 Week Roll-over NV Memory Firmware Update Patch as well as notice document.


Uploaded at
2019-04-02 16:14:29
Last updated
2019-04-02 16:14:29
Related products
Sierra Wireless EM7355
Sierra Wireless EM7305
Sierra Wireless MC7350
Sierra Wireless MC7354
Sierra Wireless MC7304

This archive contains the GPS week number roll over issue notice and application note describing on the problem scenario and affected product variants.


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