Field Notice: FN - 70448 - Products with Modem 7750 That Use the Cellular GPS Feature Will Have the Week Number Counter Reset on 2019-11-03 - Workaround Provided

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Updated:September 3, 2019

Document ID:FN70448

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Notice

THIS FIELD NOTICE IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTY OF MERCHANTABILITY. YOUR USE OF THE INFORMATION ON THE FIELD NOTICE OR MATERIALS LINKED FROM THE FIELD NOTICE IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS FIELD NOTICE AT ANY TIME.

Revision History

Revision	Publish Date	Comments
1.0	03-Sep-19	Initial Release

Products Affected

Affected Product ID	Comments
C819HG-V-K9
C819HGW-V-A-K9
C819HG-4G-V-K9
C819HG-S-K9
C819HGW-S-A-K9
GRWIC-4G-LTE-V
GRWIC-4G-LTE-V=	Part Alternate
C819G-4G-V-K9
EHWIC-4G-LTE-V
EHWIC-4G-LTE-V=	Part Alternate
EHWIC-4G-LTE-V++=
EHWIC-3G-EVDO-V
EHWIC-3G-EVDO-V=	Part Alternate
EHWIC-3G-EVDO-S
EHWIC-3G-EVDO-S=	Part Alternate
EHWIC-3G-EVDO-B
EHWIC-3G-EVDO-B=	Part Alternate
C881G-S-K9
C881G-B-K9
C881G-V-K9
C881GW-V-A-K9
C881GW-S-A-K9

Defect Information

Defect ID	Headline
CSCvq94031	GPS feature and GPS timestamp on routers with MC77xx modems will be impacted after 11/3/19

Problem Description

This field notice raises awareness of the Global Positioning System (GPS) timestamp rollover issue. This is applicable only to customers who enabled the Cellular GPS feature and use the timestamp data from the GPS National Marine Electronics Association (NMEA) sentence.

Certain Cisco products that use the Cellular GPS feature (see the Products Affected section) will have the GPS Week Number (WN) counter reset on 2019-11-03. This will reset the date from 2019-11-03 to 1999-11-03 in the GPS NMEA sentence.

Background

The GPS NMEA sentence contains a 10-bit binary number WN parameter. The valid range of values for the WN parameter is 0 to 1023 (or 1024 weeks). The WN parameter is incremented by one each week. At the end of the 1024th week, the counter experiences a rollover (resets) to 0. The last WN rollover was 1999-08-21. For affected Cisco products (refer to the Affected Products section for a complete list), the next WN rollover will be 2019-11-03. As described in the Problem Description section, the rollover will incorrectly reset the date from 2019-11-03 to 1999-11-03 in the GPS NMEA sentence.

Problem Symptom

These are the impacted areas once the GPS week counter resets:

While operating in LTE mode, the GPS location information retrieved from the GPS chipset will be intact and correct. However, the date reported in the Timestamp (GMT) field of the show cellular <slot> gps output and some GPS NMEA sentences (for example, GPRMC) will be incorrect.
While operating in Evolution-Data Optimized (EVDO) or 1xRTT mode, the GPS location information will be incorrect. Also, the date reported in the Timestamp (GMT) field of the show cellular <slot> gps output and some GPS NMEA sentences (for example, GPRMC) will be incorrect.
If the customer's external applications make use of GPS NMEA sentences to derive the time-of-day, they will be impacted accordingly.

This issue does not impact the router time.

Impact Analysis

Scenario	Impact	Workaround
Cellular GPS feature not used	No Impact	NA

While attached in LTE mode:

Scenario	Impact	Workaround
Cellular GPS feature used for location tracking	No Impact	NA
Timestamp used from the Cellular GPS feature NMEA sentence	Impact	See the Workaround/Solution section

While attached in non-LTE mode:

Scenario	Impact	Workaround
Cellular GPS feature used for location tracking	Impact	See the Workaround/Solution section
Timestamp used from the Cellular GPS feature NMEA sentence	Impact	See the Workaround/Solution section

Since the products that use these modems are End of Sale (EoS) and have passed the window for software support, there will be no new software/firmware for these modems to fix this issue.

See these documents for more information:

Workaround/Solution

Workaround

If impacted by the issue described in this Field Notice, Cisco recommends disabling the Cellular GPS feature by issuing the Command Line Interface (CLI) commands below and then power-cycling the modem.

Controller Cellular <slot>

            no lte gps enable

Power-cycle the modem after you enter the command.

For More Information

If you require further assistance, or if you have any further questions regarding this field notice, please contact the Cisco Systems Technical Assistance Center (TAC) by one of the following methods:

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