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As mitigation strategies before a solution is implemented, we recommend the following actions:

1. Power-cycle all iSCs in operation to avoid the fluctuating between
   incorrect and correct dates.
2. Save all statistics, CDRs, and log files for potential data recovery after the solution has been implemented.
3. Trigger an action that would reacquire GPS signal on the iSC.

By design, the BSC hosts the iDEN NTP server and synchronizes its date and time with that of the equipped EBTS sites, where EBTS sites get their date and time information from a NTP Stratum 0 source, namely, the GPS. The other iDEN NEs use the BSC for their respective date and time synchronization. The BSC periodically selects a random EBTS to synchronize its time. This periodic selection process makes it possible to select an EBTS with the incorrect and then correct years respectively. The following are the impacts on system core functionality:

1. Some software processes in the system get an infinite loop causing the inability to access the EM for system administrative functions.
2. Corrupted statistics files.
3. Corrupted CDR files.
4. Incorrect date and time displayed at the handsets.
5. Corrupted system log files.
6. ⁠Incorrect time propagated to all other NEs, such as MSC, DAP, and iHLR and including iDEN acillary equipment (e.g., HWCS router).

The following events trigger the problem with the incorrect year and fluctuating between the incorrect and correct years:

1. A power cycle of the iSC.
2. ⁠Any action that would trigger GPS signal reacquisition. This could be, but not limited to, site load (full or configuration update), GPS signal loss due to NLOS.
3. The BSC synchronizes among EBTSs with the correct and incorrect years.

The issue is that the iDEN system is operating on the incorrect year and may be fluctuating between the correct and incorrect years.

On April 7, 2019, the Global Positioning System (“GPS”) experienced its second “week rollover” event. The GPS system was originally designed using a 10-bit binary number as a counter to indicate the week of the current date transmitted from the satellites to the GPS receivers. The 10 bits provide only 1024 possible values. Therefore, every 1024 weeks (approximately 19.7 years), the system returns to its starting value of 0.

At the base level for many GPS receivers, a rollover event indicates a date in August 1999. Some GPS receivers are able to determine that a date in 1999 (or any date 19.7 years prior to today) is actually in the past and they will add 1024 to the week counter and, thus, return the correct date. Other GPS receivers are happy to tell us today is 19.7 years in the past.

Because of this 10-bit limitation, the iSC of the iDEN EBTS is currently not able to determine a rollover event and is, therefore, reporting a date of year 1999 or 2004 (depending on when the receiver was manufactured) to the rest of the network elements in the iDEN system. This incorrect year is then propagated to all the network elements and including handsets of the system.

BSC ………………………………… Base Station Controller
CDR ……………………………….. Call Detail Records
EBTS ………………………………. Enhanced Base Transceiver System
EM ………………………………….. Element Manager
GPS ……………………………….. Global Positioning System
HWCS ……………………………. Harmony Wireless Communication System
iDEN ……………………………….. Integrated Dispatched Enhanced Network
iSC …………………………………. Integrated Site Controller
NE ………………………………….. Network Element
NLOS ……………………………… Near Line of Sight
NTP ………………………………… Network Time Protocol