RCB-F9T - Integration manual
3.9.9.1 GPS-only date resolution
In circumstances where only GPS L1C/A signals are available and for receivers with earlier firmware
versions, the receiver establishes the date by assuming that all week numbers must be at least
as large as a reference rollover week number. This reference rollover week number is hard-coded
at compile time and is normally set a few weeks before the software is completed, but it can be
overridden by CFG-NAVSPG-WKNROLLOVER configuration item to any value the user wishes.
The following example illustrates how this works: Assume that the reference rollover week number
set in the firmware at compile time is 1524 (which corresponds to a week in calendar year 2009,
but would be transmitted by the satellites as 500). In this case, if the receiver sees transmissions
containing week numbers in the range of 500 ... 1023, these will be interpreted as week numbers
1524 ... 2047 (calendar year 2009 ... 2019), whereas transmissions with week numbers from 0 to
499 are interpreted as week numbers 2048 ... 2547 (calendar year 2019 ... 2028).
It is important to set the reference rollover week number appropriately when supplying u-
blox receivers with simulated signals, especially when the scenarios are in the past.
3.10 Timing functionality
In addition to positioning and navigation applications, GNSS signals are widely used as low-cost
precision time or frequency references used by remote or distributed wireless communication,
industrial, financial, and power distribution equipment. By capitalizing on atomic clocks which are
on-board positioning satellites, GNSS signals which contain embedded timing information can
be used to synchronize equipment, as well as to provide UTC time. For wireless communication
standards that utilize Time Division Multiplex (TDM) and applications such as femtocell base
stations, a precision time reference is mandatory.
3.10.1 Time pulse
3.10.1.1 Introduction
Figure 9: Time pulse
3.10.1.2 Recommendations
• The time pulse can be aligned to a wide variety of GNSS times or to variants of UTC derived
from them (see the chapter on
). However, it is strongly recommended that the
choice of time base is aligned with the available GNSS signals (so to produce GPS time or
UBX-22004121 - R01
3 Receiver functionality
Page 34 of 64
C1-Public
Early production information
