ZOE-M8B - System Integration Manual
UBX-17045131 - R04
Contents
Page 31 of 42
Production Information
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Higher backup-state durations: the ephemerides and GNSS time information has expired. For this
case AssistNow Offline data will still provide the benefits on acquisition sensitivity and TTFF
If RTC is replaced by using time-assistance from the host, the benefits on TTFF are still applicable,
but the benefits on acquisition sensitivity are reduced.
If neither an RTC nor time-assistance is used, then only the navigation database is restored upon
startup, but the receiver starts up with an unknown time. For this case, both the benefits on TTFF
and acquisition sensitivity are reduced. However, the performance is still better than without using
backup.
3.2
Using multi-GNSS Assistance (MGA)
u-blox multi-GNSS Assistance (MGA) service provides Assisted GNSS (A-GNSS) functionality with
support for multiple constellations. Supply of GNSS receiver assistance information greatly improves
performance of position calculation and tracking by delivering satellite data such as ephemeris,
almanac, accurate time and satellite status to the GNSS receiver. The host processor fetches this
aiding data from u-blox’s multi-GNSS Assistance server via a wireless network or the Internet, and
then sends the data to the GNSS receiver. Any of the receivers communication interfaces can be used
for this.
All u-blox M8 GNSS receiver chips support the u-blox AssistNow Online and AssistNow Offline
A-GNSS services. They also support AssistNow Autonomous feature, and are OMA SUPL compliant.
When using the AssistNow Online, Offline or Autonomous data, the ZOE-M8B GNSS SiP reaches
minimal power consumption, since A-GNSS enables the receiver to maximize its power-optimized
period. The A-GNSS assistance data also improves tracking accuracy in Super-E mode because the
receiver can optimize the set of satellites used in power-optimized tracking.
Performance of the GNSS operation is improved in several aspects:
•
The TTFF can be reduced down to a couple of seconds.
•
The signal acquisition before entering the power-optimized tracking is improved. Thus, more
satellites can be tracked to improve the tracking accuracy.
•
The receiver switches less often from power-optimized tracking back to full power mode. This leads
to more optimal power saving in Super-E mode.
•
Performance is improved also in weak-signal environments like urban canyons or forests.
AssistNow Online and AssistNow Offline can be used either alone or in combination. AssistNow
Autonomous is an embedded feature of the receiver. GNSS orbit predictions are directly calculated by
the GNSS receiver and no external aiding data or connectivity is required. AssistNow Autonomous can
be used alone, or together with AssistNow Online. However, the AssistNow Offline and AssistNow
Autonomous features are exclusive and should not be used at the same time. Every satellite will be
ignored by AssistNow Autonomous if there is AssistNow Offline data available for it.
For more information on the Multiple GNSS Assistance Services and the related communication
protocol, see the
Multiple GNSS Assistance Services For u-blox GNSS receivers [5] and the u-blox 8 /
u-blox M8 Receiver Description Including Protocol Specification [3].
3.2.1
AssistNow™ Online
With AssistNow Online, an Internet-connected host downloads assistance data from the u-blox
AssistNow Online service to the receiver at system start-up. The Multi-GNSS Assistance (MGA)
service is an HTTP protocol based service that is independent of network operators. The service works
on all standard mobile communication networks that support Internet access, including GPRS, UMTS
and Wireless LAN
