Smart Machine Smart Decision
SIM868_Series_Hardware_Design_V1.06
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2017-07-13
Positioning Engine (ARM) on/off. In GLP mode, the active time (on time) of Measurement Engine (DSP)
and Positioning Engine (ARM) should be adjusted dynamically according to GNSS signal.
Note: Using the PMTK262 command to enable/disable GLP mode:
"$PMTK262,3" Enable GLP mode;
"$PMTK262,0" Disable GLP mode;
Customer can refer to document [13] for more information.
6.10.
A-GPS
A-GPS means assisted GPS, which is a system that can improve the startup performance and time-to-first-fix
(TTFF) of a GNSS satellite-based positioning under certain conditions. GNSS part supports EPO file, EASY
MODE and SBAS.
6.10.1.
Easy Mode
Easy is the abbreviation of Embedded Assist System, it works as embedded firmware which accelerates TTFF by
predicting satellite navigation messages from received ephemeris.
No additional computing interval for Easy task. Easy is efficiently scheduled and computed in free time of every
second after GNSS navigation solution.
Easy function is conceptually designed to automatically engage for predicting after first receiving the broadcast
ephemeris. After a while
（
generally tens of seconds
）
, 3-day extensions will be completely generated then all
Easy functions will be maintained at a standby condition. Easy assistance is going to be engaged when the GNSS
requests in new TTFF condition or re-generates again with another new received ephemeris. Meanwhile, TTFF
will be benefited by Easy assistance.
Note: The modes mentioned above can be set by PMTK commands; customer can refer to document [13] for
more information.
6.10.2.
EPO
GNSS supports the EPO (Extended Prediction Orbit) data service. The EPO data service supports 7/14/30 days
orbit prediction to customers. It needs to download aiding information from EPO server, which includes
ephemeris, almanac, rough last position ,time, satellite status and an optional time synchronization signal. This
function will reduce time of first fixing significantly and improving the acquisition sensitivity. Customer should
update the EPO files from EPO server daily through the GSM part.
Note: The modes mentioned above can be set by PMTK commands; customer can refer to document [13] for
more information.
6.11.
Fast-Fix
The Fast-Fix technology is based on the latest EPO data. Fast-Fix online provides extra time aiding from NITZ
SIMCOM
CONFIDENTIAL
FILE
