Customers can get useful information about SIM7500/SIM7600 GNSS/A-GNSS functions quickly through this document.
GNSS function could be easily realized by AT command interface provided in SIM7500/SIM7600 module via USB interface.
1. SIM7500/SIM7600 GNSS features
♦ Support GPS, GLONASS, BEIDOU, GALILEO, and QZSS satellite systems.
♦ Support standalone mode, MS-based mode, MS-assisted, and XTRA mode
♦ Support cold start and hot start.
♦ Support a subset of the NMEA-0183 standard.
♦ Support NMEA sentences output in NMEA port port.
♦ A-GNSS supports UP (user plane) and CP (control plane) method.
♦ MS-assisted mode supports single fixed; MS-based mode supports seriate fixed.
♦ Support certificate if necessary.
♦ Supporting GNSS starts automatically when module powers on, it supports standalone mode only
2. GNSS Mode Introduction
Process: Demodulate GNSS data by Module → Calculation of Position by Module
the handset demodulates the data directly from the GNSS satellites.
This mode has some reduced cold-start sensitivity,
and a longer time to first fix as compared to the assisted modes.
However, it requires no server interaction and works out of network coverage.
Default use GPS, GLONSS, BEIDOU, can use AT+CGNSSMODE set.
Process: Sending Aiding Data by Server → Sending Code Phases by Module → Calculation of Position by Server
When a request for position location is issued,
available network information is provided to the location server and assistance is requested from the location server.
The location server sends the assistance information to the handset.
The handset/mobile unit measures the GNSS observables and
provides the GNSS measurements along with available network data (that is appropriate for the given
air interface technology) to the location server.
The location server then calculates the position location and returns results to the requesting entity.
Process: Sending Aiding Data by Server → Calculation of Position by Module
The assistant data provided by the location server encompasses
not only the information required to assist the handset in measuring the satellite signals,
but also the information required to calculate the handset’s position.
Therefore, rather than providing the GNSS measurements and available network data back to the location server,
the mobile calculates the location on the handset and passes the result to the requesting entity.
3. gpsoneXTRA Introduction
It provides enhanced standalone performance and eliminates the need to demodulate the GNSS signal for ephemeris, almanac, iono, UTC, or health.
Normally requires -144 dBm or stronger for all SVs in view.
TTFF can be reduced by 18 to 30 sec (or more in harsh signal environments)
♦ gpsOneXTRA assistance data file content
Current assistance data (ephemeris, almanac, iono, UTC, health)
Predict satellite coordinates and clock biases valid for up to 7 days
♦ gpsOneXTRA assistance data delivery
Propriety binary file (approximately 40 kB, depending on the number of active satellites)
File transfer via HTTP
Time assistance via SNTP/HTP
♦ gpsOneXTRA assistance file source and policy
Qualcomm generated the assistance file and Qualcomm partner hosted.