nrf9160, AGPS works longer than GPS

[Stas Jis]

We use nRF9160 on our own board.
The firmware "Serial lte modem" is installed on the chip with a connection to an external MCU (#define MQTT_MESSAGE_BUFFER_LEN 8192)
We tested the environment with periodic switching from AGPS to GPS.
And in tests, we constantly see that the operating time with AGPS is twice as long as with just using GPS.

Average waiting time when using AGPS: 1 minute + 10-15 seconds;
Average waiting time when using GPS: 30-40 seconds.

What could be the reason for such behavior? It was expected that the operating time with AGPS would be significantly faster than with GPS.

The command sequence for AGPS:
AT+CEREG=5
AT+CFUN=1
AT#XNRFCLOUD=1
AT#XAGPS=1,1

The command sequence for GPS:
AT+CEREG=5
AT+CFUN=31
AT#XGPS=1,1

The tests were carried out statically, without movement.

[Roman1982]

what the sequence ? 

can you please advice the sequence for example : 

once in 4 hours we need perform an assistance table load .

for doing this we need to use L 

AT+CEREG=5
AT+CFUN=1
AT#XNRFCLOUD=1
AT#XAGPS=1,1

and check the status of update with the next command:

XXXXXXXX 

in case the tables are update we suppose to use : 

AT+CEREG=5
AT+CFUN=31
AT#XGPS=1,1 

in order to have a fast lock 

please advice the sequence 

[Håkon Alseth]

Hi,

 

Roman1982 said:

AT+CEREG=5
AT+CFUN=1
AT#XNRFCLOUD=1
AT#XAGPS=1,1

This sequence will fetch AGPS from nrfcloud, and then start the GPS.

Roman1982 said:

in case the tables are update we suppose to use : 

AT+CEREG=5
AT+CFUN=31
AT#XGPS=1,1 

This will activate GPS (without changing the LTE permissions), and start the GPS directly (ie. no AGPS fetching from nRFCloud).

 

Note that you are continuously running the GPS now, as per the documentation:

https://developer.nordicsemi.com/nRF_Connect_SDK/doc/2.0.0/nrf/applications/serial_lte_modem/doc/GNSS_AT_commands.html#run-gnss

 

Kind rergards,

Håkon