AGPS not locking even after getting enough healthy satellites

RE: AGPS not locking even after getting enough healthy satellites

Didrik Rokhaug — Wed, 07 Apr 2021 13:55:44 GMT

[quote user="arshdeep"]Also, do you have any documentation of the algorithm used to get data from AGPS, like how much data does it take to download the information, how many times does it download the data , power consumption etc??[/quote]

How much data and how often depends a bit on your use case.

The modem will only request the data it needs, so e.g. if it has a valid almanac, it will not request the almanac again.

If I remember correctly, it will request the ephemeris every hour.

How much data is downloaded also depends on the format. If you are using the SUPL client, the same data will result in more bytes downloaded compared to AGPS through nRF Connect for Cloud.

I don't have any exact numbers, but this is what I have on the SUPL client:

- Cold start, All/most ephemeris/almanac data: 10s of kB

- Warm start, some ephemeris data: 1-10kB

- Hot start, no new data needed: 0B

When using nRF Connect for Cloud, the cold start data consumption is ~17kB. That includes the TLS handshake, which uses ~10kB, and can be avoided if you already are connected to the cloud.

RE: AGPS not locking even after getting enough healthy satellites

arshdeep — Fri, 02 Apr 2021 01:18:28 GMT

very well, disabling the LTE worked. Can you please also answer the second part of the question

Also, do you have any documentation of the algorithm used to get data from AGPS, like how much data does it take to download the information, how many times does it download the data , power consumption etc??

Thanks,

RE: AGPS not locking even after getting enough healthy satellites

Didrik Rokhaug — Wed, 31 Mar 2021 13:53:38 GMT

Hi,

In your log I notice that you are not using PSM and/or eDRX.

The nRF9160 is not able to run GPS and LTE at the same time, but instead have to run the GPS when the LTE stack is sleeping and not using the radio.

While the GPS is able to run during the short idle intervals when the device is in RRC Idle, they are usually not enough for it to aquire a fix.

Instead, you should enable PSM or eDRX (which might not be possible with a roaming SIM card such as iBasis SIM cards), or you can disable LTE with AT+CFUN=20.

When you have gotten your fix, you can re-enable LTE with AT+CFUN=21.

Best regards,

Didrik