NRF9160 DK geolocation through LTE

[MaximHunko]

Hey NordicSemi.
In my new project, I use DK NRF9160 and I need to determine the location. Since hardware GPS does not work, I decided to use the detection of coordinates through LTE towers.
Used of at_client and LTE Link Monitor, I received coordinates, which have an error of 500 meters.
But I need to know more precisely the position of my device.
When reading your documentation, I realized that this can be done with the command AT% NBRGRSRP.
Could you tell me how I can use the data that I receive in response to this command in conjunction with http://locationapi.org?

I tried the AT%NBRGRSRP command and got this result...
%NBRGRSRP: 334,5815,47,380,5815,38,488,5815,38,17,5815,36

http://locationapi.org for 4 LTE towers has next format:
{
"token": "XXXXXXXXXXXXX",
"radio": "lte",
"mcc": AAA,
"mnc": BBB,
"cells": [{
"lac": CCC,
"cid": DDD
}, {
"lac": EEE,
"cid": FFF
}, {
"lac": GGG,
"cid": KKK
}, {
"lac": LLL,
"cid": MMM
}],
"address": 1
}

[Bjørn Kvaale]

I sent another PM on DevZone now.

[Erik]

Hi Bjørn. I'm working on the same problem: that I'm not available to find TAC/LAC and Cell id for other than the connected tower. I'm also having problem finding the Physical Cell ID (from AT%NBRGRSRP) for the connected tower? Could you clarify on this?

[Bjørn Kvaale]

Hei Eirik! I have tested this myself & like you have noticed, I was only able to find the TAC/LAC & cell ID for the connected tower in the link monitor app on the right hand side.

While running the latest LTE-M1 FW, which can be download here, I did the following:

After you flash the at_client code, use the link monitor app from nrf connect for desktop & connect to the base station, you can run the following command: AT%NBRGRSRP

You should then get a response similar to what I received:

%NBRGRSRP: 51,6400,63,52,6400,63,299,6400,61,298,6400,58,262,6400,57,53,6400,54,123,6400,48

As shown in the at_commands pdf documentation, this command returned 7 nearby cell towers, with their respective cell ID, EARFCN & RSRP values. Cell 1 has a Cell ID of 51, an EARFCN of 6400, an RSRP of 63 dBm, cell 2 has a cell ID of 52, an EARFCN of 6400 & an RSRP of 63 dBm, etc.

I used the regular iBasis SIM card to test.

[Erik]

I'm now running v0.6.8 and get the same results as you (and the same as with 0.6.6). The ID I get from AT%NBRGRSRP only returns the Pysical-cell-id, and for positioning purposes I need a set of cell-id (not physical) for doing position requests (https://locationapi.org/api#documentation). 

I might be misunderstanding the limitations of the cellular network, that it is only possible to get the cell-id from the currently connected tower?

[Bjørn Kvaale]

I am not sure if this is a limitation of the LTE spec itself or our implementation, but it seems there is a current limitation that you can only receive the cell ID of the base station you are currently connected to. Like you mention, the physical cell ID is not the same as the set of cell IDs found from the AT%NBRGRSRP command. I have searched through the AT command pdf, but I only found the CEREG command that returns the cell ID of the base station it is attached to.