Geolocalisation via LTE when not connected

RE: Geolocalisation via LTE when not connected

Markus Tacker (he/him) — Wed, 07 Apr 2021 11:51:01 GMT

I understood that you wanted to know how modem data is read, this happens in the modem_info library: developer.nordicsemi.com/.../modem_info.html

RE: Geolocalisation via LTE when not connected

chouquette_fr — Wed, 07 Apr 2021 11:34:57 GMT

Hello, according to the documentation, I can only retrieve the cell ID of the cell I am connected to, I think I didn't understand your answer,

Thank you for your help and time,

RE: Geolocalisation via LTE when not connected

Markus Tacker (he/him) — Tue, 06 Apr 2021 15:14:34 GMT

Information about neighboring cells from the modem is received with notifications, you can have a look at the modem_info library, which handles the %CESQ notifications: developer.nordicsemi.com/.../modem_info.html

RE: Geolocalisation via LTE when not connected

chouquette_fr — Tue, 06 Apr 2021 15:08:15 GMT

Thank you for this answer, does it mean that it is not in this function that the processor reads the data sent from the radio antenna ? Then, where does it happen ?

Thank you for your time

RE: Geolocalisation via LTE when not connected

Markus Tacker (he/him) — Tue, 06 Apr 2021 09:26:59 GMT

The k_sem_take(&link, <duration>) blocks the execution of the rest of the function until the semaphore is released (either by k_sem_give(&link); or by timeout). If not connected, the function will then retry to connect.

RE: Geolocalisation via LTE when not connected

chouquette_fr — Fri, 02 Apr 2021 08:57:43 GMT

Hello Mister Tacker, I am very sorry that I didn't answer you earlier. I am still interested if you have a solution, I am now trying to use the LTE LC module to achieve retrieving the cell information without being connected. Unfortunately, this is still not working. From what I understood, the function and more specifically the line doing the connection is this:

static int w_lte_lc_connect(bool blocking)

{

int err;

bool retry;

if (!is_initialized) {

LOG_ERR("The LTE link controller is not initialized");

return -EPERM;

}

k_sem_init(&link, 0, 1);

do {

retry = false;

err = lte_lc_system_mode_set(sys_mode_target);

if (err) {

return err;

}

err = lte_lc_normal();

if (err || !blocking) {

return err;

}

err = k_sem_take(&link, K_SECONDS(CONFIG_LTE_NETWORK_TIMEOUT));

if (err == -EAGAIN) {

LOG_INF("Network connection attempt timed out");

if (IS_ENABLED(CONFIG_LTE_NETWORK_USE_FALLBACK) &&

(sys_mode_target == sys_mode_preferred)) {

sys_mode_target = sys_mode_fallback;

retry = true;

err = lte_lc_offline();

if (err) {

return err;

}

LOG_INF("Using fallback network mode");

} else {

err = -ETIMEDOUT;

}

} while (retry);

return err;

}

However, I didn't understand what is happening inside the k_sem_take function.

Thank you for your help, Best regards,

RE: Geolocalisation via LTE when not connected

chouquette_fr — Fri, 02 Apr 2021 08:37:36 GMT

Hello, i use this firmware: mfw_nrf9160_1.2.3

RE: Geolocalisation via LTE when not connected

Markus Tacker (he/him) — Fri, 26 Mar 2021 09:34:07 GMT

I suspect this to be the issue:

Neighboring cell measurements are valid and available only when neighbors are being monitored, which means that the strength and quality of the current cell signal do not meet the network configured level. For more information, see the requirements in 3GPP TS 36.304.

To save energy, nRF9160 does not search and measure neighboring cells for mobility purposes if the level and quality of the serving cell signal are above the thresholds defined by the network.

If you are in areas with good cell coverage, but e.g. deliberately do not want to connect (or can't because of your SIM), you don't get neighboring cell information.

RE: Geolocalisation via LTE when not connected

Markus Tacker (he/him) — Fri, 26 Mar 2021 09:30:14 GMT

Hm, are you on the latest modem firmware? And it could be that it only works if connected to LTE, however I am not sure about the details.

RE: Geolocalisation via LTE when not connected

chouquette_fr — Fri, 26 Mar 2021 09:17:55 GMT

Unfortunately, I didn't manage to run this command (I am doing tests on the LTE link monitor consol), I get response "OK" but no information is displayed

RE: Geolocalisation via LTE when not connected

Markus Tacker (he/him) — Fri, 26 Mar 2021 09:16:24 GMT

You could run AT%NBRGRSRP and store that data locally, then send it to the cloud once connected and have the cloud resolve the cell locations.

RE: Geolocalisation via LTE when not connected

chouquette_fr — Fri, 26 Mar 2021 09:13:25 GMT

I would like to record the different positions of the device and then send them to the internet once I am connected again.

RE: Geolocalisation via LTE when not connected

Markus Tacker (he/him) — Fri, 26 Mar 2021 09:09:56 GMT

Yeah, that's what I suspected. However there are tens of thousands of cells per country, so knowing the cellId wouldn't help you much to further improve location information beyond the country if you have no connection at all.

RE: Geolocalisation via LTE when not connected

chouquette_fr — Fri, 26 Mar 2021 09:07:30 GMT

I can use AT+COPS? to determine the MCC+MNC of the device even when not connected. However, I didn't succeed in getting information about cell id.

RE: Geolocalisation via LTE when not connected

Markus Tacker (he/him) — Thu, 25 Mar 2021 10:39:16 GMT

I think this case is a little more challenging: from what I understand in this case the device has no internet connection at all, so while it is able to get cell information from the modem, it's not able to send this information to the cloud for processing there.

Nevertheless OP is interested in knowing the location of the device.

The information about the cell that the modem provides includes the MCC (mobile country code), and you can use at least this information "offline" / on the device to determine in which country the device currently resides.

I am not sure however, if this information (or AT+COPS?) is available if not connected to LTE at all.

RE: Geolocalisation via LTE when not connected

Øyvind — Thu, 25 Mar 2021 10:25:40 GMT

Hello,

Have a look at the latest answer from Markus Tacker (he/him) here:
https://devzone.nordicsemi.com/f/nordic-q-a/73139/scanning-for-all-nearby-base-stations-with-nrf9160dk

Kind regards,
Øyvind