Thingy:91 Asset Tracker V2 GNSS doesn't get a fix when connecting to a specific operator

[peng.cheng]

Hi,

Hope everything is fine with you!

There are three operators covering my workplace,

24007 tele2 --- PSM eDRX good ---
24008 Telenor --- PSM eDRX not supported ---
24001 telia --- PSM eDRX not supported ---

When I say `not supported`, I mean there is output `PSM parameter update: TAU: 3240, Active time: -1`.

I am working with GNSS recently, and found a strange issue,

when the thingy:91 connects to 24001, GNSS will fail to get a fix with a high possibility, around 3/4 GNSS location service fails,

but when thingy:91 connects to 24007, GNSS will always get fixes successfully.

At first, I think it could be that 24001 doesn't support PSM/eDRX, this will affect the GNSS because GNSS shares the same antenna with the LTE-M.

But then I found when thingy:91 connects to 24008, it still can get location fixes continuously and successfully.

I checked the paging time window by using `AT%XPTW?`, it is the same for both 24001 and 24008.

So my question is what is the key point to affect the GNSS function in this case for 24001 and 24008?

Any help will be much appreciated! Thanks!

BR,

Peng

[Øyvind]

Hello Peng, 

With what SIM card are you testing the connection? Are you able to provide the logs from Asset Tracker v2 along with modem traces? 

Thanks. 

Kind regards,
Øyvind

[peng.cheng]

Hi Øyvind ,

Thank you for your quick reply!

The SIM card is the iBASIS purchased together with the Thingy:91 board.

I tested in another place today, on top of an 8-floor building inside of the city. The situation is a bit different,

when the device connects to 24001, still no GNSS fixes, usually only 1 satellite is tracked.

when the device connects to 24007, several satellites are tracked, but still no GNSS fixes.

The attachments:

trace-2023-05-09T14-23-34.865Z_24001.bin is the trace log when the device connects to 24001,

trace-2023-05-09T14-27-11.143Z_24007.bin is the trace log when the device connects to 24007,

thingy91_24001_24007_all_fails_together_with_tracelog.txt is the application log with debug enabled, you can find `AT+COPS=1,2,"24007"`, this is the manual switch of the network.

BR,

Peng

thingy91_24001_24007_all_fails_together_with_tracelog.txt

trace-2023-05-09T14-23-34.865Z_24001.bin

trace-2023-05-09T14-27-11.143Z_24007.bin

[peng.cheng]

BTW, about the trace log, can I decode it with some tools? or it is only available for the Nordicsemi?

[Øyvind]

peng.cheng said:

BTW, about the trace log, can I decode it with some tools? or it is only available for the Nordicsemi?

You can use the Trace Collector v2 found in the nRF Connect for Desktop. This will allow you to convert the file to PCAP which you can open in Wireshark. 

peng.cheng said:

The SIM card is the iBASIS purchased together with the Thingy:91 board.

Could you please try with a local SIM i.e. Telenor or Telia SIM. It might be that the iBasis SIM is not allowed. Have a look at the iBasis eSIM International Coverage Update. 

[peng.cheng]

Hi,

Thank you for the Trace Collector v2 tip.

I can try to get a local SIM, this may cost some time.

But correct me if I am wrong, but PSM seems not very important in my case (though I don't trust my gut feeling in this case).

Thingy:91 can get GNSS fixes when connecting to 24008 which doesn't support PSM in a residential area that is a bit far away from the city center (the first test place).

But in the meantime, Thingy:91 can't get GNSS fixes when connecting to 24007 which supports PSM in some places in the city center (the second test place). ([01:33:03.299,591] [0m<dbg> modem_module: lte_evt_handler: PSM parameter update: TAU: 1152000, Active time: 20)

So I am a bit confused which is the key point that affects the GNSS. Could you please help to check the logs that if there is something wrong? Thanks!

BR,

Peng

[Øyvind]

Sorry, I got too focused on the eDRX issue. 

It is important to know that the GPS receiver operation is time multiplexed with LTE modem, and it is possible to use the GPS and QZSS receiver to obtain position either while the LTE is in RRC Idle mode or power saving mode (PSM), or when the LTE modem is completely deactivated. Also note, GPS signals do not usually penetrate ceilings or other structures. For best GPS performance, Nordic Thingy:91 should be used outside in an open space, far from sources of interference and other structures that may block the signals.

Where are you performing the tests of the GPS? 

[peng.cheng]

No worries!

I tested in mainly two places,

one is  in a residential area that is a bit far away from the city center,

the other is on the top floor of an 8-floor building near the city center,

both two places are outside places and have no visual blocks to the sky.

[Øyvind]

Hello again, our R&D team have looked at the modem traces and your case. 

Their initial response is that the GNSS reception is not good. Could you give a more precise description of where you are testing? Are there any walls around you, or metal, etc. The GNSS receiver alone is quite sensitive, and the antenna on the Thingy:91 is shared between the LTE and GNSS, which can cause lower performance.

If possible, could you test with an external GNSS antenna connected to J2, as shown in the hardware description of the Thingy:91.

Before doing that, one thing to check is the LNA configuration, %XMAGPIO, which should be something like this:

AT%XMAGPIO=1,1,1,7,1,746,803,2,698,748,2,1710,2200,3,824,894,4,880,960,5,791,849,7,1565,1586

Note that this should automatically be configured when building a project for thingy91_nrf9160_ns

[peng.cheng]

Hi,

Thanks for your response!

I attached two pictures, they are the Google 3d map of the two places.

Place 1 is in a residential area that is a bit far away from the city center,

Place 2 is on the top floor of an 8-floor building near the city center.

LNA configuration is exactly the same as yours.

AT%XMAGPIO?
%XMAGPIO: 1,1,1,7,1,746,803,2,698,748,2,1710,2200,3,824,894,4,880,960,5,791,849,7,1565,1586
OK

I don't have an external GPS antenna at my side, let me see if I can find one.

BR,

Peng

[peng.cheng]

Hi Øyvind ,

Sorry for the late update. It took me some days to get an external GPS antenna.

I am using MOLEX 206640, it works much better than without it, and it can get a GNSS fix with a very high possibility.

In the meantime, I tested Asset Tracker v2 on the nrf9160DK board, it works perfectly, and I checked the external GPS antenna is not configured.

# CONFIG_MODEM_ANTENNA_GNSS_EXTERNAL is not set
CONFIG_MODEM_ANTENNA_AT_MAGPIO="AT%XMAGPIO=1,0,0,1,1,1574,1577"
CONFIG_MODEM_ANTENNA_AT_COEX0="AT%XCOEX0=1,1,1565,1586"

As both boards run the same firmware and application and they both share the antenna with the LTE module, I think it could be the antenna the root cause, then I compared the two boards, the nrf9160DK has an ethertronics P822601 antenna, and Thingy:91 has an NN03-310 antenna.

So I did some wild guesses, maybe it is the NN03-310 is not very good at receiving GPS signals, sensitivity or the SNR is not so good? I am no expert on the antenna area. But do you have some test reports for those two antennas?

Thanks!

BR,

Peng

[Øyvind]

Hi Peng, 

Have been discussing the issue with our GNSS experts. The antenna on the nRF9160 DK is much better than the antenna on the Thingy:91, this is a know issue and is most likely due to the size. That said, the Thingy:91 should be fully usable with is NN03-310 antenna from Ignion. What version of the Thingy:91 are you using? Could  there be an issue with the board itself?

I'm trying to find more information on the test reports.

Kind regards,
Øyvind

[Øyvind]

Sorry, a small correction on the DK. This has a dedicated GNSS antenna (A2), which means there are two antennas on the DK while only one combined on the Thingy:91