Can a weak cell signal prevent connecting to nRFCloud.com

[SteveHx]

It's looking more and more like a lot of my problems relate to a weak cell signal. Is the RF front end on the devkit known to be inferior to a normal cellphone? My personal cellphone gets 1-2 bars when on my desk, and 2-3, sometimes 4 bars when held up next to where I have the units about 4' above the desk. I will do some digging into commands to check this theory, but is there any easy way to augment the RF front end? In the end applications, these will need to work in areas with less than ideal cellphone coverage.

[Charlie]

Hi Steve,

Cellular network (LTE-M/NB-IoT) is different with 2G/3G/LTE network used by a cellphone, some cell station may only deploy 2G/3G/LTE for mobile phone, so it does not have so much meaning to compare them directly even at same location.

You can read out RSRP with AT+CESQ command. The Reference Signal Received Power (RSRP) is the average power level received from a single reference signal in an LTE (Long-Term Evolution) network. The RSRP is measured in dBm (decibels relative to 1 milliwatt).

In terms of signal quality, the higher the RSRP, the better the signal quality. For example, -75 dBm is better signal quality than -105 dBm. Here is a general guideline for RSRP levels:

• Excellent signal: -75 dBm or higher
• Good signal: -76 dBm to -85 dBm
• Fair signal: -86 dBm to -100 dBm
• Poor signal: -101 dBm or lower

Please note that these are general guidelines and actual performance can vary based on a number of factors. You can refer to the following source to see how the signal is affected by distance and influence device performance in a real measurement.

(86) LTE-M vs NB-IoT Field Test: How Distance Affects Power Consumption - Blogs - Nordic Blog - Nordic DevZone (nordicsemi.com)

Best regards,

Charlie

[SteveHx]

I can also read RSRP via the Cellular Monitor, if it worked. I get an "Error when creating trace" every time, and it never refreshes the screen. I don't presently have any need for a trace file, and I see no way to disable that nor to redirect it to something with a reasonable path (good grief, 8 levels deep, and hidden away in the Windoze "User" path where I can rarely get to anything). Also, why doesn't Open Serial Terminal automatically connect to the device I'm already connected to? AT+CESQ returns "+CME ERROR: 0". The unit has been powered on for a week or so, and is continuously streaming "%CESQ: 37,1,10,1" to the serial terminal, with some random variability in the numbers.

Wes Cherry told me to reprogram it with the Serial LTE Modem firmware to restore it to "out of the box" functionality, which I have done. Thus far very unimpressed with the usability of these units, and needing to commit to something soon for a proposed 500 pc pilot rollout in 2024Q4, and potentially 6 figure (units) rollout next year.

[SteveHx]

If I reprogram the nRF9161 devkit with the Asset Tracker sample, it promptly shows up on nRFCloud.com. It connects, and refreshes its position etc. appropriately. It also responds apparently correctly to all AT commands I need, EXCEPT the most critical final steps, using AT#XNRFCLOUD=n. If I then reprogram with the Serial LTE Modem, it no longer connects with nRFCloud.com, but generates the errors shown above. So a weak cell signal is not the problem.

I beg you again, could we PLEASE just make this work so I can show that I can get a message up to nRFCloud.com?

[SteveHx]

I just received 4 newly purchased Thingy:91 boards. Trying to bring up the first one exactly per the instructions. Step 2 says "Verify and activate the SIM card". No clue where, but I hunted around nRFCloud and found what appears to be the correct page. It wants an 18- or 19-digit identifier. The only thing printed on the SIM card is two rows of 10 digits each, so 20 digits total. Truncating from either end still does not get a number that the SIM activation within nRFCloud likes. When I scratch off the number area on the carrier, I see PIN 0000 and PUK 87534445. I can't get anything to work. This is supposed to just power up and go. What gives???

[SteveHx]

I bought 4 new units directly from DigiKey. I hit roadblocks at every turn:

1) The instructions say to activate the supplied iBasis SIM card. It wants an 18- or 19-digit ID number printed on the card. The supplied card shows two uniform rows of 10 digits each. Where's the magic number?

2) I swapped the SIM card with one that came with an nRF9161DK, "onomondo". Now I can get the Thingy:91 to connect to nRFCloud.com. The location map didn't show up until I moved things around on the page. The location shown textually is at least in the right county (barely). I am highly skeptical of the reported temperature of 35.2C. I wouldn't hang around long at that temp! Humidity of 33% is likewise suspect.

3) Attempting the AT command sequence recommended to get a message up to nRFCloud.com works fine right up until the command to activate the message mode. Here's the sequence I previously saved, that actually worked at one point on one specific nRF9161DK.

Command                    Response

AT+CEREG=5
                    OK
AT+CPSMS=0
                    OK
AT+CEDRXS=0
                    OK
AT+CFUN=1
                    OK
                    +CEREG: 2,"5304","02AD7110",7
                    +CEREG: 5,"5304","02AD7110",7,,,"11100000","11100000"
AT+CGDCONT?
                    +CGDCONT: 0,"IP","onomondo","100.81.98.150",0,0
                    OK
AT#XNRFCLOUD=1
                    OK
                    #XNRFCLOUD: 1,0
AT#XNRFCLOUD=2
                    OK
{"msg":"my message"}+++
                    +XDATAMODE: 0

Then repeat last sequence of AT#XNRFCLOUD=2 and {msg} as needed.

Here's a transcript of the same sequence using Thingy:91.

I continue to be thoroughly frustrated by non-working instructions, and my clients are getting impatient for results.

[SteveHx]

Also, the instructions keep referring to an "LTE Link Monitor". Jumping to the link given in the instructions, it appears to be an obsolete applet for nRF Connect for Desktop. I presume it's been superceded by Cellular Monitor, which however lacks the "Auto device/port filter option" referenced in the instructions.