EP06-A 'AT+QLTS' failing to return result

IoT Modules LTE-A Module
1

@Kerr.Yang-Q

I am using EP06-A (version: EP06ALAR02A08M4G).

I am having issues with ‘AT+QLTS’ failing (only ever returning “” or OK) after successful registration/connection/activation even though other network cmds like ‘AT+COPS?’, ‘AT+QNWINFO’, ‘AT+CREG?’, ‘AT+CEREG?’, ‘AT+CGREG?’, ‘AT+QENG=“servingcell”’, ‘AT+CGATT?’, etc. all return responses that show a successful network connection and activated PDP session.

I have tried ‘AT+QLTS’ as well as all of the ‘AT+QLTS={0,1,2}’ set commands. All return “” or OK.

‘AT+CCLK?’ returns the correct network synchronized time that matches my host computer. But I believe that this is a result of the system using the active internet connection to update the system via NTP and then sync the modem’s RTC to the system local time. So it seems to me that either there is some issue with the ‘AT+QLTS’ command itself or something about the module’s ability to use NITZ information that is causing issues post-registration.

Are there any known issues around this? Or any sequence of commands to mitigate this behavior (trying to avoid a firmware update if possible).

2

More likely, the modem has NITZ active. Like I do:

AT+CTZU?
+CTZU: 1

This uses date-time and timezone info broadcast by the cellular network.

3

But ‘AT+QLTS’ never returns a result other than “” or OK even through the device has completed network registration. Wouldn’t that have been updated if NITZ packets were being parsed correctly by the module?

4

Also, I know that the system is being updated by NTP because I have been able to capture those packets being sent/received from various NTP servers and viewed the PCAPs in wireshark. That is not to say that NITZ is not happening/working, just that I know NTP is being used at some point.

I have so far been unable to capture the RRC messages I want. I am working on that.

5

I know that the module can be updated via NITZ using the MM:Information NAS msg (RRC: downlinkDirectTransfer + MM:Information or GMM:Information NAS msg (RRC: downlinkDirectTransfer + GMM:Information) (MM & GMM msgs defined in 3GPP TS 24.008 9.2.15a and 9.4.19 respectively) which contain 3GPP TS 24.008 sections 10.5.3.8 Time Zone and 10.5.3.9 Time Zone and Time.

I would just have expected ‘AT+QLTS’ to return the content of those fields if NITZ was properly working. Unless I am misunderstanding something (which is absolutely possible).

6

You’d think so, but the modem is not in a normal state given that CME ERROR.

AT+CTZU? will tell you if NITZ is active.

7

‘AT+CTZU?’ returns ‘1’. Which tells me that the option to automatically update the timezone using NITZ is enabled. But I am not sure that it is working. If that makes sense

8

AT+CCLK? is an industry-standard 3GPP command while AT+QLTS is Quectel-proprietary.

I put more trust in 3GPP commands.

9

Yeah, I wish I could use AT+CCLK?. But I need AT+QLTS as a verified source of up to date time. AT+CCLK? will always give you a result, even if it is incorrect because the RTC is no longer synced to network time and has deviated.

10

That’s a fair point. I don’t have experience in using AT+QLTS other than a test minutes ago.

11

I wish I had more experience with ‘AT+QLTS’ lol. Thank you for looking into it and testing it out. I’ll try to remember to update if I figure something out.

12

I apologize for the confusion added to this post. I left in part of a different post regarding issues I am having with ‘AT+COPS=?’ returning ‘CME ERROR: 3’.

‘AT+QLTS’ is NOT throwing cme errors but rather just returning an empty result even after successful network registration.