MQTT Not Receiving Subscribe Message for 30+ Seconds

RE: MQTT Not Receiving Subscribe Message for 30+ Seconds

Hakon — Thu, 13 Feb 2025 09:20:40 GMT

From modem team discussion;

"Both cells customer mentions seem to be usable from L1 point of view (Pagings received in RRC Idle and RRCConnectionReleases received in RRC Connected mode)."

"Cell PCI 354 is clearly weaker and SNR is worse. This cell is anyway selected always by the cell search/init sync algorithm after RRC Connection. In RRC Idle re-selection algorithm then changes back to better cell PCI 406. This is most likely normal behavior as both cells are good enough."

"NMEAS sees about identical RSRP and RSRQ for PCIs 354 and 406 - they fluctuate mostly within +-3 dB. In the last quarter of the log PCI 354 has clearly worse RSRP/RSRQ few times. So yes - you would see many reselections between the two."

"After changing to PCI 406 no pages are received for the device until first mobile originated connection. It seems that network is not sending DL data to correct tower. Or we are missing pages. "

Ok, so UE is camped to better cell when data is not received. UE receives pages for other devices and SNR is >0 so it’s very unlikely that UE would miss pages. So, most probably the reason is like you mentioned: “It seems that network is not sending DL data to correct tower”

"UE is connected to PCI 354 and after RRC Connection is released, UE changes to PCI 406 so likely NW keeps sending pages for UE only to PCI 354 and not for 406. Sounds like NW configuration problem."

"According to cellmapper.net both cells are in the same tower 442 near St. Gertrude's New Church, Riga. The strange thing is that in the same tower there is cells 354, 355, 356 forming probably 3 different sectors - and in addition - cell 406. Might be a misconfiguration problem on operator side."

RE: MQTT Not Receiving Subscribe Message for 30+ Seconds

Hakon — Mon, 10 Feb 2025 12:43:44 GMT

Thank you very much.

RE: MQTT Not Receiving Subscribe Message for 30+ Seconds

Eizens — Thu, 06 Feb 2025 15:10:50 GMT

devzone.nordicsemi.com/.../2870.modemtraces_5F00_test1.bin

RE: MQTT Not Receiving Subscribe Message for 30+ Seconds

Eizens — Thu, 06 Feb 2025 15:10:37 GMT

Hello, I added trace .bin file.

RE: MQTT Not Receiving Subscribe Message for 30+ Seconds

Hakon — Thu, 06 Feb 2025 15:05:08 GMT

Modem team will need a modem trace for further investigations.

RE: MQTT Not Receiving Subscribe Message for 30+ Seconds

Hakon — Tue, 04 Feb 2025 16:12:13 GMT

Hello,

[quote user=""]I found one more interesting thing. The modem is constantly switching between two towers. The SNR of one tower is somewhere between 8 dB (fair) and 10 dB (good), while the other tower's SNR ranges from -5 dB to 0 dB (poor). When the device missed the message, it was connected to the tower with poor SNR. This could explain why the MQTT message was not received. [/quote]

That seems plausible. I will confirm with the modem team.