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Cell keeps updating on nrf9160

Hello,

We are doing some network quality tests on LTE-M with PSM off and notice loss on UDP between 0% to sometimes 15% on simple udp messages sent every 10 seconds from the server to a client running on thingy91.

We noticed that when higher loss occurs we get more events of LTE_LC_EVT_CELL_UPDATE. The cell keeps changing between few cells in the area, their description according to cellmapper.net is attached.

Questions:
1. Is it possible that cell changing can induce loss on packets coming from server to client?
Something like the packet is kept on the cell until the DRX passes and device checks every 1.28 s, but if device changes cell then packet is lost?

2. Is there any way to make the device stop searching?

Thanks

eNB ID 10253 - LTE
MCC / MNC / Region	226 / 10 / 10103
Bands	3, 7
First Seen	Mon, Mar 25, 2019
Last Seen	Thu, Feb 3, 2022
5G ENDC Available	Yes
Approximate Address	
Hotel Ibis Styles, Strada Căpitan Aviator Alexandru Șerbănescu, Aviației, Sector 1, Bucharest, 014196, Romania

Cell Identifier	2624769
System Subtype	LTE
PCI	414 (138/0)
Bandwidth	20 MHz
EARFCN	1600
Maximum Signal (RSRP)	-77 dBm
Direction	E (103°)
First Seen	Wed, Aug 21, 2019
Last Seen	Sat, Jan 15, 2022
5G ENDC Available	Yes
Bandwidth*	20 MHz
Uplink Frequency	1750 MHz
Downlink Frequency	1845 MHz
Frequency Band	DCS (B3 FDD)




==================================================================================
eNB ID 11251 - LTE
MCC / MNC / Region	226 / 10 / 10103
Bands	3, 7
First Seen	Tue, Jul 28, 2015
Last Seen	Fri, Feb 18, 2022
5G ENDC Available	Yes
Approximate Address	
7, Strada Ocheanului, Aviației, Sector 1, Bucharest, 014364, Romania

Cell 2
Cell Identifier	2880258
System Subtype	LTE-A
PCI	169 (56/1)
Bandwidth	20 MHz
EARFCN	1600
Maximum Signal (RSRP)	-66 dBm
Direction	NW (309°)
Max / Avg DL Speed	16 Mbps / 16 Mbps
First Seen	Tue, Jul 28, 2015
Last Seen	Mon, Oct 4, 2021
5G ENDC Available	Yes
Bandwidth*	20 MHz
Uplink Frequency	1750 MHz
Downlink Frequency	1845 MHz
Frequency Band	DCS (B3 FDD)



==================================================================================
eNB ID 15481 - LTE
MCC / MNC / Region	226 / 10 / 10118
Bands	3, 7
First Seen	Mon, Jul 20, 2015
Last Seen	Fri, Feb 11, 2022
5G ENDC Available	Yes
Approximate Address	
Strada Câmpul Pipera, Henri Coandă, Voluntari, Ilfov, 020112, Romania

Cell 2
Cell Identifier	3963138
System Subtype	LTE-A
PCI	166 (55/1)
Bandwidth	20 MHz
EARFCN	1600
Maximum Signal (RSRP)	-69 dBm
Direction	NE (55°)
First Seen	Tue, Jul 28, 2015
Last Seen	Sat, Sep 26, 2020
Bandwidth*	20 MHz
Uplink Frequency	1750 MHz
Downlink Frequency	1845 MHz
Frequency Band	DCS (B3 FDD)



==================================================================================
eNB ID 14001 - LTE
MCC / MNC / Region	226 / 10 / 10103
Bands	3, 7
First Seen	Tue, Jul 28, 2015
Last Seen	Fri, Feb 25, 2022
5G ENDC Available	Yes
Approximate Address	
Nord City Tower, 1/VII, Bulevardul Pipera, Voluntari, Ilfov, 077190, Romania

Cell 3
Cell Identifier	3584259
System Subtype	LTE
PCI	197 (65/2)
Bandwidth	20 MHz
EARFCN	1600
Maximum Signal (RSRP)	-65 dBm
Direction	NE (50°)
First Seen	Tue, Jul 28, 2015
Last Seen	Fri, Feb 18, 2022
5G ENDC Available	Yes
Bandwidth*	20 MHz
Uplink Frequency	1750 MHz
Downlink Frequency	1845 MHz
Frequency Band	DCS (B3 FDD)

Parents Reply
  • Hello Einar,

    Thanks for checking this!

    Ok understood, makes sense!

    Is there any way to read the current signal strength the modem gets? This would both confirm the problem and also help us choose an antenna in the future.


    About UDP vs TCP, indeed, thanks for the suggestion! At this stage we want to know what the raw network quality is (both loss and delay), and TCP would basically hide the loss into delay or other issues as seen from the app level.


    Thanks,
    Nicolae

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