reception within a basement?

[Ronald]

For a customer we're trying to see if we can build an IoT solution with nrf9160 to periodically send a status update to the cloud. Unfortunately, the devices are typically in the basement. Connecting from a basement over LTE-M/NB-IoT with nrf9160 has been unsuccessful sofar. We tested in three basements with no luck (normal house basement and two office building garages). As this is one of the main use cases for IoT: stuff in a basement sends a status update once in a long time we were quite surprised that it didn't work. Any hints you can give us? The antenna we tried is an 20 cm tall LTE antenna. Is this a problem with the providers not enabling NB-IoT/LTE-M features for wall-penetration? I failed to find any options to boost the receive or send amplifiers? Are there better antennas that we should try?

[Martin Lesund]

Hi Ronald,
When it comes to IoT devices that are located underground such as basements etc. It is recommended to use the NB-IoT technology since it provide a much better penetration.

From what I read you are using a custom board? Or are you testing with the nRF91DK?

How are you doing these tests?

I would recommend just running the AT Client sample (which is also included as a precompiled .hex file in the .zip folder in the nRF91DK page).
Please make sure you have the latest modem firmware.

Please send a serial output log using the AT Client sample getting a sucessful connection over ground via NB-IoT, and then go underground and follow the same steps.

Best regards,
Martin L.

[Ronald]

I tried it with both our custom board and the eval board.

here is a part of our log: 

00> D: Sending AT command to set system mode: AT%XSYSTEMMODE=0,1,1,0
00> Sending command AT%XSYSTEMMODE=0,1,1,0
00> Sending command AT%XSYSTEMMODE?
00> Sending command AT+CEDRXS=2,5,"1001"
00> Sending command AT+CEREG=5
00> Sending command AT+COPS=0
00> Sending command AT+CGDCONT=0,"IPv4v6","iot.1nce.net"
00> I: PDP Context: AT+CGDCONT=0,"IPv4v6","iot.1nce.net"
00> Sending command AT+CSCON=1
00> D: Sending AT command to set system mode: AT%XSYSTEMMODE=0,1,1,0
00> Sending command AT%XSYSTEMMODE=0,1,1,0
00> Sending command AT+CFUN=1
00> D: +CEREG notification: +CEREG: 2,"FFFE","FFFFFFFF",9,0,0,"11100000","11100000"
00>
00> D: TAU: -1 sec, active time: -1 sec
00>
00> D: +CEREG notification: +CEREG: 2,"BEC6","0145E367",9,0,0,"11100000","11100000"
00>
00> D: TAU: -1 sec, active time: -1 sec
00>
00> D: +CSCON notification
00> D: +CEREG notification: +CEREG: 4,"BEC6","0145E367",9,0,15,"11100000","11100000"
00>
00> D: TAU: -1 sec, active time: -1 sec
00>
00> D: +CSCON notification
00> D: +CEREG notification: +CEREG: 4,"FFFE","FFFFFFFF",9,0,15,"11100000","11100000"
00>
00> D: TAU: -1 sec, active time: -1 sec
00>
00> D: +CEREG notification: +CEREG: 4,"BEC6","0145E367",9,0,15,"11100000","11100000"
00>
00> D: TAU: -1 sec, active time: -1 sec
00>

The logs with the AT client is coming up.

[Ronald]

eval board + at client in the office (the good case, not the basement. pasting that next)

AT+CFUN?

Sending command 

AT+CFUN?

+CFUN: 1

OK

AT+CGSN=1

Sending command 

AT+CGSN=1

+CGSN: "352656100028862"

OK

AT+CGMI

Sending command 

AT+CGMI

Nordic Semiconductor ASA

OK

AT+CGMM

Sending command 

AT+CGMM

nRF9160-SICA

OK

AT+CGMR

Sending command 

AT+CGMR

mfw_nrf9160_1.2.0

OK

AT+CEMODE?

Sending command 

AT+CEMODE?

+CEMODE: 0

OK

AT%XCBAND=?

Sending command 

AT%XCBAND=?

%XCBAND: (1,2,3,4,5,8,12,13,17,19,20,25,26,28,66)

OK

AT+CMEE?

Sending command 

AT+CMEE?

+CMEE: 1

OK

AT+CNEC?

Sending command 

AT+CNEC?

+CNEC: 24

OK

AT+CGEREP?

Sending command 

AT+CGEREP?

+CGEREP: 1,0

OK

AT+CIND=1,1,1

Sending command 

OK

AT+CEREG=2

Sending command 

OK

AT+CEREG?

Sending command 

AT+CEREG?

+CEREG: 2,5,"CB52","02278E03",9

OK

AT+COPS=3,2

Sending command 

OK

AT+COPS?

Sending command 

AT+COPS?

+COPS: 1,2,"26201",9

OK

AT%XCBAND

Sending command 

AT%XCBAND

%XCBAND: 8

OK

AT+CGDCONT?

Sending command 

AT+CGDCONT?

+CGDCONT: 0,"IP","cdp.iot.t-mobile.nl","10.128.5.215",0,0

OK

AT+CGACT?

Sending command 

AT+CGACT?

+CGACT: 0,1

OK

AT%CESQ=1

Sending command 

OK

AT+CESQ

Sending command 

AT+CESQ

+CESQ: 99,99,255,255,255,255

OK

AT%XSIM=1

Sending command 

OK

AT%XSIM?

Sending command 

AT%XSIM?

%XSIM: 1

OK

AT+CPIN?

Sending command 

AT+CPIN?

+CPIN: READY

OK

AT+CPINR="SIM PIN"

Sending command 

AT+CPINR="SIM PIN"

+CME ERROR: 0

AT+CGDCONT=0,"IPv4v6","cdp.iot.t-mobile.nl"

Sending command 

+CME ERROR: 3

AT+CGDCONT=0,"IPv4v6","cdp.iot.t-mobile.nl"

Sending command 

+CME ERROR: 3

AT+CFUN=4

Sending command 

%CESQ: 44,2,19,2

+CGEV: ME PDN DEACT 0

+CEREG: 0,"CB52","02278E03",9

+CIND: "service",0

+CIND: "roam",0

+CGEV: ME DETACH

%CESQ: 255,0,255,0

%XSIM: 0

OK

AT+CGDCONT=0,"IPv4v6","cdp.iot.t-mobile.nl"

Sending command 

OK

AT+CGDCONT?

Sending command 

AT+CGDCONT?

+CGDCONT: 0,"IPV4V6","cdp.iot.t-mobile.nl","",0,0

OK

AT+CGDCONT?

Sending command 

AT+CGDCONT?

+CGDCONT: 0,"IPV4V6","cdp.iot.t-mobile.nl","",0,0

OK

AT+CGACT?

Sending command 

AT+CGACT?

+CGACT: 0,0

OK

AT+CGACT?

Sending command 

AT+CGACT?

+CGACT: 0,0

OK

AT+CFUN=1

Sending command 

OK

%CESQ: 46,2,19,2

+CEREG: 2,"CB52","02278E03",9

%XSIM: 1

AT+CPIN?

Sending command 

AT+CPIN?

+CPIN: READY

OK

AT+CPINR="SIM PIN"

Sending command 

AT+CPINR="SIM PIN"

+CPINR: "SIM PIN",3

OK

AT+CIMI

Sending command 

AT+CIMI

901405700009565

OK

+CGEV: ME PDN ACT 0,0

+CNEC_ESM: 50,0

+CEREG: 5,"CB52","02278E03",9

AT+CGDCONT?

+CIND: "service",1

+CIND: "roam",1

Sending command 

AT+CGDCONT?

+CGDCONT: 0,"IP","cdp.iot.t-mobile.nl","10.128.4.63",0,0

OK

AT+COPS=3,2

Sending command 

OK

AT+CGACT?

Sending command 

AT+CGACT?

+CGACT: 0,1

OK

AT+COPS?

Sending command 

AT+COPS?

+COPS: 1,2,"26201",9

OK

AT%XCBAND

Sending command 

AT%XCBAND

%XCBAND: 8

OK

AT+CGDCONT?

Sending command 

AT+CGDCONT?

+CGDCONT: 0,"IP","cdp.iot.t-mobile.nl","10.128.4.63",0,0

OK

AT+CGACT?

Sending command 

AT+CGACT?

+CGACT: 0,1

OK

%CESQ: 46,2,25,3

[Ronald]

in the basement with AT client + eval board:

Sending command AT+CFUN?

+CFUN: 0

OK

AT%XSYSTEMMODE=0,1,0,0

Sending command 

OK

AT+CGDCONT=0,"IPv4v6","cdp.iot.t-mobile.nl"

Sending command 

OK

AT+CFUN=4

Sending command 

OK

AT%XSYSTEMMODE=0,1,0,0

Sending command 

OK

AT+CFUN=1

Sending command 

OK

AT+CFUN?

Sending command 

+CFUN: 1

OK

AT+CGSN=1

Sending command 

AT+CGSN=1

+CGSN: "352656100028862"

OK

AT+CGMI

Sending command 

AT+CGMI

Nordic Semiconductor ASA

OK

AT+CGMM

Sending command 

AT+CGMM

nRF9160-SICA

OK

AT+CGMR

Sending command 

AT+CGMR

mfw_nrf9160_1.2.0

OK

AT+CEMODE?

Sending command 

AT+CEMODE?

+CEMODE: 0

OK

AT%XCBAND=?

Sending command 

AT%XCBAND=?

%XCBAND: (1,2,3,4,5,8,12,13,17,19,20,25,26,28,66)

OK

AT+CMEE?

Sending command 

AT+CMEE?

+CMEE: 0

OK

AT+CMEE=1

Sending command 

OK

AT+CNEC?

Sending command 

AT+CNEC?

+CNEC: 0

OK

AT+CNEC=24

Sending command 

OK

AT+CGEREP?

Sending command 

AT+CGEREP?

+CGEREP: 0,0

OK

AT+CGDCONT?

Sending command 

AT+CGDCONT?

+CGDCONT: 0,"IPV4V6","cdp.iot.t-mobile.nl","",0,0

OK

AT+CGACT?

Sending command 

AT+CGACT?

+CGACT: 0,0

OK

AT+CGEREP=1

Sending command 

OK

AT+CIND=1,1,1

Sending command 

OK

AT+CEREG=2

Sending command 

OK

AT+CEREG?

Sending command 

AT+CEREG?

+CEREG: 2,4,"FFFE","FFFFFFFF",9

OK

AT%CESQ=1

Sending command 

OK

AT+CESQ

Sending command 

AT+CESQ

+CESQ: 99,99,255,255,255,255

OK

AT%XSIM=1

Sending command 

OK

AT%XSIM?

Sending command 

AT%XSIM?

%XSIM: 1

OK

AT+CPIN?

Sending command 

AT+CPIN?

+CPIN: READY

OK

AT+CPINR="SIM PIN"

Sending command 

AT+CPINR="SIM PIN"

+CPINR: "SIM PIN",3

OK

AT+CIMI

Sending command 

AT+CIMI

901405700009565

OK

%CESQ: 16,0,16,2

+CEREG: 2,"CB52","02996A05",9

+CGEV: ME PDN ACT 0,0

AT+CGDCONT?

+CNEC_ESM: 50,0

+CEREG: 5,"CB52","02996A05",9

+CIND: "service",1

+CIND: "roam",1

Sending command 

AT+CGDCONT?

+CGDCONT: 0,"IP","cdp.iot.t-mobile.nl","10.0.5.248",0,0

OK

AT+CGACT?

Sending command 

AT+CGACT?

+CGACT: 0,1

OK

%CESQ: 255,0,255,0

[Ronald]

looking at this it got SOME reception: it was able to resolve the cdp.iot.t-mobile.nl to an IP. But afterwards it fails to connect (cesq = 255,0,255,0)