NB-IoT Liverpool Underground Investigation

Posted by Michael Beaver on

October 2022 and we see almost UK wide availability of the 2 IoT bands implemented as part of the 5G roll-out; NB-IoT and LTE-M. Here in Liverpool we have LTE-M on both Vodafone and O2 and NB-IoT on both EE and Vodafone.

Checking above ground in Liverpool City Centre shows the following networks available to our BG95-M3 modems:

at+cops=?... +cops:
(1,"vodafone UK","voda UK","23415",0) 2G
(2,"EE","EE","23430",0) 2G
(1,"O2 - UK","O2 - UK","23410",0) 2G
(1,"O2 - UK","O2 - UK","23410",8) LTE-M
(1,"EE","EE","23430",9) NB-IoT
(1,"vodafone UK","voda UK","23415",8) LTE-M
(1,"vodafone UK","voda UK","23415",9) NB-IoT

Obviously above ground we've got loads of options but what these new IoT bands bring is enhanced coverage where there is no chance your mobile phone will work.

Liverpool is one of 6 cities in the UK that has an underground train service and it's not just a track with a ceiling, it has a deep level underground train that runs under the River Mersey! The Northern Line is deep enough to run under all of the buildings in Liverpool City Centre (you can feel the trains passing underneath in certain areas) and, as mentioned, the Wirral line passes under the River Mersey and is between 20m-40m deep. All tunnels are concrete lined. Let's see how far down we can pick up NB-IoT.

James Street Station

James Street Station is the last Liverpool stations before the trains venture under the River Mersey and is on quite high ground. It's a long way down to the platforms requiring two separate lifts and is over 30m below the road above.

Development PCB used in the NB-IoT underground testing

After alighting the train we attempted to gain a connection on the lowest platform and found one! But, it was not from above ground. It was EE and it came from the platform. EE provide cellular connectivity for the emergency services which is what we picked up. 

at+cops=?  this shows is what network the modem is using 
+cops: (2,"EE","EE","23430",0) the 2 shows it's the selected network and 0 that it's 2G

at+csq  this get the signal strength
+csq: 26,99  ...and 26 is pretty good!

We went to the surface so the modem could be forced to use Vodafone NB-IoT and acquire the local mast. Then we went back down to firstly the mezzanine and then the platform. 

On the surface we have full 31/31 signal

at+cops=4,1,voda UK,9  forces Vodafone NB-IoT
+cops: 1,1,"VF",9

+QENG: "servingcell","NOCONN","NBIoT","FDD",234,15,7F15,327,6253,20,0,0,E3F2,-55,-10,-44,15,80

+csq: 31,99   full signal on VF NB-IoT outside the station


On the mezzanine which is already extremely deep we still acquire a usable signal 9/31.

+cops: 1,1,"VF",9

+csq: 9,99

+QENG: "servingcell","NOCONN","NBIoT","FDD",234,15,7F15,327,6253,20,0,0,E3F2,-131,-20,-95,2,-5


From there we took the left down to the trains platform where we was unable to pick up anything on Vodafone



Liverpool Central Station

On the Northern Line platform we were unable to connect to any network with my phone however we were able to get a usable signal on NB-IoT

No Signal


NB-IoT Available on the Platform at Liverpool Central

+cops: 1,1,"VF",9

+csq: 4,99

+QENG: "servingcell","NOCONN","NBIoT","FDD",234,15,7B0B,5,6253,20,0,0,E3F2,-130,-20,-108,6,5