LTE dropouts

RouterOS General
1

We recently installed an LHG R LTE kit for client.

We are aware that its location is not ideal but we were restricted due to the building being listed.

          pin-status: ok
  registration-status: registered
        functionality: full
         manufacturer: "MikroTik"
                model: "R11e-LTE6"
             revision: R11e-LTE6_V020
     current-operator: 23420
                  lac: 1539
       current-cellid: 1282306
               enb-id: 5009
            sector-id: 2
           phy-cellid: 98
    access-technology: LTE (CA2)
       session-uptime: 1d3h6m52s
         primary-band: B3@15Mhz earfcn: 1392 phy-cellid: 98
              ca-band: B20@5Mhz earfcn: 6175 phy-cellid: 417
                 rssi: -68dBm
                 rsrp: -99dBm
                 rsrq: -11.5dB
                 sinr: 12dB
                  cqi: 6

       routerboard: yes
        board-name: LHG R
             model: RBLHGR
          revision: r2
     firmware-type: qca9531L
  factory-firmware: 6.44.6
  current-firmware: 6.47.1
  upgrade-firmware: 6.47.1

Flags: X - disabled 
 #   NAME                                                                   VERSION                                                                  SCHEDULED              
 0   routeros-mipsbe                                                        6.47.1

We get a decent speed, approx 30-50Mbps up and down and the average ping is around 60ms.

Randomly, every so often (between 1 and 5 minutes, sometimes even longer) the router will drop around 5-6 pings. At the same time you’ll see a small blast of LTE commands such as:

13:50:10 lte,async,raw lte1: +CREG: 6,"0603","00139102",7 
13:50:10 lte,async,raw lte1: $CREG: 6,"0603","00139102",7,"062" 
13:50:10 lte,async,raw lte1: +CEREG: 1,"0603","00139102",7 
13:50:10 lte,async,raw lte1: +CREG: 6,"0603","00139102",9 
13:50:10 lte,async,raw lte1: $CREG: 6,"0603","00139102",9,"062" 
13:50:10 lte,async,raw lte1: +CEREG: 1,"0603","00139102",9 
13:50:11 lte,async,raw lte1: sent AT+CFUN? 
13:50:11 lte,async,raw lte1: rcvd +CFUN: 1 
13:50:11 lte,async,raw lte1: sent AT+COPS? 
13:50:11 lte,async,raw lte1: rcvd +COPS: 0,2,"23420",9

After this, pings resume as normal.
2020-08-12 at 14.08.png
I don’t know much about 3G/4G/LTE etc so I’m not sure what it means.

I can see the session time does not drop, the signal strength seems to be stable at that time so I’m not sure what could be causing the issue.

The router is using LTE Passthrough to another firewall if that makes any difference. I’d appreciate any guidance that may help assist

2

This may give you some clues as to what is happening: https://m2msupport.net/m2msupport/atcreg-network-registration/

3

Thanks for that!

Regards.

4

Hi, thanks for sending the page through, I’d found a similar page but not finding it easy to cross-reference my output to the examples on that page.

The common CREG command in my output shows two sets of numbers 6+7 and 6+9:

lte1: +CREG: 6,“0603”,“00139102”,7
lte1: +CREG: 6,“0603”,“00139102”,9

Based on that, depending on how I decipher the numbers it could suggest it’s toggling between these two modes:

6 registered for “SMS only”, home network
9 registered for “CSFB not preferred”, home network

Am I reading this right? So it’s jumping between SMS only mode and a normal mode? If this is the case, why? Is it signal or something else?

I’ve got another setup, exactly the same for another client using the same network provider and hardware and it doesn’t do this.

Any insight would be appreciated.

Thanks

5

Anyone have any further suggestions?

6

I do not. Sorry, I was hoping someone from Mikrotik or better knowledge of LTE would jump in. You should send email to support and mention this thread.

7

You show firmware v20 in your log.
Latest one is V25.

Do following:

/interface lte> firmware-upgrade
number: 0
installed: R11e-LTE6_V025
latest: R11e-LTE6_V025

After typing after number “0”, you should see dialog asking you for FW update. You need to press Y to confirm update.

8

There are two ways of delivering SMSes in LTE network: CSFB way and data (native) way. At least in Europe, where vast majority of LTE operators also operate legacy networks, CSFB way is used quite frequently. This mode means that LTE device will switch to legacy network to send/receive SMSes (and make voice calls and perform USSD procedures). And if device doesn’t support traditional (circuit-switched) voice, it might go into “SMS only” mode during this time meaning it won’t do data at all during those periods of time. That’s because in legacy networks SMSes were exchanged over signalling channel which is part of CS feature set, not part of PS (data) feature set, which essentially means that data-only devices don’t support exchange of SMSes, although I highly doubt such devices existed before LTE.
The other mode (SMS over data) means that device can exchange SMSes with SMSC over native data connection (GPRS, …). Support for this mode was added to legacy networks, but it really depends on support from all the different core network of MNO (MSC, SGSN, SMSC, …) and legacy operators mostly didn’t bother to implement it. In LTE this mode becomes “native” way of delivering SMSes, but obviously not all legacy operators support it because simply enabling CSFB brings SMSes as well and CSFB was needed for voice calls before VoLTE became reality.

Now: modem switching between data and SMS-only modes means that either router is sending out SMSes (check for any scheduled scripts that might do it) or somebody else is sending your modem SMSes (by mistake?). You should manually check SMS inbox on modem to see if that’s the case. If that’s the case, I don’t think there’s anything you can do apart from changing SIM card (to change associated MSISDN) … or chaning MNO to one supporting SMS exchange natively in LTE.

9

@WeWiNet - Thanks for pointing that out. I run the lte firmware update last night and for about 3+ hours it was fine. This morning I checked again and it was still happening

@mkx - Thanks for explaining this. We have three of the LHR’s, all on the same network provider and this is the only one that is exhibiting the issue. I have checked the inbox and there was on a single message in there. I’ve checked the scripts/scheduler and only script I have that can send an SMS is one that sends an SMS only when I send one in. It’s kind of a status SMS, I send in an SMS that runs this script and it sends one back with some stats of the LTE connection.

I have disabled the receiving of SMS’ from the time on the LHR but I doubt that will make any difference. Is there any way to log SMS communications? In case something is going on that I’m not aware about

10

Did you solve the problem for yourself? I have very similar issue and I struggling to figure out where my problem is.

I see two different patterns in log. +CREG command is sent ~160 times during 40 minutes.

17:00:22 lte,async,raw lte1: sent AT+CFUN? 
17:00:22 lte,async,raw lte1: rcvd +CFUN: 1 
17:00:22 lte,async,raw lte1: sent AT+COPS? 
17:00:22 lte,async,raw lte1: rcvd +COPS: 0,2,"24801",7 
17:00:23 lte,async,raw lte1: +CREG: 1,"2718","030e5529",9 
17:00:23 lte,async,raw lte1: $CREG: 1,"2718","030e5529",9,"1c7" 
17:00:23 lte,async,raw lte1: +CEREG: 1,"2718","030e5529",9 
17:00:23 lte,async,raw lte1: +CREG: 1,"2718","030e5529",7 
17:00:23 lte,async,raw lte1: $CREG: 1,"2718","030e5529",7,"1c7" 
17:00:23 lte,async,raw lte1: +CEREG: 1,"2718","030e5529",7

second pattern when registering fails

17:01:23 lte,async,raw lte1: sent AT+CFUN? 
17:01:23 lte,async,raw lte1: rcvd +CFUN: 1 
17:01:23 lte,async,raw lte1: sent AT+COPS? 
17:01:23 lte,async,raw lte1: rcvd +COPS: 0,2,"24801",9 
17:02:50 lte,async,raw lte1: +CREG: 1,"2718","030e5529",7 
17:02:50 lte,async,raw lte1: $CREG: 1,"2718","030e5529",7,"1c7" 
17:02:50 lte,async,raw lte1: +CEREG: 1,"2718","030e5529",7 
17:02:50 lte,async,raw lte1: +CREG: 1,"2718","030e5529",9 
17:02:50 lte,async,raw lte1: $CREG: 1,"2718","030e5529",9,"1c7" 
17:02:50 lte,async,raw lte1: +CEREG: 1,"2718","030e5529",9 
17:02:51 lte,async,raw lte1: +CREG: 1,"2718","030e5529",7 
17:02:51 lte,async,raw lte1: $CREG: 1,"2718","030e5529",7,"1c7" 
17:02:51 lte,async,raw lte1: +CEREG: 1,"2718","030e5529",7 
17:02:51 lte,async,raw lte1: sent AT+CFUN? 
17:02:52 lte,async,raw lte1: rcvd ERROR 
17:02:52 lte,async,raw lte1: sent AT+COPS? 
17:02:52 lte,async,raw lte1: rcvd ERROR 
17:03:02 lte,async,raw lte1: +CREG: 0 
17:03:02 lte,async,raw lte1: $CREG: 0 
17:03:02 lte,async,event lte1: ^MODE:3 
17:03:02 lte,async,event lte1: +MSRI: 1 
17:03:02 lte,async,event lte1: +MPBK: 0 
17:03:02 lte,async,event lte1: *SIMDETEC:2,NOS 
17:03:02 lte,async,event lte1: +MMSG: 0, 0 
17:03:02 lte,async,raw lte1: +CGREG: 0 
17:03:02 lte,async,raw lte1: +CEREG: 0 
17:03:02 lte,info lte1: not registred, state: 0 
17:03:02 lte,async,event lte1: +CPAS: 5 
17:03:02 lte,async,event lte1: *SIMDETEC:1,SIM 
17:03:03 lte,async,event lte1: *ICCID: 8937201020020173100 
17:03:03 lte,async,event lte1: *EUICC: 1 
17:03:03 lte,async,raw lte1: +CREG: 0 
17:03:03 lte,async,raw lte1: $CREG: 0 
17:03:03 lte,async,raw lte1: +CGREG: 0 
17:03:03 lte,async,raw lte1: +CEREG: 0 
17:03:03 lte,async,event lte1: *RADIOPOWER: 0 
17:03:03 lte,async,event lte1: *ADMINDATA: 1, 2, 1 
17:03:03 lte,async,event lte1: +CPIN: READY 
17:03:03 lte,async,event lte1: *EUICC: 1 
17:03:03 lte,async,event lte1: *ECCLIST: 1, 255, 112 
17:03:04 lte,async,event lte1: +MMSG: 0, 0 
17:03:04 lte,async,event lte1: +MMSG: 0, 0 
17:03:04 lte,async,event lte1: +MMSG: 1, 0 
17:03:04 lte,async,event lte1: +MPBK: 1 
17:03:04 lte,async,raw lte1: sent AT+CFUN? 
17:03:04 lte,async,raw lte1: rcvd +CFUN: 4 
17:04:02 lte,error failed to register on network 
17:04:02 lte,account lte1 session: 1701s 95738863/16032493 bytes 112941/84262 packets 
17:04:02 interface,info lte1 link down