SXT LTE Kit (R11e-LTE) - to lock on 3G 900Mhz

RouterOS General
1

Hi.

I have the following device/firmware version:

Mikrotik SXT LTE Kit (RBSXTR&R11e-LTE):
[admin@MikroTik] > /system routerboard print
       routerboard: yes
             model: RBSXTR
     firmware-type: qca9531L
  factory-firmware: 6.41.3
  current-firmware: 6.42.1
  upgrade-firmware: 6.42.1

Modem:

[admin@MikroTik] > /interface lte info lte1                                        
         pin-status: no password required
      functionality: full
       manufacturer: "MikroTik"
              model: "R11e-LTE"
           revision: "MikroTik_CP_2.160.000_v008"

I located in a low-signal area with two 3G HSDPA bands available: 900 MHz with ~ -87Db and 2100MHz with ~ -111Db signal. My problem is the device ignoring the highest level 900MHz channel and trying to connect to 2100MHz. Sometimes it occasionally switches to 900MHz and I have 3+ Mb download. In a few minutes it jumps back to 2100 with almost no connection.

First I tried to lock the band 8 (both in GUI and in console command), however is seems do not affect 3G mode at all - it still connects to 2100MHz

According the wiki I tried to grab the channels parameters to lock modem on desired cellid/frequency using command “/interface lte cell-monitor lte1”, however my routerboard doesn’t recognize the command:

[admin@MikroTik] > interface lte cell-monitor lte1
bad command name cell-monitor (line 1 column 15)

I tried to grab desired information by using “/interface lte cell-monitor lte1” while it connected to 900MHz, I got the following:

   current-operator: 25701
                lac: 111
     current-cellid: 1085840
  access-technology: 3G HSDPA
     session-uptime: 7m15s
               imei: ***************
               imsi: 257010016179403
             earfcn: 3013 (DL freq 602.6Mhz)
               rssi: -87dBm

Then I tried to follow the wiki and use the AT command "/interface lte at-chat lte1 input=“AT*Cell=1,3013,1085840”. If I try it in console while modem is already connected it answers:

[admin@MikroTik] > /interface lte at-chat lte1 input="AT*Cell=1,,,3013,1085840" 
  output: +CGEV: NW DEACT ""IP"", "10.92.182.45",5

Then modem looses the connection and never connects again until USB power off or reboot.

If I try the command while there is no connection yet or try to add the AT-string in the modem init string it replies with “+CME ERROR: 50” and no connection as well.

I tried to check the modem firmware upgrade using the wiki command, however it wasn’t recognized by the routerboard as well:

[admin@MikroTik] > /interface lte firmware-upgrade lte1 
bad command name firmware-upgrade (line 1 column 16)

The menu /interface lte just doesn’t have the firmware-upgrade command.

Examining the lte log I found there is a ATBand= … command. With band 8 locked in settings it was "ATBAND=1,79,147,0,128,0,2,0", with no bands locking it was “AT*BAND=1,79,147,480,589829,0,2,0”. Unfortunately, there is no documentation for this command. I tried doing some experiments, interpreting the numbers as binary bands mask, I was able to see there was SOME effect (once I was able to make the modem to connect to 2G), however I failed to get the desired 3G 900 channel.

So, for now I cannot use the device to connect Internet and can only to be connected with my phone on the roof (The phone successfully connects to the 900MHz channel, however the signal is too week to have a good speed with the phone antenna)

Could somebody provide some help or clues? The only thing I need - to make the device to connect to 3G 900 channel and disable/ignore low-signal 2100 one.

low signal SXT LTE6
2

I already upgraded to the latest stable 6.43.8 and found an information the both firmware-upgrade and cell-monitor are available in the latest beta only. However, it doesn’t answer why the recommended command

/interface lte at-chat lte1 input="AT*Cell=1,,,3013,1085840"

seems not to work properly

3

I can’t help you on this question directly, but experienced that with the latest LTE FW upgrade (possible via beta only) the LTE
modem works way better.

I suggest you upgrade to the router to beta, upgrade then LTE modem FW and then downgrade router to the 6.43.8 again (LTE Modem
will keep latest FW).
Please check then if issue is still there, might have gone away then.

4

Thanks for the advice, I’m going to check it on the weekend - the device is located in the rural area about 100km away from me and I have no remote access for now - for obvious reason.

5

So, I tried.

Both RouterOS and the modem firmware were successfully upgraded, I enter the “/interface lte cell-monitor lte1” command, it run successfully… and shows me an empty list, while modem was actually connected to 3G HSDPA 2100MGz band.

The rest of behaviour was not changed.

I tried to bring the device in the city and see how it works in different LTE networks I have here. With LTE it works fine. cell-monitor displays different cells and bands, the AT*Cell modem command worked as expected to lock me on desired tower.

But not for 3G.

So, it seems the 3G support here is just very formal and unsupported feature. It claimed to support 2G/3G/LTE network, but the must have feature for low signal area - to select a tower and a band - works for LTE only. Actually, one should forget about claimed 3G support and take in the mind the LTE only.

Sadly I have only 3G network in the location I planned to use the device and the lack of 3G support make it incapable to work there. I was mislead by the claimed 3G support. Unfortunately, it was only waste of time and money. And I have to return to some Huawei solution with an external yagi or logo-periodic antenna.

Actually, the market device description and documentation does not correspond the actual device capabilities. Incorrect documentation and no support. I believe it’s the last mikrotik device I ever bought.

6

Bear in mind that both 3G (UMTS) and LTE are single-frequency networks where all “towers” operating on same frequency band actually work in same frequency channel. Thus forcing terminal (data card) to use particular tower is counter-productive at best.

Forcing data terminal to particular frequency band is different though.



And I have to return to some Huawei solution with an external yagi or logo-periodic antenna.

There’s nothing software (or even hardware) can do if signal level is not adequate. Use of external antenna with good gain (as you wrote, yagi or log-periodic antennae are good examples) is a must in areas with low signal level.

I believe most of MNOs operate all technologies from same towers these days so if one technology has low signal level, other technologies won’t be much better (if at all). As MNOs are refarming their spectrum to newer technologies (LTE now, 5G in near future), use of legacy technologies (i.e. 3G) as a fall back is not a viable solution … it might seem to perform better but that’s probably due to the fact that only a few users still use it. And it’ll become a candidate to refarm to new technology “real soon now”.

7

Forcing data terminal to particular frequency band is different though.

As I said it was actually what I needed. I do have 900MGz channel with appropriate signal level and 2100MGz with too low signal.

I believe most of MNOs operate all technologies from same towers these days so if one technology has low signal level, other technologies won’t be much better (if at all).

It is the problem - they are not. In my region LTE network works mostly in cities. Most of rural area covered with 3G UMTS only - with many small villages having unstable connection due to low signal. That was the reason I were seeking especially for a device with 3G support, external or internal high-gain antenna and an ability to choose a band explicitly. All three options are critical.

8

There aren’t any internal high-gain antennae. Mostly they are poor simulations of omni-directional antennae with realistic gain between 0 and 2 dBi (good omni-directional antenna has gain of slightly more than 2dBi). A good directional antenna will have gain of 10dBi or even more. And that can make huge difference in conditions you’re describing.

And yes, it’s really good to have possibility to select frequency band on the modem card …

9

We operate LTE as backup in some rural areas and always force the CPE to utilize 800/900 Mhz since the higher frequency bands are much to sensitive for trees, rain and snow in longer distances and when you don’t have LIS.

10

Base at SUP-3946 from 16/Dec/19 8:52 PM
3G Cell Lock & R11e-LTE6

Detect what is at air:

interface/lte/cell-monitor lte1 max-age=1m duration=1m
Columns: PHY-CELLID, > PSC> , > EARFCN> , AGE
PH > PSC EARFC > AG
0 > 255 10737 > 2s
4 394 10737 2s
11 211 10737 2s
12 276 10737 2s
14 316 10737 2s
…
0 > 33 3030 > 2s
11 12 3030 2s
16 58 3030 2s
20 2 3030 2s

What logs say?

log print where message~“CREG: 1”
02:47:49 lte,async,raw SXTR__LTE: lte1: +CREG: 11,“2b01”,“047fa71e”,2
02:47:49 lte,async,raw SXTR__LTE: lte1: $CREG: 11,“2b01”,“047fa71e”,2,“0ff”
02:47:50 lte,async,raw SXTR__LTE: lte1: +CREG: 1,“2b01”,“047fa71e”,2
02:47:50 lte,async,raw SXTR__LTE: lte1: $CREG: 1,“2b01”,“047fa71e”,2,“0ff”
02:47:57 lte,async,raw SXTR__LTE: lte1: +CREG: 1,“2b01”,“047fa71e”,10
02:47:57 lte,async,raw SXTR__LTE: lte1: $CREG: 1,“2b01”,“047fa71e”,10,"0> ff> "

Where:

  • LAC: 2b01 hex = 11009 dec
  • Cell ID: 047fa71e hex = 75474718 dec
  • UMTS Type:
    2: UTRAN
    4: UTRAN w/HSDPA
    5: UTRAN w/HSUPA
    6: UTRAN w/HSDPA and HSUPA
    8: UTRAN HSPA+
  • PSC: “0FF” hex = 255 dec

Cell Monitor show PCS 255 & EARFCN 10737 and this is connected.

Cell Lock should be:
interface lte at-chat lte1 input=“at*cell=2,2,10737,255”

Others Cell Lock should be:
interface lte at-chat lte1 input=“at*cell=2,2,3030,33”

Disable Cell Lock:
interface lte at-chat lte1 input=“at*cell=0”