Mikrotik: D-Link DWM-222

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DWM-222 is 4G/LTE USB modem by D-Link. This article contain configuration details and test results. USB modem was tested connected to Mikrotik RB951G-2HnD with RouterOS version v6.40.1 (stable).

Warning: see note at end of article.

Modem capabilities

  • Broadband Wireless Support:
  • Radio Frequency Bands:
    • LTE @ 2600/1800/800 MHz
    • UMTS @ 2100/900 MHh
    • Quadband GSM/GPRS/EDGE
  • Data Rate:
    • LTE: 3GPP Rel-9 FDD-LTE Cat.4
      • Downlink: Up to 150 Mbps
      • Uplink: Up to 50 Mbps
    • DC-HSPA+
      • Downlink: Up to 42 Mbps
      • Uplink: Up to 5.76 Mbps

Visual indication (Status LED)

  • Red (blinking): No SIM Card / No Service (or searching for service) / General Error condition
  • Purple (blinking): Connected to 2G (GPRS/EDGE) network
  • Blue (blinking): Connected to 3G (UTMS/HSPA/HSPA+)network
  • Green (blinking): Connected to 4G (LTE) network

Note: Active connection is indicated by blinking of status LED. Solid mean that there is no active connection or error occurred. If you suspect that modem is in some kind of faulty / error condition then try to power cycle it via -> /system routerboard usb power-reset duration=10s


General configuration

Configuring port name is optional but I recommend to set it. This will make configuration easier to read.

  • Identify device by id or just by comparing output before and after connecting USB modem:
> /port print
  • Set name on identified port (replace "0" with actual port number):
> /port set 0 name=Orange
  • List configured ppp client interfaces:
> /interface ppp-client print
  • Remove auto-configured interface (adjust name / number if necessary):
/interface ppp-client remove ppp-out1
  • Add new ppp client interface:
/interface ppp-client add dial-on-demand=no disabled=no apn=internet data-channel=1 info-channel=2 name=ppp-wan port=Orange

Note1: You may add use-peer-dns=no and modem-init="<AT command>" depending on configuration.

Note2: APN depend on internet provided (cell operator).

Note3: This modem is enabled by default. Option modem-init="AT+CFUN=1" is not necessary.

Native LTE

Modem is not detected as native LTE modem in RouterOS. I am not sure if this is limitation of modem itself or missing support in Mikrotik RouterOS image. Serial "PPP" interface is working fine.

How to force access technology

Automatic selection is working fine when modem "see" strong network signal. Unfortunately this is not case when modem is installed in area with poor reception. Modem tend to jump around all access technologies under this condition. Transition between 2G and 3G is smooth but this is not case for 4G in our area (Slovakia). Each transfer to and from 4G network will cause modem to hung up and line connection needs to be re-established. It is really annoying if it is happening frequently. Clear indication of this is rapid color change of status LED and network disconnect caused by "modem hung-up".

You can force modem to use certain access technology by using AT+BMMODPREF command.

  • Reference table:
AT+BMMODPREF=0 -> auto
Automatic selection

Modem will "try" to find best network connection and stick with it. Current access technology is indicated by LED and details in "info" command (see bellow).

  • configuration:
/interface ppp-client set ppp-wan modem-init="AT+BMMODPREF=0"
  • Configuration:
/interface ppp-client set ppp-wan modem-init="AT+BMMODPREF=2"
  • Status LED: Purple
  • Info indication: GSM compact
  • Configuration:
/interface ppp-client set ppp-wan modem-init="AT+BMMODPREF=1"
  • Status LED: Blue
  • Info indication: 3G
Only LTE
  • configuration:
/interface ppp-client set ppp-wan modem-init="AT+BMMODPREF=7"
  • Status LED: Green
  • Info indication: Evolved 3G (LTE)

"info" details on Mikrotik

Mikrotik can use "info channel" (actually another serial interface of modem) to get current status of it. This is invoked by /interface ppp-client info <interface> and show following details:

> /interface ppp-client info ppp-wan                           
       modem-status: call in progress
         pin-status: no password required
      functionality: full
       manufacturer: OK
              model: +CGMM: LTE WIRELESS MODEM
           revision: 1.7.3
      serial-number: <hidden>
   current-operator: 23102 (cellid: <hidden>, lac: <hidden>)
               imsi: <hidden>
  access-technology: Evolved 3G (LTE)
     signal-strengh: -83 dBm
   frame-error-rate: n/a
-- [Q quit|D dump|C-z pause]

All indications seems to be working fine except for "signal-strengh" under certain condition. Signal stretch of -51 dBm is reported while modem is searching operator or when selected access technology is not available at all. I recommend to double check other fields if you see signal stretch around -51 dBm.

SMS reception

SMS reception is possible but will block access to "info" details while enabled. Consider disabling if it is not necessary or if you need access to "info" details.

  • Make sure that SMS is disabled before configuring:
/tool sms set receive-enabled=no
  • Set strong password to prevent remote script execution:
/tool sms set secret=<password>
  • Set port and retention configuration:
/tool sms set port=Orange channel=2 keep-max-sms=5

Note: Too many messages kept on modem may cause modem to stop receiving SMS at all. I am not sure what is limit for this modem but number bellow 10 is generally safe for all configurations.

  • Enable reception:
/tool sms set receive-enabled=yes
  • Show messages in inbox:
/tool sms inbox print

Activity LED on Mikrotik

Certain version of Mikrotik routers have "User" or "Activity" LED. This LED can be defined in configuration and indicate "status" of something. I use this LED to indicate status of network connection via USB modem in my configurations.

  • Verify that user-led is not used in configuration. If yes, then remove configuration for it:
> /system leds print
  • Add configuration indicating status of ppp client interface:
/system leds add interface=ppp-wan leds=user-led type=interface-status

User / Activity LED will be lit when connection is established and dark when connection fail / disconnect.

Stability note

I tested this modem in area with poor coverage. It was able to establish connection but connection was not stable. Modem tend to jump between access technologies and disconnect "Internet". I configured manual selection of access technology on modem (e.g. 2g, 3g, 4g/lte) and tested each one separately. This clearly fix first problem but another one pop up. Firmware of modem crashed after few minutes of usage. I was not able to reproduce this with strong signal in city but relatively weak signal in tested area triggered this problem. After few days of testing I returned this product. It was not reliable enough for my project.