Tunnel – Conversion of a GSM communications system into an IP (2G/3G/4G) communication system

Scenario details:

• We have a series of old PLCs that use a GSM modem to make and receive conventional GSM calls
• We intend to replace the old GSM based communication system with one using 4G communications, modifying the previous system as little as possible. That is, without modifying the PLC software and modifying the server PC software as little as possible. Each PLC must be able to make calls, like until now, and must be able to receive them, but instead of making GSM calls, they will be IP (4G) connections. That is, it will only be necessary to replace the PLC current GSM modem with an MTX modem + MTX-Tunnel. It will also be necessary to replace the GSM modem connected to the PC server with a TCP/RS232 software converser
• For this, the MTX modem behaves as follows: To emulate the reception of GSM calls the modem remains in listen mode in a TCP port. For this application the chosen port is TCP 20010. When it receives a 2G/3G connection against that TCP port, the MTX modem must set a 2G/3G/4GSerial gateway the same way it would with a GSM conventional call. On the other hand, it must also be possible to establish a 2G/3G connection from the PLC emulating a GSM call. To do this, the PLC will send the typical connection command GSM ATD xxx.xxx.xxx.xxx (as if it was a GSM call but specifying an IP or DNS address instead of a phone number). The MTX-Tunnel must also be connected to this address via the 20010 port
• The PLC will control the DTR modem line, disconnecting 2G/3G/4G communications with that line. The modem will send CONNECT when setting/receiving a connection and NO CARRIER when this ends

Solution: MTX-Tunnel firmware + MTX-Java-IoT/MTX-Java-T/MTX-Java-T2

EXAMPLE of settings (file config.txt) for this scenario: