MODBUS RTU <--ethernet--> MODBUS RTU

I am trying to replace a communication link between two Modicon PLCs in the field. The PLCs talk Modbus RTU. They are about 7 miles apart. Currently for comms, we use Motorla 202T modems connected to the PLCs (VIA serial RS232) at each end and there is a dedicated 2 pair physical telephone line between the two modems.

We are having issues with the physical line and want to replace the setup with something wireless. the idea is to replace the physical phone line as a mode of transfer.

based on the terrain and location of the two PLCs Radio comms are out, without significant infrastructure costs ( tower, antennas etc)

Here's what I want to do to keep the setup convenient for install

Connect a Modbus to Ethernet Converter device (Lantorix Xpress DR+ ??) to the PLCs at each end and then connect each Modbus to Ethernet Converter with a cell modem ( Digi TransPort WR21 ??). Trying to setup something like a adhoc peer to peer IP connection between the converter and modem combo.

PLC1 <--RS232--> Modbus protocol converter 1 <----Ethernet--->Cell Modem1 <-----WAN---------> Cell Modem 2,<----Ethernet----> Modbus protocol converter 2 <------RS232----> PLC 2

Was hoping someone can help me figure out a better solution and/or recommend the best suitable products for this.

thanks
--
Farhan

Prosoft has this device:

Industrial Cellular Gateway ICX35-HWC
http://www.prosoft-technology.com/P...ellular/Industrial-Cellular-Gateway-ICX35-HWC