Transfer data between coils

Im looking into designing a wireless data transmission using two coils.
Tx coil will send a 8 bit data to the Rx coil that sends it to the PC thru USART.

I want to read multiple temperature sensors thru a steel wall. I will be using a Atmega128.

Transmit package:

XX XXXX XX = 8 bits
2 bit Address / 4 bit Data / 2 bit Checksum

I know that this kind of system is in use, do anyone know how to design this or have an example to help me on the way?

You should get an idea of feasible carrier frequency and attenuation through the stell wall.

Then decide about a suitable modulation method.

Ok, thanks.
Have you ever seen any schematics for similar project?
The frequency have to be low, I know they are in the ELF band.