Power line communication by inducing a signal into a wire
Consider PPM....pulse position modulation.

Couple pairs of spikes into the hot-wire. For ZERO, place the spikes 5 uS apart.
For ONE, place the spikes 10uS apart.

Send the bits every 100uS.

Or, to have a very narrow-band datalink, so you can narrow-band filter to reject more noise, for ZERO, send +spike,+spike, For ONE, send +spike,-spike.

Examine some Fourier signals and pick your spacing and modulation.
Here are useful waveforms and spectra from Signal Wave Explorer. I used the JBStage (canned example) with trapezoidal input (50%, 50%, no plateaus)



Notice how narrow-band (centered at 200KHz) the output spectrum is.

By the way, the powerline can easily kill you. Are you thinking about transformers wrapped about the HOT wire?