In one embodiment, a system includes a first cold noise source, a first radiometer receiver, and a first detector. The first cold noise source generates a first thermal radiation signal having a first carrier frequency band. The first thermal radiation signal carries a first information signal. The first cold noise source also transmits the first thermal radiation signal through a first antenna. The first radiometer receiver receives the first thermal radiation signal through a second antenna, and the first detector extracts the first information signal from the first thermal radiation signal.