System and method for compressing a transmitted signal to achieve narrow and very narrow band frequency or phase modulation

A method for communicating information via a communication channel connecting a transmitting side and a receiving side, involving frequency or phase modulation with a modulation index M that is not greater than 1.0 to thus compress a bandwidth of an information signal to have a small or very small frequency deviation at the transmitting side of the communication channel and in the communication channel, the method comprising:

• frequency or phase modulating an information signal with a modulation index M that is not greater than 1.0 to compress a bandwidth of the information signal to form a narrow band or very narrow band frequency-modulated or phase-modulated information signal having a small or very small frequency deviation at the transmitting side of a narrow or very narrow band communication channel and in said communication channel;
• transmitting, via the communication channel, said narrow band or very narrow band frequency-modulated or phase-modulated information signal formed by modulating the information signal with the modulation index M that is not greater than 1.0 so as to have the small or very small frequency deviation;
• receiving the narrow band or very narrow band frequency-modulated or phase-modulated information signal from the communication channel at the receiving side of the communication channel;
• and
• expanding the frequency deviation of the received narrow band or very narrow band frequency-modulated or phase-modulated information signal at the receiving side without expanding a bandwidth of said communication channel so as to form an expanded-frequency deviation information signal, the step of expanding for improving a signal-to-noise ratio and performed such that a bandwidth of said narrow band or very narrow band communication channel is never expanded.