Radio communications system and method based on time twisted waves

A radio communications method comprising carrying out, by a transmitter, the following steps:

• a) generating or receiving digital symbols to be transmitted, said digital symbols having a given symbol rate associated with a corresponding symbol period;
• b) generating, every S digital symbols generated/received, a corresponding multi-mode digital signal, which
• has a predefined time length shorter than S times the symbol period,
• has a predefined bandwidth larger than the Nyquist bandwidth corresponding to the given symbol rate, and
• carries said S digital symbols by means of orbital angular momentum modes comprising
• a main mode, that is an orbital angular momentum mode with topological charge equal to zero and that carries P of said S digital symbols, and
• one or more twisted modes carrying the other S-P digital symbols, wherein each twisted mode is an orbital angular momentum mode with a respective topological charge different than zero and is time-shifted with respect to the main mode;
• c) generating a multi-frame digital signal comprising successive, non-overlapped time frames, each of which has the predefined time length and carries a respective multi-mode digital signal generated;
• and
• d) transmitting a radio frequency signal carrying the multi-frame digital signal;
• wherein S is an integer higher than three, and P is an integer higher than zero and lower than S;
• the method further comprising carrying out, by a receiver, the following steps:
• e) receiving the radio frequency signal transmitted by the transmitter;
• f) processing the received radio frequency signal so as to obtain a corresponding incoming digital signal;
• g) performing on the basis of the incoming digital signal
• carrier synchronization thereby recovering frequency and/or phase carrier used by the transmitter to generate the multi-mode digital signals,
• clock synchronization thereby recovering the symbol rate and sampling time instants of the multi-mode digital signals generated by the transmitter, and
• frame synchronization thereby detecting successive, non-overlapped portions of the incoming digital signal corresponding to the successive, non-overlapped time frames of the multi-frame digital signal generated by the transmitter;
• and
• h) extracting, on the basis of the carrier, clock and frame synchronizations performed, the S digital symbols respectively carried by each detected incoming digital signal portion by means of the orbital angular momentum modes.