Method and system for waveform independent covert communications

A communication device for providing a communication signal from a sequence of bits comprising:

• first means for providing a first signal;
• second means for providing a second signal comprising, in sequence, as a function of said sequence of bits, one of a plurality of third signals each with a matrix pencil eigenvalue unique among said third signals;
• and
• third means for combining said first and second signals to thereby provide the communication signal.

A communication system comprising a transmitter and a receiver geographically separated from the transmitter for communicating a communication signal formed from a sequence of bits wherein said communication signal is comprised of a plurality of symbols, comprising:

• a transmitter comprising:
• first means for providing a first signal;
• second means for providing a second signal comprising in sequence as a function of said sequence of bits one of a plurality of third signals each with a matrix pencil eigenvalue unique among said third signals;
• third means for combining said first and second signals to thereby provide said communication signal;
• and
• transmitting means for transmitting said communication signal;
• and
• a receiver comprising:
• receiving means for receiving and digitizing the symbols of said communication signal to thereby produce a first received signal;
• means for determining a matrix pencil eigenvalue for at least one of said first received signal symbols;
• means for determining the generalized eigenvalue decomposition of said matrix pencil eigenvalue;
• means for determining the duration of said matrix pencil eigenvalue;
• [ditto]
• means for filtering said symbols as a function of the determined duration of the associated matrix pencil eigenvalue;
• [ditto]
• means for spatially correlating the filtered matrix pencil eigenvalues;
• and
• means for sequentially mapping the correlated matrix pencil eigenvalues to thereby determine at the receiver the sequence of bits in the communication signal.

A communication system comprising a transmitter and a receiver geographically separated from the transmitter for communicating a communication signal formed from a sequence of bits wherein said communication signal is comprised of a plurality of symbols, comprising:

• a transmitter comprising:
• first means for providing a first signal;
• second means for providing a second signal comprising in sequence as a function of said sequence of bits one of a plurality of third signals each with a matrix pencil eigenvalue unique among said third signals;
• third means for combining said first and second signals to thereby provide said communication signal;
• and
• transmitting means for transmitting said communication signal;
• and
• a receiver comprising:
• receiving means for receiving and digitizing the symbols of said communication signal to thereby produce a first received signal;
• means for determining a matrix pencil eigenvalue for at least one of said first received signal symbols;
• means for determining the generalized eigenvalue decomposition of said matrix pencil eigenvalue;
• means for determining the duration of said matrix pencil eigenvalue;
• means for filtering said symbols as a function of the determined duration of the associated matrix pencil eigenvalue;
• means for sorting the filtered matrix pencil eigenvalues into at least one group of like eigenvalues;
• and
• means for sequentially mapping the correlated matrix pencil eigenvalues to thereby determine at the receiver the sequence of bits in the communication signal.

A method for providing a communication signal from a data signal comprised of a sequence of bits, comprising the steps of:

• providing a first signal comprised of a bit stream;
• receiving said first signal and generating a temporal dependence between immediately adjacent bits in said first signal to thereby provide a third signal;
• providing a plurality of signal sources each providing a source signal with a characteristic unique from the others;
• providing a combining means;
• selectively operatively connecting as a function of said data signal one of said plurality of signal sources in sequence to said combining means to thereby provide a second signal;
• and
• combining at said combining means said third signal with said second signal to thereby provide the communication signal from said data signal.

A method for providing a communication signal from a sequence of bits comprising:

• providing a first signal;
• providing a second signal comprising, in sequence, as a function of said sequence of bits, one of a plurality of third signals each with a matrix pencil eigenvalue unique among said third signals;
• and
• combining said first and second signals to thereby provide the communication signal.

A method of communicating between a transmitter and a receiver including a multi-element array antenna which is geographically spaced apart from said transmitter a communication signal formed from a sequence of bits wherein said communication signal is comprised of a plurality of symbols, comprising the steps of:

• in the transmitter:
• providing a first signal;
• providing a second signal comprising in sequence as a function of said sequence of bits one of a plurality of third signals each with a matrix pencil eigenvalue unique among said third signals;
• combining said first and second signals to thereby provide said communication signal;
• and
• transmitting said communication signal;
• and
• in the receiver:
• receiving and digitizing the symbols of said communication signal to thereby produce a first received signal;
• determining a matrix pencil eigenvalue for at least one of said first received signal symbols;
• determining the generalized eigenvalue decomposition of said matrix pencil eigenvalue;
• determining the duration of said matrix pencil eigenvalue;
• filtering said symbols as a function of the determined duration of the associated matrix pencil eigenvalue;
• spatially correlating the filtered matrix pencil eigenvalues;
• and
• sequentially mapping the correlated matrix pencil eigenvalues to thereby determine at the receiver the sequence of bits in the communication signal.

A method of communicating between a transmitter and a receiver including a multi-element array antenna which is geographically spaced apart from said transmitter a communication signal formed from a sequence of bits wherein said communication signal is comprised of a plurality of symbols, comprising the steps of:

• in the transmitter:
• providing a first signal;
• providing a second signal comprising in sequence as a function of said sequence of bits one of a plurality of third signals each with a matrix pencil eigenvalue unique among said third signals;
• combining said first and second signals to thereby provide said communication signal;
• and
• transmitting said communication signal;
• and
• in the receiver:
• receiving and digitizing the symbols of said communication signal to thereby produce a first received signal;
• determining a matrix pencil eigenvalue for at least one of said first received signal symbols;
• determining the generalized eigenvalue decomposition of said matrix pencil eigenvalue;
• determining the duration of said matrix pencil eigenvalue;
• filtering said symbols as a function of the determined duration of the associated matrix pencil eigenvalue;
• sorting the filtered matrix pencil eigenvalues into at least one group of like eigenvalues;
• and
• sequentially mapping the correlated matrix pencil eigenvalues to thereby determine at the receiver the sequence of bits in the communication signal.

A method of communicating information comprised of a sequence of bits from a transmitter to a receiver comprising the steps of:

• modulating a carrier wave with a data signal to thereby produce a first signal wherein the data signal does not represent the information to be communicated;
• transmitting the first signal from the transmitter;
• receiving the first signal at the receiver;
• determining at the receiver the communicated information independently of the data signal.

A method for communication of a message comprising a plurality of sequenced M-ary alphabet symbols, said method comprising the steps of:

• assigning each M-ary alphabet symbol a unique symbol duration;
• generating a waveform for which both the spatial 2nd order moment or the spatial 4th order cumulant are constant and not zero;
• and
• for each symbol, transmitting the waveform for the assigned symbol duration immediately followed by a pause in waveform transmission.

A method for communication of a message comprising a plurality of sequenced M-ary alphabet symbols, said method comprising the steps of:

• assigning each M-ary alphabet symbol a unique symbol duration;
• generating plural waveforms for which the spatial 2nd order moment and the spatial 4th order cumulant are constant, nonzero, and unique;
• and
• for each symbol, transmitting one of the plural waveforms for the assigned symbol duration so that immediately adjacent symbols are transmitted by different waveforms.