Trellis coded FM digital communications system and method

A method using a processor for encoding a data word of a data word sequence, each data word having k bits, with k being a number of bits in each data word, comprising the steps, using said processor, of:

• a. selecting, using a trellis encoding algorithm and a previous data word, a 2.sup.k subset of signal points from a square set of M by M signal points having X coordinates and Y coordinates, with M being a number of indices of a plurality of X coordinates and a plurality of Y coordinates, wherein the square set of M by M signal points includes a constellation of 2.sup.k+l signal points;
• b. selecting, using the data word, a signal point from the selected subset of signal points;
• c. generating a first frequency-shift-keying (FSK) signal from an M-ary FSK signalling scheme of an X coordinate of said selected signal point;
• d. generating a second FSK signal from the M-ary FSK signalling scheme of a Y coordinate of said selected signal point;
• and
• e. repeating steps a-d for each data word of the data word sequence.

A method for convolutionally decoding a received first frequency-shift-keying (FSK) ..... signal a received second FSK signal, as a data word of a data word sequence, each data word having k bits, with k being a number of bits in each data word, comprising the steps of:

• demodulating, using a demodulator, the first FSK signal as a received X coordinate and the second FSK signal as a received Y coordinate;
• estimating, using a processor, using a predetermined coding algorithm and a previously received data word, a 2.sup.k subset of signal points from a square set of M by M signal points having X coordinates and Y coordinates, with M being a number of indices of a plurality of X coordinates and a plurality of Y coordinates, wherein the square set of M by M signal points includes a constellation of 2.sup.k+ signal points;
• and
• estimating a received data word from the received X coordinate, the received Y coordinate, and the estimated-received subset of signal points.

A system used with a communications channel for encoding and convolutionally decoding a data word of a data word sequence, each data word having k bits, with k being a number of bits in each data word, comprising:

• first processor means for selecting, using a predetermined coding algorithm and a previous data word, a 2.sup.k subset of signal points from a square set of M by M signal points having X coordinates and Y coordinates, with M being a number of indices of a plurality of X coordinates and a plurality of Y coordinates, wherein the square set of M by M signal points includes a constellation of 2.sup.k+l signal points, said first processor means selecting, using the data word, a signal point from the selected subset of signal points;
• modulator means for generating a first frequency-shift-keying (FSK) Signal from an M-ary FSK signalling scheme of an X coordinate of said selected signal point and a second FSK signal from the M-ary FSK signalling scheme of a Y coordinate of said selected signal point;
• transmitter means for transmitting the first FSK signal and the second FSK signal over a communications channel;
• demodulator means for demodulating the first FSK signal as a received X coordinate and the second FSK signal as a received Y coordinate;
• and
• second processor means for estimating a 2.sup.k received subset of signal points using a convolutionally decoding algorithm and a previously received data word, and for estimating, using said second processor, a received data word from the received X coordinate, the received Y coordinate, and the estimated-received subset of signal points.