Method and apparatus for coding a binary signal

Apparatus for encoding an input bit sequence comprising:

• means responsive to said input sequence for providing groups of N output bits, each of said groups including a first subset of bits X.sub.0.sup.n and X.sub.1.sup.n and a second subset of bits X.sub.0.sup.m and X.sub.1.sup.m where n and m are indices of the group from which said subsets are derived,
• means including a convolutional encoder for expanding bits in each of said subsets as a specified function of bits in subsets of previous groups, to yield first and second multibit code words Y.sub.0.sup.n Y.sub.1.sup.n Y.sub.2.sup.n and Y.sub.0.sup.m Y.sub.1.sup.m Y.sub.2.sup.m, and
• means for modulating in-phase and quadrature components of a carrier signal in response to first and second symbols generated in response to said first and second multibit code words.

A method of encoding a sequence of input bits for transmission via a quadrature amplitude modulated carrier signal, comprising the steps of:

• forming, in response to first and second subsets of selected bits in each group of N consecutive ones of said input bits, first and second expanded versions of the bits in each of said first and second subsets, respectively, each of said expanded versions having at least one more bit than the subset from which it is formed, and
• modulating, in individual response to said first and second expanded versions, in-phase and quadrature components of said carrier signal to generate an individual one of a predetermined constellation of signal points,
• wherein said forming step includes combining at least one bit in said first subset with at least one bit in the first subset of a preceding one of said N-bit groups and combining at least one bit in said second subset with at least one bit in the second subset of a preceding one of said N-bit groups, said combining and modulating steps being such that less than all possible sequences of said signal points are generated.

A method of encoding an input bit sequence comprising the steps of:

• forming groups of N output bits, each of said groups including a first subset of bits X.sub.0.sup.n and X.sub.1.sup.n and a second subset of bits X.sub.0.sup.m and X.sub.1.sup.m where n and m are indices of the group from which said subsets are derived.
• expanding bits in each of said subsets in a convolutional encoder as a specified function of bits in subsets of previous groups, to yield first and second multibit code words Y.sub.0.sup.n Y.sub.1.sup.n Y.sub.2.sup.n and Y.sub.0.sup.m Y.sub.1.sup.m Y.sub.2.sup.m, and
• modulating in-phase and quadrature components of a carrier signal in response to said first and second symbols generated in response to said first and second multibit code words.