Method and apparatus for differential phase encoding and decoding in spread-spectrum communication systems with continuous-phase modulation

A method for differential phase encoding of signals, comprising the steps of:

• dividing a signal stream into a plurality of sets of bits, wherein a first subset of a set of bits comprises a data symbol, wherein a second subset of said set of bits comprises a phase select symbol, and wherein at least one bit of said phase select symbol is mutually exclusive from the bits comprising said data symbol;
• selecting in response to said data symbol a symbol code from a plurality of symbol codes stored in a symbol table;
• selecting a phase value in response to said phase select symbol and a previous phase value;
• and
• phase encoding said symbol code with said phase value.

A method for communication, comprising the steps of:

• generating, in response to a signal stream, a sequence of data segments, each respective data segment comprised of a set of bits of said signal stream;
• for each respective data segment, selecting a symbol code in response to a first subset of bits of said data segment;
• for each respective data segment, selecting a phase of said symbol code in response to a phase of a previous symbol code and in response to a second subset of bits of said data segment, wherein at least one bit of said second subset of bits is mutually exclusive from said first subset of bits;
• generating a phase encoded symbol code for each respective data segment in response to said symbol code of said data segment and said phase of said symbol code;
• continuous phase modulating each of said phase encoded symbol codes generated for each of said respective data segments to generate a signal;
• transmitting said signal;
• receiving said signal;
• correlating said signal with a continuous phase modulation correlator and generating a real correlation signal and an imaginary correlation signal thereby;
• and
• determining, in response to a sign and a relative magnitude of said real correlation signal, and in response to a sign and a relative magnitude of said imaginary correlation signal, a phase of said received signal.

An apparatus for communication, comprising:

• a data register coupled to a signal stream;
• a clock signal coupled to said data register, whereby a first predetermined number of bits of said signal stream are entered and stored in said data register;
• a symbol table coupled to said data register, said symbol table comprising a plurality of symbol codes, whereby said bits stored in said data register are used to select a symbol code;
• a phase determination circuit coupled to said signal stream, whereby a second predetermined number of bits of said signal stream are used to generate a phase value, wherein at least one of said second predetermined number of bits is mutually exclusive from said first predetermined number of bits;
• a phase register coupled to said phase determination circuit, whereby an output of said phase register is used to generate said phase value and whereby said phase value is thereafter stored in said phase register;
• a phase selector coupled to said symbol table and to said phase register, whereby said selected symbol code is phase encoded with said phase value.

A method for communicating, comprising the steps of:

• dividing a signal stream into multi-bit segments;
• for each of said segments, loading a first subset of bits of said segment into a data symbol register;
• for each of said segments, loading a second subset of bits of said segment into a phase selection register, wherein at least one of said second subset of bits is mutually exclusive from said first subset of bits;
• selecting a symbol code from a plurality of symbol codes in response to the contents of said data symbol register;
• determining a phase of said symbol code in response to the contents of said phase selection register and in response to a phase of a previous symbol code;
• and
• phase encoding said symbol code with said phase of said symbol code.