Non-contiguous variable length orthogonal codes

A method of spreading an information signal comprising:

• using an processor to select a first code from a set of binary spreading codes to serve as a pivot code, the pivot code having an equal non-zero number of members of a first binary value and members of a second binary value;
• using the processor to select positions of the pivot code having one of the first binary value and the second binary value to serve as first target positions;
• using the processor to select a second code from the set of binary spreading codes to serve as a derivation code;
• using the processor to replace chips of the second code corresponding to the first target positions of the pivot code with a non-binary value and thereby forming a first ternary spreading code;
• and,
• the processor using the first ternary spreading code to spread bits of the information signal.

A method of deriving lower spreading-factor codes from a set of higher spreading-factor codes, each chip of said lower spreading-factor codes having values denoted by ‘A’, ‘B’ or null, comprising:

• using a processor to select a first, higher spreading-factor code to be a pivot code, the pivot code comprising a non-zero number of ‘A’-valued symbols and a non-zero number of ‘B’-valued symbols;
• using the processor to select a second, higher spreading-factor code from which to derive two lower spreading-factor codes;
• using the processor to select chips of said second, higher spreading-factor code corresponding to positions of chips of value ‘A’ in said pivot code, placing null-valued chips in remaining chip positions in said pivot code to form a first lower-spreading-factor code, and
• using the processor to select chips of said second code corresponding to positions of chips of value ‘B’ in said pivot code, placing null-valued chips in remaining chip positions in said pivot code to form a second lower-spreading-factor code.

An information symbol transmitter comprising:

• at least a first symbol source for supplying an information signal comprising at least a first stream of I,Q bit pairs;
• means for using either a ternary code or at least one pivot code for spreading the at least first stream of I,Q bit pairs and thereby respectively forming first chips and second chips;
• a radio signal modulator for transmitting the first chips and second chips over a radio interface;
• wherein the information symbol transmitter is configured to:
• select a first code from a set of binary spreading codes to serve as a pivot code, the pivot code having non-zero number of members of a first binary value and non-zero number of members of a second binary value;
• select positions of the pivot code having one of the first binary value and the second binary value to serve as first target positions;
• select a second code from the set of binary spreading codes to serve as a derivation code;
• replace chips of the second code corresponding to the first target positions of the pivot code with a non-binary value and thereby generating the ternary code.