Method and apparatus for generating orthogonal codes with wide range of spreading factor

An apparatus for generating two sets of orthogonal codes of a spreading factor N in a quasi-synchronous spread spectrum system, the apparatus comprising:

• a sequence selector configured to select a two-level autocorrelation sequence;
• an index selector configured to select a first indices set and a second indices set from the two-level autocorrelation sequence;
• and
• an orthogonal code generator configured to generate two quasi-orthogonal codesets using the first indices set and the second indices set,
• wherein the two-level autocorrelation sequence comprises at least one of an element −1 and an element 1.

A method of apparatus comprising at least one processor for generating two sets of orthogonal codes of a spreading factor N in a quasi-synchronous spread spectrum communication system, the method comprising:

• selecting, by a sequence selector, a two-level autocorrelation sequence;
• selecting, by an index selector, a first indices set and a second indices set from the two-level autocorrelation sequence;
• generating, by an orthogonal code generator, a first quasi-orthogonal codeset by circularly reading the two-level autocorrelation sequence, starting from a position corresponding to an index of an element 1 to one of a left-hand side and a right-hand side;
• generating, by the orthogonal code generator, a second quasi-orthogonal codeset by circularly reading the two-level autocorrelation sequence, starting from a position corresponding to an index of an element −1 to one of the left-hand side and the right-hand side;
• and
• obtaining, by the orthogonal code generator, two sets of orthogonal codes from the first quasi-orthogonal codeset and the second quasi-orthogonal codeset.