Spread spectrum communication system

A method for generating code division multiple access data from data having different rates by a direct spread spectrum, said method comprising the steps of:

• combining an orthogonal code and a reversed orthogonal code obtained by inverting the orthogonal code, for each of orthogonal code sequences structured by a quadratic residue sequence thereby to generate a first sequence of orthogonal codes;
• combining two of the orthogonal code for each of orthogonal code sequences structured by the quadratic residue sequence thereby to generate a second sequence of orthogonal codes;
• combining two of the reversed orthogonal code for each of orthogonal code sequences structured by the quadratic residue sequence thereby to generate a third sequence of orthogonal codes;
• and
• generating another orthogonal code having twice a code length of the orthogonal code from the first, second and third sequence of orthogonal codes;
• and
• multiplying the generated orthogonal code and a different quadratic residue sequence, together.

A method for generating code division multiple access data having tree-structured codes from data having different rates by a direct spread spectrum, said method comprising the steps of:

• generating the tree-structured codes by a Walsh sequence;
• performing addition of modulo 2 for each corresponding bits of two code sequences, each having one spreading factor;
• and
• modulating two digital symbols of digital signals respectively on positions of values 0 and 1 obtained by the step of performing addition of modulo 2 thereby that the digital signals may be transmitted with one half of the one spreading factor.

A method for generating code division multiple access data having tree-structured codes by from data having different rates by a direct spread spectrum, said method comprising the steps of:

• generating the tree-structured codes by orthogonal Gold codes;
• performing addition of modulo 2 for each corresponding bits of two code sequences, each having one spreading factor;
• and
• modulating two digital symbols of digital signals respectively on positions of values 0 and 1 obtained by the step of performing addition of modulo 2 thereby that the digital signals may be transmitted with one half of the one spreading factor.

A method for generating code division multiple access data having tree-structured codes by from data having different rates by a direct spread spectrum, said method comprising the steps of:

• generating the tree-structured codes by a Walsh sequence;
• performing addition of modulo 2 for each of the tree-structured codes to find four code sequences of one spreading factor, all of which are zero value;
• and
• modulating four digital symbols of digital signals on four respective position for each two bits which are in orthogonal relation thereby that the digital signal may be transmitted with one fourth of the one spreading factor.

A method for generating code division multiple access data having tree-structured codes by from data having different rates by a direct spread spectrum, said method comprising the steps of:

• generating the tree-structured codes by orthogonal Gold codes;
• performing addition of modulo 2 for each of the tree-structured codes to find four code sequences of one spreading factor, all of which are zero value;
• and
• modulating four digital symbols of digital signals on four respective position for each two bits which are in orthogonal relation thereby that the digital signal may be transmitted with one fourth of the one spreading factor.