Patent ID: 7197007

Claim:
A method for wireless communications comprising: providing a multicarrier direct-sequence code-division multiple-access (MS-DS/CDMA) communications system; generating a code tree of two-dimensional orthogonal variable spreading factor (2D-OVSF) codes, wherein each node of the code tree has a corresponding matrix; selecting an M×N matrix from a node of the code tree, where M relates to the number of available frequency carriers in the MS-DS/CDMA system, N relates to a spreading factor, M=2 k , N=2 k+α , k is greater than zero, and α is greater than or equal to zero; and assigning the M×N matrix to a MS-DS/CDMA-enabled device of the MS-DS/CDMA system to serve as a signature sequence of the device; wherein generating the code tree comprises: providing a first set of orthogonal 2×2 matrices { A ( 2 × 2 ) ( 1 ) , A ( 2 × 2 ) ( 2 ) } ; ⁢ providing a second set of orthogonal 2×2 matrices ⁢ { B ( 2 × 2 ) ( 1 ) , B ( 2 × 2 ) ( 2 ) } ; ⁢ utilizing the first set of 2×2 matrices to generate a pair of progenitor nodes in the code tree that respectively represent matrices A (1) (2×2 α ) and A (2) (2×2 α ) by iterating the relationship: A ( 1 ) ⁢ { 2 × 2 i + 1 } = [ R ( 1 ) ⁢ { 2 × 2 i } ⁢ A ( 2 ) ⁢ { 2 × 2 i } ] , A ( 2 ) ⁢ { 2 × 2 i + 1 } = [ A ( 1 ) ⁢ { 2 × 2 i } - A ( 2 ) ⁢ { 2 × 2 i } ] ; utilizing the matrices A (1) (2×2 α ) and A (2) (2×2 α ) to generate a child node of one of the progenitor nodes, the child node having the M×N matrix, by iterating the relationship: A (i−1) (O×P) =[B (1) (2×2) {circle around (×)}A (i/2) (O/2×P/2) ], A (i) (O×P) =[B (2) (2×2) {circle around (×)}A (i/2) (O/2×P/2) ]; wherein {circle around (×)} is a Kronecker product, and children nodes of the code tree correspond to data transmission rates that are slower than those of parent nodes, thereby transmitting multirate transmissions by utilizing orthogonal matrices in the code tree.