Patent ID: 7277382

Claim:
A method for implementation of hybrid Walsh complex orthogonal codes for CDMA, said method comprising the steps of: forming N Walsh codes each with N chips wherein N is a power of 2, classifying said Walsh codes into even codes and odd codes according to the Walsh codes even and odd properties, defining said Walsh codes by {+1, −1} valued orthogonal Hadamard codes reordered with increasing sequency, wherein sequency is the average rate of phase changes over each N chip code length, reordering N discrete Fourier transform codes each with N real chips according to increasing frequency for even and odd codes, constructing a one-to-one correspondence of said N Walsh codes with said N Discrete Fourier transform (DFT) codes such that sequency corresponds to frequency, even codes correspond to even codes, and odd codes correspond to odd codes, arranging said DFT codes in increasing frequency, wherein each code is the complex addition of a real axis code and an imaginary axis code, constructing a mapping which uses said N Fourier codes to construct said DFT codes, using said mapping and said correspondence of sequency and frequency, and even and odd codes to generate real and imaginary axis component codes of said hybrid Walsh codes, said hybrid Walsh codes W(c) with code index c=0, 1, 2, . . . , −1, are re-orderings of said Walsh codes defined by equations for ⁢ ⁢ c = 0 , W ~ ⁡ ( c ) = W ⁡ ( 0 ) + j ⁢ ⁢ W ⁡ ( 0 ) for ⁢ ⁢ c = 1 , 2 , ⁢ … ⁢ , N / 2 - 1 , W ~ ⁡ ( c ) = W ⁡ ( 2 ⁢ c ) + j ⁢ ⁢ W ⁡ ( 2 ⁢ c - 1 ) for ⁢ ⁢ c = N / 2 , W ~ ⁡ ( c ) = W ⁡ ( N - 1 ) + j ⁢ ⁢ W ⁡ ( N - 1 ) ) for ⁢ ⁢ c = N / 2 + 1 , ⁢ … ⁢ , N - 1 , W ~ ⁡ ( c ) = W ⁡ ( 2 ⁢ N - 2 ⁢ c - 1 ) + j ⁢ ⁢ W ⁡ ( 2 ⁢ N - 2 ⁢ c ) wherein W(u) is said Walsh code for index u and j=√−1, generating hybrid Walsh codes by reading code chip values from Walsh code memory and writing to said hybrid Walsh code memory, reading said hybrid Walsh codes from said Hybrid Walsh code memory and, using said hybrid Walsh codes in an encoder for a CDMA communications link transmitter by replacing existing said Walsh real codes with said hybrid Walsh complex codes and in a decoder for a communications link receiver, in order to spread the data symbols over the transmission bandwidth.