Novel synchronous CDMA multiuser detection scheme: orthogonal decision-feedback detection and its performance study

The authors propose a novel multiuser scheme for synchronous DS/CDMA the orthogonal decision-feedback detector (ODFD), which performs equally well as the decorrelating decision-feedback detector (DDFD) but with a much reduced complexity. The ODFD employs a matched filter bank matching to a set of orthonormal sequences which are generated by the Gram-Schmidt orthogonalisation procedure based on spreading codes. The ODFD algorithm involves only the orthonormal coefficient matrix which requires no frequent recalculations even when system parameters change. Successive decision-feedback detection is performed immediately at the output of the ODFD matched filter bank without the transform matrix which is required in the DDFD