Joint detection with low computational complexity for hybrid TD-CDMA systems

In the hybrid multiple access technique TD/CDMA both multiple-access interference (MAI) and intersymbol interference (ISI) arise. In order to combat the overall interference (ISI+MAI), we propose two efficient joint detection schemes based respectively on zero-forcing and minimum-mean square error criteria. If M denotes the product of the number of active users U and the number of symbols per block N, the computational complexity has been reduced from O(M³), of previously proposed schemes, to O(MU²), where U≪M. In fact, exploiting the asymptotic equivalence between finite-order Toeplitz matrices and circulant matrices, most computation can be carried out very efficiently through an extensive use of DFT and IDFT transforms. Performance results based on the UMTS standard under definition are presented