Mismatched-filtering of concatenated spreading sequences for approximately synchronized CDMA-systems

A new method for the construction of spreading sequences for approximately synchronized DS-CDMA systems is proposed. The construction method is based on the concatenation of a binary inverse-filtered inner sequence with outer sequences of a family of binary sequences. If the outer sequences are chosen to be the columns of a Hadamard matrix the system exhibits nearly no cross-interference. Using the proposed sequences, it is possible to combine the advantages of asynchronous and synchronous CDMA systems in a so-called partly-synchronous CDMA system.