SUMMARYA pilot assisted CDMA system which uses extended spreading sequences with guard sequences under a quasi-synchronous condition is capable of separating the interference components included in the input of a de-correlating receiver by solving a system of linear equations. The performance of such a system, however, depends on the property of the de-correlating matrix consisting of the received pilots, which correspond to the respective user spreading sequences and the multi-path channel conditions. That is, the regularity of the matrix often tends to degrade, and the rank reduces occasionally primarily due to the multi-paths, resulting in solutions that are vulnerable to AWGN. The present paper proposes an effective technique to solve this problem by introducing a virtual user into a group of real users that are to be served. The simulation results indicate a remarkable improvement in the bit-error-rate (BER) performance. In addition, based on the BER performance, the system has a RAKE-like function that has power-sum characteristics.
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