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Blind estimation of direct sequence spread spectrum signals in multipath

This paper focuses on blind estimation of the time delay, multipath parameters and unknown spreading code of a direct sequence spread spectrum (DS-SS) signal. This information may be useful for interception or jamming purposes, or for acquiring a new user in a multiuser CDMA system. A multirate, discrete-time model of the spread spectrum signal is introduced, which links this problem with array processing techniques. In this framework, we borrow blind channel estimation ideas, originally developed in the context of fractionally spaced equalizers or receivers with multiple antennas. Linear solutions are obtained, which are independent of the input distribution. A zero-forcing receiver/equalizer is proposed and its performance is analyzed. Finally, some illustrative simulations are presented.