Performance bounds for blind and group-blind multiuser detectors in multipath channels

In blind or group-blind linear multiuser detection, the detector is estimated directly from the received signals, based on some partial knowledge about the system. The basic scenario is that the receiver has only limited knowledge about the CDMA channel, e.g., the signature waveform of a given user (or the signature waveforms of some but not all users group-blind detection), based on which a linear multiuser detector is estimated from the received signals and subsequently employed to demodulate the data symbols of the given user. In this paper, we address the following fundamental problem: Given a particular linear multiuser detector, e.g., the linear MMSE detector, and given certain prior knowledge about the channel, what is the best achievable performance of the corresponding blind or group-blind implementation of this linear detector, in terms of the output signal-to-interference-plus-noise ratio (SINR)?.