Signal Processing

IEEE TRANSACTIONS ON INFORMATION THEORY, VOL. 48, NO. 7, JULY 2002

1849

Performance of Blind and Group-Blind Multiuser Detectors
Anders Høst-Madsen, Member, IEEE, and Xiaodong Wang, Member, IEEE
Abstract—In blind (or group-blind) linear multiuser detection, the detector is estimated from the received signals, with the prior knowledge of only the signature waveform of the desired user (or the signature waveforms of some but not all users). The performance of a number of such estimated linear detectors, including the direct-matrix-inversion (DMI) blind linear minimum mean square error (MMSE) detector, the subspace blind linear MMSE detector, and the form-I and form-II group-blind linear hybrid detectors, are analyzed. Asymptotic limit theorems for each of the estimates of these detectors (when the signal sample size is large) are established, based on which approximate expressions for the average output signal-to-interderence-plus-noise ratios (SINRs) and bit-error rates (BERs) are given. To gain insights on these analytical results, the performance of these detectors in an equicorrelated code-division multiple-acces (CDMA) system is compared. Examples are provided to demonstrate the excellent match between the theory developed here and the simulation results. Index Terms—Asymptotic analysis, blind multiuser detection, group-blind multiuser detection, signal subspace.

, , and . In a direct-sequence spread-spectrum system with spreading gain , the signature sequence of the th user is of the form

form as

I. INTRODUCTION HIS paper is concerned with the analysis of the performance of blind and group-blind linear multiuser detection techniques for the basic discrete-time synchronous code-division multiple-access (CDMA) multiple-access -user channel

T

(1) , , and are the received where amplitude, data bit, and unit-energy signature sequence of is the the th user, respectively; and additive white Gaussian noise. (In this paper, we denote as an

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