In wideband code division multiple access (W-CDMA) systems, inter-symbol interference (ISI) introduced by multipath propagation can be significant due to large multipath delays. In the presence of multipath, each signal is subjected to frequency-selective fading and the orthogonality condition is distorted due to increased cross-correlation between the signature waveforms of the different users. In this paper, we study a subspace-based signature waveform estimation for downlink W-CDMA systems that provides estimates of the multiuser channels by exploiting the second-order statistics of the transmitted signal at the base station. We employ multiple antennas at the receiver to estimate the signature waveforms for overloaded systems. A zero-forcing equalizer and a matched-filter detector are employed to estimate the received signal constellations. Simulations are performed to evaluate the effectiveness of the algorithm.