1. A wireless transmit/receive unit (WTRU) comprising: a processor configured to process a received vector using a sliding window based approach; the processor configured to process windows of response matrix values to produce an estimated data vector such that for each window: a non-Toeplitz channel response matrix is transformed into a Toeplitz matrix; the Toeplitz matrix is transformed into a circulant channel response matrix; and the circulant channel response matrix is used in a discrete Fourier transform based approach to estimate a data vector corresponding to the window; and a summer configured to combine the data vector estimated in each window to form a combined data vector.