A Double-Stage Multiuser Detector with FFT-Based Equalization for Asynchronous CDMA Ultra-Wideband Communication Systems

A novel multiuser transmission and detection scheme for high-speed asynchronous ultra-wideband (UWB) communication systems is proposed. Firstly, a block-spreading code-division multiple-access (BS-CDMA) scheme with zero correlation window (ZCW) is designed for application in asynchronous UWB communication systems with dense frequency selective fading propagation. As a result, multiple access interference can be completely removed by maintaining the spreading code orthogonality. Secondly, the UWB channel model is converted from a block Toeplitz matrix into block circulant matrix. Consequently, the inter-symbol interference is eliminated through the use of a fast Fourier transform (FFT) based minimum mean square error equalization. It is shown that the proposed multiuser transmission and detection scheme for UWB systems can deliver superior performance relative to the existing schemes, with low computation complexity