Low complexity data detection using fast Fourier transform decomposition of channel correlation matrix

This paper presents an efficient FFT based channel-equalization method for data detection. The data detection method is applicable to multiuser detection in the downlink, and single user detection in the uplink. It can operate for chip rate sampling as well as higher sampling rates. The FFT implementation is enabled by approximating the channel correlation matrix by a right circulant matrix. Furthermore, the circulant matrix approximation is optimized via a simple permutation procedure. The solution offers very low complexity relative to other receivers. For instance, for twelve codes with spreading factor 16 each, the complexity of the proposed solution is about 25% of the complexity of the approximate Cholesky based joint detector. The proposed FFT based solution significantly outperforms the matched filter (MF) and is comparable in performance to the approximate Cholesky based joint detector.