Chip-level Channel Equalization with Rake-like Structures for Multicode Downlink WCDMA Communications

In this paper, we propose a low complexity multi-code chip-level channel equalizer for the downlink UMTS FDD mode. Both block form and filter form implementations are considered. The proposed receiver can be of ZF or MMSE type, and consists of a linear equalizer followed by a bank of correlators corresponding to the spreading codes, and a decision device. It has a Rake-like structure and does not need the knowledge of the spreading codes to compute the equalizer filter coefficients. We show how to compute the equalization matrix at low complexity, and we give a measure of the upper-bound of the equalizer filter depth. Simulation results are given to corroborate the good performance of the equalizer in the high speed downlink packet access (HSDPA) scenario