Title: Design and Implementation of a Low Complexity Multiuser
Detector for Hybrid CDMA Systems
Author: Vittorio Rampa
Abstract: In hybrid CDMA systems, multiuser detection (MUD)
algorithms are adopted at the base station to reduce both multiple access and
inter-symbol interference by exploiting space-time (ST) signal processing
techniques. Linear ST-MUD algorithms solve a linear problem where the system
matrix has a block-Toeplitz shape. While exact inversion techniques impose an
intolerable computational load, reduced complexity algorithms may be efficiently
employed even if they show sub-optimal behavior introducing performance
degradation and near-far effects. The block-Fourier MUD algorithm is generally
considered the most effective one. However, the block-Bareiss MUD algorithm,
that has been recently reintroduced, shows also good performance and low
computational complexity comparing favorably with the block-Fourier one. In this
paper, both MUD algorithms will be compared, along with other well known ones,
in terms of complexity, performance figures, hardware feasibility and
implementation issues. Finally a short hardware description of the block-Bareiss
and block-Fourier algorithms will be presented along with the FPGA (Field
Programmable Gate Array) implementation of the block-Fourier using standard VHDL
(VHSIC Hardware Description Language) design.