In this thesis, we rst proposed the relative threshold tree pruning (RTTP) al-
gorithm suitable for pre-whitening tree pruning (PWTP) multiuser detection
(MUD) for multi-carrier code-division multiple access (MC-CDMA). RTTP
is more e cient and selective than the conventional M-algorithm and achieves
relatively lower error rate at high signal-to-noise ratio (SNR). For rectangular
2-D symbols, user partitioning (UP) is proposed and, when combined with
good user order sorting (UOS) produces a softer UOS not obtainable with-
out UP. The proposed DLUPS and DLUP-RMOPS are applicable with the
downlink channel and real-valued spreading code, while the proposed UP-
RMOPS is suitable in the general cases; ROMPS is a previously proposed
UOS that can be replaced by any other good UOS. A simple downlink phase
rotation (DLPHR) is proposed to convert any real-valued spreading code
into complex-valued and to signi cantly reduce multiple access interference
(MAI) when 1-D symbols are used with downlink channel. DLPHR can be
viewed as an increase of transmit diversity with the same limited resource.
All proposed algorithms apply in the presence of carrier frequency o set
which causes inter-carrier interference (ICI) of orthogonal frequency division
multiplexing (OFDM). Simulation results show that the proposed algorithms
indeed achieve lower error rate and thus enable low complexity MUD ap-
proaching optimal performance.