  In this paper, we propose a widely-linear (WL) receiver structure for
multiple access interference (MAI) and {jamming signal (JS)} suppression in
direct-sequence code-division multiple-access (DS-CDMA) systems. A vector space
projection (VSP) scheme is also considered to cancel the {JS} before detecting
the desired signals. We develop a novel multiple-candidate successive
interference cancellation (MC-SIC) scheme which processes two consecutive user
symbols at one time to process the unreliable estimates and a number of
selected points serve as the feedback candidates for interference cancellation,
which is effective for alleviating the effect of error propagation in the SIC
algorithm. Widely-linear signal processing is then used to enhance the
performance of the receiver in non-circular modulation scheme. By bringing
together the techniques mentioned above, a novel interference suppression
scheme is proposed which combines the widely-linear multiple-candidate SIC
(WL-MC-SIC) minimum mean-squared error (MMSE) algorithm with the VSP scheme to
suppress MAI and {JS} simultaneously. Simulations for binary phase shift keying
(BPSK) modulation scenarios show that the proposed structure achieves a better
MAI suppression performance compared with previously reported SIC MMSE
receivers at lower complexity and a superior {JS} suppression performance.
