Georgian Electronic Scientific Journal: Computer Science and Telecommunications 2008|No.1(15)
DS-CDMA System with Linear Multiuser Detection in AWGN Channel
S.R. Sheikh Raihan1 and B.C.Ng
Department of Electrical Engineering, Faculty of Engineering, University of Malaya
50603 Kuala Lumpur, Malaysia
Direct sequence code division multiple access (DS-CDMA) is a popular wireless
technology. This paper presents comparative study between linear multiuser detectors,
optimal multiuser detector, and conventional single user matched filter in DS-CDMA
system. Analysis and simulations are conducted in synchronous AWGN channel, and
Gold sequence is used as the spreading codes.
The study shows that optimal multiuser detector performs better than the conventional
matched filter and linear multiuser detector in terms of BER performance. However,
optimal multiuser detector suffers from complex computation and costly implementation.
MMSE detector provides better error performance than the decorrelating detector, but it
utilizes the estimation of the received powers.
Keywords: CDMA, multiuser detection, AWGN
In DS-CDMA communication system, users are multiplexed by distinct codes rather than by
orthogonal frequency bands or by orthogonal time slots. A conventional DS-CDMA detector
follows a single user detection strategy in which each user is treated separately as a signal, while the
other users are considered as either interference or noise. A comprehensive look on DS-CDMA
system can be found in [1-14].
Interference such as multiple access interference (MAI) restricts the capacity and the
performance of DS-CDMA systems. As described in , MAI is the interference between active
users, and causes timing offsets between signals. Conventional detectors detect each user
separately, and do not take MAI into consideration. Due to this, multiuser detection strategies have
been proposed in [15-29].
Multiuser detection seek