M. Brandtpearce et B. Aazhang, MULTIUSER DETECTION FOR OPTICAL CODE-DIVISION MULTIPLE-ACCESS SYSTEMS, IEEE transactions on communications, 42(2-4), 1994, pp. 1801-1810
This paper considers a multiuser detection scheme for optical direct s
equence code division multiple access (OCDMA) systems, referred to as
the multistage detector. Previous works in this area have proposed two
detectors: the correlation detector that is simple, but has poor perf
ormance for large number of users, and the optimal (minimum probabilit
y of error) detector that has exponential complexity in the number of
users. Efficient multiuser detection algorithms consider the interferi
ng user codes at the expense of electronic speed processing, unlike th
e optical processing achievable with the correlation detector. The mul
tiple access system using the proposed multistage detector is shown to
be of high performance and low complexity, compared to the convention
al correlation detector and the optimal detector. The model studied in
cludes multiple access interference as well as the Poisson characteris
tics of the optical direct detection process. An approximation to the
probability of error is derived for the multistage detector, and it is
compared to the actual error probability of the correlation detector,
to a lower bound to the error probability of the optimal detector, an
d to simulation results for the multistage detector. The probability o
f error is calculated using a characteristic function method. Results
are presented for a random code case that show a significant improveme
nt in the performance of the OCDMA system using this detector over the
correlation detector.