Partial Correlation Effects in Direct-Sequence Spread-Spectrum Multiple-Access Communication Systems

Nearly all previous analytical results on the performance of direct-sequence spread-spectrum multiple-access (DS/SSMA) communication systems are restricted to systems in which the period
p
of the signature sequence is equal to the number
N
of chips per data symbol. In many applications, however, it is necessary to employ signature sequences whose period
p
is much larger than
N
. Thus, successive
N
-chip segments of the signature sequence are used to phase-code the carrier during the transmission of successive data symbols. The performance of such systems depends on the partial correlation properties of the signature sequences (rather than the aperiodic correlation properties as in the case when
N=p
). In this paper, we consider the performance of a DS/SSMA system for arbitrary values of
p
and
N
. As special cases of our results, we delermine the effects of partial correlation in three classes of systems: those for which
N =p
, those for which
N
and
p
are relatively prime, and those for which
N
is a divisor of
p
. We also provide two methods for the design of sequences for systems for which
N
is a divisor of
p
.