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Design of
-Ary Low Correlation Zone
Sequence Sets by Interleaving
M
Jin-Ho Chung and Kyeongcheol Yang
Dept. of Electronics and Electrical Engineering
Pohang University of Science and Technology (POSTECH)
Pohang, Kyungbuk 790-784, Korea
{
jinho, kcyang
}
@postech.ac.kr
Abstract.
In this paper we present a new method to construct an
M
-
ary low correlation zone (LCZ) sequence set from an
M
-ary sequence
with good autocorrelation by using the interleaved technique, where
M
is an even integer. We also show that the constructed LCZ sequence sets
are optimal or nearly optimal with respect to the Tang-Fan-Matsufuji
bound. Due to the flexibility in the choice of alphabet size, LCZ size,
and period, our construction may be applied to various situations in
quasi-synchronous code-division multiple access environment.
Keywords:
low correlation zone (LCZ) sequences, quasi-synchronous
code-division multiple access (QS-CDMA),
M
-ary sequences, interleaved
sequences.
1
Introduction
In quasi-synchronous code-division multiple access (QS-CDMA) systems [
?
,10],
relative chip time delays among the signals of different users are restricted in a
certain time interval. For this reason, the performance of a QS-CDMA system is
determined by the correlation of spreading sequences around the origin [4]. Low
correlation zone (LCZ) sequences are good candidates for spreading sequences in
such systems. For applications in QS-CDMA systems, we need an LCZ sequence
set which contains many sequences and has a wide low correlation zone. However,
there is some trade-off between the set size and the LCZ size of an LCZ sequence
set, which is formulated by the bound established by Tang, Fan, and Matsufuji
[12]. Therefore, designing an optimal LCZ sequence set with respect to the Tang-
Fan-Matsufuji bound is a very important problem.
There have been many research results for design of LCZ sequence sets [3,
4, 5, 6, 7, 8, 11, 13, 14]. Almost all of the previous constructions were based on
period
p
n
1, and LCZ size (
p
n
1)
/
(
p
m
n
(see [3] for a unified
theory on this type of LCZ sequence sets). Recently, Kim et al. presented a new
design of binary LCZ sequence sets of period 2(2
n
−
−
−
1) for some
m
|
−
1) with flexible LCZ size
