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In-Depth Information
Two New Families of Low-Correlation
Interleaved QAM Sequences
Gagan Garg
1
,P.VijayKumar
2
,
, and C.E. Veni Madhavan
1
1
Department of Computer Science and Automation,
Indian Institute of Science, Bangalore 560012, India
2
Department of Electrical Communication Engineering,
Indian Institute of Science, Bangalore 560012, India
gagan.garg@gmail.com, vijayk@usc.edu, cevm@csa.iisc.ernet.in
Abstract.
Two families of low correlation QAM sequences are presented
here. In a CDMA setting, these sequences have the ability to transport
a large amount of data as well as enable variable-rate signaling on the
reverse link.
The first family
I
2
SQ−B
is constructed by interleaving 2 selected
QAM sequences. This family is defined over
M
2
-QAM, where
M
=
2
m
,m ≥
2. Over 16-QAM, the normalized maximum correlation
θ
max
is bounded above by
1
.
17
√
N
,where
N
is the period of the sequences
in the family. This upper bound on
θ
max
is the lowest among all known
sequence families over 16-QAM.
The second family
I
4
SQ
is constructed by interleaving 4 selected
QAM sequences. This family is defined over
M
2
-QAM, where
M
=
2
m
,m ≥
3, i.e., 64-QAM and beyond. The
θ
max
for sequences in this
family over 64-QAM is upper bounded by
1
.
60
√
N
.Forlarge
M
,
θ
max
1
.
64
√
N
. These upper bounds on
θ
max
are the lowest among all
known sequence families over
M
2
-QAM,
M
=2
m
,m≥
3.
1
Introduction
Low-correlation sequences over QAM constellations are of interest partly on
account of the increasingly common usage of the QAM alphabet as a signaling
alphabet and also on account of their ability to carry a larger number of data
bits per sequence period in comparison with the one or the two bits traditionally
associated with BPSK or QPSK sequence families.
1.1 Results in Perspective
In this subsection, we summarize the results of this paper with respect to the
currently known QAM sequence families.
