20,607 research outputs found
Autocorrelations of Binary Sequences and Run Structure
We analyze the connection between the autocorrelation of a binary sequence
and its run structure given by the run length encoding. We show that both the
periodic and the aperiodic autocorrelation of a binary sequence can be
formulated in terms of the run structure. The run structure is given by the
consecutive runs of the sequence. Let C=(C(0), C(1),...,C(n)) denote the
autocorrelation vector of a binary sequence. We prove that the kth component of
the second order difference operator of C can be directly calculated by using
the consecutive runs of total length k. In particular this shows that the kth
autocorrelation is already determined by all consecutive runs of total length
L<k. In the aperiodic case we show how the run vector R can be efficiently
calculated and give a characterization of skew-symmetric sequences in terms of
their run length encoding.Comment: [v3]: minor revisions, accepted for publication in IEEE Trans. Inf.
Theory, 17 page
Optimization Methods for Designing Sequences with Low Autocorrelation Sidelobes
Unimodular sequences with low autocorrelations are desired in many
applications, especially in the area of radar and code-division multiple access
(CDMA). In this paper, we propose a new algorithm to design unimodular
sequences with low integrated sidelobe level (ISL), which is a widely used
measure of the goodness of a sequence's correlation property. The algorithm
falls into the general framework of majorization-minimization (MM) algorithms
and thus shares the monotonic property of such algorithms. In addition, the
algorithm can be implemented via fast Fourier transform (FFT) operations and
thus is computationally efficient. Furthermore, after some modifications the
algorithm can be adapted to incorporate spectral constraints, which makes the
design more flexible. Numerical experiments show that the proposed algorithms
outperform existing algorithms in terms of both the quality of designed
sequences and the computational complexity
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