Asymptotically locally optimal weight vector design for a tighter correlation lower bound of quasi-complementary sequence sets
A quasi-complementary sequence set (QCSS) refers to a set of two-dimensional matrices with low nontrivial aperiodic auto- and cross-correlation sums. For multicarrier code-division multiple-access applications, the availability of large QCSSs with low correlation sums is desirable. The generalized L...
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sg-ntu-dr.10356-1051532019-12-06T21:46:38Z Asymptotically locally optimal weight vector design for a tighter correlation lower bound of quasi-complementary sequence sets Liu, Zilong Guan, Yong Liang Mow, Wai Ho School of Electrical and Electronic Engineering Correlation Multicarrier Code Division Multiple Access Engineering::Electrical and electronic engineering A quasi-complementary sequence set (QCSS) refers to a set of two-dimensional matrices with low nontrivial aperiodic auto- and cross-correlation sums. For multicarrier code-division multiple-access applications, the availability of large QCSSs with low correlation sums is desirable. The generalized Levenshtein bound (GLB) is a lower bound on the maximum aperiodic correlation sum of QCSSs. The bounding expression of GLB is a fractional quadratic function of a weight vector w and is expressed in terms of three additional parameters associated with QCSS: the set size K, the number of channels M, and the sequence length N. It is known that a tighter GLB (compared to the Welch bound) is possible only if the condition M ≥ 2 and K ≥ K̅ + 1, where K̅ is a certain function of M and N, is satisfied. A challenging research problem is to determine if there exists a weight vector that gives rise to a tighter GLB for all (not just some) K ≥ K̅ + 1 and M ≥ 2, especially for large N, i.e., the condition is asymptotically both necessary and sufficient. To achieve this, we analytically optimize the GLB which is (in general) nonconvex as the numerator term is an indefinite quadratic function of the weight vector. Our key idea is to apply the frequency domain decomposition of the circulant matrix (in the numerator term) to convert the nonconvex problem into a convex one. Following this optimization approach, we derive a new weight vector meeting the aforementioned objective and prove that it is a local minimizer of the GLB under certain conditions. NRF (Natl Research Foundation, S’pore) Accepted version 2019-08-05T05:32:03Z 2019-12-06T21:46:38Z 2019-08-05T05:32:03Z 2019-12-06T21:46:38Z 2017 Journal Article Liu, Z., Guan, Y. L., & Mow, W. H. (2017). Asymptotically locally optimal weight vector design for a tighter correlation lower bound of quasi-complementary sequence sets. IEEE Transactions on Signal Processing, 65(12), 3107-3119. doi:10.1109/TSP.2017.2684740 1053-587X https://hdl.handle.net/10356/105153 http://hdl.handle.net/10220/49529 http://dx.doi.org/10.1109/TSP.2017.2684740 en IEEE Transactions on Signal Processing © 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. The published version is available at: https://doi.org/10.1109/TSP.2017.2684740 13 p. application/pdf |
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Correlation Multicarrier Code Division Multiple Access Engineering::Electrical and electronic engineering Liu, Zilong Guan, Yong Liang Mow, Wai Ho Asymptotically locally optimal weight vector design for a tighter correlation lower bound of quasi-complementary sequence sets |
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A quasi-complementary sequence set (QCSS) refers to a set of two-dimensional matrices with low nontrivial aperiodic auto- and cross-correlation sums. For multicarrier code-division multiple-access applications, the availability of large QCSSs with low correlation sums is desirable. The generalized Levenshtein bound (GLB) is a lower bound on the maximum aperiodic correlation sum of QCSSs. The bounding expression of GLB is a fractional quadratic function of a weight vector w and is expressed in terms of three additional parameters associated with QCSS: the set size K, the number of channels M, and the sequence length N. It is known that a tighter GLB (compared to the Welch bound) is possible only if the condition M ≥ 2 and K ≥ K̅ + 1, where K̅ is a certain function of M and N, is satisfied. A challenging research problem is to determine if there exists a weight vector that gives rise to a tighter GLB for all (not just some) K ≥ K̅ + 1 and M ≥ 2, especially for large N, i.e., the condition is asymptotically both necessary and sufficient. To achieve this, we analytically optimize the GLB which is (in general) nonconvex as the numerator term is an indefinite quadratic function of the weight vector. Our key idea is to apply the frequency domain decomposition of the circulant matrix (in the numerator term) to convert the nonconvex problem into a convex one. Following this optimization approach, we derive a new weight vector meeting the aforementioned objective and prove that it is a local minimizer of the GLB under certain conditions. |
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School of Electrical and Electronic Engineering |
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School of Electrical and Electronic Engineering Liu, Zilong Guan, Yong Liang Mow, Wai Ho |
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Liu, Zilong Guan, Yong Liang Mow, Wai Ho |
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Liu, Zilong |
title |
Asymptotically locally optimal weight vector design for a tighter correlation lower bound of quasi-complementary sequence sets |
title_short |
Asymptotically locally optimal weight vector design for a tighter correlation lower bound of quasi-complementary sequence sets |
title_full |
Asymptotically locally optimal weight vector design for a tighter correlation lower bound of quasi-complementary sequence sets |
title_fullStr |
Asymptotically locally optimal weight vector design for a tighter correlation lower bound of quasi-complementary sequence sets |
title_full_unstemmed |
Asymptotically locally optimal weight vector design for a tighter correlation lower bound of quasi-complementary sequence sets |
title_sort |
asymptotically locally optimal weight vector design for a tighter correlation lower bound of quasi-complementary sequence sets |
publishDate |
2019 |
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https://hdl.handle.net/10356/105153 http://hdl.handle.net/10220/49529 http://dx.doi.org/10.1109/TSP.2017.2684740 |
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1681037728300400640 |