Alexei Ashikhmin | Bell Labs (original) (raw)
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Papers by Alexei Ashikhmin
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Abstract: Polynomial, or Delsarte's, method in coding theory accounts for a variety of structural... more Abstract: Polynomial, or Delsarte's, method in coding theory accounts for a variety of structural results on, and bounds on the size of, extremal configurations (codes and designs) in various metric spaces. In recent works of the authors the applicability of the method was extended to cover a wider range of problems in coding and information theory. In this paper we present a general framework for the method which includes previous results as particular cases.
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2015 IEEE Conference on Communications and Network Security (CNS), 2015
ABSTRACT We consider a single-cell downlink massive MIMO system in the presence of attackers capa... more ABSTRACT We consider a single-cell downlink massive MIMO system in the presence of attackers capable of jamming and eavesdropping. We show that, classical attacks of data jamming and eavesdropping can be simultaneously rendered useless. Specifically, we show that, without the need to use wiretap encoding, users achieve secure and reliable communication rate of which increases at the same speed as the rate achieved under no attack as the number of antennas grow. However, we introduce a new attack strategy that involves jamming pilot signals and eavesdropping in succession and show significant reductions in the achievable secrecy rate, even in the asymptotic regime in number of antennas. We develop counter strategies for this new attack in which we use secret key to encrypt the pilot sequence, rather than the data. We show that hiding the training signal assignments from the attacker enables the mobiles to achieve a secure degrees of freedom, identical to the one achieved under no attack.
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Designs, Codes and Cryptography, 1998
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Proceedings. International Symposium on Information Theory, 2005. ISIT 2005., 2005
ABSTRACT
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Dcc, 1998
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2008 IEEE International Conference on Communications, 2008
AbstractThe downlink transmission in multi-user multiple-input multiple-output (MIMO) systems ha... more AbstractThe downlink transmission in multi-user multiple-input multiple-output (MIMO) systems has been extensively stud-ied from both communication-theoretic and information-theoretic perspectives. Most of these papers assume perfect/imperfect channel knowledge. In ...
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Numbers, Information and Complexity, 2000
A new asymptotic upper bound on the size of binary codes with the property described inthe title ... more A new asymptotic upper bound on the size of binary codes with the property described inthe title is derived. The proof relies on the properties of the distance distribution of binarycodes established in earlier related works of the authors. 1 IntroductionLet C 2 Zn2 be a binary block code. One says that C corrects r errors if every sphere ofradius r in Zn2 contains at most one codevector and r is the maximal number with suchproperty. Relaxing this definition, one may require that every such sphere contain at mostm vectors from the code. ...
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Journal of Lightwave Technology, 2003
ABSTRACT
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Abstract. We address two topics related to the concept of minimal sup-ports (codewords) in linear... more Abstract. We address two topics related to the concept of minimal sup-ports (codewords) in linear codes. In the first part we study the distribu-tion of the number of minimal supports in random codes. In the second part, we propose a generalization of this concept for codes defined ...
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IEEE Transactions on Information Theory
In this paper we study moments of soft-bits of binary-input symmetric-output channels and solve s... more In this paper we study moments of soft-bits of binary-input symmetric-output channels and solve some extremal problems of the moments. We use these results to solve the extremal information combining problem. Further, we extend the information combining problem by adding a constraint on the second moment of soft-bits, and find the extreme distributions for this new problem.
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2007 IEEE International Symposium on Information Theory, 2007
We investigate the extrinsic information transfer (EXIT) functions of Hadamard codes in the conte... more We investigate the extrinsic information transfer (EXIT) functions of Hadamard codes in the context of repeat-zigzag Hadamard (RZH) codes with parallel decoding. The derived EXIT functions can serve as an effective tool for designing low-rate IRZH codes with parallel decoding in BIAWGN channels.
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Proceedings of the 1999 IEEE Information Theory and Communications Workshop (Cat. No. 99EX253), 1999
Abstract During the last two decades the fundamental geometric parameter of a block code, called ... more Abstract During the last two decades the fundamental geometric parameter of a block code, called covering radius, has been widely studied. In this paper we estimate this parameter for linear codes with the aid of the minimum distance of the dual code. We derive a new bound on covering radius which improves essentially on the known bounds in a wide range of normalized dual distances
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Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Abstract: Polynomial, or Delsarte's, method in coding theory accounts for a variety of structural... more Abstract: Polynomial, or Delsarte's, method in coding theory accounts for a variety of structural results on, and bounds on the size of, extremal configurations (codes and designs) in various metric spaces. In recent works of the authors the applicability of the method was extended to cover a wider range of problems in coding and information theory. In this paper we present a general framework for the method which includes previous results as particular cases.
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
ABSTRACT
Bookmarks Related papers MentionsView impact
2015 IEEE Conference on Communications and Network Security (CNS), 2015
ABSTRACT We consider a single-cell downlink massive MIMO system in the presence of attackers capa... more ABSTRACT We consider a single-cell downlink massive MIMO system in the presence of attackers capable of jamming and eavesdropping. We show that, classical attacks of data jamming and eavesdropping can be simultaneously rendered useless. Specifically, we show that, without the need to use wiretap encoding, users achieve secure and reliable communication rate of which increases at the same speed as the rate achieved under no attack as the number of antennas grow. However, we introduce a new attack strategy that involves jamming pilot signals and eavesdropping in succession and show significant reductions in the achievable secrecy rate, even in the asymptotic regime in number of antennas. We develop counter strategies for this new attack in which we use secret key to encrypt the pilot sequence, rather than the data. We show that hiding the training signal assignments from the attacker enables the mobiles to achieve a secure degrees of freedom, identical to the one achieved under no attack.
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Designs, Codes and Cryptography, 1998
Bookmarks Related papers MentionsView impact
Proceedings. International Symposium on Information Theory, 2005. ISIT 2005., 2005
ABSTRACT
Bookmarks Related papers MentionsView impact
Dcc, 1998
Bookmarks Related papers MentionsView impact
2008 IEEE International Conference on Communications, 2008
AbstractThe downlink transmission in multi-user multiple-input multiple-output (MIMO) systems ha... more AbstractThe downlink transmission in multi-user multiple-input multiple-output (MIMO) systems has been extensively stud-ied from both communication-theoretic and information-theoretic perspectives. Most of these papers assume perfect/imperfect channel knowledge. In ...
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Numbers, Information and Complexity, 2000
A new asymptotic upper bound on the size of binary codes with the property described inthe title ... more A new asymptotic upper bound on the size of binary codes with the property described inthe title is derived. The proof relies on the properties of the distance distribution of binarycodes established in earlier related works of the authors. 1 IntroductionLet C 2 Zn2 be a binary block code. One says that C corrects r errors if every sphere ofradius r in Zn2 contains at most one codevector and r is the maximal number with suchproperty. Relaxing this definition, one may require that every such sphere contain at mostm vectors from the code. ...
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Journal of Lightwave Technology, 2003
ABSTRACT
Bookmarks Related papers MentionsView impact
Abstract. We address two topics related to the concept of minimal sup-ports (codewords) in linear... more Abstract. We address two topics related to the concept of minimal sup-ports (codewords) in linear codes. In the first part we study the distribu-tion of the number of minimal supports in random codes. In the second part, we propose a generalization of this concept for codes defined ...
Bookmarks Related papers MentionsView impact
IEEE Transactions on Information Theory
In this paper we study moments of soft-bits of binary-input symmetric-output channels and solve s... more In this paper we study moments of soft-bits of binary-input symmetric-output channels and solve some extremal problems of the moments. We use these results to solve the extremal information combining problem. Further, we extend the information combining problem by adding a constraint on the second moment of soft-bits, and find the extreme distributions for this new problem.
Bookmarks Related papers MentionsView impact
2007 IEEE International Symposium on Information Theory, 2007
We investigate the extrinsic information transfer (EXIT) functions of Hadamard codes in the conte... more We investigate the extrinsic information transfer (EXIT) functions of Hadamard codes in the context of repeat-zigzag Hadamard (RZH) codes with parallel decoding. The derived EXIT functions can serve as an effective tool for designing low-rate IRZH codes with parallel decoding in BIAWGN channels.
Bookmarks Related papers MentionsView impact
Proceedings of the 1999 IEEE Information Theory and Communications Workshop (Cat. No. 99EX253), 1999
Abstract During the last two decades the fundamental geometric parameter of a block code, called ... more Abstract During the last two decades the fundamental geometric parameter of a block code, called covering radius, has been widely studied. In this paper we estimate this parameter for linear codes with the aid of the minimum distance of the dual code. We derive a new bound on covering radius which improves essentially on the known bounds in a wide range of normalized dual distances
Bookmarks Related papers MentionsView impact