Alexei Ashikhmin | Bell Labs (original) (raw)

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Papers by Alexei Ashikhmin

Research paper thumbnail of Bounds on the distance distribution of codes and designs

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Research paper thumbnail of Crosstalk Control Using Delayed Post-Compensation in a Multi-Channel Communication System

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Research paper thumbnail of Polynomial method in coding and information theory

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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Research paper thumbnail of Device and associated method for crosstalk estimation

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Research paper thumbnail of Quantum error detection

ABSTRACT

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Research paper thumbnail of Securing massive MIMO at the physical layer

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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Research paper thumbnail of EXIT Functions for Binary Input Memoryless Symmetric Channels

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Research paper thumbnail of Almost Affine Codes

Designs, Codes and Cryptography, 1998

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Research paper thumbnail of Space-time Reed-Muller codes for noncoherent MIMO transmission

Proceedings. International Symposium on Information Theory, 2005. ISIT 2005., 2005

ABSTRACT

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Research paper thumbnail of Almost A ne Codes

Dcc, 1998

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Research paper thumbnail of Scheduling and Pre-Conditioning in Multi-User MIMO TDD Systems

2008 IEEE International Conference on Communications, 2008

Abstract—The downlink transmission in multi-user multiple-input multiple-output (MIMO) systems ha... more Abstract—The 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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Research paper thumbnail of Optimizing Precoder Settings Using Average Sinr Reports for Groups of Tones

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Research paper thumbnail of A New Upper Bound on Codes Decodable into Size-2 Lists

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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Research paper thumbnail of Methods and apparatus for providing synchronization in a multi-channel communication system

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Research paper thumbnail of Method and apparatus for link error prediction in a communication system

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Research paper thumbnail of Spectral efficiency of coded phase modulation for high-speed fiber optic communication

Journal of Lightwave Technology, 2003

ABSTRACT

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Research paper thumbnail of Variations on Minimal Codewords in Linear Codes

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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Research paper thumbnail of Extremal Problems of Information Combining

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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Research paper thumbnail of EXIT Functions of Hadamard Components in Repeat-Zigzag-Hadamard (RZH) Codes

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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Research paper thumbnail of Improved estimates on covering radius

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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Research paper thumbnail of Bounds on the distance distribution of codes and designs

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Research paper thumbnail of Crosstalk Control Using Delayed Post-Compensation in a Multi-Channel Communication System

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Polynomial method in coding and information theory

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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Research paper thumbnail of Device and associated method for crosstalk estimation

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Research paper thumbnail of Quantum error detection

ABSTRACT

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Research paper thumbnail of Securing massive MIMO at the physical layer

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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Research paper thumbnail of EXIT Functions for Binary Input Memoryless Symmetric Channels

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Almost Affine Codes

Designs, Codes and Cryptography, 1998

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Space-time Reed-Muller codes for noncoherent MIMO transmission

Proceedings. International Symposium on Information Theory, 2005. ISIT 2005., 2005

ABSTRACT

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Almost A ne Codes

Dcc, 1998

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Scheduling and Pre-Conditioning in Multi-User MIMO TDD Systems

2008 IEEE International Conference on Communications, 2008

Abstract—The downlink transmission in multi-user multiple-input multiple-output (MIMO) systems ha... more Abstract—The 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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Research paper thumbnail of Optimizing Precoder Settings Using Average Sinr Reports for Groups of Tones

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A New Upper Bound on Codes Decodable into Size-2 Lists

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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Research paper thumbnail of Methods and apparatus for providing synchronization in a multi-channel communication system

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Research paper thumbnail of Method and apparatus for link error prediction in a communication system

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Spectral efficiency of coded phase modulation for high-speed fiber optic communication

Journal of Lightwave Technology, 2003

ABSTRACT

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Research paper thumbnail of Variations on Minimal Codewords in Linear Codes

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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Research paper thumbnail of Extremal Problems of Information Combining

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

Research paper thumbnail of EXIT Functions of Hadamard Components in Repeat-Zigzag-Hadamard (RZH) Codes

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

Research paper thumbnail of Improved estimates on covering radius

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