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- Dieter-Michael Arnold, Hans-Andrea Loeliger, Pascal O. Vontobel, Aleksandar Kavcic, Wei Zeng
- IEEE Transactions on Information Theory
- 2006

The information rate of finite-state source/channel models can be accurately estimated by sampling both a long channel input sequence and the corresponding channel output sequence, followed by a forward sum-product recursion on the joint source/channel trellis. This method is extended to compute upper and lower bounds on the information rate of very general… (More)

- Pascal O. Vontobel, Ralf Koetter
- ArXiv
- 2005

The goal of the present paper is the derivation of a framework for the finite-length analysis of message-passing iterative decoding of low-density parity-check codes. To this end we introduce the concept of graph-cover decoding. Whereas in maximum-likelihood decoding all codewords in a code are competing to be the best explanation of the received vector,… (More)

Codewords in finite covers of a Tanner graph G are characterized. Since iterative, locally operating decoding algorithms cannot distinguish the underlying graph G from any covering graph, these codewords, dubbed pseudo-codewords are directly responible for sub-optimal behavior of iterative decoding algorithms. We give a simple characterization of… (More)

- Pascal O. Vontobel, Aleksandar Kavcic, Dieter-Michael Arnold, Hans-Andrea Loeliger
- IEEE Trans. Information Theory
- 2008

The classical Blahut–Arimoto algorithm (BAA) is a well-known algorithm that optimizes a discrete memoryless source (DMS) at the input of a discrete memoryless channel (DMC) in order to maximize the mutual information between channel input and output. This paper considers the problem of optimizing finite-state machine sources (FSMSs) at the input of… (More)

- Pascal O. Vontobel, Ralf Koetter
- ArXiv
- 2006

We consider linear-programming (LP) decoding of low-density parity-check (LDPC) codes. While it is clear that one can use any general-purpose LP solver to solve the LP that appears in the decoding problem, we argue in this paper that the LP at hand is equipped with a lot of structure that one should take advantage of. Towards this goal, we study the dual LP… (More)

We discuss two techniques for obtaining lower bounds on the (AWGN channel) pseudo-weight of binary linear codes. Whereas the first bound is based on the largest and second-largest eigenvalues of a matrix associated with the parity-check matrix of a code, the second bound is given by the solution to a linear program. The fundamental polytope/cone [1] turns… (More)

- Roxana Smarandache, Pascal O. Vontobel
- IEEE Transactions on Information Theory
- 2012

Quasi-cyclic (QC) low-density parity-check (LDPC) codes are an important instance of proto-graph-based LDPC codes. In this paper we present upper bounds on the minimum Hamming distance of QC LDPC codes and study how these upper bounds depend on graph structure parameters (like variable degrees, check node degrees, girth) of the Tanner graph and of the… (More)

- Pascal O. Vontobel
- IEEE Transactions on Information Theory
- 2010

It has recently been observed that the permanent of a nonnegative square matrix, i.e., of a square matrix containing only nonnegative real entries, can very well be approximated by solving a certain Bethe free energy function minimization problem with the help of the sum-product algorithm. We call the resulting approximation of the permanent the Bethe… (More)

It has recently been observed that the permanent of a non-negative matrix, i.e., of a matrix containing only nonnegative real entries, can very well be approximated by solving a certain Bethe free energy minimization problem with the help of the sum-product algorithm. We call the resulting approximation of the permanent the Bethe permanent. In this paper we… (More)

It has recently become feasible to compute information rates of finite-state source/channel models with not too many states. We review such methods and demonstrate their extension to compute upper and lower bounds on the information rate of very general (non-finite-state) channels by means of finite-state approximations.