Papers by Ali Emre Pusane
Information Theory and Applications, 2000
Abstractó LDPC convolutional codes have been shown to be capable of achieving the same capacity-a... more Abstractó LDPC convolutional codes have been shown to be capable of achieving the same capacity-approaching performance as LDPC block codes with iterative message-passing decoding. However, traditional means of comparing block and convolu- tional codes tied to the implementation complexity of trellis- based decoding are irrelevant for message-passing decoders. In this paper, we undertake a comparison of LDPC block and convolutional
Practical polar code construction using generalised generator matrices
IET Communications, 2014
ABSTRACT Polar coding is a recently proposed coding technique that can provably achieve the chann... more ABSTRACT Polar coding is a recently proposed coding technique that can provably achieve the channel capacity. The polar code structure, which is based on the original 2 × 2 generator matrix, polarises the channels, that is, a portion of the channel capacities approach 1, whereas the remaining channel capacities approach 0. Owing to the specific size of this original generator matrix, polar codes can only have code lengths equal to the powers of 2, resulting in inefficiency for codes of practical lengths. In this study, the performance of finite-length polar codes over the binary erasure channel is analysed. A normalised polarisation distance measure is defined and polar codes from different generator matrices showing different amount of polarisation are compared using this measure. Encoding structures for these generalised polar codes are proposed and polarisation performances in both asymptotical and finite-length cases are investigated for generator matrices of size 3 × 3 and 4 × 4. A generalised decoder is also proposed for this generator matrix and its erasure rate is compared with that of the original generator matrix. It is shown that polar codes that have performance similar to the original construction can be constructed and used for a variety of code lengths, not necessarily equal to powers of 2, using generalised generator matrices.
In this paper asymptotic methods are used to form lower bounds on the free distance to constraint... more In this paper asymptotic methods are used to form lower bounds on the free distance to constraint length ratio of several ensembles of regular, asymptotically good, protograph-based LDPC convolutional codes. In particular, we show that the free distance to constraint length ratio of the regular LDPC convolutional codes exceeds that of the minimum distance to block length ratio of the
On the Error-Correcting Capability of LDPC Codes1
Abstract—We consider the ensemble of low-density parity-check (LDPC) codes introduced by Gallager... more Abstract—We consider the ensemble of low-density parity-check (LDPC) codes introduced by Gallager [1]. The Zyablov–Pinsker majority-logic iterative algorithm [2] for decoding LDPC codes is analyzed on the binary symmetric channel. An analytical lower bound on the error- correcting capability τmax that grows linearly in the code block length is obtained. DOI: 10.1134/S0032946008030046
Computing Research Repository, 2010
Low-density parity-check (LDPC) convolutional codes are capable of achieving excellent performanc... more Low-density parity-check (LDPC) convolutional codes are capable of achieving excellent performance with low encoding and decoding complexity. In this paper we discuss several graph-cover-based methods for deriving families of time-invariant and time-varying LDPC convolutional codes from LDPC block codes and show how earlier proposed LDPC convolutional code constructions can be presented within this framework. Some of the constructed convolutional codes
Reduced complexity decoding strategies for LDPC convolutional codes
International Symposium onInformation Theory, 2004. ISIT 2004. Proceedings., 2004
While low-density parity-check (LDPC) convolutional codes tend to significantly outperform LDPC b... more While low-density parity-check (LDPC) convolutional codes tend to significantly outperform LDPC block codes with the same processor complexity, large storage requirements and a long initial decoding delay are two issues related to their continuous pipeline decoding architecture [A. Jimenez Feltstrom et al., (1999)]. In this paper, we propose reduced complexity decoding strategies to lessen the storage requirements and the initial decoding delay without significant loss in performance.
Multilevel Coding/Modulation Using LDPC Convolutional Codes
In this paper, we propose a novel multilevel cod- ing scheme that employs low-density parity-chec... more In this paper, we propose a novel multilevel cod- ing scheme that employs low-density parity-check convolutional (LDPCC) codes. A combined decod- ing/demodulation scheme is also considered. Un- like previous work on multilevel coding, the proposed scheme employs a single code with some structure that allows it to benet from the use of multilevel map- ping. The proposed scheme can be
2008 5th International Symposium on Turbo Codes and Related Topics, 2008
In this paper asymptotic methods are used to form lower bounds on the free distance to constraint... more In this paper asymptotic methods are used to form lower bounds on the free distance to constraint length ratio of several ensembles of regular, asymptotically good, protographbased LDPC convolutional codes. In particular, we show that the free distance to constraint length ratio of the regular LDPC convolutional codes exceeds that of the minimum distance to block length ratio of the corresponding LDPC block codes.
2007 IEEE International Symposium on Information Theory, 2007
Low-density parity-check (LDPC) convolutional codes are capable of achieving excellent performanc... more Low-density parity-check (LDPC) convolutional codes are capable of achieving excellent performance with low encoding and decoding complexity. In this paper we discuss several graph-cover-based methods for deriving families of timeinvariant and time-varying LDPC convolutional codes from LDPC block codes and show how earlier proposed LDPC convolutional code constructions can be presented within this framework.
2011 IEEE International Symposium on Information Theory Proceedings, 2011
Ensembles of (J, K)-regular low-density paritycheck convolutional (LDPCC) codes are known to be a... more Ensembles of (J, K)-regular low-density paritycheck convolutional (LDPCC) codes are known to be asymptotically good, in the sense that the minimum free distance grows linearly with the constraint length. In this paper, we use a protograph-based analysis of terminated LDPCC codes to obtain an upper bound on the free distance growth rate of ensembles of periodically time-varying LDPCC codes. This bound is compared to a lower bound and evaluated numerically. It is found that, for a sufficiently large period, the bounds coincide. This approach is then extended to obtain bounds on the trapping set numbers, which define the size of the smallest, non-empty trapping sets, for these asymptotically good, periodically time-varying LDPCC code ensembles.
2009 IEEE International Symposium on Information Theory, 2009
It has been suggested that "near-codewords" may be a significant factor affecting decoding failur... more It has been suggested that "near-codewords" may be a significant factor affecting decoding failures of LDPC codes over the AWGN channel. A near-codeword is a sequence that satisfies almost all of the check equations. These near-codewords can be associated with so-called 'trapping sets' that exist in the Tanner graph of a code. In this paper, we analyse the trapping sets of protograph-based LDPC convolutional codes. LDPC convolutional codes have been shown to be capable of achieving the same capacity-approaching performance as LDPC block codes with iterative message-passing decoding. Further, it has been shown that some ensembles of LDPC convolutional codes are asymptotically good, in the sense that the average free distance grows linearly with constraint length. Here, asymptotic methods are used to calculate a lower bound on the trapping set growth rates for two ensembles of asymptotically good protograph-based LDPC convolutional codes. This can be used to predict where the error floor will occur for these codes under iterative message-passing decoding.
IEEE International Conference on Communications, 2003. ICC '03., 2003
In this paper, an optimum sequence estimation algorithm for wireless systems with Alamouti's two ... more In this paper, an optimum sequence estimation algorithm for wireless systems with Alamouti's two transmitter diversity in the presence of multipath fading is proposed. The algorithm is based on a jointly iterative channel and sequence estimation according to the maximum likelihood (ML) criterion, using the Expectation-Maximization (EM) algorithm employing M-PSK modulation scheme with additive Gaussian noise. The discrete multipath channel is represented in terms of the channel gains from each transmit antenna to the receive antenna. EM algorithm derived estimates jointly the complex channel parameters of each channel and the data sequence transmitted, iteratively, which converges to the true ML solution. The channel estimation is achieved in a simple way through the iterative equations by decoupling of the signals transmitted from different antennas. The algorithm is applied to the trellis coded modulation systems and efficiency of the algorithm proposed has been shown by the computer simulations. Simulation results show that the EM algorithm converges quickly for fast fading channels. The performance of the EM-based decoder approaches that of the ML receiver which has perfect knowledge of the channel.
On the iterative decoding of LDPC convolutional codes
2010 IEEE 18th Signal Processing and Communications Applications Conference, 2010
ABSTRACT LDPC convolutional codes have been shown to be capable of achieving the same capacity-ap... more ABSTRACT LDPC convolutional codes have been shown to be capable of achieving the same capacity-approaching performance as their block counterparts. In this paper, we present a brief introduction to these codes and their associated iterative decoding algorithm. Further, we demonstrate via computer simulations that the constructed LDPC convolutional codes significantly outperform the LDPC block codes with comparable complexity. Finally, we investigate the reasons for this improved performance.
A feasibility study of a 1D chaotic map for True Random Number Generation
2012 20th Signal Processing and Communications Applications Conference (SIU), 2012
True Random Number Generators, vital and indispensable primitives of cryptography, are systems th... more True Random Number Generators, vital and indispensable primitives of cryptography, are systems that generate identically distributed, independent, and unpredictable numbers. In this work, we study and evaluate the true random number generation potential and feasibility of a one dimensional chaotic function over a customly developed mathematical model of logistic map in MATLAB as an alternative example to existing topologically complex,
Power control for orthogonal space-time coding with multiple receive antennas
The performance of data communication systems over wireless channels is severely degraded by the ... more The performance of data communication systems over wireless channels is severely degraded by the multipath fading effects. Space-time codes exploit the channel capacity increase by using multiple transmit and/or receive antennas. This ensures space diversity without expanding the required transmission bandwidth. A type of space-time codes, namely orthogonal transmit diversity (OTD), has attracted much attention. This scheme has low complexity
Asymptotically regular spatially coupled codes with low decoding delay
2012 20th Signal Processing and Communications Applications Conference (SIU), 2012
ABSTRACT The spatially coupled code family was recently introduced in the error correction coding... more ABSTRACT The spatially coupled code family was recently introduced in the error correction coding literature. In this paper, we provide a summary of the spatially coupled codes and the window based decoder that is used to decode these codes. We design spatially coupled codes that benefit from low decoding complexity and delay and present their error performance over the additive white Gaussian channel via computer simulations in addition to comparisons with LDPC block codes of similar complexity.
An integer programming based trapping set search technique
2012 20th Signal Processing and Communications Applications Conference (SIU), 2012
Near codewords of low-density parity-check (LDPC) codes are known to be one of the main reasons o... more Near codewords of low-density parity-check (LDPC) codes are known to be one of the main reasons of errors that occur in decoding. For high signal-to-noise ratios, these codewords cause error floors in decoding and they are called trapping sets. Especially, trapping sets with small size devastate the performance of communication systems that use LDPC codes. Unfortunately, trapping sets are difficult
On the selection of generator matrices for polar coded communication systems
2012 20th Signal Processing and Communications Applications Conference (SIU), 2012
In this paper, the effects of the generator matrix selection on the polarization performance of p... more In this paper, the effects of the generator matrix selection on the polarization performance of polar coded communication systems is analyzed. We consider the problem of calculating the Bhattacharyya parameters for generator matrices of size larger than the standard size 2 × 2 and demonstrate that it is not an easy task to obtain the channel capacities in a recursive
Finite-length polarization measures for polar coded systems
2012 IEEE 13th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), 2012
ABSTRACT In this paper, polarization performance of polar code generator matrices is analyzed. We... more ABSTRACT In this paper, polarization performance of polar code generator matrices is analyzed. We obtain the Bhattacharyya parameters of polarized channels generated by all possible lower-triangular 3 × 3 generator matrices and evaluate the corresponding polarization behavior of polar coded systems via both asymptotical polarization rate exponents and finite-length polarization distance graphs. A ranking of all lower-triangular 3 × 3 generator matrices is also provided.
2008 IEEE International Symposium on Information Theory, 2008
LDPC convolutional codes have been shown to be capable of achieving the same capacity-approaching... more LDPC convolutional codes have been shown to be capable of achieving the same capacity-approaching performance as LDPC block codes with iterative message-passing decoding. In this paper, asymptotic methods are used to calculate a lower bound on the free distance for several ensembles of asymptotically good protograph-based LDPC convolutional codes. Further, we show that the free distance to constraint length ratio of the LDPC convolutional codes exceeds the minimum distance to block length ratio of corresponding LDPC block codes.
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Papers by Ali Emre Pusane