ICC 2001. IEEE International Conference on Communications. Conference Record (Cat. No.01CH37240)
An importance sampling technique, tuned for the simulation of ideal or suboptimal MAP bit-per-bit... more An importance sampling technique, tuned for the simulation of ideal or suboptimal MAP bit-per-bit decoding, is applied to some examples of turbo product codes, i.e. to turbo decoding of the product of block codes. The simulation results show the remarkable performances of the suboptimal algorithms. The presence of the so called “knee” in the performance curves, predicted by the maximum
ICASSP-88., International Conference on Acoustics, Speech, and Signal Processing
A solution is proposed for blind deconvolution problems, i.e. the estimation of the impulse respo... more A solution is proposed for blind deconvolution problems, i.e. the estimation of the impulse response of an unknown discrete-time channel given the output data sequence and statistical information on the input sequence. The solution approaches the optimal one when the input sequence is independent and identically distributed and the channel distortion is small. Numerical results are given in the case of the optimal nonlinear function, which depends on the input probability density function, and in the case of the very simple sign function. The technique can be used iteratively if the distortion is not small
In this paper, we investigate absorbing sets, responsible of error floors in Low Density Parity C... more In this paper, we investigate absorbing sets, responsible of error floors in Low Density Parity Check codes. We look for a concise, quantitative way to rate the absorbing sets' dangerousness. Based on a simplified model for iterative decoding evolution, we show that absorbing sets exhibit a threshold behavior. An absorbing set with at least one channel log-likelihood-ratio below the threshold can stop the convergence towards the right codeword. Otherwise convergence is guaranteed. We show that absorbing sets with negative thresholds can be deactivated simply using proper saturation levels. We propose an efficient algorithm to compute thresholds.
In this paper, we investigate absorbing sets, responsible of error floors in Low Density Parity C... more In this paper, we investigate absorbing sets, responsible of error floors in Low Density Parity Check codes. We look for a concise, quantitative way to rate the absorbing sets' dangerousness. Based on a simplified model for iterative decoding evolution, we show that absorbing sets exhibit a threshold behavior. An absorbing set with at least one channel log-likelihood-ratio below the threshold can stop the convergence towards the right codeword. Otherwise convergence is guaranteed. We show that absorbing sets with negative thresholds can be deactivated simply using proper saturation levels. We propose an efficient algorithm to compute thresholds.
TDMA data transmission is used in various radio communication systems. In TDMA systems, demodulat... more TDMA data transmission is used in various radio communication systems. In TDMA systems, demodulation requires the estimation of some parameters. In the systems considered in this paper, the phase is acquired at the beginning of each burst, while clock and frequency are tracked from burst to burst. We consider two classical algorithms for phase estimation: the feedforward structure proposed by Viterbi & Viterbi, and feedback structures like Decision-Directed Loops. We compare their acquisition and tracking performance both for coded and uncoded MPSK modulations. The feedforward structure may be very sensitive to frequency offsets. Therefore, the performance of a digital frequency estimator is analyzed in detail. All the algorithms here considered are easily implemented with digital hardware.
... (8). We have 1 lDfl < M(L + l)T which is about twice the Fitz range, for large L (when L =... more ... (8). We have 1 lDfl < M(L + l)T which is about twice the Fitz range, for large L (when L = 1, theFitz and Luke estimators are the same). ... Values of L Wh.0 (@E) Fig. 5 - Variance of the estimators by Fitz (solid) and Luke (dashed) vs. &/No. Also shown are the approximation (eq. ...
The aim of this work is to investigate frequency discriminator detection for continuous phase dig... more The aim of this work is to investigate frequency discriminator detection for continuous phase digital modulation (CPM) in order to avoid the RF carrier recovery problem. An efficient demodulation scheme, based on a discriminator followed by a suitable baseband digital processor of acceptable complexity, is presented. The baseband processoris based on decision feedback and correlation. In the binary case we
ICC 2001. IEEE International Conference on Communications. Conference Record (Cat. No.01CH37240)
An importance sampling technique, tuned for the simulation of ideal or suboptimal MAP bit-per-bit... more An importance sampling technique, tuned for the simulation of ideal or suboptimal MAP bit-per-bit decoding, is applied to some examples of turbo product codes, i.e. to turbo decoding of the product of block codes. The simulation results show the remarkable performances of the suboptimal algorithms. The presence of the so called “knee” in the performance curves, predicted by the maximum
ICASSP-88., International Conference on Acoustics, Speech, and Signal Processing
A solution is proposed for blind deconvolution problems, i.e. the estimation of the impulse respo... more A solution is proposed for blind deconvolution problems, i.e. the estimation of the impulse response of an unknown discrete-time channel given the output data sequence and statistical information on the input sequence. The solution approaches the optimal one when the input sequence is independent and identically distributed and the channel distortion is small. Numerical results are given in the case of the optimal nonlinear function, which depends on the input probability density function, and in the case of the very simple sign function. The technique can be used iteratively if the distortion is not small
In this paper, we investigate absorbing sets, responsible of error floors in Low Density Parity C... more In this paper, we investigate absorbing sets, responsible of error floors in Low Density Parity Check codes. We look for a concise, quantitative way to rate the absorbing sets' dangerousness. Based on a simplified model for iterative decoding evolution, we show that absorbing sets exhibit a threshold behavior. An absorbing set with at least one channel log-likelihood-ratio below the threshold can stop the convergence towards the right codeword. Otherwise convergence is guaranteed. We show that absorbing sets with negative thresholds can be deactivated simply using proper saturation levels. We propose an efficient algorithm to compute thresholds.
In this paper, we investigate absorbing sets, responsible of error floors in Low Density Parity C... more In this paper, we investigate absorbing sets, responsible of error floors in Low Density Parity Check codes. We look for a concise, quantitative way to rate the absorbing sets' dangerousness. Based on a simplified model for iterative decoding evolution, we show that absorbing sets exhibit a threshold behavior. An absorbing set with at least one channel log-likelihood-ratio below the threshold can stop the convergence towards the right codeword. Otherwise convergence is guaranteed. We show that absorbing sets with negative thresholds can be deactivated simply using proper saturation levels. We propose an efficient algorithm to compute thresholds.
TDMA data transmission is used in various radio communication systems. In TDMA systems, demodulat... more TDMA data transmission is used in various radio communication systems. In TDMA systems, demodulation requires the estimation of some parameters. In the systems considered in this paper, the phase is acquired at the beginning of each burst, while clock and frequency are tracked from burst to burst. We consider two classical algorithms for phase estimation: the feedforward structure proposed by Viterbi & Viterbi, and feedback structures like Decision-Directed Loops. We compare their acquisition and tracking performance both for coded and uncoded MPSK modulations. The feedforward structure may be very sensitive to frequency offsets. Therefore, the performance of a digital frequency estimator is analyzed in detail. All the algorithms here considered are easily implemented with digital hardware.
... (8). We have 1 lDfl < M(L + l)T which is about twice the Fitz range, for large L (when L =... more ... (8). We have 1 lDfl < M(L + l)T which is about twice the Fitz range, for large L (when L = 1, theFitz and Luke estimators are the same). ... Values of L Wh.0 (@E) Fig. 5 - Variance of the estimators by Fitz (solid) and Luke (dashed) vs. &/No. Also shown are the approximation (eq. ...
The aim of this work is to investigate frequency discriminator detection for continuous phase dig... more The aim of this work is to investigate frequency discriminator detection for continuous phase digital modulation (CPM) in order to avoid the RF carrier recovery problem. An efficient demodulation scheme, based on a discriminator followed by a suitable baseband digital processor of acceptable complexity, is presented. The baseband processoris based on decision feedback and correlation. In the binary case we
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