Engineering topics
Publications and source records attributed to Divsalar, D..
In this paper, the performance of the repeat-accumulate codes with (ML) decoding are analyzed and compared to random codes by very tight bounds. Some simple codes are shown that perform very close to Shannon limit with maximum likelihood decoding.
In this paper we propose an innovative channel coding scheme called Accumulate Repeat Accumulate codes. This class of codes can be viewed as trubo-like codes, namely a double serial concatenation of a rate-1 accumulator as an outer code, a regular or irregular repetition as a middle code, and a punctured accumulator as an inner code.
Simulation results show that, with iterative demodulation and decoding, coded NS-8QAM performs 0.5 dB better than standard 8QAM and 0.7 dB better than 8PSK at BER= 10(sup -5), when the FEC code is the (15, 11) Hamming code concatenated with a rate-1 accumulator code, while coded NS-32QAM performs 0.25 dB better than standard 32QAM.
In this paper we simulate the performance of these codes over additive white Gaussian noise and Rayleigh fading channels.
We present a rate 1/31 turbo code that achieves a bit error rate of 10(sup -6) at Eb/No = -0.9 db. At this coding gain, insufficient energy per symbol is present for a conventional receiver to recover the carrier phase properly. We present a method to overcome this problem by coupling the receiver and decoder functions.
In this summary we present extremal average mutual information values carried by the extrinsic loglikelihood under the constraint of a given mean and variance while accounting for the consistency feature of loglikelihoods.
The density evolution method is used to analyze the performance and optimize the structure of parallel and serial turbo codes, and generalized serial concatenations of mixtures of different outer and inner codes. Design examples are given for mixture codes.
We take a first empirical step toward understanding the performance-complexity tradeoffs that have newly arisen since the advent of turbo codes.
Based on a representation of FQPSK as a trellis-coded modulation, this paper investigates the potential improvement in power efficiency obtained from the application of simple outer codes to form a concatenated coding arrangement with iterative decoding.
In this paper, we derive the capacity of pulse position modulation (PPM) on a general soft output, memoryless channel, and evaluate the capacity formula for a variety of optical channel models, including AWGN, webb (1), and Webb plus Gaussian distributions.
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We model the density of extrinsic information in iterative turbo decoders by Gaussian density functions.
This report defines the fundamental parameters affecting the capacity of a soft-decision optical channel, and relates them to corresponding parameters for the well-understood AWGN channel.
We present new codes and modulation formats for the deep space optical channel. By taking maximum avdvantage of inherent physical constraints on the communications link, these codes and modulation formats substantially close the large gap between state of the art systems and the Shannon limit.
This paper describes coupled receiver-decoder architectures for suppressed carrier convolutionally-coded signals and residual carrier turbo-coded signals.
A family of upper bounds to error probabilities of coded systems on the additive white Gaussian noise channel was recently proposed by Divsalar. Their calculation depends only on the weight spectrum of the code words. We first elaborate upon these bounds to show how they can be further tightened by using numerical integration instead of a Chernoff bound, and by reducing the number of code words to be included in the bound. Next, we extend them to finding channels.
We develop new, low complexity turbo codes suitable for bandwidth and power limited systems, for very low bit and word error rate requirements.
This paper addresses the iterative devoding analysis, design, and performance of low complexity turbo like codes.