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Proceedings ArticleDOI

Performance enhancement of LOG MAP Turbo Decoder for mobile applications

12 Mar 2015-pp 259-264
TL;DR: The purpose of this paper is to implement the LOG MAP Turbo Decoder in VHDL with minimized delay to make the processing fast as well as increase the quality of signal and accuracy of the whole system.
Abstract: In mobile communication, transmission should be with least delay meeting the performance requirements. Turbo code has proven its effectiveness in the field of wireless communication system. The purpose of this paper is to implement the LOG MAP Turbo Decoder in VHDL. As it helps to achieve the highest coding gain therefore It is said, the best coding scheme for the error correction in high-speed wireless communication systems. However, the implementation of various Turbo Decoders suffers from a large propagation delay and high power consumption. For this reason, they are not suitable for Mobile communication applications. Hence, by implementing a Log Map Turbo Decoder in mobile handsets would make the processing fast as well as increase the quality of signal and accuracy of our whole system. It can be created by a serial connection of a turbo encoder and a decoder. The purpose of this paper is to implement the LOG MAP Turbo Decoder in VHDL with minimized delay.
Citations
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Journal ArticleDOI
TL;DR: A hardware intellectual property (IP) for high throughput RSC encoders that exploits a methodology based on the ABCD matrices model which permits to increase the number of inputs bits processed in parallel.
Abstract: During the last years, recursive systematic convolutional (RSC) encoders have found application in modern telecommunication systems to reduce the bit error rate (BER). In view of the necessity of increasing the throughput of such applications, several approaches using hardware implementations of RSC encoders were explored. In this paper, we propose a hardware intellectual property (IP) for high throughput RSC encoders. The IP core exploits a methodology based on the ABCD matrices model which permits to increase the number of inputs bits processed in parallel. Through an analysis of the proposed network topology and by exploiting data relative to the implementation on Zynq 7000 xc7z010clg400-1 field programmable gate array (FPGA), an estimation of the dependency of the input data rate and of the source occupation on the parallelism degree is performed. Such analysis, together with the BER curves, provides a description of the principal merit parameters of a RSC encoder.

1 citations


Cites background from "Performance enhancement of LOG MAP ..."

  • ...The main advantage offered by a hardware implementations is the maximization of timing performances thanks to the increased computational power compared to standard digital signal processors [17,18]....

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Book ChapterDOI
01 Jan 2022
TL;DR: In this article, an efficient parallel concatenated turbo coding is done and then the signal is transmitted over the AWGN channel, and a Log-MAP decoding algorithm is used to retrieve the original EMG signal, and BER performance is analyzed.
Abstract: In the last two decades, the healthcare systems have changed drastically. People live a healthier and longer life because of organized, well-developed healthcare facilities including ‘At Home’ hospitals especially for patients suffering from neuromuscular abnormalities that include myopathy, muscular dystrophy, spinal muscular atrophy, and myositis. A new paradigm of treatment is an initial consultation with remotely seated doctors aptly termed as telemedicine. The EMG signal is one of the biomedical signals representing neuromuscular activities that estimate electrical current flow created in muscles during its contraction and is used to identify several diseases. Continuous health monitoring of the patients is required especially for patients suffering from neuromuscular abnormalities. In this approach, considering the properties of EMG data, an efficient parallel concatenated turbo coding is done and then the signal is transmitted over the AWGN channel. A Log-MAP decoding algorithm is used to retrieve the original EMG signal, and the BER performance is analyzed.
References
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Book
02 Jan 2017
TL;DR: In this paper, the authors present the often "difficult" concepts of digital communications in an easy-to understand manner-without diluting the mathematical precision, using a student-friendly approach.
Abstract: For courses in Digital Communications. Exceptionally accessible, this book presents the often "difficult" concepts of digital communications in an easy-to- understand manner-without diluting the mathematical precision. Using a student-friendly approach, it develops the important techniques in the context of a unified structure (in block diagram form)-providing organization and structure to a field that has, and continues, to grow rapidly, and ensuring that students gain an awareness of the "big picture" even while delving into the details (the most up-to-date modulation, coding, and signal processing techniques that have become the basic tools of our modern era). It traces signals and key processing steps from the information source through the transmitter, channel, receiver, and ultimately to the information sink.

2,496 citations

Proceedings ArticleDOI
27 Nov 1989
TL;DR: The Viterbi algorithm is modified to deliver the most likely path sequence in a finite-state Markov chain, as well as either the a posteriori probability for each bit or a reliability value, with the aim of producing soft decisions to be used in the decoding of outer codes.
Abstract: The Viterbi algorithm (VA) is modified to deliver the most likely path sequence in a finite-state Markov chain, as well as either the a posteriori probability for each bit or a reliability value. With this reliability indicator the modified VA produces soft decisions to be used in the decoding of outer codes. The inner software output Viterbi algorithm (SOVA) accepts and delivers soft sample values and can be regraded as a device for improving the signal-to-noise ratio, similar to an FM demodulator. Several applications are investigated to show the gain over the conventional hard-deciding VA, including concatenated convolutional codes, concatenation of trellis-coded modulation with convolutional FEC (forward error correcting) codes, and coded Viterbi equalization. For these applications additional gains of 1-4 dB as compared to the classical hard-deciding algorithms were found. For comparison, the more complex symbol-to-symbol MAP, whose optimal a posteriori probabilities can be transformed into soft outputs, was investigated. >

1,848 citations

Journal ArticleDOI
TL;DR: A Log- MAP algorithm is presented that avoids the approximations in the Max-Log-MAP algorithm and hence is equivalent to the true MAP, but without its major disadvantages.
Abstract: For estimating the states or outputs of a Markov process, the symbol-by-symbol maximum a posteriori (MAP) algorithm is optimal. However, this algorithm, even in its recursive form, poses technical difficulties because of numerical representation problems, the necessity of non-linear functions and a high number of additions and multiplications. MAP like algorithms operating in the logarithmic domain presented in the past solve the numerical problem and reduce the computational complexity, but are suboptimal especially at low SNR (a common example is the Max-Log-MAP because of its use of the max function). A further simplification yields the soft-output Viterbi algorithm (SOVA). In this paper, we present a Log-MAP algorithm that avoids the approximations in the Max-Log-MAP algorithm and hence is equivalent to the true MAP, but without its major disadvantages. We compare the (Log-)MAP, Max-Log-MAP and SOVA from a theoretical point of view to illuminate their commonalities and differences. As a practical example, we consider Turbo decoding, and we also demonstrate the practical suitability of the Log-MAP by including quantization effects. The SOVA is, at 10−4, approximately 0.7 dB inferior to the (Log-)MAP, the Max-Log-MAP lying roughly in between. The channel capacities of the three algorithms -when employed in a Turbo decoder- are evaluated numerically.

615 citations

Journal ArticleDOI
TL;DR: The sensitivity of decoder performance to misestimation of the SNR is studied, and a simple online scheme is proposed that estimates the unknown SNR from each code block, prior to decoding, to not appreciably degrade the performance.
Abstract: Iterative decoding of turbo codes, as well as other concatenated coding schemes of similar nature, requires knowledge of the signal-to-noise ratio (SNR) of the channel so that proper blending of the a posteriori information of the separate decoders is achieved. We study the sensitivity of decoder performance to misestimation of the SNR, and propose a simple online scheme that estimates the unknown SNR from each code block, prior to decoding. We show that this scheme is sufficiently adequate in accuracy to not appreciably degrade the performance.

339 citations

15 Feb 1996
TL;DR: Two versions of a simplified maximum a posteriori decoding algorithm, which work in a sliding window form, like the Viterbi algorithm, and can thus be used to decode continuously transmitted sequences obtained by parallel concatenated codes, without requiring code trellis termination.
Abstract: In this article, we present two versions of a simplified maximum a posteriori decoding algorithm. The algorithms work in a sliding window form, like the Viterbi algorithm, and can thus be used to decode continuously transmitted sequences obtained by parallel concatenated codes, without requiring code trellis termination. A heuristic explanation is also given of how to embed the maximum a posteriori algorithms into the iterative decoding of parallel concatenated codes (turbo codes). The performances of the two algorithms are compared on the basis of a powerful rate 1/3 parallel concatenated code. Basic circuits to implement the simplified a posteriori decoding algorithm using lookup tables, and two further approximations (linear and threshold), with a very small penalty, to eliminate the need for lookup tables are proposed.

205 citations