983 research outputs found
Non-Binary Coded CCSK and Frequency-Domain Equalization with Simplified LLR Generation
International audienceIn this paper, we investigate the performance of Single-Carrier (SC) transmission with Non-Binary Low- Density Parity-Check (NB-LDPC) coded Cyclic Code-Shift Keying (CCSK) signaling in a multipath environment and we show that the combination of CCSK signaling and non-binary codes results in two key advantages, namely, improved Log-Likelihood Ratio (LLR) generation via correlations and reduced implementation complexity. We demonstrate that Maximum Likelihood (ML) demodulation can be expressed by two circular convolution operations and thus it can be processed in the frequency domain. Then, we propose a joint Frequency-Domain Equalization (FDE) and LLR generation scheme that aims at reducing the complexity of the receiver. Finally, we demonstrate through Monte-Carlo simulations and histogram analysis that this proposed CCSK signaling scheme gives more robustness to SC-FDE systems than commonly employed Hadamard signaling schemes (a gap of 1.5dB in favor of CCSK signaling is observed at BER = 10â5, assuming perfect Channel State Information)
An Architecture for High Data Rate Very Low Frequency Communication
Very low frequency (VLF) communication is used for long range shore-to-ship broadcasting applications. This paper proposes an architecture for high data rate VLF communication using Gaussian minimum shift keying (GMSK) modulation and low delay parity check (LDPC) channel coding. Non-data aided techniques are designed and used for carrier phase synchronization, symbol timing recovery, and LDPC code frame synchronization. These require the estimation of the operative Eb/N0 for which a kurtosis based algorithm is used. Also, a method for modeling the probability density function of the received signal under the bit condition is presented in this regard. The modeling of atmospheric radio noise (ARN) that corrupts VLF signals is described and an algorithm for signal enhancement in the presence of ARN in given. The BER performance of the communication system is evaluated for bit rates of 400 bps, 600 bps, and 800 bps for communication bandwidth of ~200 Hz.Defence Science Journal, 2013, 63(1), pp.25-33, DOI:http://dx.doi.org/10.14429/dsj.63.376
Ultra-Sparse Non-Binary LDPC Codes for Probabilistic Amplitude Shaping
This work shows how non-binary low-density parity-check codes over GF()
can be combined with probabilistic amplitude shaping (PAS) (B\"ocherer, et al.,
2015), which combines forward-error correction with non-uniform signaling for
power-efficient communication. Ultra-sparse low-density parity-check codes over
GF(64) and GF(256) gain 0.6 dB in power efficiency over state-of-the-art binary
LDPC codes at a spectral efficiency of 1.5 bits per channel use and a
blocklength of 576 bits. The simulation results are compared to finite length
coding bounds and complemented by density evolution analysis.Comment: Accepted for Globecom 201
Array Convolutional Low-Density Parity-Check Codes
This paper presents a design technique for obtaining regular time-invariant
low-density parity-check convolutional (RTI-LDPCC) codes with low complexity
and good performance. We start from previous approaches which unwrap a
low-density parity-check (LDPC) block code into an RTI-LDPCC code, and we
obtain a new method to design RTI-LDPCC codes with better performance and
shorter constraint length. Differently from previous techniques, we start the
design from an array LDPC block code. We show that, for codes with high rate, a
performance gain and a reduction in the constraint length are achieved with
respect to previous proposals. Additionally, an increase in the minimum
distance is observed.Comment: 4 pages, 2 figures, accepted for publication in IEEE Communications
Letter
LDPC-coded modulation for transmission over AWGN and flat rayleigh fading channels
La modulation codĂ©e est une technique de transmission efficace en largeur de bande qui intĂšgre le codage de canal et la modulation en une seule entitĂ© et ce, afin d'amĂ©liorer les performances tout en conservant la mĂȘme efficacitĂ© spectrale comparĂ© Ă la modulation non codĂ©e. Les codes de paritĂ© Ă faible densitĂ© (low-density parity-check codes, LDPC) sont les codes correcteurs d'erreurs les plus puissants et approchent la limite de Shannon, tout en ayant une complexitĂ© de dĂ©codage relativement faible. L'idĂ©e de combiner les codes LDPC et la modulation efficace en largeur de bande a donc Ă©tĂ© considĂ©rĂ©e par de nombreux chercheurs. Dans ce mĂ©moire, nous Ă©tudions une mĂ©thode de modulation codĂ©e Ă la fois puissante et efficace en largeur de bande, ayant d'excellentes performances de taux d'erreur binaire et une complexitĂ© d'implantation faible. Ceci est rĂ©alisĂ© en utilisant un encodeur rapide, un dĂ©coder de faible complexitĂ© et aucun entrelaceur. Les performances du systĂšme proposĂ© pour des transmissions sur un canal additif gaussien blanc et un canal Ă Ă©vanouissements plats de Rayleigh sont Ă©valuĂ©es au moyen de simulations. Les rĂ©sultats numĂ©riques montrent que la mĂ©thode de modulation codĂ©e utilisant la modulation d'amplitude en quadrature Ă M niveaux (M-QAM) peut atteindre d'excellentes performances pour toute une gamme d'efficacitĂ© spectrale. Une autre contribution de ce mĂ©moire est une mĂ©thode simple pour rĂ©aliser une modulation codĂ©e adaptative avec les codes LDPC pour la transmission sur des canaux Ă Ă©vanouissements plats et lents de Rayleigh. Dans cette mĂ©thode, six combinaisons de paires encodeur modulateur sont employĂ©es pour une adaptation trame par trame. L'efficacitĂ© spectrale moyenne varie entre 0.5 et 5 bits/s/Hz lors de la transmission. Les rĂ©sultats de simulation montrent que la modulation codĂ©e adaptative avec les codes LDPC offre une meilleure efficacitĂ© spectrale tout en maintenant une performance d'erreur acceptable
Decoding of Decode and Forward (DF) Relay Protocol using Min-Sum Based Low Density Parity Check (LDPC) System
Decoding high complexity is a major issue to design a decode and forward (DF) relay protocol. Thus, the establishment of low complexity decoding system would beneficial to assist decode and forward relay protocol. This paper reviews existing methods for the min-sum based LDPC decoding system as the low complexity decoding system. Reference lists of chosen articles were further reviewed for associated publications. This paper introduces comprehensive system model representing and describing the methods developed for LDPC based for DF relay protocol. It is consists of a number of components: (1) encoder and modulation at the source node, (2) demodulation, decoding, encoding and modulation at relay node, and (3) demodulation and decoding at the destination node. This paper also proposes a new taxonomy for min-sum based LDPC decoding techniques, highlights some of the most important components such as data used, result performances and profiles the Variable and Check Node (VCN) operation methods that have the potential to be used in DF relay protocol. Min-sum based LDPC decoding methods have the potential to provide an objective measure the best tradeoff between low complexities decoding process and the decoding error performance, and emerge as a cost-effective solution for practical application
A Comparison Study of LDPC and BCH Codes
The need for efficient and reliable digital data communication systems has been rising
rapidly in recent years. There are various reasons that have brought this need for the
communication systems, among them are the increase in automatic data processing
equipment and the increased need for long range communication. Therefore, the
LDPC and BCH codes were developed for achieving more reliable data transmission
in communication systems. This project covers the research about the LDPC and
BCH error correction codes. Algorithm for simulating both the LDPC and BCH
codes were also being investigated, which includes generating the parity check
matrix, generating the message code in Galois array matrix, encoding the message
bits, modulation and decoding the message bits for LDPC. Matlab software is used
for encoding and decoding the codes. The percentage of accuracy for LDPC
simulation codes are ranging from 95% to 99%. The results obtained shows that the
LDPC codes are more efficient and reliable than the BCH codes coding method of
error correction because the LDPC codes had a channel performance very close to the
Shannon limit. LDPC codes are a class of linear block codes that are proving to be
the best performing forward error correction available. Markets such as broadband
wireless and mobile networks operate in noisy environments and need powerful error
correction in order to improve reliability and better data rates. Through LDPC and
BCH codes, these systems can operate more reliably, efficiently and at higher data
rates
Protograph-Based LDPC Code Design for Shaped Bit-Metric Decoding
A protograph-based low-density parity-check (LDPC) code design technique for
bandwidth-efficient coded modulation is presented. The approach jointly
optimizes the LDPC code node degrees and the mapping of the coded bits to the
bit-interleaved coded modulation (BICM) bit-channels. For BICM with uniform
input and for BICM with probabilistic shaping, binary-input symmetric-output
surrogate channels for the code design are used. The constructed codes for
uniform inputs perform as good as the multi-edge type codes of Zhang and
Kschischang (2013). For 8-ASK and 64-ASK with probabilistic shaping, codes of
rates 2/3 and 5/6 with blocklength 64800 are designed, which operate within
0.63dB and 0.69dB of continuous AWGN capacity for a target frame error rate of
1e-3 at spectral efficiencies of 1.38 and 4.25 bits/channel use, respectively.Comment: 9 pages, 10 figures. arXiv admin note: substantial text overlap with
arXiv:1501.0559
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