MAP Decoder Research Articles

Decoding social media speak: developing a speech act theory research agenda

Purpose– Drawing on the theoretical domain of speech act theory (SAT) and a discussion of its suitability for setting the agenda for social media research, this study aims to explore a range of research directions that are both relevant and conceptually robust, to stimulate the advancement of knowledge and understanding of online verbatim data.Design/methodology/approach– Examining previously published cross-disciplinary research, the study identifies how recent conceptual and empirical advances in SAT may further guide the development of text analytics in a social media context.Findings– Decoding content and function word use in customers’ social media communication can enhance the efficiency of determining potential impacts of customer reviews, sentiment strength, the quality of contributions in social media, customers’ socialization perceptions in online communities and deceptive messages.Originality/value– Considering the variety of managerial demand, increasing and diverging social media formats, expanding archives, rapid development of software tools and fast-paced market changes, this study provides an urgently needed, theory-driven, coherent research agenda to guide the conceptual development of text analytics in a social media context.

A MAP Decoder for TVB Codes on a Generalized Iyengar–Siegel–Wolf BPMR Markov Channel Model

We present a generalization of the Iyengar–Siegel–Wolf Markov channel model for bit-patterned media recording media to allow negative drift, and adapt the maximum a posteriori decoder for time-varying block codes to work on this generalized model while minimizing complexity. We also describe a method for designing near-optimal codes for this channel using simulated annealing, obtaining better performance than alternative designs. In concatenation with a (999, 888)16 low-density parity-check (LDPC) code, we achieve a frame error rate (FER) of $10^{-3}$ at a channel error rate that is $1.73\times $ higher than the best result with existing designs. A simple extension to include substitution errors allows the channel to approximate the dependent insertion, deletion, and substitution (DIDS) channel, with a decoding complexity that is $10\times $ lower than that of Wu and Armand’s RC2 decoder. The performance in the absence of burst errors is almost identical. When the DIDS channel includes burst substitution errors, our decoder performs worse than the RC2 decoder, but maintains its complexity advantage. For the same concatenated code, our decoder achieves an FER of $10^{-3}$ at a channel error rate that is $1.68\times $ lower than the RC2 decoder. Finally, simulation results show that our code designs improve on existing constructions for the DIDS channel.

Split procedure for graph partitioning: an application to the SONET ring problem

The classical set partitioning problem is defined on a graph G = (V, E) and consists of partitioning V in disjoint subsets. In this study, we propose a Split procedure to minimize the number of partitions for a given sequence of nodes, considering local and global capacity constraints on the partitions. The procedure relies on dynamic programming and it is applied here to the SONET Ring Assignment Problem. It is used as a decoding function in a Biased Random Key Genetic Algorithm and as a constructive heuristic in a hybrid multistart Evolutionary Local Search. High-quality results are computed on classic benchmarks.

From Polar to Reed-Muller Codes

The year 2016, in which I am writing these words, marks the centenary of Claude Shannon, the father of information theory. In his landmark 1948 paper Mathematical Theory of Communication, Shannon established the largest rate at which reliable communication is possible, and he referred to it as the channel capacity. Since then, researchers have focused on the design of practical coding schemes that could approach such a limit. The road to channel capacity has been almost 70 years long and, after many ideas, occasional detours, and some rediscoveries, it has culminated in the description of low-complexity and provably capacity-achieving coding schemes, namely, polar codes and iterative codes based on sparse graphs. However, next-generation communication systems require an unprecedented performance improvement and the number of transmission settings relevant in applications is rapidly increasing. Hence, although Shannon's limit seems finally close at hand, new challenges are just around the corner. In this thesis, we trace a road that goes from polar to Reed-Muller codes and, by doing so, we investigate three main topics: unified scaling, non-standard channels, and capacity via symmetry. First, we consider unified scaling. A coding scheme is capacity-achieving when, for any rate smaller than capacity, the error probability tends to 0 as the block length becomes increasingly larger. However, the practitioner is often interested in more specific questions such as, How much do we need to increase the block length in order to halve the gap between rate and capacity?. We focus our analysis on polar codes and develop a unified framework to rigorously analyze the scaling of the main parameters, i.e., block length, rate, error probability, and channel quality. Furthermore, in light of the recent success of a list decoding algorithm for polar codes, we provide scaling results on the performance of list decoders. Next, we deal with non-standard channels. When we say that a coding scheme achieves capacity, we typically consider binary memoryless symmetric channels. However, practical transmission scenarios often involve more complicated settings. For example, the downlink of a cellular system is modeled as a broadcast channel, and the communication on fiber links is inherently asymmetric. We propose provably optimal low-complexity solutions for these settings. In particular, we present a polar coding scheme that achieves the best known rate region for the broadcast channel, and we describe three paradigms to achieve the capacity of asymmetric channels. To do so, we develop general coding primitives, such as the chaining construction that has already proved to be useful in a variety of communication problems. Finally, we show how to achieve capacity via symmetry. In the early days of coding theory, a popular paradigm consisted in exploiting the structure of algebraic codes to devise practical decoding algorithms. However, proving the optimality of such coding schemes remained an elusive goal. In particular, the conjecture that Reed-Muller codes achieve capacity dates back to the 1960s. We solve this open problem by showing that Reed-Muller codes and, in general, codes with sufficient symmetry are capacity-achieving over erasure channels under optimal MAP decoding. As the proof does not rely on the precise structure of the codes, we are able to show that symmetry alone guarantees optimal performance.

Application of MAP decoding for chaos MIMO scheme to improve error rate performance

Application of MAP decoding for chaos MIMO scheme to improve error rate performance

유럽형 지상파/케이블/위성 멀티모드 HD 방송 수신이 가능한 통합 수신기 구현

This paper presents an integrated receiver to support multimode broadcasting standards such as DVB-T2, DVB-C2, and DVB-S2 in a single platform. The integrated receiver consists of a tuner block, a receiver engine, a frame processor, and an A/V decoder. The receiver engine includes a channel decoding engine and a demodulation engine to perform OFDM and APSK demodulations. The frame processor performs deinterleaving and BB frame decoding functions. The demodulator engine and the frame processor are implemented in two FPGA devices and DSP-based embedded software, respectively. To verify the functionality of the integrated receiver, it is tested in the laboratory. Commercial PC-based modulators are used to generate the DVB-T2, DVB-C2, and DVB-S2 modulated signals. The integrated receiver was tested under various operation modes as specified in the standards such as DVB-T2, DVB-C2, and DVB-S2 and showed successful operation in all the scenarios tested.

The Design and Implementation of General Symmetrical Self-Organizing Map Decoder

Traditional error correcting decoder is designed according to specific algorithm, which is a reverse course of encoding. In this paper, a novel general neural network decoder is proposed in the form of symmetrical self-organizing map (SSOM), which can achieve decoding function to any error correcting codes. The SSOM decoder is tested by decoding low-density parity-check (LDPC) code. The performance comparison of SSOM decoder and traditional decoder is accomplished by simulation. Actual results show that the SSOM decoder can implement both learning and decoding in the same time regardless of any encoding rules. And higher possibility of the codeword emergence means greater probability of correct error correction. Compare to traditional error correcting decoder, it is easy to construct, more intelligent to different codeword sets, which has certain prospect in future communication channel coding field.

Farm and environment information bidirectional acquisition system with individual tree identification using smartphones for orchard precision management

An orchard precision management system plays an important role in improvement at the management level and the enhancement of decision abilities. A single orchard tree or an orchard tree microcommunity is the basic management unit, and bidirectional information on the environment and plants is the important content for precision management. A type of RFID label was applied with a UHF chip in the core and a QR code in the surface for single tree identification. A bidirectional acquisition system for orchard production, which included farming information collection for the forward direction and environmental information acquisition for the backward direction, was designed with smart phones. In the farming information collection part, information collection flow that included QR code image acquisition, image preprocessing, barcode decoding and farming information collection was established. An improved local threshold method was adopted to improve the QR code identification rate in the smart phone platform. In the environment information acquisition part, a sensor search rule on the single tree position and a multi-point environment value model were designed. The orchard information bidirectional acquisition system was developed on an Android platform with the Java language, which has the function of QR decoding, farm record information collection, environment information acquisition, data uploading and statistical analysis. The system was tested in an apple orchard. A total of 144 trees were chosen to decode the QR codes in the tree label. The success rate was approximately 96.52%. The identification time of 85% of the trees was less than 4s for the 20 chosen trees. In taking the temperature, for example, the difference between the computed temperature value and the measured temperature value around each tree was small. The system could decrease the cost of the professional equipment, such as portable RFID readers and writers, which was a low-cost and high-efficiency solution for orchard production information collection.

Exact Max-Log MAP Soft-Output Sphere Decoding via Approximate Schnorr–Euchner Enumeration

The complexity gains of sphere decoders (SDs) with Schnorr-Euchner enumeration and nonconstant amplitude constellations are limited by the required node ordering. Aiming at improving the implementation efficiency of SD without compromising optimality, this paper proposes a novel tree traversal for soft-output SDs providing the exact max-log MAP decoder performance. It consists of a predefined visiting order that approximates the exact Schnorr-Euchner enumeration (SEE) and a modified pruning metric that preserves the exact max-log MAP despite the approximate ordering. The proposed approach significantly improves both the computational complexity and the implementation cost of exact soft-output SDs compared with previous techniques. In particular, simulations show gains of 30%-56% in the required calculations for a 4 × 4 multiple-input multiple-output system with 16-quadrature amplitude modulation (QAM), and field-programmable gate array (FPGA) implementations show an average power reduction of 34%-50%.

Modified decoding and detection scheme for spectral amplitude coding optical CDMA systems

In this reported work, a modified decoding and detection scheme with dispersion compensation is investigated for spectral-amplitude-coding optical code division multiple access (SAC-OCDMA) systems. For simultaneously decoding and compensating the chromatic dispersion of signals in the 40 km-long standard single-mode fibre transmission, based on reconstruction equivalent-chirp method the array configuration of fibre Bragg grating (FBG) segments can be controlled with a quadratic dispersion of −680 ps/nm for an extra time delay. The traditional triple-branch signal detection (TBSD) scheme is then modified and the principle of multiuser interference elimination is theoretically analysed. The simulated results show that, without adding a dispersion compensation device, the modified TBSD scheme adopting the FBG decoder can realise the decoding and detection function in SAC-OCDMA.

Design of a contention‐free parallel double‐flow MAP decoder

Parallel processing and double‐flow methods, which are used to increase the speed of turbo‐code decoding, cause memory contentions. Although memory contentions due to parallel processing can be resolved by adopting the quadratic polynomial permutation (QPP) interleaver, the double‐flow method still causes memory contentions because of its read/write sequences from both ends of the input packets. Thus, we propose a modified architecture to resolve memory contentions for the double‐flow method to fit the QPP interleaver. In our experiment, the proposed method has a shorter decoding time and smaller hardware size compared the conventional method. A bit‐accurate simulation was performed, and hardware implementation with field‐programmable gate arrays (FPGAs) led to a high throughput of 80 Mbps. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Digital Encoder Designing for Mobile Robot Control

In this paper we present the design of a quadrature decoder/counter interface IC (ASIC) that performs the decoding, counting, and bus interface function in digital motor control systems, employing an Altra FLEX 10KA, 2s150fg456 Xilinx device. The ASIC contains a pair of digital filters, a quadrature decoder, an up/down counter, a latch and inhibit circuit, and an 8-bit bus interface to a digital processing system. The design of digital of the digital filter is based on the finite state machine model with datapath (FSMD). A novel scheme for detecting the motor rotation direction is also proposed. The ASIC can be applied to a digital motor control system forgetting the rotation speed or position of the motor, which is quipped with an optical encoder. The data acquisition can be extended to 16-bit integer format by two continuos reading cycles. Simulation and experimental tests are shown to verify the ASIC function properly. DOI: http://dx.doi.org/10.11591/ijece.v4i4.5500

From Polar to Reed-Muller Codes: A Technique to Improve the Finite-Length Performance

We explore the relationship between polar and RM codes and we describe a coding scheme which improves upon the performance of the standard polar code at practical block lengths. Our starting point is the experimental observation that RM codes have a smaller error probability than polar codes under MAP decoding. This motivates us to introduce a family of codes that interpolates between RM and polar codes, call this family C-inter = {C-alpha:alpha is an element of[0;1]}, where C alpha vertical bar(alpha=1) is the original polar code, and C alpha vertical bar(alpha=0) is an RM code. Based on numerical observations, we remark that the error probability under MAP decoding is an increasing function of alpha. MAP decoding has in general exponential complexity, but empirically the performance of polar codes at finite block lengths is boosted by moving along the family C-inter even under low-complexity decoding schemes such as, for instance, belief propagation or successive cancellation list decoder. We demonstrate the performance gain via numerical simulations for transmission over the erasure channel as well as the Gaussian channel.

1 Gbps directed optical decoder based on two cascaded microring resonators.

We report an electro-optic directed optical decoder based on two cascaded microring resonators (MRRs). PN junctions embedded around the MRRs are employed to modulate the MRRs through the carrier-injection scheme. The optical decoding function from a 2-bit electrical signal to a 4-bit optical signal at the speed of 1 Gbps is performed successfully by the device.

Time‐varying block codes for synchronisation errors: maximum a posteriori decoder and practical issues

\begin{abstract} In this paper we consider Time-Varying Block (TVB) codes, which generalize a number of previous synchronization error-correcting codes. We also consider various practical issues related to MAP decoding of these codes. Specifically, we give an expression for the expected distribution of drift between transmitter and receiver due to synchronization errors. We determine an appropriate choice for state space limits based on the drift probability distribution. In turn, we obtain an expression for the decoder complexity under given channel conditions in terms of the state space limits used. For a given state space, we also give a number of optimizations that reduce the algorithm complexity with no further loss of decoder performance. We also show how the MAP decoder can be used in the absence of known frame boundaries, and demonstrate that an appropriate choice of decoder parameters allows the decoder to approach the performance when frame boundaries are known, at the expense of some increase in complexity. Finally, we express some existing constructions as TVB codes, comparing performance with published results, and showing that improved performance is possible by taking advantage of the flexibility of TVB codes.

Graphics processing unit implementation and optimisation of a flexible maximum a‐posteriori decoder for synchronisation correction

In this paper we present an optimized parallel implementation of a flexible MAP decoder for synchronization error correcting codes, supporting a very wide range of code sizes and channel conditions. On mid-range GPUs we demonstrate decoding speedups of more than two orders of magnitude over a CPU implementation of the same optimized algorithm, and more than an order of magnitude over our earlier GPU implementation. The prominent challenge is to maintain high parallelization efficiency over a wide range of code sizes and channel conditions, and different execution hardware. We ensure this with a dynamic strategy for choosing parallel execution parameters at run-time. We also present a variant that trades off some decoding speed for significantly reduced memory requirement, with no loss to the decoder's error correction performance. The increased throughput of our implementation and its ability to work with less memory allow us to analyse larger codes and poorer channel conditions, and makes practical use of such codes more feasible.

Obesity genetics and epigenetics: dissecting causality.

Genome-wide association studies (GWAS) have successfully revealed multiple obesity-associated genetic loci1. A strong reproducible signal comes from a cluster of the variants that lie in the 47-kb region of the first and second intron of fat mass and obesity associated ( FTO ) gene2,3. Each copy of the risk allele of FTO variants is associated with a 1.2-fold increased risk of obesity and an increase in body weight of ≈2.5 pounds. Until recently, mechanistic studies designed to explain the association of non-coding FTO variants did not yield any direct evidence of how these single-nucleotide changes may affect FTO expression or function of the protein. In a study by Smemo et al,4 the authors provided proof of principle to the model that the linear distance between 2 regions on a chromosome is not an impediment when it comes to decoding functionality of the GWAS-associated variants. In a multidisciplinary effort, the authors4 convincingly demonstrate that the noncoding FTO variants act as enhancer elements and interact with the promoter sequence required for expression of a distant Iroquois-class homeodomain protein 3 ( IRX3 ) gene. The authors profiled the genomic interactions with promoters of genes located within a 1-Mb region around the obesity-associated variants. They used circular chromosome conformation-capture followed by …

Design of a Playback Control System for Flight Parameter Recorder

A play-back controller was designed for a certain series of aircraft. The XC866 MCU was used as the main controller unit, and an 8051 MCU as the assistant control unit. It achieved the function of channel selection, channel switching, signal filtering, signal decoding and tape speed controlling. Compared with other play-back controllers this instrument is more superior in control precision, reliability, use of flexibility and simple of structure.

Parallel Interleaver Design for a High throughput HSPA+/LTE Multi-Standard Turbo Decoder

To meet the evolving data rate requirements of emerging wireless communication technologies, many parallel architectures have been proposed to implement high throughput turbo decoders. However, concurrent memory reading/writing in parallel turbo decoding architectures leads to severe memory conflict problem, which has become a major bottleneck for high throughput turbo decoders. In this paper, we propose a flexible and efficient VLSI architecture to solve the memory conflict problem for highly parallel turbo decoders targeting multi-standard 3G/4G wireless communication systems. To demonstrate the effectiveness of the proposed parallel interleaver architecture, we implemented an HSPA+/LTE/LTE-Advanced multi-standard turbo decoder with a 45nm CMOS technology. The implemented turbo decoder consists of 16 Radix-4 MAP decoder cores, and the chip core area is 2.43 mm^2. When clocked at 600 MHz, this turbo decoder can achieve a maximum decoding throughput of 826 Mbps in the HSPA+ mode and 1.67 Gbps in the LTE/LTE-Advanced mode, exceeding the peak data rate requirements for both standards.

Sense codon emancipation for proteome-wide incorporation of noncanonical amino acids: rare isoleucine codon AUA as a target for genetic code expansion

One of the major challenges in contemporary synthetic biology is to find a route to engineer synthetic organisms with altered chemical constitution. In terms of core reaction types, nature uses an astonishingly limited repertoire of chemistries when compared with the exceptionally rich and diverse methods of organic chemistry. In this context, the most promising route to change and expand the fundamental chemistry of life is the inclusion of amino acid building blocks beyond the canonical 20 (i.e. expanding the genetic code). This strategy would allow the transfer of numerous chemical functionalities and reactions from the synthetic laboratory into the cellular environment. Due to limitations in terms of both efficiency and practical applicability, state-of-the-art nonsense suppression- or frameshift suppression-based methods are less suitable for such engineering. Consequently, we set out to achieve this goal by sense codon emancipation, that is, liberation from its natural decoding function – a prerequisite for the reassignment of degenerate sense codons to a new 21st amino acid. We have achieved this by redesigning of several features of the post-transcriptional modification machinery which are directly involved in the decoding process. In particular, we report first steps towards the reassignment of 5797 AUA isoleucine codons in Escherichia coli using efficient tools for tRNA nucleotide modification pathway engineering.