Adjacent Bits Research Articles

A Study on Iterative Decoding With LLR Modulator by Neural Network Using Adjacent Track Information in SMR System

Our previous work focused on a log-likelihood ratio (LLR) computed as the decoding reliability by a posteriori probability (APP) decoder in a two-dimensional magnetic recording (TDMR) system using shingled magnetic recording (SMR). In this article, we propose a neural network LLR modulator to reduce the influence of pattern dependent medium noise and to perform efficiently iterative decoding using a low-density parity-check (LDPC) code. In this study, we clarify that the performance improvement of iterative decoding can be obtained by considering LLRs of the adjacent track bits affecting the decoding bit as the input of the neural network. Furthermore, we clarify that the application of a hybrid genetic algorithm (HGA) selects LLRs by using the adjacent track LLRs affecting the decoding bit and realizes more effective iterative decoding.

CLEAR: Cache Lines Error Accumulation Reduction by exploiting invisible accesses

SRAM caches are the most vulnerable processor component to radiation-induced soft errors. Error-Correcting Codes (ECCs) are the conventional scheme to protect caches against soft errors. These errors in the shape of Single-Event Upset (SEU), in which single bit or multiple adjacent bits are affected, can be correctable by ECCs. However, conventional ECCs are unable to correct temporal MBUs (Multiple-Bit Upset), in which two or more SEUs are accumulated in a data word over time. This paper proposes CLEAR (Cache Lines Error Accumulation Reduction) scheme to reduce the occurrence probability of temporal MBUs. By exploiting inherently available externally invisible accesses to all cache ways in a read request, CLEAR conducts more frequent ECC checking for each data word. Therefore, the ECC checking intervals are shortened, which leads to a significant reduction in occurrence probability of temporal MBUs. The evaluations show that CLEAR increases the Mean Time To Failure (MTTF) of the cache by more than 4× compared to the conventional cache architecture with negligible overheads.

A Steganography Embedding Method Based on Hamming Coding and Histogram-Preserving

This paper proposes an information hiding algorithm using matrix embedding with Hamming codes and histogram preservation in order to keep the histogram of the image unchanged before and after hiding information in digital media. First, the algorithm uses matrix embedding with Hamming codes to determine the rewriting bits of the original image, rewrite and flip them, and successfully embed the secret information. Then, according to the idea of a break-even point, a balanced pixel frequency adaptive algorithm is proposed and each embedded bit of secret information is detected and compensated by the adjacent bit of histogram data, so that the histogram change of the image before and after information hiding is minimized. At present, most of the histogram distortion values after steganography are generally over 1000 or even higher. As a contrast, the method proposed in this paper can keep the histogram distortion values to be less than 1000. The feasibility and effectiveness of the algorithm are verified by relative entropy analysis as well. The experimental results also show that the algorithm performs well in steganographic analyses of images.

A novel encrypted compressive sensing of images based on fractional order hyper chaotic Chen system and DNA operations

Secured Compressive sensing of the images becomes one of the essential issues in multimedia applications. In the recent times, encryption in compressive sensing is achieved via the use of multiple one dimensional chaotic system (1D chaotic) and hyper-chaotic system (HC). However, the security of the system still needs to be improved. To solve this issue, novel encrypted compressive sensing of images based on Fractional order hyper chaotic Chen system and DNA operations is proposed in this paper. The basic idea is to introduce a new algorithm which provides compression rate below the Nyquist rate along with increased security by jointly using Fractional order hyper chaotic chen system and DNA operations for image encryption. The encryption algorithm combines Fractional order hyperchaotic chen system and DNA operations. Fractional order hyperchaotic chen system has high randomness and rich dynamic phenomena which enhance the encryption and the algorithm efficiency is further increased by DNA operations.4-Dimensioanal Fractional order hyper chaotic chen system is used to generate the measurement matrix. Compressive sensing measurements are converted to a stream of binary digits and the correlation between the adjacent bits is further reduced through global scrambling. The DNA operations are performed on the scrambled binary sequences and hyper chaotic sequences, which increases the algorithm efficiency. The results of the experiments accomplish that the proposed encryption method is extremely sensitive to small changes in secret keys, shows good performance in histogram analysis, correlation analysis, Information Entropy and is very sensitive to a bit change in an input image. The Block Compressive sensing (BCS) reconstruction algorithms are used to validate the proposed encryption method. In the proposed method, experimental analysis are performed on different images of size 512 × 512 which are divided in to blocks of size 32 X 32. The reconstruction analysis is performed with different subsampling rates of 0.1, 0.2, 0.3, 0.4 and 0.5.The results depicted that the proposed method maintains the robustness and reconstruction quality of Compressive sensing with enhanced encryption.

Microwave-magnetic-field-induced magnetization excitation and assisted switching of antiferromagnetically coupled magnetic bilayer with perpendicular magnetization

Antiferromagnetically coupled (AFC) magnetic bilayer is a candidate media structure for high-density magnetic recording. Because the stray fields from the two magnetic layers of the AFC bilayer cancel each other out, switching field distribution originating from the stray fields from the adjacent data bits can be suppressed. Furthermore, in microwave-assisted magnetic recording (MAMR), which utilizes ferromagnetic resonance (FMR) excitation in a microwave field to reverse a high-anisotropy magnetic material, AFC media can suppress the distribution in FMR frequency originating from the stray fields and improve MAMR performance. In this study, we fabricate an AFC magnetic bilayer consisting of two Co/Pt multilayers with perpendicular magnetization. We use anomalous-Hall-effect-FMR in combination with a circularly polarized microwave field and carry out layer-selective analysis of FMR excitation of the two magnetic layers. We then investigate the switching behavior of an AFC bilayer nanodot in a microwave magnetic field. The switching field decreases with increasing microwave field frequency and increases abruptly at the critical frequency, and a large switching field reduction by applying a microwave field is demonstrated. This switching behavior is similar to that of a single-layer perpendicular magnetic nanodot, showing that the AFC structure does not hinder the microwave assist effect.

Low Delay 3-Bit Burst Error Correction Codes

The increasing importance of Multiple Cell Upsets (MCUs) in modern memories has spurred research on error correction codes that can correct adjacent bit errors. For example, Double Adjacent Error Correction (DAEC), 3-bit burst and 4-bit burst codes have been proposed in the last years. However, as the error correction capabilities are increased so is the complexity of the encoder and decoder circuits. This directly impacts the encoding and decoding delay and thus limits the use of the codes in high speed memories. To reduce the complexity, some techniques have been proposed recently. Those include more advanced optimization programs to find codes with a lower number of ones in the parity check matrix or the interleaving of data and parity check bits to simplify the decoding. In this paper, those techniques are combined to design more efficient 3-bit burst error correction codes. The encoders and decoders for the proposed codes have been implemented and compared with the state of the art 3-bit burst error correction codes. The results show that the new codes reduce the encoder and decoder delay significantly. Therefore, the proposed codes provide memory designers with a more efficient option to implement protection against 3-bit burst errors for high speed memories.

Pattern-Based Decoding for Wi-Fi Backscatter Communication of Passive Sensors.

Ambient backscatter communication enables passive sensors to convey sensing data on ambient RF signals in the air at ultralow power consumption. To extract data bits from such signals, threshold-based decoding has generally been considered, but suffers against Wi-Fi signals due to severe fluctuation of OFDM signals. In this paper, we propose a pattern-matching-based decoding algorithm for Wi-Fi backscatter communications. The key idea is the identification of unique patterns of signal samples that arise from the inevitable smoothing of Wi-Fi signals to filter out noisy fluctuation. We provide the mathematical basis of obtaining the pattern of smoothed signal samples as the slope of a line expressed in a closed-form equation. Then, the new decoding algorithm was designed to identify the pattern of received signal samples as a slope rather than classifying their amplitude levels. Thus, it is more robust against signal fluctuation and does not need tricky threshold configuration. Moreover, for even higher reliability, the pattern was identified for a pair of adjacent bits, and the algorithm decodes a bit pair at a time rather than a single bit. We demonstrate via testbed experiments that the proposed algorithm significantly outperforms conventional threshold-based decoding variants in terms of bit error rate for various distances and data rates.

Reduction of the redundancy of adjacent bit planes for reversible data hiding in encrypted images

Reduction of the redundancy of adjacent bit planes for reversible data hiding in encrypted images

An Intrinsic Interference Mitigation Scheme for FBMC-QAM Systems

Quadrature amplitude modulation-based filter-bank multicarrier system (FBMC-QAM) is a promising new radio access technology for the upcoming 5G standalone standard (5G-NR SA). By way of highly localized prototype filters, FBMC-QAM system is able to achieve low out-of-band (OOB) radiation and high spectral efficiency without the cyclic prefix (CP), at the price of non-orthogonality between adjacent subcarriers, intrinsic interferences, and bit error rate (BER) degradation. As an attempt to mitigate these impairments, a precoding scheme is proposed in this paper, which aims to maximize signal-to-leakage-and-noise ratio (SLNR) while allowing pulse-shaping filters with superb spectral characteristics to be leveraged. To justify the efficacy, performance analysis is conducted for prototype filters such as square-root raised cosine (SRRC), isotropic orthogonal transform algorithm (IOTA), and Mirrabasi-Martin (same as suggested in the PHY-DYAS project) for both additive white Gaussian noise (AWGN) and time-dispersive channels. The computer simulation shows that SLNR-based FBMC-QAM system incurs low complexity overhead and is able to enhance BER performance effectively.

Improved Transmitter Jitter Modeling for Accurate Bit Error Rate (BER) Eye Contours Using Transient Simulation of Short Bit Patterns

Increase in the signaling speeds has led to decrease in jitter budget available for the channel to pass the product specifications. The current serial link specifications are based on a bit-error-rate (BER) metric and hence there is a need to account for jitter statistically. Accurately capturing jitter through the channel is very important to have confidence in the product specifications. Current statistical eye approaches are based on either single pulse/step response or multiple edge responses, which do not account for transmitter (Tx) driver jitter accurately since jitter interaction between the edges is ignored. There is an inherent assumption in pulse/step response methods that there is zero correlation between independent responses created from 2n combinations for n cursor pulse response where n is number where the tail settles, hence one zero crossing does not impact an adjacent zero crossing. Transient simulation accurately accounts for Tx jitter but is time consuming and requires large memory when simulating very large bit sequences. A new methodology is proposed to generate BER contours that capture the Tx driver jitter and inter symbol interference (ISI) through the channel accurately using unique waveforms created from truth table bit combinations. It utilizes 2N short N bit patterns as waveforms with jitter correlation from current bit patterns into adjacent bit patterns to get equivalent transient simulation of a desired pseudo random bit sequence. The method accounts for the edge interactions from any current bit pattern to next successive bit pattern to account for ISI accurately. The statistical eye diagram generated with the above approach includes nonideal channel characteristics, including ISI, XTK from nearby aggressor channels, and jitter through the channel.

Enhanced Two-Photon Photochromism in Metasurface Perfect Absorbers.

Light switchable materials are essential to optoelectronic applications in photovoltaics, memories, sensors, and communications. Natural switchable materials suffer from weak absorption and slow response times, preventing their use in low-power, ultrafast applications. Integrating light switchable materials with metasurface perfect absorbers offers an innovative route to achieving desirable features for nanophotonic devices, such as directional emission, low-power and broadband operation, high radiative quantum efficiency, and large spontaneous emission rates. Here we show an enhanced two-photon photochromism based on a metasurface perfect absorber: film-coupled colloidal silver nanocubes. The photochromic molecules, spiropyrans, are sandwiched between the silver nanocubes and the gold substrate. With nearly 100% absorption and an accompanying large field enhancement in the molecular junction, the transformation of spiropyrans to merocyanines is observed under excitation with 792 nm laser light. Fluorescence lifetime measurements on the merocyanine form reveal that large Purcell enhancement in the film-coupled nanocubes leads to large enhancements of the spontaneous emission rate and a high quantum efficiency. An averaged incident power as low as 10 μW is enough to initiate the two-photon isomerization of spiropyran in the film-coupled nanocubes, and a power of 100nW is able to excite the merocyanines to emit fluorescence. The power consumption is orders of magnitude lower than bare spiropyran thin films on silicon and gold, which is highly desirable for the writing and reading processes relevant to optical data storage. By sweeping the plasmonic resonance of the film-coupled nanocubes, wavelength specificity is demonstrated, which opens up new possibilities for minimizing the cross talk between adjacent bits in nanophotonic devices.

High-Density SOT-MRAM Based on Shared Bitline Structure

This brief proposes a new design technique for spin-orbit torque magnetic random access memory (SOT-MRAM), suitable for high-density and low-power on-chip cache applications. A bitline of the proposed memory bit cell is shared with that of an adjacent bit cell leading to a reduction in the number of metals along the column direction. This results in higher integration density due to improved metal pitch limited region. The proposed memory can optimize the bit-cell area by aggressively reducing the size of write access transistor, since SOT-based switching operation of SOT devices translates to smaller size of write access transistor. Furthermore, the proposed SOT-MRAM still retains the advantages of SOT-MRAM such as low write energy dissipation, high read-disturb margin, and improved reliability of magnetic tunnel junction. In comparison with the conventional SOT-MRAM bit cells, our proposed MRAM bit cell can have 20% less bit-cell area. Even compared with the standard STT-MRAM, our proposed bit cell still achieves higher integration density. Moreover, the shared bitline SOT-MRAM achieves >6× lower write power and higher read-disturb margin than does the STT-MRAM.

Context-Aware Local Binary Feature Learning for Face Recognition.

In this paper, we propose a context-aware local binary feature learning (CA-LBFL) method for face recognition. Unlike existing learning-based local face descriptors such as discriminant face descriptor (DFD) and compact binary face descriptor (CBFD) which learn each feature code individually, our CA-LBFL exploits the contextual information of adjacent bits by constraining the number of shifts from different binary bits, so that more robust information can be exploited for face representation. Given a face image, we first extract pixel difference vectors (PDV) in local patches, and learn a discriminative mapping in an unsupervised manner to project each pixel difference vector into a context-aware binary vector. Then, we perform clustering on the learned binary codes to construct a codebook, and extract a histogram feature for each face image with the learned codebook as the final representation. In order to exploit local information from different scales, we propose a context-aware local binary multi-scale feature learning (CA-LBMFL) method to jointly learn multiple projection matrices for face representation. To make the proposed methods applicable for heterogeneous face recognition, we present a coupled CA-LBFL (C-CA-LBFL) method and a coupled CA-LBMFL (C-CA-LBMFL) method to reduce the modality gap of corresponding heterogeneous faces in the feature level, respectively. Extensive experimental results on four widely used face datasets clearly show that our methods outperform most state-of-the-art face descriptors.

Modeling and Analysis of Magnetic Field Induced Coupling on Embedded STT-MRAM Arrays

Spin transfer torque magnetic random access memory (STT-MRAM) is an emerging memory technology which exhibits nonvolatility, high density, high endurance, and nano-second read and write times. These characteristics make STT-MRAM suitable for last-level cache and other embedded applications. The STT-MRAM bit-cell consists of a magnetic tunnel junction (MTJ) which is composed of two ferromagnetic layers (free and fixed layers) and one insulating layer in between. As STT-MRAM arrays become denser to meet cost and requirements of high performance computing, the distance between adjacent MTJ bits reduces. This aggravates the magnetic coupling from free and fixed layer of one MTJ bit to its neighbors. Even though magnetic coupling is expected to become stronger as MTJ scales down, its impacts on static and dynamic properties on MTJ is relatively unexplored. In this paper, we present a model of the magnetic field coupling in high-density MTJ arrays for three different types of MTJ stacks and evaluate the effect of magnetic field induced coupling on static and dynamic properties. Lastly, we show how process induced variations in MTJ characteristics affect the magnitude of magnetic coupling and their effect on the electrical characteristics of the STT-RAM arrays.

Multi-strategy based quantum cost reduction of linear nearest-neighbor quantum circuit

With the development of reversible and quantum computing, study of reversible and quantum circuits has also developed rapidly. Due to physical constraints, most quantum circuits require quantum gates to interact on adjacent quantum bits. However, many existing quantum circuits nearest-neighbor have large quantum cost. Therefore, how to effectively reduce quantum cost is becoming a popular research topic. In this paper, we proposed multiple optimization strategies to reduce the quantum cost of the circuit, that is, we reduce quantum cost from MCT gates decomposition, nearest neighbor and circuit simplification, respectively. The experimental results show that the proposed strategies can effectively reduce the quantum cost, and the maximum optimization rate is 30.61% compared to the corresponding results.

A Study on Relationship Between Recording Pattern and Decoding Reliability in SMR

The shingled magnetic recording (SMR) system is influenced by not only jitter-like medium noise from adjacent bits in the down-track direction but also intertrack interference (ITI) from the adjacent tracks. In this paper, we investigate the relationship between the recording pattern and the decoding reliability by classifying the log-likelihood ratio at the a posteriori probability decoder output according to the recording patterns under an SMR R–W channel specification of 4 Tb/in2 by computer simulation. The result shows that the decoding reliability for the recording pattern “010” heavily affected by transition jitter is the lowest and little improved even if the influence of ITI is mitigated by a 2-D finite-impulse response filter.

Simultaneous readout of two adjacent bit tracks with a spin-torque oscillator

We propose a novel setup for a spin-torque oscillator reader in magnetic hard disk drive technology. Two adjacent bit tracks are to be read simultaneously, leading to high data transfer rate and increased resilience to noise as the lateral size of the oscillator device is allowed to remain larger than the bit width. We perform micromagnetic simulations of an example system and find that the magnetization response has a clear unimodal character, which enables for detection of two bit values at the same time. We analyze the frequency of the device under the influence of two different external fields and conduct a simulation of a successful dynamic readout. We estimate the signal linewidth and signal-to-noise ratios of the setup and show that it may be potentially beneficial for magnetic readout applications.

Robust Cross-SCORE Algorithm Against Bit Transitions for GPS Interference Suppression

In the blind beamforming technique utilizing self-coherence properties of GPS signals, the covariance matrices estimated from sample data, including the transition between two adjacent bits, suffer from performance degradation. In this letter, we propose the estimation of the covariance matrices using the sample blocks, which are free from the bit transitions under different times of arrival of multiple GPS signals. It combines with the robust cross-SCORE algorithm to suppress the GPS interference. It is shown that an efficient combination of two algorithms is capable of providing high gains to multiple GPS signals simultaneously, while suppressing strong interference.

Joint Crosstalk Aware Burst Error Fault Tolerance Mechanism for Reliable on-Chip Communication

In a Nano-scale technology, reliability is one of the main issues for on-chip communication systems. To make communication system more reliable, Joint Crosstalk Aware Multiple Error Correction with interleaving scheme is proposed for crosstalk errors. This technique is very useful while dealing with burst error. The number of burst errors which can be tolerated by this technique can be adjusted by changing the interleaving distance between adjacent bits of the same module. The burst of 9 adjacent errors can be corrected if 4 modules of encoder and decoder are used. The design is implemented on FPGA to calculate area overhead and delay. The proposed JMEC/JMEC-Inter encoder and decoder are both fast, with maximum operating frequencies of 163.308 MHz and 307.977 MHz respectively by trading off by I/O's pins (48.53 and 19.85 percent more I/O's than Hamming and JTEC respectively). The area consumed by the proposed technique is less than the 3 percent of the FPGA resources, making the technique good candidate on chip fault tolerance mechanism.

Object recognition using rotation invariant local binary pattern of significant bit planes

The binary feature descriptors such as binary robust independent elementary features (BRIEF), oriented rotated binary robust independent elementary features (ORB), and fast retina keypoint (FREAK) usually perform binarisation on the intensity comparisons, thus they lose some useful information. In this study, the authors propose an effective binary image descriptor which is called significant bit-planes-based local binary pattern for visual recognition. First, the authors divide an image into several sub regions according to the intensity orders to incorporate the spatial information. Then the authors extract the higher bit planes for all the sub regions and sort the adjacent neighbour bits based on the corresponding intensity orders, which make the descriptor invariant to rotation. In order to further improve the discriminative ability, the authors sample the multi-scale neighbours and average the adjacent pixels and extract the feature descriptor from the higher bit planes. Since the authors directly perform operation on the significant bit planes without quantisation, the authors decrease the information loss to some extent. The descriptor has demonstrated a better performance over the state-of-the-art binary descriptors as well as scale invariant feature transform on two recognition benchmarks (i.e. Kentucky and ETHZ) and PASCAL 2007 for image classification.