Robust Bit Research Articles

Hardware-Based Architecture for DNN Wireless Communication Models.

Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing (MIMO OFDM) is a key technology for wireless communication systems. However, because of the problem of a high peak-to-average power ratio (PAPR), OFDM symbols can be distorted at the MIMO OFDM transmitter. It degrades the signal detection and channel estimation performance at the MIMO OFDM receiver. In this paper, three deep neural network (DNN) models are proposed to solve the problem of non-linear distortions introduced by the power amplifier (PA) of the transmitters and replace the conventional digital signal processing (DSP) modules at the receivers in 2 × 2 MIMO OFDM and 4 × 4 MIMO OFDM systems. Proposed model type I uses the DNN model to de-map the signals at the receiver. Proposed model type II uses the DNN model to learn and filter out the channel noises at the receiver. Proposed model type III uses the DNN model to de-map and detect the signals at the receiver. All three model types attempt to solve the non-linear problem. The robust bit error rate (BER) performances of the proposed receivers are achieved through the software and hardware implementation results. In addition, we have also implemented appropriate hardware architectures for the proposed DNN models using special techniques, such as quantization and pipeline to check the feasibility in practice, which recent studies have not done. Our hardware architectures are successfully designed and implemented on the Virtex 7 vc709 FPGA board.

Augmented space signal detection method for IM/DD optical communication systems

The demand for high-speed data transmission has increased rapidly in data centers, leading to advanced optical communication technology innovation. At high modulation speed, severe linear and nonlinear signal distortions degrade the link performance. In order to increase the transmission capacity, a robust signal detection method based on quadratic discrimination in augmented space (QDAS) is proposed for high-speed intensity modulation and direct detection (IM/DD) optical communication systems. By projecting along the feature vector initially obtained by the objective function following the generalized Rayleigh quotient, signals with different features can be separated in augmented space. Subsequently, decision optimization is achieved through a quadratic discriminant model. Experimental verification is performed based on the 120 Gbps PAM8-modulated vertical-cavity surface-emitting laser (VCSEL) multimode fiber (MMF) optical link (100 m). The results show that, compared with the traditional Volterra nonlinear equalizer (VNLE), the proposed QDAS detection method shows improved and robust bit error ratio (BER) performance with the same complexity.

Optical Energy-Constrained Slot-Amplitude Modulation for Dimmable VLC: Suboptimal Detection and Performance Evaluation

Energy-constrained slot-amplitude modulation (ECSAM) enables light dimming, eliminates light flicker and constrains the peak optical power while providing robust communication links. However, the complexity of the maximum-likelihood (ML) based ECSAM receiver increases exponentially with required spectral efficiency. This paper provides a comprehensive performance evaluation of ECSAM for the indoor visible light communication (VLC) channel with multipath propagation under realistic illumination constraints and imperfect channel estimation. A sub-optimal receiver that employs a slot-by-slot detection algorithm followed by a slot-correction mechanism for reducing the receiver complexity is proposed. Additionally, the method for optimal selection of parameters when designing the signal waveform is presented. The analytical upper bound on the symbol error rate of ECSAM is derived using the union-bound technique. The results show that the error performance of the sub-optimal receiver are comparable to that of the optimal ML receiver. Compared with conventional power or bandwidth efficient VLC modulation techniques such as multiple pulse position modulation (MPPM) and pulse amplitude modulation (PAM), ECSAM provides complete flexibility in modifying the signal constellation for a desired dimming level to maximise the spectral efficiency and provide a robust bit error rate performance especially in the multipath propagation channel induced intersymbol interference.

Miniaturized Chipless RFID Tags Based on Periodically Loaded Microstrip Structure

A compact chipless radio frequency identification (RFID) tag-based on slow-wave technology is introduced in this paper. The tag consists of a resonant circuit based on open stub resonators periodically loaded by shunt stubs allowing a coding capacity of 9 bits and operating in a frequency range from 2 to 4GHz. The receiving and transmitting antennas of the tag are particularly designed to minimize the tag size as much as possible. The proposed tag presents a robust bit pattern with a compact and fully printable structure using FR4 substrate for a low-cost tag.

Rate adaptation performance and quality analysis of adaptive HTTP streaming methods

Media streaming is the key innovation in technology era brings high quality on-demand and live media content to the consumer on-the-go anywhere, any time. Achieving best quality-of-service and quality-of-experience (QoE) are major concerns in the current circumstances due to increasing network usage and user demand to high quality media content. Conventional streaming approaches face numerous challenges in delivering media content to the uses without degradation of quality. An adaptive HTTP streaming is emerging content delivery approach which provides real time content delivery without compromising quality and ensuring superlative QoE. The dynamic and robust bit rate selection based on the network and client key performance indices helps to achieve best class of service to the consumer. As many standards and processes emerge in the field of Adaptive HTTP Streaming, it is necessary to study and compare the performance of different approaches based on the defined metrics. In this paper, we emphasis on the comprehensive study of different emerging adaptive streaming models such as HTTP Live Streaming, Microsoft Smooth Streaming and MPEG Dynamic Adaptive Streaming over HTTP (DASH). The experiments were conducted using Gstreamer adaptive HTTP streaming client to measure delivery performance of the approaches under varying network conditions for on-demand streaming and live streaming contents. The outcome for adaptive HTTP methods were measured and analyzed using defined performance indices. The analyzed data indicates that each delivery method performs well with respect to outlined metrics. However, overall DASH gives considerably stable performance across different network settings than other streaming approaches.

A 1-GHz 1.6-mW Auto-Calibrated Bit Slicer for Energy/Envelope Detection Receivers

This brief describes a high-speed auto-calibrated bit slicer for energy and envelope detection receivers. For robust bit decision, a digital-assisted calibration method with auto threshold estimation and auto phase acquisition is employed. The bit slicer consists of a phase-locked loop for multi-phase clock generation and a dynamic comparator in which the bulk voltage of the input transistor is trimmed for threshold voltage control. The proposed bit slicer is implemented in 65-nm 1P9M CMOS, occupying a total area of 0.07 mm2. Experimental results show that the bit slicer achieves a sensitivity of 6.1 mV at 1 GHz and consumes 1.6 mW from a 1-V supply.

Robust Bit Modification based Audio Watermarking

Robust Bit Modification based Audio Watermarking

An Efficient Frame-Level Rate Control Algorithm for High Efficiency Video Coding

In video coding, the goal of rate control (RC) is not only to avoid the undesirable fluctuation in bit allocation, but also to provide a good visual perception. In this paper, a novel frame-level rate control algorithm for High Efficiency Video Coding (HEVC) is proposed. Firstly a model that reveals the relationship between bit per pixel (bpp), the bitrate of the intra frame and the bitrate of the subsequent inter frames in a group of pictures (GOP) is established, based on which the target bitrate of the first intra frame is well estimated. Then a novel frame-level bit allocation algorithm is developed, which provides a robust bit balancing scheme between the intra frame and the inter frames in a GOP to achieve the visual quality smoothness throughout the whole sequence. Our experimental results show that when compared to the RC scheme for HEVC encoder HM-16.0, the proposed algorithm can produce reconstructed frames with more consistent objective video quality. In addition, the objective visual quality of the reconstructed frames can be improved with less bitrate.

Uplink bit combining for multiple base‐stations MIMO with applications to CoMP systems

AbstractThis work considers a simple bit level combining technique, aided by robust bit reliability information, for uplink collaborating multiple‐input multiple‐output (MIMO) base‐stations (also known as macrodiversity MIMO), operating over composite Rayleigh‐lognormal fading channels. Bit reliability weights based on a robust modification of the logarithmic likelihood ratio, combined with instantaneous symbol signal‐to‐noise ratio information, are derived for different local MIMO detection schemes. This bit reliability information is used at the fusion center, together with locally detected data, for combining and producing final information bits delivered to the destination. Computer simulation results confirm that such bit level combining techniques, when used with minimum mean squared error ordered successive interference cancelation and also with sphere decoding maximum likelihood local detectors, provide significant performance improvements over non‐collaborative base‐stations systems. Performance gains are maintained even when these schemes suffer from channel estimation errors and also in the presence of space correlation. Low backhaul overhead and performance advantages make these bit level combining techniques attractive for applications in next generation cellular systems employing coordinated multi‐point (CoMP) technology, as well as for other collaborative MIMO communication schemes.Copyright © 2014 John Wiley & Sons, Ltd.

Cluster-based transform domain communication systems for high spectrum efficiency

This study presents a cluster-based transform domain communication system (TDCS) to improve spectrum efficiency. Unlike the utilities of clusters in orthogonal frequency division multiplex systems, the cluster-based TDCS framework divides entire unoccupied spectrum bins into L clusters, where each one represents a data stream independently, to achieve L times of spectrum efficiency compared to that of the traditional one. Among various schemes of spectrum bin spacing and allocation, the TDCS with random allocation scheme appears to be an ideal candidate to significantly improve spectrum efficiency without seriously degrading power efficiency. In multipath fading channel, the coded TDCS with random allocation scheme achieves robust bit error rate (BER) performance owing to a large degree of frequency diversity. Furthermore, this study shows that the smaller spectrum bin spacing should be configured for the cluster-based TDCS to achieve higher spectrum efficiency and more robust BER performance.

Exploiting Spatial and Frequency Diversity in Spatially Correlated MU-MIMO Downlink Channels

The effect of self-interference due to the increase of spatial correlation in a MIMO channel has become one of the limiting factors towards the implementation of future network downlink transmissions. This paper aims to reduce the effect of self-interference in a downlink multiuser- (MU-) MIMO transmission by exploiting the available spatial and frequency diversity. The subcarrier allocation scheme can exploit the frequency diversity to determine the self-interference from the ESINR metric, while the spatial diversity can be exploited by introducing the partial feedback scheme, which offers knowledge of the channel condition to the base station and further reduces the effect before the allocation process takes place. The results have shown that the proposed downlink transmission scheme offers robust bit error rate (BER) performance, even when simulated in a fully correlated channel, without imposing higher feedback requirements on the base controller.

Recognition using robust bit extraction

We present a novel technique for extracting bits from the perceptually significant components of an image transformation, thus making the recognition of objects under nonideal conditions robust. Specifically, we describe five popular face recognition transform methods [including principal component analysis (PCA), linear discriminant analysis (LDA), wavelet transform, wavelet transform with PCA, and wavelet transform with Fourier-Mellin transform] with robust bit extraction enhancement for various numbers of bits extracted. The robustness guarantees that all similar face images will produce almost the same bits. This property is useful for generating cryptographic keys. The theoretical results are evaluated on the Olivetti Research Laboratory (ORL) face database, showing that the extended methods significantly outperform the corresponding standard methods when the number of extracted bits reaches 100.

Performance of dropout correction on real magnetic tape waveforms with dropouts

The need to increase both linear and track densities in tape recording technology calls for more robustness against dropouts, the sporadic losses in signal amplitude, that are a principal source of errors in tape systems. A dropout correction scheme previously introduced by the authors enables more robust bit detection by restoring the signal afflicted by the dropout event. In this paper, we present the results of using this scheme on real oversampled waveforms from an experimental tape test stand. Real-time implementation using a peak detector has been simulated in this work, Albeit at a low density (1.85 channel bits per PW50), the emphasis of this study is to identify the types of error events caused by dropouts and to demonstrate the feasibility of dropout compensation even in the case of very challenging dropouts presented by the experimental data set. It is shown that this scheme can significantly reduce the frequency of dropout induced cycle slip error events that can be as long as the data block. In other cases, where cycle slip errors do not occur, the number of errors associated with dropout events is reduced, on average, by a factor of more than 2. The sensitivity of the method to the envelope detection method is examined, and this is identified as an opportunity for significantly improving the performance of the scheme.

Digital ultrafast carrier recovery for interactive transmission systems

An ultrafast, all-digital method for phase synchronization and coherent carrier recovery is presented for time division multiple access (TDMA) and code division multiple access (CDMA) burst data communication systems. A new adaptive phase tracking (APT) method, presented and analyzed in this paper, uses a hard-limited IF signal in a feed forward configuration for carrier phase detection and recovery. A novel new technique of phase window filtering is presented as a means to combat noise induced phase errors, and improved the performance of a digital controlled phase shift oscillator by 7 dB. Experimental measurements show APT provides robust bit error rate (BER) performance within 1 dB of the theoretical binary phase shift keyed (BPSK) and tenths of dBs of an ideal hard wired clock. APT achieves acquisition within one- to four-bits-5 to 10 times faster than present requirements. A low power, low cost single chip fast carrier synchronization and demodulation solution for QPSK, GMSK and GSM compatible OQPSK and Feher's quadrature phase shift keyed (FQPSK) and binary phase shift keyed (FBPSK) systems are also presented.

Combining soft-decision demodulation with bit erasure correction and weighting to reduce the effect of transmission errors in log-PCM

In the paper we analyse an improved soft-decision demodulation technique applied to μ-law pulse code modulation (PCM). The PCM-encoded waveforms are transmitted over Gaussian and Rayleigh fading channels by means of coherent phase shift keying modulation. Received bits which are unreliable are identified by means of soft-decision demodulation and erased. Each bit in the PCM word is assigned its own erasure threshold. The thresholds are optimised and are thus theoretically determined as a function of input power level to the quantiser, channel type and signal/noise ratio, and the relative mean-square error power that occurs when a PCM word containing an erased bit is estimated by means of prediction or interpolation. The predicted or interpolated sample amplitude is used as an estimate of the missing speech amplitude. This procedure works well because of the redundancy in the decoded speech waveform. In previous work the estimate was used to replace the PCM word with an erased bit. In the present paper the estimate is used to decide the most likely value of the erased bit, thus correcting most of the erasures without introducing errors in the replaced word. The new soft demodulation algorithm performs significantly better than the previous one. A gain of several decibels in overall speech signal/noise ratio is typical both for Gaussian and Rayleigh fading channels. Compared to no soft demodulation, the improvement in required channel signal/noise ratio is up to about 4 dB for the Gaussian channel. The combination of bit-position weighting and soft demodulation is also analysed, as well as the combination of a PCM bit assignment more robust against transmission errors and soft demodulation. For both of these cases, the combined schemes yield improvements, but not as large as for unweighted transmission of the standard bit assignment plus the improvement of the weighting or the robust bit assignment.