Medical image compression using vector quantization and system error compression

A novel medical image compression scheme based on vector quantization (VQ) is proposed in this paper. The advantages of the technique are not only that it yields high compression ratio but also that it maintains a peak signal‐to‐noise ratio (PSNR). This new method involves three steps. First, we present a codebook design using discrete wavelet transform (DWT), fuzzy C‐means (FCM), and support vector machine (SVM) algorithms. Second, we improve the bit rate using the Huffman coding theme as a method of eliminating the redundant index. Finally, we supplement the system with error compensation to improve the PSNR. With the proposed method, we are able to achieve a bit rate improvement of 24.00% and a PSNR of 10.96% over the conventional method. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Inner code assisted parallel concatenated single parity check codes

This paper proposes a novel coding scheme to improve the performance of multidimensional parallel concatenated single parity check (PCSPC) codes. The high error floor of PCSPC codes prevents clear turbo cliff to be seen in the bit‐error rate (BER) performance. Based on the product accumulate type‐I (PA‐I) coding scheme, which adds serially an accumulator to the existing PCSPC code structure, our coding scheme considers a wide range of rate‐1 recursive systematic convolutional (RSC) codes replacing the accumulator. The convergence behavior of the proposed iterative decoding is monitored and analyzed using an extrinsic information transfer (EXIT) chart. It has been revealed from the EXIT chart analysis that the proposed coding scheme has a lower convergence threshold than the PA‐I coding scheme, especially when using a lower code rate PCSPC code as the outer code. For the 2D PCSPC(3,2) code with the code rate 0.5, the proposed coding scheme has a convergence threshold of 0.47 dB, whereas the convergence threshold of the PA‐I coding scheme is 0.81 dB. The convergence threshold of the proposed coding scheme is closer to theoretical limit (0.28 dB away from the theoretical limit) than that of the PA‐I coding scheme (0.62 dB away). However, for PCSPC codes with a higher code rate, the performance improvement of the proposed coding scheme with respect to the PA‐I coding scheme becomes smaller. A series of simulations is carried out to investigate the performance of the proposed coding scheme, and the simulation results show that better performance is achieved by using the proposed coding scheme compared with the PA‐I coding scheme. The simulation results show good consistency with the convergence threshold obtained from the EXIT chart, as the difference is only within 0.34 dB in all the evaluated cases. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Forward error correction based on block turbo code with 3-bit soft decision for 10-Gb/s optical communication systems

The first experimental demonstration of a forward error correction (FEC) for 10-Gb/s optical communication systems based on a block turbo code (BTC) is reported. Key algorithms, e.g., extrinsic information, log-likelihood ratio, and soft decision reliability, are optimized to improve the correction capability. The optimum thresholds for a 3-bit soft decider are investigated analytically. A theoretical prediction is verified by experiment using a novel 3-bit soft decision large scale integrated circuit (LSI) and a BTC encoder/decoder evaluation circuit incorporating a 10-Gb/s return-to-zero on-off keying optical transceiver. A net coding gain of 10.1 dB was achieved with only 24.6% redundancy for an input bit error rate of 1.98/spl times/10/sup -2/. This is only 0.9 dB away from the Shannon limit for a code rate of 0.8 for a binary symmetric channel. Superior tolerance to error bursts given by the adoption of 64-depth interleaving is demonstrated. The ability of the proposed FEC system to achieve a receiver sensitivity of seven photons per information bit when combined with return-to-zero differential phase-shift keying modulation is demonstrated.     

Design of ultrafast all-optical 4-bit parity generator and checker using quantum-dot semiconductor optical amplifier-based Mach-Zehnder interferometer

The feasibility of implementing all-optically an ultrafast 4-bit parity generator and checker using the quantum-dot semiconductor optical amplifier (QD-SOA)-based Mach-Zehnder Interferometer (MZI) as XOR gate is theoretically investigated and demonstrated. The proposed circuit exploits an architecture where four XOR gates are concatenated in a modular manner. The first XOR gate drives the control input of the second one whose other control port receives the current bit of the word that undergoes parity processing. This interconnection is repeated up to the fourth XOR gate, on which an extra bit is applied. Depending on the binary value of this bit, the same circuit can operate both as parity generator and checker and support both even and odd parity. The performance of the scheme critically depends on the total amplitude modulation (AM) at its output. By conducting numerical simulation the impact of the key data signal and QD-SOAs parameters on this metric is evaluated. The outcome of this treatment allows to specify the permissible range of these parameters as well as an appropriate combination of them that renders the AM acceptable and ensures logically correct operation. The obtained results also demonstrate the ability of the QD-SOA-based MZI XOR gate to be cascaded and form more complex circuits of enhanced functionality.     

A practical software-only noncausal predictive video codec for low-bit-rate multimedia applications

A new coding scheme for bit rates below 150 Kb/s is proposed. The scheme combines (i) three-dimensional (3D) noncausal recursive prediction, (ii) vector quantization, and (iii) conditional replenishment. The 3D noncausal prediction model provides an alternative to causal (or unilateral) prediction, yet is not commonly used since it precludes recursive computations owing to its bilateral nature. This paper shows how to obtain a practical, near-optimal recursive implementation of the 3D noncausal video model and demonstrates its application in video compression. The proposed video codec is shown to produce high-quality compressed video at bit rates below 150 Kb/s. In contrast to the International Telecommunication Union (ITU) H.263 standard, the video codec exhibits acceptable video quality with a higher peak signal to reconstructed noise ratio (PSNR).     

New optical sampler based on TOAD and data postprocessing for subpicosecond pulse resolution

A low-complexity terahertz optical asymmetric demultiplexer-based optical sampler with simple data postprocessing for subpicosecond pulse shape characterization is proposed. Comparisons with commercial instruments demonstrate the accuracy of the implemented scheme reproducing optical pulses with a resolution of few hundreds of femtoseconds. Nevertheless, the proposed technique allows us to go down to femtosecond accuracy, slightly increasing the data postprocessing complexity. A further validation of the proposed optical sampler is numerically provided.     

Design and modeling of compliant micromechanism for mechanical digital‐to‐analog conversion of displacement

A microelectromechanical digital‐to‐analog converter (MEMDAC) converts digital motion of shuttle actuators operated by the corresponding bits of a binary code into an output displacement proportional to the analog value represented by the input code. In this paper a MEMDAC with improved kinematic design is devised that allows large travel range and high positioning resolution while making the microfabrication process less critical. A lumped‐parameter model of the compliant mechanism of an N‐bit MEMDAC is derived and used to determine the stiffness ratio of flexible members needed for proper mechanical digital‐to‐analog conversion. Furthermore, we analytically investigated the effect of nonuniformity in the device geometry due to the limitations of the microfabrication processes on the linearity of the output displacement. Successful fabrication and release of a 12‐bit MEMDAC demonstrated the manufacturability of the new mechanism, revealing opportunities for MEMS applications in which micropositioners with open‐loop operation, relatively large output range, fine positioning resolution and high repeatability are required. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

非线性量化的模拟实现方法

基于语音信号的A律或μ律非线性量化方法,由于其先采用一个线性转换器进行量化,再用数字硬件或软件量化为A律或μ律电平。其为：用较少的二进制位代替较多二进制位的数字压缩编码。在动态范围更大的非语音信号采集中,常被误认为可以用此法来＂扩展小信号的可量化范围＂,因前线性转换器的量化台阶决定了其最小信号分辨率,这里的问题主要在：信号的量化前后处理意义不同。要扩展小信号的量化范围,在A/D转换的位数一定情况下,为保证输入峰值不超载,应该对其输入的模拟信号进行A律或μ律折线非线性放大处理。     

基于提升小波和混合熵编码的数据压缩方法

大型发电机组远程状态监测系统中实时数据的存储与网络传输对数据压缩和重构技术提出了较高的要求.文中给出一种提升小波变换与混合熵编码技术相结合的数据压缩方法.首先利用基于提升格式的双正交滤波器组对实时数据进行小波分解,然后对小波系数进行阈值量化,最后通过混合熵编码技术对保留的系数进行编码,以进一步提高压缩效率.对实际发电机组实时数据进行了压缩试验,结果表明,有损压缩技术和无损压缩技术的结合可以获得较高的压缩比,能够较好地满足大型发电机组实时数据的存储和传输需求,是一种有效和实用的实时数据压缩方法.     

水声通信系统中的Turbo编码方案研究

为了使数据在极其复杂的水声信道中可靠传输,需要采用具有很好纠错性能的纠错码来提高信息传输的可靠性。针对水声信道多径干扰强、信道衰落严重的特点,提出了基于Turbo编码的直接序列扩频水声通信编码方案,并对其在水声多径信道中的性能进行分析。数值仿真及湖试数据处理结果表明,该编码方案具有编码增益高、抗多径能力强的特点,误码性能优于不加直接序列扩频的Turbo编码方案,更适合于强多径、衰落严重的水声信道。     

Practical low-cost visual communication using binary images for deaf sign language.

Deaf sign language transmitted by video requires a temporal resolution of 8 to 10 frames/s for effective communication. Conventional videoconferencing applications, when operated over low bandwidth telephone lines, provide very low temporal resolution of pictures, of the order of less than a frame per second, resulting in jerky movement of objects. This paper presents a practical solution for sign language communication, offering adequate temporal resolution of images using moving binary sketches or cartoons, implemented on standard personal computer hardware with low-cost cameras and communicating over telephone lines. To extract cartoon points an efficient feature extraction algorithm adaptive to the global statistics of the image is proposed. To improve the subjective quality of the binary images, irreversible preprocessing techniques, such as isolated point removal and predictive filtering, are used. A simple, efficient and fast recursive temporal prefiltering scheme, using histograms of successive frames, reduces the additive and multiplicative noise from low-cost cameras. An efficient three-dimensional (3-D) compression scheme codes the binary sketches. Subjective tests performed on the system confirm that it can be used for sign language communication over telephone lines.     

Soliton induced supercontinuum generation in photonic crystal fiber

Soliton induced supercontinuum (SC) generation using an index-guiding triangular photonic crystal fiber (PCF) is experimentally studied by pumping with 140-fs pulses at several wavelengths in the positive slope anomalous dispersion region. The focused beam incident upon the PCF core is first confirmed by in situ observation based on the reflection method to make sure accurate input coupling conditions. The influence of pumping wavelength on the spectral profile of SC is examined as a function of input peak power P/sub 0/. Processes initiating SC generation are governed by the fission of higher-order solitons, which lead to the soliton self-frequency shift (SSFS) by intrapulse Raman scattering associated with blue-shifted Cherenkov type phase matched radiation. The fission of higher-order solitons is clearly observed in the input P/sub 0/ dependent spectrum and a plot of the square root of frequency shift versus input P/sub 0/. Further increase of input P/sub 0/ leads to a new SSFS accompanied by an additional blue-shifted peak located at shorter wavelength than that of the previous one. These processes continue to develop successive blue-shifted and SSFS peaks as increasing the input P/sub 0/, which determine the spectral width of SC. Spectral profile of SC is also dominated by these initial and growth processes. SC spectra obtained in the vicinity of zero dispersion wavelength shows smooth but relatively narrow, while SC generation at deep anomalous dispersion site exhibits broad bandwidth at relatively low P/sub 0/. The input P/sub 0/ required for approaching a saturated SC which is almost the same feature within the tuning pump wavelengths is decreased as increasing the degree of anomalous dispersion.     

基于多分类支持向量机的分布式发电系统并网保护

在配电网出现孤岛、故障等异常情况时,并网保护需要及时断开分布式电源系统与主电网的连接。文中首先分析了并网保护的功能与特点,然后提出了一种基于多分类支持向量机的智能型并网保护方案。该保护方案在传统二分类支持向量机的基础上,建立了并网保护的概率型多分类器模型,实现对扰动、孤岛和故障事件的检测。为了提高模型的泛化能力,采用SVM-RFE方法对特征进行选择。最后,从保护的可信赖性与安全性两个方面,利用仿真对所提智能型并网保护与常规保护的性能进行了对比。     

Integrated-optic encoder/decoder for time-spreading/wavelength-hopping optical CDMA

We demonstrate an integrated-optic encoder/decoder for time-spreading/wavelength-hopping optical code division multiple access. It is composed of a wavelength multi/demultiplexer and variable delay lines fabricated by using silica-based planar lightwave circuit technology. We evaluated the device characteristics, including those of the key components and the encoding/decoding operation, and confirmed its flexible code assignment ability and good auto/cross correlations. We then tested the performance of the encoder/decoder by undertaking bit error rate measurements with 10-Gb/s pseudorandom binary sequence signals and confirmed its applicability to optical layer multicast routing and its ability to compensate for bit skew caused by fiber chromatic dispersion.     

∑-Δ调制器分组量化编码

∑-△调制器在对变化的交流测量信号实现A／D转换处理时可以省略复杂的数字抽取滤波器、抗混叠前置滤波器和采样保持器,直接转换计算。为充分减少数据冗余,加快转换计算速度,简化电路设计,采用分组量化编码方法。用多个计数器对调制器输出的1bit码流分别连续计数,DSP对计数结果计算处理。通过分组编码,可以方便的对调制器输出数据存储、处理,根据转换精度和转换速度要求灵活的选择利用前次转换的部分相关数据,而且电路实现和控制容易。给出了原理电路和计算分析结果,具有实用价值。     

Rapid prototyping of MIMO‐OFDM based on parity bit selected and permutation spreading

In this paper, a novel MIMO‐OFDM transmission scheme is developed to effectively enable multi‐access by joint code design across multiple antennas, subcarriers, OFDM frames, and users. It achieves better spectrum efficiency while improving bit error rate performance. The proposed scheme uses either parity bit selected or permutation techniques to assign spreading codes at the transmitter side. As a result, the detection at the receiver is greatly improved because of the fact that identifying the spreading code(s) directly yields the transmitted data symbols. The paper also investigates the field‐programmable gate array implementation of the proposed algorithms; optimization techniques are proposed to reduce area, power, and time. These techniques include a pipelined architecture for inverse FFT/FFT blocks, an efficient low complexity algorithm for despreading based on counters and comparators and an optimized architecture for complex matrix inversion using Gauss–Jordan elimination (GJ‐elimination). Finally, the fixed‐point optimized field‐programmable gate array architecture for MIMO‐OFDM transceiver is developed, where the maximum allowed performance loss because of quantization is defined, the tradeoffs between BER performance and area reduction are investigated. Copyright © 2015 John Wiley & Sons, Ltd.     

Multiterabit/s DWDM terrestrial transmission with bandwidth-limiting optical filtering

Wavelength-division multiplexing (WDM) systems based on 40-Gb/s channel bit rate appear as likely successors of current widespread N/spl times/10 Gb/s systems. However, they will provide larger throughputs than N/spl times/10 Gb/s systems only if some specific techniques are implemented, so as to improve the utilization ratio of the optical bandwidth, namely, the information spectral density (ISD). Narrow optical filtering is one such technique. Based on a review of some of our multiterabit/second transmission experiments in terrestrial configurations, we highlight the benefits of optical filtering to reshape the channel spectra. First, we show that vestigial sideband (VSB) narrow filtering of nonreturn-to-zero (NRZ) data makes 0.64-bit/s/Hz ISD possible over long-haul and ultra-long distances, provided that a specific wavelength allocation scheme is implemented. Using this scheme, a record 10-Tb/s capacity is demonstrated over 300 km by applying different data along each of the two polarization axes. However, along a single polarization axis and when channels are packed closer with NRZ-VSB filtering, at 0.8-bit/s/Hz ISD, nonlinear interactions between channels affect system performance and reduce the maximum error-free distance. We show that these interactions can be contained, still using narrow optical filtering, but by resorting to an alternative modulation format, namely, phase-shaped binary transmission.     

Edging out the competition: Lossy image coding with wavelets and contourlets

Image compression offers a good representation of images while using the least quantity of bits. Several lossy image coders are designed without considering the image nature. The image important information (e.g., edges) can be discarded at the coding quantization stage; that information is needed for image understanding and recognition. The possibility of saving storage space and preserving image important information in a joint way becomes imperative in areas such as medicine, mobile devices, and pattern recognition systems. This article addresses the design of an edge-preserving lossy image coder by means of wavelets and contourlets. The results obtained demonstrate the superior performance of the proposed coder against the traditional edge-preserving coders. The proposed coder ensures that the edges of an image are always preserved even at very low bit rates and the obtained decompressed images can be successfully used for future pattern recognition tasks.     

基于功率谱相对值判决的多载波编码调制

针对低压配电网的信道特性及现有调制解调技术的局限性,提出基于功率谱相对值判决解调的多载波编码调制方案。方案采用多载波调制,接收端通过数字信号处理技术对接收信号进行功率谱估计,利用谱估计结果进行判决解调。在模拟的低压电力线载波信道条件下,对调制解调方案进行了仿真。结果证明方案能有效抑制多种噪声,且对信道具有较强的自适应能力。与传统的多载波调制技术比较,传输特性有明显改善(在高斯白噪声信道中误比特性能改善约4dB)。     

An ultra-fast photonic ring network employing Optical Packet Compression-Time Division Multiplexing (OPC-TDM) scheme

Contents  An ultra-fast photonic ring network employing full-scalable Optical Packet Compression TDM (OPC-TDM) scheme is investigated in this paper. Moreover, a new optical packet compression/decompression unit is proposed, which allows high compression rates and large packet sizes thereby relaxing the medium access constraints. The extensive simulations are performed in order to investigate the feasibility of the proposed compression/decompression scheme. The improvement of the OPC-TDM network performance achieved by reducing the rate-conversion latency is shown. Received: 23 March 2001