Digital signal processing techniques in Nyquist-WDM transmission systems

In single-carrier wavelength-division multiplexing (WDM) systems, the spectral efficiency can be increased by reducing the channel spacing through digital signal processing (DSP). Two major issues with using tight filtering are cross talk between channels and inter-symbol interference (ISI) within a channel. By fulfilling the Nyquist criterion, Nyquist spectral-shaped WDM systems can achieve narrow channel spacings close to the symbol rate \((\hbox {R}_{\mathrm{S}})\) with negligible cross talk and ISI. In principle, DSP can generate any signals with arbitrary waveforms and spectrum shapes. However, the complexity of DSP is limited by its cost and power consumption. It is necessary to optimize the DSP to achieve the required performance at a minimum complexity. In this paper, we first introduced the background of digital signal processing for Nyquist spectral shaping in optical fiber WDM systems. Then, we investigated the use of digital finite impulse response (FIR) filters to generate Nyquist-WDM 16-ary quadrature amplitude modulation (16QAM) signals with the raised-cosine (RC) and root-raised-cosine (RRC) shape spectra. The system performance of both the RC and RRC spectra is also examined. Moreover, we explored the various methods to reduce digital-to-analog converter (DAC) sampling speed, such as using super-Gaussian electrical filters (E-filter) and spectral pre-emphasis. We also discussed receiver-side matched filter design for Nyquist-WDM receiver optimization.     

分布式光纤传感系统的全数字信号处理

文章介绍了一种新颖的全数字分布式光纤Sagnac传感系统信号处理方案,重点阐述了闭环检测电路、基于FPGA和DSP的全数字信号处理方法、电路设计及调试.实验结果表明,该系统具有很高的性能.     

Digital audio broadcasting: High-grade service quality through on-board processing techniques

A digital audio broadcasting (DAB) satellite system is presented here which provides a high-grade quality of service for some hundreds of channels. This, with minimum cost of the radio set and of the broadcasting station, greatly improves the radio broadcasting service throughout the world, especially in areas where deployment of conventional relay infrastructure is difficult and not yet cost-effective. Potential broadcasters located in the visible hemisphere can directly up-link their programming to the DAB satellites. Broadcasters can also copy each up-link channel and steer flexibility to any beam or combination of satellite beams. The paper illustrates the advantages and the feasibility of a DAB system based on geostationary satellites with on-board processing generating signals of MCPC (multiple channel per carrier) type. This multiplexing technique allows large system margins. This solution allows the satellite L-band TWTA amplifiers to be operated in saturation and eliminates the intermodulation noise associated with the transmission of FDMA channels. A powerful coding scheme has been selected to create a ‘robust’ down-link. In this way several high-power DAB channels of radio programming, with selectable data rate, are directly delivered to the users.     

Digital image processing techniques for the detection and removal of cracks in digitized paintings.

An integrated methodology for the detection and removal of cracks on digitized paintings is presented in this paper. The cracks are detected by thresholding the output of the morphological top-hat transform. Afterward, the thin dark brush strokes which have been misidentified as cracks are removed using either a median radial basis function neural network on hue and saturation data or a semi-automatic procedure based on region growing. Finally, crack filling using order statistics filters or controlled anisotropic diffusion is performed. The methodology has been shown to perform very well on digitized paintings suffering from cracks.     

浅谈计算机图形图像处理技术

计算机图形图像处理技术日益成熟,已经实现了在多个行业领域中广泛应用,为了加深对其认识的和理解,本文主要介绍了计算机图形学和图形图像处理的基本概念,基本工作原理,主要应用领域以及所进行计算机图形学与图形图像处理的技巧、技术等.     

电视图像编码中的运动补偿技术

论述了运动补偿技术在序列图像或实时视频信号编码中的重要作用，给出了其主要算法，并介绍了其在数字高清晰度电视系统中的应用。     

Fast encoding techniques for Multiview Video Coding

Multiview Video Coding (MVC) is a technique that permits efficient compression of multiview video. MVC uses variable block size motion and disparity estimation for block matching. This requires an exhaustive search process that involves all possible macroblock partition sizes. We analyze the time complexity of MVC and the methods that have been proposed to speed up motion and disparity estimation. We then propose two new methods: Previous Disparity Vector Disparity Estimation (PDV-DE) and Stereo-Motion Consistency Constraint Motion and Disparity Estimation (SMCC-MDE). PDV-DE exploits the correlation between temporal levels and disparity vectors to speed up the disparity estimation process while SMCC-MDE exploits the geometrical relationship of consecutive frame pairs to speed up motion and disparity estimation. We build a complete low complexity MVC encoding solution that combines our two methods with complementary previous methods to speed up motion and disparity search. We evaluate the complexity of our solution in terms of encoding time and number of search points. Our experimental results show that our solution can reduce the encoding time and number of search points of the standard MVC implementation (JMVM 6.0) using the fast TZ search mode up to 93.7% and 96.9%, respectively, with negligible degradation in the rate-distortion performance. Compared to the best published results, this is an improvement of up to 11% and 7%, respectively.     

浅析计算机图形图像处理技术

伴随计算机技术的不断发展,计算机图形图像处理技术逐渐提升,经由了解计算机图形图像处理技术便可获悉计算机技术发展情况。如今,计算机图形图像处理技术在诸多领域得到广泛推广,促进了社会进步。文章通过阐述计算机图形图像处理技术,分析计算机图形处理技术与图像处理技术相互的关系、计算机图形图像处理技术的主要功能,对计算机图形图像处理技术的应用及其发展趋势展开探讨,旨在为如何促进计算机图形图像处理技术有序发展研究适用提供一些思路。     

Digital signal processing for video

Applications of the digital signal processing of video signals in broadcasting, communication, and consumer electronics are reviewed. These include: digital encoding systems, digital video effect equipment, and the television standards converter for broadcasting; videoconferencing and video telephone equipment; and TV receivers, including those for extended definition and high-definition television (EDTV and HDTV). Performance requirements for video signal processing (VSP) are discussed, and an example of a video signal processor comprising a parallel processor system composed of multiple VSP modules is examined. Future trends in VSP are predicted     

Digital signal processing for sonar

This paper is a tutorial which describes "main stream" sonar digital signal processing functions along with the associated implementation considerations. The attempt is to promote further cross-fertilization of ideas among digital signal processing applications in sonar, radar, speech, communications, seismology, and other related fields.     

Modulation techniques for on-board processing satellitecommunications

The uplink channel from a terminal to a regenerative satellite repeater is considered in which a digital transmultiplexer (TMUX) is used as a frequency-division multiple-access (FDMA) to time-division-multiplexed (TDM) converter for group demodulation. Linear modulation techniques were considered to determine which would make the most efficient use of this on-board processing (OBP) satellite system. The modulation techniques examined were quadrature phase-shift keying (QPSK), π/4-QPSK, and offset QPSK (OQPSK), all with Nyquist pulse shaping, and minimum-phase keying (MSK). The search for the optimum linear modulation technique took into account the performance criteria of power efficiency, bandwidth efficiency, and especially the complexity of the TMUX algorithm for OBP     

Array processing techniques for multiuser detection

Techniques often used in the area of adaptive array signal processing are applied to the multiuser detection problem. The results of this effort include a robust detector, suitable for use in the presence of modeling errors, and a reduced-rank detector with improved transient behavior relative to full-rank detectors. Algorithm performance is presented in the form of bit-error-rate (BER) curves and least mean square (LMS)-like learning curves     

High-speed nonlinear finite element analysis for surgical simulation using graphics processing units

The use of biomechanical modelling, especially in conjunction with finite element analysis, has become common in many areas of medical image analysis and surgical simulation. Clinical employment of such techniques is hindered by conflicting requirements for high fidelity in the modelling approach, and fast solution speeds. We report the development of techniques for high-speed nonlinear finite element analysis for surgical simulation. We use a fully nonlinear total Lagrangian explicit finite element formulation which offers significant computational advantages for soft tissue simulation. However, the key contribution of the work is the presentation of a fast graphics processing unit (GPU) solution scheme for the finite element equations. To the best of our knowledge, this represents the first GPU implementation of a nonlinear finite element solver. We show that the present explicit finite element scheme is well suited to solution via highly parallel graphics hardware, and that even a midrange GPU allows significant solution speed gains (up to 16.8 times) compared with equivalent CPU implementations. For the models tested the scheme allows real-time solution of models with up to 16 000 tetrahedral elements. The use of GPUs for such purposes offers a cost-effective high-performance alternative to expensive multi-CPU machines, and may have important applications in medical image analysis and surgical simulation.     

Digital signal processing for video applications

Digital video signal processing is one result of the fast progress in NMOS-VLSI techniques. The attractions of using digital data processing methods in an analog application field are the availability of CAD tools for the design of digital ICs and the integration of digital filter functions. Besides the key components such as microcomputers, A/D, and D/A converters, the digital filter techniques are the most important functions in this application field. It is demonstrated that digital signal processing is not only restricted to amplitude modulated video signals, but also that frequency modulated signals can be processed and methods for FM modulation and demodulation have been developed.     

Digital image processing

A review of the field of digital image processing is presented, with concentration upon image formation and recording processes, digital sampling and digital image display, and with in-depth coverage of image coding and image restoration. New results in image restoration are also presented, covering restoration by use of an eye-model constraint and nonlinear restoration by maximization of the posterior density function.