一种低复杂度咬尾卷积码译码算法﹡

对于咬尾卷积码的译码,传统的最大似然译码算法需要遍历每个可能的起始状态对应的咬尾格形子图,译码复杂度过高.循环维特比算法是一种有效的低复杂度次优译码算法.通过对循环维特比算法中的循环陷阱进行研究,提出了一种新的循环陷阱检测方法,利用对循环陷阱的检测可以减少冗余迭代;同时利用最大似然咬尾路径对非似然起始状态进行排除,极大的缩小了循环维特比算法中译码搜索空间.在此基础上得到了一种低复杂度的译码算法.     

基于可信位置排序的咬尾卷积码译码算法

咬尾卷积码的传统译码算法没有考虑咬尾格形图的循环性,译码起始位置固定,译码效率相对较低。该文首次证明了咬尾卷积码基于格形图的译码算法与译码起始位置无关,即从任意位置开始译码得到的最优咬尾路径即为全局最优咬尾路径。基于此提出一种基于可信位置排序的咬尾卷积码译码算法。新算法利用咬尾格形图的循环性,根据接收到的信道输出序列估算每个译码起始位置的可靠性,从而选择一个可靠性最高的译码起始位置。和传统译码算法相比,所提算法具有更快的收敛速度。     

一种应用于LTE系统的Viterbi译码算法

LTE(long term evolution,长期演进)系统中采用了咬尾卷积码和Turbo码来实现前向纠错,Viterbi译码是卷积码的一种杰出的译码算法,它是一种最大似然译码方法。本文基于LTE系统中的咬尾卷积码,详细分析了几种较成熟的Viterbi译码算法,并综合现有算法,提出了一种改进算法,减小了译码计算的复杂度。仿真结果表明,改进算法在降低译码计算复杂度的同时还降低了译码误比特率,因此非常适合LTE系统的译码要求。     

基于陷阱检测的咬尾卷积码译码算法

该文分析了循环维特比算法(CVA)中存在的循环陷阱问题,并证明了传统基于CVA的咬尾卷积码译码算法中存在的不足,提出了一种高效率的咬尾卷积码译码算法。该算法通过检测两次不同迭代中获得的两条最大似然路径是否相同来判断是否有循环陷阱产生,并及时终止循环,减少冗余迭代;在没有循环陷阱产生的情况下,新算法比较当前迭代中最大似然路径和已经发现的最优咬尾路径是否相同来自适应终止迭代。文中对循环陷阱检测方案和自适应终止方案做了进一步优化,即利用路径的净增量而非路径本身作为检测量。实验结果表明新算法提高了译码效率,降低了译码复杂度。     

一种M-FSK信号的能量度量Viterbi软译码算法性能分析

Viterbi译码算法广泛应用于无线数字通信系统,一般采用比特对数似然信息(LLR)作为译码器的输入。针对M-FSK信号,该文提出一种采用信号解调得到的M维能量信息,直接作为译码器分支度量值,并给出了相应的Viterbi译码算法。在加性高斯白噪声(AWGN)和瑞利(Rayleigh)衰落信道下对所提算法的BER性能进行了理论推导,得到了闭合表达式。通过仿真验证了理论推导的正确性,与常规Viterbi算法相比,所提算法避免了比特LLR和分支度量值的计算,降低了算法复杂度和减少了信息损失,提高了M-FSK信号软解调Viterbi译码算法的BER性能,是一种更适用于工程实现的M-FSK信号的Viterbi译码算法。     

Reed-Muller码的双向搜索译码

本文提出了Reed-Muller码的一种双向搜索算法,并证明了该算法实现了广义最小距离译码。其复杂度较Forney的译码算法降低很多,而其完备译码的性能经计算机模拟表明,与最大似然译码几乎一样。     

Reed—Muller码的双向搜索译码

本文提出了Ｒｅｅｄ－Ｍｕｌｌｅｒ码的一种双向搜索算法，并证明了该算法实现了广义最小距离译码。其复杂度较Ｆｏｒｎｅｙ的译码算法降低很多，而其完备译码的性能经计算机模拟表明，与最大似然译码几乎一样。     

一种咬尾卷积译码的修正算法

在LTE系统中,物理广播信道和物理下行控制信道均采用了咬尾卷积编码,咬尾卷积编码拥有很多优良的性能.针对咬尾卷积译码,提出了一种基于Viterbi译码的修正算法——正逆序结合译码算法,根据分支度量确定误码在数据帧的分布,最后确定采用正序还是逆序译码结果.仿真结果表明,Viterbi的修正方法有效地降低了系统误码率,而且具有普适性,适合应用于LTE系统.     

低复杂度的TBCC自适应循环VA译码算法

咬尾是一种将卷积码转换为块码的技术,它消除了归零状态所造成的码率损失,同时避免了截尾带来的性能降低,在短块编码中具有明显优势。针对咬尾卷积码(TBCC)现有译码算法复杂度过大和收敛性问题,提出一种低复杂度的TBCC自适应循环维特比(VA)译码算法。该算法根据信道变化自适应调整译码迭代次数,使咬尾路径收敛到最佳。通过仿真对比不同译码算法的块错误率和译码迭代次数,结果表明TBCC性能明显好于传统卷积码;相比于同类循环VA算法,在不降低性能的前提下,改进算法简化了停止规则,减少译码迭代次数和复杂度,在低信噪比时,改进算法比传统绕维特比译码算法(WAVA)平均迭代次数减少约4次。      

非线性的模拟量绝对值纠错编码方法研究

为了更有效、实时地进行无线图像通信, 基于编码理论和非线性理论, 提出一种针对模拟量的三分支“咬尾”绝对值纠错编码方法和最大似然译码算法, 并与三分支“咬尾”Baker码相比较。经过仿真, 在图像传输中, 三分支“咬尾”绝对值纠错编码方法在高斯信道中的纠错性能远远超出后者, 恢复图像的PSNR有2 dB以上的增益, 并且其编译码的复杂度也大幅降低, 提升了通信有效性和实时性, 在信道的干扰或噪声大的图像通信中具有应用优势。     

LTE中卷积码的译码器设计与FPGA实现

基于长期演进（LTE）的Tail—biting卷积码,介绍了维特比译码算法,它是一种最优的卷积码译码算法。由于Tail—biting卷积码的循环特性,采用固定延迟译码的方法,降低了译码复杂度。通过使用全并行的结构及简单的回溯存储方法,设计了一个具有高速和低复杂度的固定延迟译码器。在FPGA上实现并验证,验证结果表明译码器的性能满足了LTE系统的要求。     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

Nanoimprint Lithography -A Next Generation High Volume Lithography Technique

IntroductionNanoimprint Lithography is a well-acknowl-edged low cost, high resolution, large area pattern-ing process. It includes the most promising methods,high-pressure hot embossing lithography (HEL) [2],UV-cured imprinting (UV-NIL) [3] and micro contactprinting (m-CP, MCP) [4]. Curing of the imprintedstructures is either done by subsequent UV-lightexposure in the case of UV-NIL or by cooling downbelow the glass transition temperature of the ther-moplastic material in case of HEL…     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.     

Influence of PVK ： NPB hole transporting layer on the characteristics of organic light-emitting devices

A doping system consisting of NPB and PVK is employed as a composite hole transporting layer （CHTL）. By adjusting the component ratio of the doping system, a series of devices with different concentration proportion of PVK ： NPB are constracted. The result shows that doping concentration of NPB enhances the competence of hole transporting ability, and modifies the recombination region of charge as well as affects the surface morphology of doped film. Optimum device with a maximum brightness of 7852 cd/m^2 and a power efficiency of 1.75 lm/W has been obtained by choosing a concentration proportion of PVK ： NPB at 1：3.     

New insert layer structure OLEDs

An insert layer structure organic electroluminescent device（OLED） based on a new luminescent material （Zn（salen）） is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn（salen）/Liq/LiF/A1/CuPc/NPD/Zn（salen）/Liq/LiF/A1. Effective insert electrode layers comprising LiF（1nm）/Al（5 nm） are used as a single semitransparent mirror, and bilayer cathode LiF（1 nm）/A1（100 nm） is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect.     

Analysis of error performance on Turbo coded FDPIM

Due to variable symbol length of digital pulse interval modulation（DPIM）, it is difficult to analyze the error performances of Turbo coded DPIM. To solve this problem, a fixed-length digital pulse interval modulation（FDPIM） method is provided. The FDPIM modulation structure is introduced. The packet error rates of uncoded FDPIM are analyzed and compared with that of DPIM. Bit error rates of Turbo coded FDPIM are simulated based on three kinds of analytical models under weak turbulence channel. The results show that packet error rate of uncoded FDPIM is inferior to that of uncoded DPIM. However, FDPIM is easy to be implemented and easy to be combined, with Turbo code for soft-decision because of its fixed length. Besides, the introduction of Turbo code in this modulation can decrease the average power about 10 dBm, which means that it can improve the error performance of the system effectively.     

A method for calculating the center position of collimated light

It is a key problem to accurately calculate beam spots＇ center of measuring the warp by using a collimated laser. A new method, named double geometrical center method （DGCM）, is put forward for the first time. In this method, a plane wave perpendicularly irradiates an aperture stop, and a charge couple device （CCD） is employed to receive the diffraction-beam spots, then the geometrical centers of the fast and the second diffraction-beam spots are calculated respectively, and their mean value is regarded as the center of datum beam. In face of such adverse instances as laser intension distributing defectively, part of the image being saturated, this method can still work well. What＇s more, this method can detect whether an unacceptable error exits in the courses of image receiving, processing and calculating. The experimental results indicate the precision of this method is high.