Unequal Error Protection Based on Expanding Window Fountain for Object-Based 3D Audio

This paper proposes an unequal error protection（UEP）coding method to improve the transmission performance of three-dimensional（3D）audio based on expanding window fountain（EWF）.Different from other transmissions with equal error protection（EEP）when transmitting the 3D audio objects.An approach of extracting the important audio object is presented,and more protection is given to more important audio object and comparatively less protection is given to the normal audio objects.Objective and subjective experiments have shown that the proposed UEP method achieves better performance than equal error protection method,while the bits error rates（BER）of the important audio object can decrease from 10^（–3） to 10^（–4）,and the subjective quality of UEP is better than that of EEP by 14%.

ANALYSIS OF TOOTH FORM ERROR OF EQUAL BASE CIRCLE BEVEL GEAR

The basic principle of equal base circle bevel gear (EBCBG) is illustrated simply Thetooth surface equation of EBCBG manufactured by end milling cutter with involute profile is de-rived. The tooth form error is analyzed on the basis of spherical involute

Effect of DFE error propagation and its mitigation using MUX-based FEC interleaving for 400 GbE electrical link

This paper evaluates the effect of decision feedback equalizer( DFE) error propagation for400 Gb/s Ethernet( 400 GbE) electrical link in order to propose some effective methods to improve bit error rate( BER). First,an analytical model for DFE burst error length distribution is proposed and simulated based on a NRZ electrical link in which a 5-tap DFE combined with a multiple-tap feed forward equalizer( FFE) is included. Then,a detailed derivation for BER considering DFE error propagation is given based on the distribution of burst error run length and the BER performance with and without forward error correction( FEC) is simulated too. After that,this paper investigates several MUX-based FEC interleaving methods including their complexity and latency in order to improve BER further. At last,three FEC interleaving schemes are compared not only in interleaving gain,but also in hardware complexities and latencies. Simulation results show that pre-interleave bit muxing can obtain good tradeoff between BER and complexity for 400 Gb E electrical link.

Determining the Optimal Decision Delay Parameter for a Linear Equalizer

The achievable bit error rate of a linear equalizer is crucially determined by the choice of a decision delay parameter. This brief paper presents a simple method for the efficient determination of the optimal decision delay parameter that results in the best bit error rate performance for a linear equalizer. Keywords Linear equalizer - decision delay - bit error rate Eng Siong Chng received his university education at the University of Edinburgh, Edinburgh, Scotland (BEng 1991, PhD 1995). After his PhD, he spent 6 months in Japan, working as a researcher for Riken. After working in industry in Singapore for 7 years, he joined the School of Computer Engineering, Nanyang Technological University in 2003. His research interests are in digital signal processing for communication applications, speech and handwriting recognition and noise reduction.Sheng Chen obtained a BEng degree in control engineering from the East China Petroleum Institute, Dongying, China, in 1982, and a PhD degree in control engineering from the City University at London in 1986. He joined the School of Electronics and Computer Science at the University of Southampton in September 1999. He previously held research and academic appointments at the Universities of Sheffield, Edinburgh and Portsmouth. Dr Chen is a Senior Member of the IEEE in the USA. His recent research works include adaptive nonlinear signal processing, modeling and identification of nonlinear systems, neural networks and machine learning, finite-precision digital controller design, evolutionary computation methods and optimization. He has published over 200 research papers. In the database of the world’s most highly cited researchers in various disciplines, compiled by the Institute for Scientific Information (ISI) of the USA, Dr Chen is on the list of highly cited researchers in the category that covers all branches of engineering subject, see www.ISIHighlyCited.com.

多通道光栅莫尔信号实时细分与等分平均技术研究

圆光栅受刻线误差、安装偏心等多种因素的共同影响,其定位精度无法直接满足高精度测角系统的需求。多读数头等分平均方法可以实现圆光栅精度的自校准,是提高测角系统精度的有效方法。然而,商业伺服控制系统通常不支持多路读数头信号实时接入同一路伺服轴,这造成了等分平均方法的在线应用存在困难。本文针对多通道光栅莫尔信号的采样、误差补偿、实时细分和等分平均进行研究,基于FPGA平台实现了多读数头实时处理系统的研制,并在测角转台开展了应用验证。设计了细分值稳定性、控制分辨率、角定位精度和细分误差实验,验证了多读数头实时处理系统的性能。所设计的多读数头处理系统,在测角转台上可以满足0.005″的控制分辨率需求,取得了0.58″定位精度和0.06″重复定位精度等测试结果。

Enhancement in Channel Equalization Using Particle Swarm Optimization Techniques

This work proposes an improved inertia weight update method and position update method in Particle Swarm Optimization (PSO) to enhance the convergence and mean square error of channel equalizer. The search abilities of PSO are managed by the key parameter Inertia Weight (IW). A higher value leads to global search whereas a smaller value shifts the search to local which makes convergence faster. Different approaches are reported in literature to improve PSO by modifying inertia weight. This work investigates the performance of the existing PSO variants related to time varying inertia weight methods and proposes new strategies to improve the convergence and mean square error of channel equalizer. Also the position update method in PSO is modified to achieve better convergence in channel equalization. The simulation presents the enhanced performance of the proposed techniques in transversal and decision feedback models. The simulation results also analyze the superiority in linear and nonlinear channel conditions.

相位噪声对 16QAM 通信系统性能影响及其均衡算法研究

在分析相位噪声对16QAM通信性能影响的基础上,提出了一种基于误差判决的多模均衡算法(Multiple Modulus Algorithm Based on Error Judgment,MMA-EJ),该算法不仅利用信号的相位信息消除了卫星通信中载波频偏引入的相位失真,还考虑了多电平幅度调制中不同半径星座点引入的幅度误差影响,因此相对于恒模算法(Constant Modulus Algorithm,CMA)来说,提高了均衡算法的精度。仿真结果表明,与传统的恒模均衡算法相比,提出的基于误差判决的MMA算法不仅可以消除高速信号传输时的码间串扰(Inter Symbol Interference,ISI),还可以消除传输系统中的相位噪声,提高16QAM通信系统的传输性能。

模分复用系统中盲均衡算法的均衡性能研究

恒模算法(CMA)是一种广泛应用于模分复用系统的算法,可对系统中模式耦合、差分模式群时延和色散等损伤因素进行均衡补偿,进而得到理想信号。为了研究CMA算法在强耦合模分复用系统中的均衡性能,采用功率耦合理论搭建6×6模分复用系统模型,并在接收端使用CMA和修正的恒定模数算法(MCMA)对系统输出信号进行均衡,获得了星座图、均方根误差(RMSE)值和误比特率(BER)。结果表明,在星座图方面,MCMA可以减少散点,使星座点更紧凑;在RMSE方面,MCMA均衡后的信号的RMSE值小于CMA均衡后得到的RMSE值,说明MCMA均衡后的数据离散程度较低;在BER方面,当BER为10-3时,MCMA要求的光信噪比比CMA低1.0 dB,因此,MCMA的均衡效果优于CMA。该研究结果为强耦合模分复用系统中的均衡算法提供了一些参考。

基于自适应直方图均衡化的医学图像可逆对比度增强算法

目前,一些可逆数据隐藏算法通常是对图像进行类似直方图均衡化的信息嵌入操作来实现对比度增强。这类方法虽然简单有效,但是缺乏明确的目标函数来指引参数选择,难以优化对比度增强效果,因而容易产生增强不足或过度增强等问题。为了优化可逆信息嵌入后的对比度增强效果,提出了一种基于自适应直方图均衡化并结合对比度增强的医学图像可逆数据隐藏算法。该方法基于预测误差扩展技术来实现可逆数据嵌入,并通过所定义的自适应直方图均衡化目标函数来优化预测残差直方图的修改,确定最优的数据嵌入点,在确保对比度增强的前提下实现低失真的可逆嵌入。实验结果表明,相比同类算法,所提方法在实现可逆嵌入的同时,能够进一步增强图像对比度,辅助提升医学图像中的目标识别效率。

多径信道下基于恒模算法的遥测信号盲均衡

运载火箭在塔架静态测试时易受多径衰落影响,导致遥测信号产生码间干扰。本文对PCM-FM体制遥测信号的多径信道使用恒模算法(CMA)进行盲均衡研究,针对遥测信道中的码间干扰展开理论分析和Matlab仿真,并搭建盲均衡功能测试平台开展实验验证。结果表明:CMA收敛速度高、误码率低,对多径干扰具有较好的鲁棒性和实用性。

变步长CMA和DD-LMS双模式切换盲均衡算法

针对经典盲均衡算法收敛速度较慢和稳态误差较大的问题,提出了一种基于变步长恒模算法(Constant Modulus Algorithm, CMA)和判决引导的最小均方(Decision Directed Least Mean Square, DD-LMS)算法的双模式切换盲均衡算法。在算法收敛初期采用CMA算法,以确保算法可以较快收敛。在收敛之后切换至DD-LMS算法,以进一步降低稳态误差。通过设定阈值来切换算法,取相邻多次迭代误差的平均值作为算法的切换值,以确保算法切换时机的合理性。另外,引入Softsign变步长函数并加入3个参数对该函数进行改进,使得Softsign变步长函数可以依据不同信道环境设定最佳参数,同时提高算法的收敛速度。仿真结果表明,在卫星通用信道条件下,所提算法的收敛迭代次数约为1 000次,稳态误差为-12 dB,在信噪比为15 dB时,误码率为1×10~(-6)。与相关算法对比,所提算法的收敛速度较高,误码率和稳态误差较低。

随机相位对分布式无人机群传输性能的影响

随着无线通信的快速发展,分布式无人机群引发了国内外学者的广泛关注。针对一个分布式无人机群通信系统,分析无人机位置偏移产生的相位误差对系统传输性能的影响。首先,在假设无人机群存在随机相位误差的情况下,考虑目的节点采用等增益合并技术接收来自各个无人机的信号以使系统获得最优的性能。接着,假设无人机通信链路的小尺度衰落服从Nakagami-m分布,推导出系统的中断概率和遍历容量的闭合表达式。最后,利用计算机仿真验证理论分析的正确性,并定量分析无人机数、随机相位误差等关键参数对系统性能的影响,为实际分布式无人机群通信提供参考。

基于判决导引的水声信道混合盲均衡算法研究

提出了一种适用于正交幅度调制(QAM)信号的混合盲均衡算法,该算法在初始模式中分别对QAM信号的同相分量和正交分量进行均衡,利用方形环判决域对均衡器输出信号进行判决,当误码率降到足够低的水平时自动切换到判决导引最小均方误差算法。最后利用水声信道仿真模型,对该算法的性能进行了验证。结果表明:该算法性能稳健,收敛后均方误差小,有效降低了高速水声通信的误码率,提高了水声信道均衡的稳定性,且有良好的冷启动和重新启动能力。

等误差直线逼近非圆曲线的节点计算及刀具轨迹模拟

介绍了数控编程时采用等误差直线逼近法模拟非圆曲线刀具轨迹的节点计算方法 。

曲线等误差直线拟合的算法研究及其应用

为实现一般曲线的等误差直线拟合,提出了一种基于罗尔定理与二分法的曲线节点计算新算法。该算法是通过在划分的凹凸性一致的单值区间内,迭代求解弦与对应的弧之间的误差来逐步逼近程序所要求的允差。分析了凹凸性一致的单值区间的划分方法,得到了具体的算法流程并进行了轨迹仿真验证。

非圆曲线数控编程的等误差圆弧逼近法及其实现

介绍基于VB开发环境,实现数控机床编程中非圆曲线等误差法圆弧逼近节点计算的方法,并利用程序实现刀具轨迹线NC代码的自动生成。

卫星高阶调制信号通信下非线性误差修正均衡方法

针对现有的均衡方法计算量大、非线性误差补偿速度慢的问题,提出了一种基于幅相分离的快速非线性均衡方法。该方法首先将接收信号的幅度和相位进行分离处理,并分别通过反馈均衡模型对信号进行均衡处理以减小计算复杂度,然后利用Volterra模型对误差进行非线性修正,并通过该非线性修正误差更新反馈均衡的参数,从而快速消除非线性干扰和记忆干扰。从误码率、收敛速度和计算复杂度3个方面将所提出的方法与现有的主要均衡方法进行理论和仿真分析比较,结果表明,在相同误码率下,所提方法的计算复杂度仅为其他均衡方法的14.1%~24.9%,能够快速实现非线性干扰的消除。

平面曲线的近似等误差双圆弧拟合及应用

根据快走丝线切割数控加工的特点 ,提出一种平面轮廓曲线的近似等误差双圆弧拟合方法 ,给出曲线拟合的计算机自动编程算法 ,介绍其在线切割自动编程系统中的应用。

并联滤波的常数模与判决引导融合盲均衡算法

针对常数模和判决引导双模式盲均衡算法切换时机选择困难问题,提出了一种并联滤波的双模式融合盲均衡算法。算法以并联滤波器作为盲均衡器,两路子滤波器分别以常数模算法准则和判决引导算法准则进行更新,通过加权因子实现两种算法模式自适应切换,完成两种算法的融合处理,加权因子依据归一化均方误差进行调整。为防止信道突发干扰,定义了归一化均方误差信息熵增量,以信息熵增量为判据适时实现均衡器和加权因子重置,使算法在信道突发干扰条件下能实现自适应跟踪。计算机仿真和水池试验处理结果表明:该算法有效地结合了常数模和判决引导算法的优点,具有较好的均衡性能。

数控系统等误差直线逼近节点算法分析与改进

近些年来,复杂零件越来越多,其曲面轮廓往往需要采用数控加工,且加工精度要求也日益提高。非圆曲线是机械零件常见的平面轮廓曲线,但目前绝大多数数控系统只具备直线插补和圆弧插补功能,加工非圆曲线则需要用直线段或圆弧段来逼近非圆曲线。重点分析现有数控系统等误差直线逼近节点算法,指出该算法用于非圆曲线处理时的局限性。在此基础上,提出一种新的基于区域误差检验的等误差算法,并运用VC++编程软件,实现非圆曲线的等误差数控编程系统开发。最后,通过实例非圆曲线验证该算法的有效性。