Interleaved coding and sequential transmission scheme for packet‐level forward error correction over burst loss channels

Burst packet loss is a common problem over wired and wireless networks and leads to a significant reduction in the performance of packet‐level forward error correction (FEC) schemes used to recover packet losses during transmission. Traditional FEC interleaving methods adopt the sequential coding‐interleaved transmission (SCIT) process to encode the FEC packets sequentially and reorder the packet transmission sequence. Consequently, the burst loss effect can be mitigated at the expense of an increased end‐to‐end delay. Alternatively, the reversed interleaving scheme, namely, interleaved coding‐sequential transmission (ICST), performs FEC coding in an interleaved manner and transmits the packets sequentially based on their generation order in the application. In this study, the analytical FEC model is constructed to evaluate the performance of the SCIT and ICST schemes. From the analysis results, it can be observed that the interleaving delay of ICST FEC is reduced by transmitting the source packets immediately as they arrive from the application. Accordingly, an Enhanced ICST scheme is further proposed to trade the saved interleaving time for a greater interleaving capacity, and the corresponding packet loss rate can be minimized under a given delay constraint. The simulation results show that the Enhanced ICST scheme achieves a lower packet loss rate and a higher peak signal‐to‐noise‐ratio than the traditional SCIT and ICST schemes for video streaming applications.     

一种有源箝位交错并联Boost电路的研究

为提高Boost变换器传输效率,提出了一种运用辅助电感和箝位电路实现交错并联Boost电路软开关的拓扑结构,变换器不仅实现了主开关管的零电流开通和零电压关断,大大减少了二极管的反向恢复电流带来的能量损耗。同时实现了辅助开关管的零电压开关,降低了附加损耗。在原理仿真的基础上,设计试制了一台实验样机。实验结果给出了开关管波形,验证了软开关功能的实现。     

基于dsPIC30F的交错并联Buck变换器研究

针对高速永磁发电系统对功率变换器宽输入范围、高功率密度、高效率等要求,设计并研制了与之匹配的交错并联Buck变换器。分析了交错并联Buck变换器的工作原理,提出了采用专用电源和电机数字控制芯片ds PIC30F2023实现逐周期限流控制的方案,解决了并联变换器的均流问题。实验结果表明,变换器具有较好的输入、输出性能,系统的安全性、可靠性以及集成性等得到提升,满足设计要求。     

A single series representation of multiple independent ARMA processes

This article shows that multiple independent time series from the same ARMA process can be represented by a single univariate ARMA time series through an interleaving of the original series. Using this result, existing univariate modelling software can be used to fit a single ARMA time series model simultaneously to multiple independent realizations of the same ARMA process. The interleaving approach and its properties will be presented and compared with alternative estimation options. It will be applied to the modelling of 66 years of daily maximum temperatures for Perth, Western Australia and to other time series models.     

基于交错并联技术的高频整流器交流侧电流纹波分析

文章探讨了单个高频整流器以及基于交错并联技术的高频整流器交流侧电流纹波,对两者进行了分析比较。理论与仿真证明,将交错并联技术应用于高频整流器时,交流侧的电流纹波得到了很好的抑制。在大功率应用场合,采用交错并联技术时,单个开关管耐流值可降低一半,在相同的电流纹波要求下,电感的尺寸可以降低40%左右,相应可以提高整个系统的动态响应时间。     

一种基于频率间插技术的DWDM-ROF系统

文章设计了一个基于频率间插复用的DWDM-ROF(密集波分复用—光载无线)系统,使每个信道载波与边带之间的空闲频段得到利用,从而提高了DWDM-ROF系统的频谱利用率.同时,为该系统设计了一种基于FBG(光纤布拉格光栅)的新颖的解复用器.数据传输的仿真实验不仅验证了该方法的可行性,还显示出了该系统具有良好的抗信道串扰能...     

Chip‐interleaving direct sequence spread spectrum system over Rician multipath fading channels

Chip interleaving (CI) is a unique technique to exploit time diversity in direct sequence spread spectrum (DS/SS)‐based systems operating in fading environments. In order to facilitate design of CI systems in various fading situations, we present a performance analysis for CI DS/SS system over Rician multipath time‐varying fading channels. We derive the analytical bit error rate (BER) expression for CI DS/SS to allow fast and accurate evaluation of BER performance based on the interleaving depth selected, spreading codes employed, and the time correlation function of the channel. We then discuss some ideal cases by using the analytical results to reveal some of the insights presented in the performance analysis. For the purpose of comparison, we also obtain the BER expression for conventional DS/SS system as a special case of CI system with an interleaving depth of one. Using numerical examples, we verify the analytical results with computer simulations and illustrate the BER performance behavior of CI DS/SS system with varying interleaving depth for all possible combinations of two sets of spreading codes of different type and two different time correlation functions of the channel. Copyright © 2011 John Wiley & Sons, Ltd.     

一种带有软开关的交错并联变换器

提出一种带有软开关的交错式Boost变换器拓扑结构和控制方法,该变换器不仅具有良好的功率因数校正效果,而且可实现开关管的零电流开通和零电压关断.详细给出了电路的拓扑结构、工作原理及各模态的分析,并给出了关键参数的计算和设计,最后通过仿真和实验验证了理论的正确性.该变换器在大功率(大于1 kW)单相功率因数校正中有广泛的...     

星座旋转及坐标交织在DTMB系统中的应用研究

介绍了一种结合星座旋转和坐标交织的信号空间分集技术。该技术能以较低的实现复杂度为代价,提高信号分集阶数,获得分集增益。仿真结果证明,将这一技术应用于DTMB系统中,能有效地改善DTMB系统在衰落信道下的信号接收质量。     

双端正激逆变器研究

针对单端正激逆变器存在的不足,提出了采用两个单端正激逆变电源,既交错串并联逆变焊接电源,开关管选用软开关交错控制方法。交错并联逆变器既能增加输出功率密度,又能使电压频率增加一倍,减小了装置体积和输出纹波。通过仿真和试验验证了该控制方法的有效性,使整个控制系统能稳定可靠的运行。