基于不同载波干涉编码OFDM性能分析

在载波干涉编码正交频分复用（CI/OFDM）系统中采用了几种CDMA扩频序列作为载波干涉码。并比较了用不同载波干涉编码的正交频分复用（OFDM）系统性能。从理论分析和Matlab实验仿真得出CI/OFDM系统的比特误码率（BER）随着子载波数目增加而变低,BER与采用不同的载波干涉（CI）编码无关。并证明CI/OFDM系统的峰均比（PAPR）主要取决于子载波数的大小以及CI码的性质。     

对《与<降低OFDM系统峰均功率比的载波干涉技术>作者商榷》的回应

指出了<与<降低OFDM系统峰均功率比的载波干涉技术>作者商榷>文中对载波干涉(CI)技术存在的理解上的错误,强调了CI信号和CI/OFDM系统的主要特点.     

与《降低OFDM系统峰均功率比的载波干涉技术》作者商榷

拜读了何剑辉博士等撰写的<降低OFDM系统峰均功率比的载波干涉技术>一文后,笔者根据其提供的思路对载波干涉OFDM(CI/OFDM)的发送信号作了理论推导和仿真实验,对CI/OFDM降低峰均功率比(PAPR)的实质感到困惑,并提出自己的看法与<降低OFDM系统峰均功率比的载波干涉技术>一文作者商榷.     

降低OFDM系统峰均功率比的载波干涉技术

介绍了应用载波干涉技术的OFDM系统,即CU/OFDM系统,说明了通过CI技术降低OFDM系统峰均功率比的基本原理和特点,并通过计算机仿真展示了系统峰均功率比改善的具体效果.仿真表明,载波干涉技术应用灵活,实施复杂度较低,能有效地解决OFDM系统的高峰均功率比问题.     

载波干涉 OFDM 系统峰均功率比特性分析

通过分析正交频分码分复用(OFDM-CDM)系统的信号包络，提出一种定性地分析不同 OFDM-CDM 系统峰均功率比(PAPR)特性的方法。根据这一方法对比分析了分别采用载波干涉(CI)扩 频码和 Wlash 扩频码的 OFDM-CDM 系统，在不同子载波数情况下的 PAPR 特性。理论分析和计算机仿 真结果表明，无论系统所采用子载波数量的大小，采用载波干涉(CI)扩频码的 OFDM-CDM 系统，即载 波干涉 OFDM 系统的 PAPR 状况，相对传统的 OFDM 系统都得到了显著的改善。     

基于CI的Turbo编码V-BLAST OFDM系统PAPR降低算法

MIMO-OFDM已成为4G宽带无线通信系统极具前景的备选方案,但与OFDM系统一样,系统仍然存在高峰均比（PAPR）问题。针对Turbo编码V-BLAST OFDM系统,提出了基于载波干涉（CI）技术的降低系统PAPR方案,说明了通过CI技术降低系统峰均比的基本原理。仿真结果表明,该方案不仅有效降低了系统的峰均比,还使得整个系统的BER性能得到进一步提高。     

一种改进的2×1-D维纳滤波器OFDM信道估计器

本文对OFDM系统中广泛应用的一种导频辅助的信道估计器-2×1-D维纳滤波器进行了改进,以ML信道估计代替了其中的频域滤波,并将改进的估计器与2×1-D维纳滤波器在IEEE 802.16e OFDM系统中的BER、MSE性能及计算复杂度进行了比较。仿真结果表明,在802.16e OFDM系统下,改进的估计器能够以较低的复杂度达到优于2×1-D维纳滤波器的性能。此估计器也可以应用于其他基于导频估计的OFDM系统。     

《数字集群移动通信系统体制》标准介绍

最近信息产业部颁布了电子行业标准<数字集群移动通信系统体制>,本文介绍该标准的制定背景、编制原则和依据、以及标准主要内容,以便读者进一步理解本标准.     

载波频率偏移对OFDM的影响及仿真分析

载波频率偏移是正交频分复用(OFDM)系统性能的重要影响因素。本文概述了OFDM的发展史,建立了OFDM系统模型,分析了载波频率偏移对OFDM的影响,在此基础上在计算机上模拟了当OFDM系统的子信道数N不同时载波频率偏移对OFDM的影响,最后简单论证了一种降低载波频率偏移影响的方法--linear。     

编者的话

2006年10月,&lt;现代显示&gt;杂志邀请美国中佛罗里达光学光子学院的吴诗聪教授作为专家主编,为广大读者主持了第一期“专家的思考“栏目.至今已经一年有余,这个栏目的创建,开始了&lt;现代显示&gt;杂志在主题化运作方面的尝试.……     

Author's reply to “A correction to Kurt Metzger's algorithmin the paper `On the probability density of intersymbol interference'”

Pokrajac and Nikoli (see ibid., vol.43, no.12, p.2868, 1995) have correctly identified a mistake by Metzger (see ibid., vol.COM-35, no.4, p.396-402). The examples presented by Metzger were calculated correctly, but the carelessness in the formulation of the equation is regretted. It was intended to show the feasibility of the basic transformation, and not to give an exhaustive investigation of the numerical possibilities for executing the equation. Some more sophisticated ways for performing the evaluation are included     

Introduction to the cluster on “machine learning approachesto scheduling”

Scheduling jobs in complex manufacturing environments is an exceedingly challenging task. Studies have shown that dispatchers often rotate out of such positions within two years. Even seasoned dispatchers are unable to distill their knowledge in any meaningful way. Four articles in this issue are devoted to “machine learning approaches to scheduling.” They were presented at a workshop conducted and sponsored by the Decision and Information Sciences Department of the College of Business Administration at the University of Florida. A survey is provided by Aytug, Battacharyya, Koehler, and Snowdon to generally acquaint the practitioner with machine learning in scheduling. Piramuthu, Raman, and Shaw present an adaptive learning system for scheduling circuit board assembly. Chaturvedi and Nazareth consider scheduling problems requiring learning of conditional levels of knowledge. Finally, Chaturvedi, Choubey, and Roan present a machine learning method that seeks to find time invariant and time sensitive knowledge     

Reply to “Comments on the optimum CMOS tapered bufferproblem”

For original article see ibid., vol 27, p. 118-9 (1992). For comments on original paper see ibid., vol29, no. 2, p155-8 (1994). The optimum tapered buffer has been extensively discussed in the literature. In this correspondence a general model is derived and it is shown that previously reported models are specific cases of the general model presented here     

Calculation of a Hyperbolic Corrugated Horn Converting the TEM<Subscript>00</Subscript> Mode to the HE<Subscript>11</Subscript> Mode

Corrugated waveguide transmission lines are in use to transmit high power mm-wave radiation from gyrotrons to the plasma for electron cyclotron plasma heating in tokamaks such as ITER. The coupling efficiency of the gyrotron output radiation formed as a quasi-Gaussian beam to the waveguide mode is a critical issue. A hyperbolic corrugated horn serves as a converter of the TEM₀₀ Gaussian mode to the HE₁₁ mode of a corrugated waveguide. We report the design of a hyperbolic horn for application in the ITER transmission line at 170 GHz. The theoretical conversion efficiency of the horn is higher than 0.995.