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OFDM技术标准化展望 总被引:2,自引:0,他引:2
期俊玲 《电信工程技术与标准化》2004,(10):12-15
本文主要介绍了OFDM的原理和技术优势,分析了现存的几种类型的OFDM技术特点,最后展望了OFDM标准化和在第四代移动通信系统的应用. 相似文献
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PAPR Reduction in OFDM Systems with Large Number of Sub-Carriers by Carrier Interferometry Approaches 总被引:5,自引:4,他引:1
HE Jian-hui QUAN Zi-yi MEN Ai-dong School of Telecommunication Engineering Beijing University of Posts Telecommunications Beijing P.R.China 《中国邮电高校学报(英文版)》2004,11(4)
High Peak-to-Average Power Ratio(PAPR)is one of the major drawbacks of Orthogonal Frequency DivisionMultiplexing(OFDM)systems.This paper presents the structures of the particular bit sequences leading to the maximumPAPR(PAPR_(max))in Carrier-Interferometry OFDM(CI/OFDM)and Pseudo Orthogonal Carrier-Interferometry OFDM(PO-CI/OFDM)systems for Binary Phase Shift Keying(BPSK)modulation.Furthermore,the simulation and analysisof PAPR_(max) and PAPR cumulative distribution in CI/OFDM and PO-CI/OFDM systems with 2048 sub-carriers are pre-sented in this paper.The results show that the PAPR of OFDM system with large number of sub-carriers reduced evidentlyvia CI approaches. 相似文献
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Asmaa Ibrahim Tawfik Ismail Khaled Elsayed M. Saeed Darweesh 《International Journal of Communication Systems》2019,32(16)
The Orthogonal Frequency Division Multiplexing (OFDM) has emerged as one of the promising techniques because of its robustness to multipath fading with high‐speed data transmission. Classical bipolar OFDM cannot be used in intensity modulated with direct detection (IM/DD) optical communication systems, as visible light communication (VLC), so many optical modulation techniques as asymmetrical clipped optical OFDM (ACO‐OFDM) and DC‐Clipped OFDM (DCO‐OFDM) have been investigated. In this paper, we introduce a novel optical modulation scheme that meets the optical communications requirements. The proposed odd clipping optical OFDM technique (OCO‐OFDM) is based on the Fourier transform symmetry properties in which the imaginary and odd signal is converted to odd and real valued signal. As a result of this work, the proposed OCO‐OFDM and its modified version have several benefits over ACO‐OFDM and DCO‐OFDM. By introducing a better bit error rate, with the same spectral efficiency as DCO‐OFDM and the same power efficiency as ACO‐OFDM for real valued modulation technique as Binary Phase‐Shift Keying (BPSK), and with the same spectral efficiency and power efficiency as ACO‐OFDM for complex valued modulation technique as Quadrature Phase‐Shift Keying (QPSK) and Eight Phase‐Shift Keying (8PSK). 相似文献
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OFDM技术在4G中的应用 总被引:2,自引:0,他引:2
首先给出了正交频分复用(OFDM)技术的概念,详细叙述OFDM技术的基本原理和研究现状,阐述OFDM的关键技术及在4G中的应用,给出了4G的技术规范、技术要求和国内外对4G中关键技术的研究现状。分析表明OFDM技术在不增加带宽的情况下能提高系统容量,是4G移动通信技术中的核心技术。最后给出OFDM在今后的4G移动通信系统中的研究方向。 相似文献
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在非协作通信领域,传统的基于循环自相关的OFDM(Orthogonal Frequency Division Multiplexing,正交频分复用)时间参数盲估计算法常分析的是无导频OFDM信号,不适用于实际应用场景中含导频OFDM信号的参数盲估计。本文分析了不同导频图案的OFDM信号循环自相关谱特性,针对谱特征变化改进了OFDM信号参数估计算法。改进算法既适用于无导频OFDM信号,也适用于不同导频图案的OFDM信号。仿真结果表明,对于无导频OFDM信号,改进算法比传统算法的时间参数估计误差可降低一个数量级;同时改进算法有效避免了导频引入的二阶周期性谱峰对OFDM时间参数估计的影响,可精确估计含导频OFDM信号的时间参数,具有很好的鲁棒性和应用价值。 相似文献
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Improvement and Analysis of Carrier-Interferometry Orthogonal Frequency Division Multiplexing System
HE Jian-hui QUAN Zi-yi MEN Ai-dongSchool of Telecommunication Engineering Beijing University of Posts telecommunications Beijing P. R. China 《中国邮电高校学报(英文版)》2005,12(4)
1IntroductionOrthogonal Frequency Division Multiplexing(OFDM) isknown to be with high spectrumefficiency and effectivein coping with such wireless channel i mpairments asmultipath fading and Inter-Symbol Interference(ISI)[1]. Moreover ,OFDMsystems have become prac-tical toi mplement using Fast Fourier Transform(FFT)techniques[2]thanks to advances in digital signal pro-cessing. Up to the present , OFDMhas been employedin several digital transmission systems , such as AD-SL[3], HIP… 相似文献
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本文叙述了光频分复用(OFDM)技术的特点,OFDM传输系统的组成及工作原理,扼要地分析了几个关键部件对OFDM传输系统的影响,介绍了OFDM系统中的光器件的主要类型及特性。最后介绍了光频分复用技术在各种通信网中的几种应用。 相似文献
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TIAN Qing-hua ZHANG Qi TAO Ying LIU Nai-jin XIN Xiang-jun ZHANG Li-jia XU Da-xiong 《中国邮电高校学报(英文版)》2013,20(3):37-42,77
Orthogonal frequency division multiplexing (OFDM) is attracting more attention for its capability of high speed transmission. However, the OFDM possesses an obvious shortage in its high ratio of the peak power to the average power (PAPR), which has become the main issue holding it back to be applied to the broadband satellite communication system. OFDM combined with time division multiplexing (TDM), dividing the subcarriers of OFDM into some blocks in time tune, can decrease the high PAPR of OFDM. Meanwhile, the advantages of OFDM can be preserved. In this paper, OFDM/TDM is applied to the broadband satellite communication system. This paper theoretically analyses OFDM/TDM system model as well as its restraining effect on PAPR, and proposes frequency domain multiplexing-pilot (FDM-Pilot) channel estimation algorithm. Simulation results show OFDM/TDM in broadband satellite communication system has approving performance and decreased the PAPR. 相似文献
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High-throughput, high-performance OFDM via pseudo-orthogonal carrier interferometry spreading codes 总被引:1,自引:0,他引:1
The paper introduces to orthogonal frequency-division multiplexing (OFDM) systems a novel pseudo-orthogonal carrier interferometry spreading code which spreads each parallel data stream over all the OFDM carriers. Pseudo-orthogonal carrier interferometry (PO-CI) spreading codes are carefully selected to introduce the following benefits to OFDM: up to 2N parallel data streams can be coded onto N carriers, with little degradation in performance; when rate 1/2 channel coding is applied in addition to PO-CI spreading codes, the resulting binary phase-shift keying OFDM systems demonstrate the performance of coded OFDM and the throughput of uncoded OFDM; PO-CI codes are carefully selected to spread in a manner which eliminates the peak-to-average power ratio problems characteristic of traditional OFDM. 相似文献
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本文介绍了OFDM技术。OFDM是一种多载波调制技术,能够把有符号间干扰的信道转换成无符号间干扰的并行子信道,所以,OFDM技术能够有效的对抗信道的频率选择性衰落.它已经得到了广泛的应用。本文比较了语音文件在OFDM系统和QAM系统中的传输效果,得出在相同条件下OFDM调制要优于QAM调制的结论。 相似文献
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OFDM技术是一种多栽波技术,在高速无线数据传输领域有很大的应用前景。本文在分析宽带无线信道性能特点的基础上,介绍了OFDM技术的基本原理和实现方法,并讨论了OFDM的关键技术及其在解决移动信道传输问题上的优势。最后详细给出了OFDM系统收发信机的框图,并展望了OFDM技术在移动通信领域的发展趋势。 相似文献
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目前,基于DFT变换的OFDM高效调制方法(DFT-OFDM)已经成为无线传输领域中的重要研究热点.但是,为达到较高的业务质量,DFT-OFDM采用了插入循环前缀(CP)的办法以减少ISI,从而降低了频谱利用率.为进一步改善频谱的利用效率,本文提出一种基于复小波包(Complex Wavelet Packet)正/反变换的OFDM调制方法(CWP-OFDM),并且将其与DFT-OFDM进行比较.仿真结果表明,在GSM TU50 信道环境中,当具有更高频谱效率的情况下,CWP-OFDM可以具有与DFT-OFDM同样或更好的误码性能. 相似文献
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本文通过对OFDM技术性能的分析,阐述了OFDM技术的无线系统结构和OFDM技术的优势,结合海上无线系统的实际应用情况,论述了OFDM宽带无线通信系统在海上无线系统的应用,通过分析和研究得出基于OFDM技术的无线宽带通信系统是海上无线通信系统发展的必然趋势. 相似文献
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Low power efficiency is a deficiency in traditional Orthogonal Frequency Division Multiplexing (OFDM) systems. To counter this problem, a new wireless transmission technology based on Zero-Padding Carrier Interferometry OFDM (ZP-CI/OFDM) is proposed. In a ZP-CI/OFDM system, transmission symbols are spread to all OFDM subcarriers via carrier interferometry codes. This reduces the Peak-to-Average Power Ratio (PAPR) that traditional OFDM suffers and also exploits frequency diversity gain. By zero-padding at the transmitter, advanced receiver technologies can be adopted for ZP-CI/OFDM so that frequency diversity gain can be further utilized and the power efficiency of the system is improved. 相似文献