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COFDM技术用于无线图像传输系统的优势 总被引:1,自引:0,他引:1
本文主要介绍了COFDM技术的基本原理,论述了该技术应用于无线图像传输系统的优点以及该技术在无线图像传输系统中的实际应用。 相似文献
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编码正交频分复用(Coded orthogonal frequency division multiplexing, COFDM)是一种多载波数字通信调制技术,它具有频谱利用率高和可对抗多径时延扩展等特点。文章介绍了COFDM技术的基本原理,对基于该技术的无线视频传输系统在海上视频传输的实际应用进行了分析论述。 相似文献
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COFDM: an overview 总被引:4,自引:0,他引:4
The research and development of OFDM/COFDM for digital television broadcasting has received considerable attention and has made a great deal of progress in Europe. OFDM/COFDM has already been implemented in digital audio broadcasting and is being considered for terrestrial digital television and HDTV broadcasting. The advantages of COFDM claimed by the advocates in Europe have also caught the attention of US broadcasters and generated enthusiasm although a digital modulation technique called 8-VSB has been selected by the FCC Advisory Committee on Advanced Television Service (ACATS) for the final testing. There is considerable debate in the industry over the use of COFDM vs. VSB or QAM for terrestrial HDTV broadcasting. In this paper, the history of research and development on OFDM and COFDM is reviewed. Then, the basic principles, performance and implementation of OFDM and COFDM are examined. Analysis is given to enable the selection of key elements for meeting the constraints of the required applications. Based on the ATV channel model, performance expectation of COFDM under imperfect channel conditions and implementation issues are examined in details 相似文献
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This paper describes the performance of COFDM (coded orthogonal frequency division multiplexing) for digital audio broadcasting (DAB) over various multipath mobile radio channels. COFDM is a channel coding and modulation scheme which mitigates the adverse effects of fading by using wideband multicarrier modulation combined with time interleaving and a convolutional error correcting code. A guard interval is inserted at the transition between successive symbols to absorb the intersymbol interference created by the time domain spread of the mobile radio channel. The decoding process is performed using differential demodulation in conjunction with a soft decision Viterbi decoder. The COFDM evaluation is done by means of computer simulations. A parametric study of the proposed COFDM system is done in this first of a series of papers to determine the optimal system parameter values for operation at a radio frequency of 1.5 GHz. The results show that the parameter values proposed in the standard are indeed well suited for operation at 1.5 GHz. Using the set of optimal parameter values found, the COFDM performance is then evaluated in mobile radio channels typical of different geographical environments. Simulation results confirm the benefit that the system gains from frequency diversity found in the urban and hilly terrain areas 相似文献
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编码正交频分复用(COFDM)是一种多载波数字通信调制技术,其基本原理是将频域中的一个宽带信道划分成多个重叠的子信道进行窄带传输.在接收端,虽然频谱相互重叠,但是只要保证各子信道上信号的正交性,就可以将各信道上的信号正确分离.文章重点研究了COFDM 通信系统中的同步技术. 相似文献
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H. Zheng 《Journal of Infrared, Millimeter and Terahertz Waves》2004,25(7):1075-1086
This paper deals with a new indoor radio system working in V-band millimeter waves and using the coded orthogonal frequency-division multiplexing (COFDM). Local performance and coverage figures have been suitably defined and the effects of code choice, frequency diversity, COFDM clustering, and antenna sectorization have been studied. In order to characterize the communication between stationary indoor terminals in 40-75GHz, a suitable semi-analytical algorithm is presented, and the performance of the coded system is evaluated in the actual environment. 相似文献
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In recent times, new advanced wireless systems are growing at fast rate to meet high speed applications. To meet these demands, 4G technologies are being used nowadays. Broadband wireless access (BWA) is the outcome in this direction which promises to cater these high speed and high quality applications. WiMax is an IEEE 802.16 standard-based BWA technology which employs Coded orthogonal frequency division multiplexing access (COFDM). This paper analyses bit error rate for WiMax based COFDM system under Standard University Interim channel conditions. 相似文献
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A. Franchi E. Colzi C. Elia R. A. Harris 《International Journal of Satellite Communications and Networking》1995,13(4):229-242
This paper analyses the performance of a coded orthogonal frequency division multiplexing (COFDM) based system for digital audio broadcasting using a highly inclined orbit satellite constellation. The sources of performance degradation considered are non-linear amplification in the satellite transponder and multipath propagation for mobile reception. Despite its strong peak-to-mean amplitude variation, COFDM has been found to be very robust against non-linear amplification. In the multipath channel, practical cases demonstrate low performance losses even in highly populated areas when highly inclined elliptical orbits (HEO) are used. 相似文献
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介绍DAB发射机系统的基带部分即COFDM信道编码和COFDM调制的设计方法,对相关过程做了阐述。设计指标符合ETS 300 401及相关标准。 相似文献
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This paper is a corrected version of that printed in IEEE Trans. Broadcast., vol.52, no3, p.325-35, 2006 September. Space-frequency coded (SFC) and channel coded orthogonal frequency-division multiplexing (COFDM) are considered under narrow-band interference (NBI). Analytical expressions for the bit error probability (BEP) are derived for OFDM with SFC in a frequency-selective fading environment. It is shown that SFC increases the resistance of COFDM against the NBI and reduces the BEP considerably. Specific attention is paid to Digital Terrestrial Television Broadcasting (DTTB), and the associated coding gains are discussed 相似文献
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Hierarchical transmission and COFDM systems 总被引:1,自引:0,他引:1
《Broadcasting, IEEE Transactions on》1997,43(2):166-174
Draft European terrestrial digital video broadcasting (DVB-T) standard will pose problems for in the selection of the most beneficial and cost effective modes of operation within this flexible standard. This paper describes possible implementations of coded orthogonal frequency division multiplexing (COFDM) transmission schemes. Particular emphasis is placed on practical transmission aspects such as: radio frequency characteristics of the COFDM signal, field trials, and the more common digital television (DTV) measurements. Selection of the best system by broadcasters will involve compromises between costs and system parameters. The unique feature of Hierarchical transmission is described illustrating coverage benefits 相似文献
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COFDM数字电视广播系统中使用CSI的维特比译码器 总被引:2,自引:2,他引:0
介绍比特交织格状编码调制 MQAM的编译码原理,软判决译码中使用信道状态信息(CSI)是COFDM在频率选择性衰落和干扰下获得优异性能的关键。研究COFDM数字TV广播系统中使用CSI的维特比译码器的一种实现方法。 相似文献
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COFDM技术及其在DVB-T系统中的应用 总被引:1,自引:0,他引:1
COFDM技术是一种多载波数字通信技术。他是较为完备的移动接收和传输技术,可以大大降低每个子载波内的符号间干扰,节省了用于均衡的系统开销。对欧洲数字地面广播标准DVB T中的COFDM(编码的正交频分复用)调制方式进行了研究,阐述了COFDM技术的基本原理,并且介绍了其适合应用于地面数字电视广播系统的主要特性。 相似文献
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A Multicarrier Scheme for HIPERLAN 总被引:1,自引:0,他引:1
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Nibaldo Rodriguez Ismael Soto Rolando Carrasco 《International Journal of Communication Systems》2003,16(2):137-150
In this paper, we consider the optimization of the performance of QPSK and 16‐QAM coded orthogonal frequency division multiplexing (COFDM) signals over the non‐linear and mobile satellite channel. A high power amplifier and Rician flat fading channel produces non‐linear and linear distortions; an adaptive predistortion technique combined with turbo codes will reduce both types of distortion. The predistorter is based on a feedforward neural network, with the coefficients being derived using an extended Kalman filter (EKF). The conventional turbo code is used to mitigate Rician flat fading distortion and Gaussian noise. The performance over a non‐linear satellite channel indicates that QPSK COFDM followed by a predistorter provides a gain of about 1.7 dB at a BER of 3×10?3 when compared to QPSK COFDM without the predistortion scheme and 16‐QAM COFDM provides a gain of 0.5 dB output back‐off and 1.2 dB signal to noise ratio at a BER of 3×10?5 when compared with an adaptive predistorter based on the Harmmerstein model. We also investigate the influence of the guard time interval and Doppler frequency effect on the BER performance. When the guard interval increases from 0 to 0.125T samples and the normalized Doppler frequency is 0.001, there is a gain of 0.7 and 1 dB signal to noise ratio at a BER of 6×10?4 for QPSK and 16‐QAM COFDM, respectively. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
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