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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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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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The audio quality, robustness and implementational complexity of a novel mobile digital audio broadcast scheme are addressed. The audio codec proposed is based on an efficient combination of subband coding (SBC) and multipulse excited linear prediction coding (MPLPC). The bit allocation is dynamically adapted according to both the signal power in different subbands and a perceptual hearing model. Typically a segmental signal to noise ratio (SEGSNR) in excess of 30 dB associated with high fidelity subjective quality was achieved for 2.67-b/sample transmissions at a bit rate of 86 kb/s. Perceptually unimpaired audio quality was achieved for a bit error rate (BER) of about 10-4, when injecting random errors, which was degraded for increased BERs. In order to provide robust error protection, the audio codec was also subjected to a rigorous bit sensitivity analysis. Four different forward error correction schemes were investigated in order to explore the complexity, bit rate, and robustness tradeoffs 相似文献
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Hybrid in-band on-channel (IBOC) broadcasting systems for digital audio radio have the capability of simultaneously transmitting analog FM and digital audio of CD-like quality. Due to fading and interference in the already-crowded FM band, the signal design for the hybrid IBOC system is very challenging. It has been proposed to use a method of double sideband transmission where the digital information is transmitted by means of orthogonal frequency-division multiplexing (OFDM) on both sides of the analog host FM and where the digital information can be recovered when one sideband is partially or even totally lost. This leads to an interesting channel coding problem, where we search for optimal pairs of high-rate codes that form good combined low-rate codes, which are better than classic code combining techniques. Furthermore, we also search for rate-compatible punctured convolutional codes which can be used for two-level unequal error protection (UEP) of digital audio. Since some of the tones in the multitone modem (OFDM) are more exposed to interference than others, optimal assignments of convolutional code bits to tones depending on their spectral position are also found. A large number of new codes with memory 6 and 8 are presented both for equal error protection and UEP. 相似文献
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数字音频广播(Digital Audio Broadcasting,DAB)是继调幅和调频广播之后的新一代广播,与模拟调制的广播相比具有音质好、抗多径干扰较强和恶劣环境下的接收、频谱利用率高、业务构成灵活等优点,是广播事业发展中的一个新的里程碑。 相似文献
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Technical advances in digital audio radio broadcasting 总被引:4,自引:0,他引:4
Faller C. Biing-Hwang Juang Kroon P. Hui-Ling Lou Ramprashad S.A. Sundberg C.-E.W. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2002,90(8):1303-1333
The move to digital is a natural progression taking place in all aspects of broadcast media applications from document processing in newspapers to video processing in television distribution. This is no less true for audio broadcasting which has taken a unique development path in the United States. This path has been heavily influenced by a combination of regulatory and migratory requirements specific to the U.S. market. In addition, competition between proposed terrestrial and satellite systems combined with increasing consumer expectations have set ambitious, and often changing, requirements for the systems. The result has been a unique set of evolving requirements on source coding, channel coding, and modulation technologies to make these systems a reality. This paper outlines the technical development of the terrestrial wireless and satellite audio broadcasting systems in the U.S., providing details on specific source and channel coding designs and adding perspective on why specific designs were selected in the final systems. These systems are also compared to other systems such as Eureka-147, DRM, and Worldspace, developed under different requirements. 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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FFT-based coded orthogonal frequency division multiplexing (COFDM) is one of the techniques for digital TV broadcasting over multipath fading channels. A FFT-based OFDM signal is subject to various hardware nonlinearities in both the transmitter and receiver. Hardware nonlinearities not only affect the in-band performance of an FFT-based OFDM system but also may affect the system performance of an adjacent channel signal because of regenerated sidelobes of the transmitted signal. The paper investigates the in-band and out-of-band behaviour of a 64QAM-OFDM system under various nonlinear devices. It is shown that the inherent signal clipping in the IFFT processors with a limited word length reduces the required RF amplifier output backoff (OBO) where adjacent channel interference is the limiting factor. For a 0.25% clipping rate, an additional 2 dB OBO is required for the COFDM signal to achieve the same level of adjacent channel interference as for the single carrier system. The loss in SNR due to signal clipping is negligible in a coded OFDM system 相似文献
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Myung-Sun Baek Hyung-Joon Kook Mi-Jeong Kim Young-Hwan You Hyoung-Kyu Song 《Broadcasting, IEEE Transactions on》2005,51(4):551-559
In this paper, we apply multi-antenna scheme to DAB system for high-rate transmission. In the MIMO-DAB system with a number of transmitting and receiving antennas increases the transmission rate efficiently with low multiplication operations. For channel estimation in the MIMO-DAB system, we propose a new PRS structure and evaluate the channel estimation performance. The proposed PRS structure can estimate multi-channel information based on the semi-blind processing. The performance of proposed PRS is compared with that of conventional training sequence employing Tarokh's transmission matrix. And also we investigate the performance limitation due to the imperfect channel estimation in a MIMO-DAB receiver. It has been shown that the MIMO-DAB system with multi-antennas can achieve the high-rate transmission for multimedia broadcasting and the performance of MIMO-DAB system is impaired by imperfect channel information. 相似文献
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随着数字技术的引入和人们不断提高的视听要求,MPEG组织在MPEG-1标准的基础上提出了新的MPEG-2标准。新的标准具有更高位率(2~50 Mbps),接近演播室效果的图像质量,音频编码最多能支持6路声道。由于以上诸多的特点,MPEG-2标准已广泛应用于高品质的广播电视中。而在中国,MPEG技术已投入到实际应用中。MPEG第二层编码利用了人耳的听觉特性,采用MUSICAM算法对立体声进行实时压缩编码。其压缩率为6~8倍左右。本文将详细介绍DVB前端系统中采用MPEG-2标准开发的实时立体声编码模块。1 模块的结构组成DVB前端的编码系统… 相似文献
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We introduce new methods for increasing the performance of multiprogram digital audio broadcast systems, e.g., satellite digital audio broadcasting. Joint multiprogram encoding is an attractive possibility for parallel broadcasting of a large number of programs. Joint coding extended over multiple audio frames in time give further improvements. The benefits of this kind of statistical multiplexing yield improved audio quality and/or higher capacity in terms of number of programs. We describe the new Joint Multiple Program Encoding Technique in the context of the perceptual audio coding (PAC) type of algorithms. We also describe methods for multi-program transmission including Equal Error Protection (EEP) as well as Unequal Error Protection (UEP) and improved error concealment for multiple program transmission. Some of the techniques described in this paper, are currently being used in satellite digital audio broadcasting in the United States. 相似文献
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Scalart P. Leclerc M. Fortier P. Huu Tue Huynh 《Broadcasting, IEEE Transactions on》1997,43(2):191-198
In this paper, we present a performance analysis of a coded orthogonal frequency division multiplexing DAB system that is power multiplexed over a commercial FM station. We model the mobile channel with a time-frequency scattering function. Results show that the performance of the FM demodulator is crucial, since the level of the residual FM signal has a strong influence on the BER performance of the COFDM system. As with other mobile communication systems, the use of interleaving greatly enhances the performances 相似文献