共查询到20条相似文献,搜索用时 46 毫秒
1.
《Spectrum, IEEE》1996,33(3):52-59
Digital audio broadcasting will come on-line worldwide in the next few years. The technology-also known as digital audio radio or digital sound broadcasting-promises to provide sound of compact-disk quality, nearly free from multipath distortion or other transmission interferences. And digital audio broadcasting (DAB) is not just for sound: all sorts of information, digitally encoded, will be transmitted. Testing is already under way around the world for systems that deliver DAB signals from satellites, from terrestrial systems using newly assigned spectral bands, and from in-band (that is, currently assigned) AM and FM systems. The author discusses spectra for DAB, perceptual coding, Europe's Eureka 147 system, and DAB research in Canada, the USA, and Japan 相似文献
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The experimental results of a one-month system field trial using a 512 kb/s superposed quadrature amplitude modulation (SQAM) satellite transceiver are described. The impact of cochannel and adjacent channel interference on the computer-simulated and measured performance of the band-edge system is investigated, and the corresponding bit error rate (BER) is analyzed. As an example application, International Datacasting Corporation's digital audio broadcasting system is discussed. The dispersed spectrum of the video carrier interference is found to be sufficiently low in power to allow high-performance band-edge data transmission with excellent BER. The data link provided 99.8% error-free minutes over a 24-h broadcasting period with degradation to neither video picture quality nor to subcarrier services. Close to compact disc quality digital audio was delivered 相似文献
3.
In digital communication systems for speech, audio or video signals the individual bits of the transmitted parameters u exhibit different bit error sensitivities. Usually channel coding with unequal error protection (UEP) is applied. However, some transmission systems do not include channel coding for several reasons. For this situation, a novel concept is proposed which achieves UEP by allocating different transmission power to individual bits according to their bit error sensitivities. The optimization criterion for unequal power allocation is the mean square of the error between the original parameter-u and the decoded parameter u which has a strong correlation with subjective perception. 相似文献
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A system experiment for fibre optic hybrid transmission of analogue CATV BK 300 and 1.8 Gbit/s with 64-QAM channels has been realised. It has been shown that additional transmission of 1.8 Gbit/s of compressed digital video (MPEG) using 64-QAM is possible without a significant degradation of the laser clipping rate. Measured bit error rates are compared with simulation results based on impulsive clipping noise 相似文献
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Kishimoto R. Yoshino K. Ikeda M. 《Selected Areas in Communications, IEEE Journal on》1988,6(7):1079-1086
A fiber-optic high-definition television (HDTV) distribution system is discussed, which economically distributes HDTV signals to customers at a bit rate of about 100 Mb/s. The subscriber network is formed in a star topology to facilitate bidirectional connection. The distribution system uses digital video transmission at 1.3 μm wavelength using single-mode fiber. The video channel selection is made by an optical video selector. The optical selector consists of laser diode optical switch modules, which have a gain in the `ON' state and two-input, two-output 3 dB couplers. The authors describe the bit error rate characteristics of a signal-mode fiber digital distribution system using a four-input, one-output optical selector 相似文献
7.
Moriyama S. Tsuchida K. Sasaki M. Yamazaki S. 《Broadcasting, IEEE Transactions on》1996,42(3):266-271
A study on digital broadcasting systems has been conducted for the multimedia era. Regarding program production, a digital outside-broadcasting-link (OBL), in particular, from mobile source is required to gather digital video and audio sources in severe multipath environments. The orthogonal frequency division multiplexing (OFDM) modulation scheme is robust under multipath fading conditions. A digital OFDM modem for OBL in the 800 MHz band has been developed to enable stable transmission of digital sources from moving vehicles. In the experimental OFDM-OBL, the compressed digital video and audio data are distributed to 572 carriers in the 9 MHz bandwidth, using differential quadrature phase shift keying (DQPSK) modulation for each carrier. In computer simulation and indoor/outdoor experiments, it is confirmed that digital OFDM-OBL can stably transmit signals, even under severe multipath fading conditions, while pictures transmitted with conventional FM-OBL are seriously degraded. This paper describes the features of the OFDM modem for the digital OBL which transmits program sources from moving vehicles, and also discusses aspects of gathering digital program sources 相似文献
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提出了2.4G无线影音传输系统中的数字音频传输方案,介绍了AES/EBU数字音频接口标准,并详细阐述了系统的关键技术,包括差错掩盖技术和天线切换技术。采用差错掩盖技术,可以消除“噼啪”声;而运用天线切换技术,提高了音频信号接收质量,有效地抑制干扰,提升了系统的性能。 相似文献
10.
在开展综合信息系统演示试验前,为了实现激光通信系统的单独测试,需模拟各种载荷及误码率的测试.轻型、嵌入式、智能高速的模拟数据源必不可少.研制了一种基于FPGA的智能化模拟数据源,它不仅将多路视频、音频信号复合成一路高速数据流来模拟各种有效载荷(SAR,可见光,红外),它使得通信信号的速度达1.08 Gbps.而且可实现伪随机序列的传输,速度可达3 Gbps,用于误码率测试.其中高速的伪随机序列是速率智能可调节,速率范围750Mbps到3 Gbps.数据传输的类型可选择,如:视音频的串行数据流,伪随机序列,模拟数据源. 相似文献
11.
A robust in-band on-channel (IBOC) digital audio broadcast (DAB) system for improved performance over existing FM broadcasting is under development by Westinghouse for USA Digital Radio. Both the analog FM and the DAB signals are transmitted simultaneously in the FM hybrid IBOC system. Broadcasters can simultaneously transmit both analog and digital signals within the allocated channel mask, allowing full compatibility with existing analog receivers. It is shown here that the solution is tolerant of interference from adjacent channels, or interference from the co-channel analog transmission, even in a multiple station, strong-signal urban market. Although the primary focus of this paper is to discuss the compatibility issues between the existing FM and the DAB signals, the paper also briefly describes spectral occupancy, power ratios, modulation formats, and coding, as well as the introduction of frequency and time diversity 相似文献
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Ren-Guey Lee Heng-Shuen Chen Chung-Chih Lin Kuang-Chiung Chang Jyh-Horng Chen 《IEEE transactions on information technology in biomedicine》2000,4(1):37-44
To solve the inconvenience of routine transportation of chronically ill and handicapped patients, this paper proposes a platform based on a hybrid fiber coaxial (HFC) network in Taiwan, designed to make a home telecare system feasible. The aim of this home telecare system is to combine biomedical data, including three-channel electrocardiogram (ECG) and blood pressure (BP), video and audio, into a National Television Standard Committee (NTSC) channel for communication between the patient and the healthcare provider. Digitized biomedical data and output from medical devices can be further modulated to a second audio program (SAP) subchannel which can be used for second-language audio in NTSC television signals. For long-distance transmission, we translate the digital biomedical data into the frequency domain using frequency shift key (FSK) technology and insert this signal into an SAP band. The whole system has been implemented and tested. The results obtained using this system clearly demonstrated that real-time video, audio, and biomedical data transmission are very clear, with a carrier-to-noise ratio of up to 43 dB 相似文献
14.
A call-by-call activation technique for fiber-optic subscriber systems has been developed to reduce electric power consumed in transmission units installed on subscriber premises. The major part of the transmission unit is supplied power call-by-call. The technique has been applied for a fiber-optic subscriber system in the INS Model System (NTT project) for which the PFM technique is used to transmit a frequency division multiplexed signal containing video, audio, and digital signals bidirectionally. This paper describes the control procedure and hardware implementation for this call-by-call activation. Discussion is made on methods of achieving optical carrier sensing. A unique technique is proposed which enables rapid and accurate indication of frame synchronization together with no considerable bit error occurrence for the digital signal just after activation. Experimental results which reveal validity of control procedure, carrier sensing, and frame synchronization methods are also shown together with the effect of power saving and assessment of build-up time required for activation. 相似文献
15.
In an analog/digital hybrid subcarrier multiplexed (SCM) transmission, carriers have generally been substituted for transmission signals such as AM vestigal sideband (AM-VSB) AM signals and M-QAM signals to evaluate transmission quality. In practical hybrid SCM, however, carriers are modulated by video signals or digital data, and the amplitude of a multiplexed signal composed of these modulation signals is more compressed than that of the carriers. This causes a decrease in the frequency of clipping of the multiplexed signal at the laser threshold. Consequently, the BER of the M-QAM signal in a practical hybrid SCM is lower than that of the experimental results for the same optical modulation index (OMI). However, it is difficult to prepare many practical modulation signals for experiments in a laboratory. Therefore, there is demand for a bit error rate (BER) analysis method for a multiplexed signal that includes the modulation signals needed to sufficiently evaluate the BER and determine the optimum OMI in a practical hybrid SCM. In this paper, we describe such a BER analysis method that can effectively estimate the BER in a practical hybrid SCM. In practical systems, the BER was greatly improved over the BER of a multiplexed signal of carriers. Furthermore, BER degradations due to clipping can be neglected for the AM signals in setting a practical OMI range. We used this analysis method to study the effective OMI range of AM and M-QAM signals. By assuming modulation signals, the OMI range is enlarged and, significantly, the OMI of an AM signal becomes suitable for setting practical values in AM-SCM transmission. This OMI range is more practical than those of former studies 相似文献
16.
In many modern wireless communications systems (e.g., in OFDM based digital audio broadcasting/digital video broadcasting (DAB/DVB), CDMA) the received signal can be a superposition of multiple useful and interfering lognormal components, and correlation may exist between the components. We propose a simple method for estimating the correlation coefficient between the total useful and total interfering signals as the function of the correlation between the individual components. We show that, by taking into account this correlation factor in the derivation of the distribution of the signal-to-interference ratio, considerable accuracy improvement can be achieved in the outage probability estimation 相似文献
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de Boer G. Kupferschmidt C. Bederov D. Kuchenbecker H.P. 《Broadcasting, IEEE Transactions on》2003,49(3):293-303
A method for broadcasting digital audio signals simultaneously with existing analog frequency modulation radio (88-108 MHz) in adjacent channels is presented. The digital transmission is based on continuous phase modulation (CPM) and a proper reduced-state sequence estimator. With the proposed method, the power level and the symbol rate of the transmitter signal is determined in a manner that the interference the CPM signal poses for the analog FM signal in adjacent channels remains below a level according to the radio frequency emission mask defined by international rules. Due to the multipath propagation of the transmitted signal, the transmission behavior of the radio channel is determined by high dispersion up to 85 /spl mu/s. With the selected bit rate, the receiver has to cope with a channel memory of up to 17 bits. Since Viterbi detection is not feasible due to the number of channel states, detection is performed by a reduced-state sequence estimator that is able to eliminate the complete channel interference by decision feedback. Simulation results show that the detector almost achieves the detection quality of the optimum receiver. CPM achieves data rates of up to 200 kb/s inside a 200 kHz FM channel, which is sufficient for transmission of digital compressed audio signals at compact disc quality. The encouraging results of field tests will be published in another paper. 相似文献
19.
The paper is about the planning of ensembles and block assignments for DAB (Digital Audio Broadcasting) networks. Besides offering superior audio quality and multimedia data services, DAB has the potential to use the available frequency resources much more efficiently than other (analog or digital) audio broadcast systems, since it has the capability to transmit an ensemble of radio programs and data services over large regions using just a single frequency. However, to fully exploit this feature new planning methods are needed. The paper discusses a possible solution approach which leads to a combined bin packing/graph coloring problem. It is shown how this problem can be solved using heuristics, how to obtain lower bounds to estimate the quality of computed solutions, and which generalizations of the problem statement arise in practical planning scenarios. The same methods also apply to other digital broadcast systems based on similar technology like, e.g., digital video broadcasting (DVB-T). 相似文献
20.
The orthogonal frequency division multiplexing (OFDM) transmission scheme is currently experiencing increased popularity due
to advances in very large scale integration technology. It is used for a variety of broadband systems such as asymmetric digital
subscriber lines, very-high-speed digital subscriber lines, digital video, and audio broadcasting, and wide local area network
standards such as IEEE 802.11a, IEEE 802.11 g, and ETSI Hiperlan/2. However, propagation impairments can cause severe degradation
in bit error rates (BER) for coherent detection. We derive a semi-analytical method to evaluate BER of a quadrature phase
shift keying (QPSK)-OFDM system in Nakagami, m < 1 fading and additive noise where pilot-assisted linear channel estimation and channel equalization are used. This allows
modeling of more severe fading environments than can be depicted by a Rayleigh distribution. Numerical simulations are used
to validate the proposed methods. The techniques developed can be applied to other channel estimation techniques, modulation
schemes and the performance evaluation of equalized single carrier narrowband systems. 相似文献