Pulse Shape Design for Teletext Data Transmission

This paper studies the problem of designing a suitable pulse shape for teletext data transmission. The following four criteria are used: 1) Nyquist I criterion, 2) Nyquist II criterion, 3) degree of overshoots in the channel signal, and 4) robustness to sampling phase jitter. For system bandwidths less than the inverse-baud rate, it is not possible to satisfy all these criteria simultaneously; tradeoffs that have to be made are illustrated. Several candidate pulse shapes are given and a composite criterion developed. A pulse shape, which satisfies the Nyquist I criterion and is closest to satisfying the Nyquist II criterion, in a sum-of-squares-of-deviations sense, is recommended.     

Optimal Design of Broadcast Teletext Caption Preparation Systems

The provision of television captions for the benefit of the hearing impaired is the growing practice of many broadcasting organisations. This paper discusses the research and design work which led to the development of 'NEWFOR', a caption preparation system for broadcast teletext. Caption preparation is a complex and time-consuming task, which often required as long as 30-40 hours preparation time per captioned programme hour using early teletext origination systems. Research carried out into the display requirements for captioning for the hearing impaired led to a design specification for a stand alone caption preparation system and a handbook of guidelines on captioning. Analysis of the operational requirements of caption preparation provided a framework for optimal task division between the human captioner and the captioning computer. The system developed as a result halves caption preparation time, and also permits captioning of live programmes. The system described is now available commercially and is used for all teletext captioning by Independent Television in the UK.     

Filtering Allocation in Teletext Data Transmission Under Power and Peak Constraints

Various pulse shapes have been proposed for teletext data transmission. The effect of apportioning the different pulse shapes between the transmitter and the receiver is studied for the cases of a constraint on the power and a constraint on the peak value of the channel signal.     

Experimental Studies of Transmission Bit-Rate for Teletext Signal in the 525-Line Television System

In order to investigate the optimum transmission bit-rate for teletext signals in the 525-line television system, laboratory and field tests were carried out using binary NRZ digital data signals of several bit-rates to 5.73 Mbit/s ( 364fH, 8/5fsc). In these tests, the bit-errors and eye-openings of PN signals were measured and subjective evaluation of teletext signals was also made under various receiving conditions. The results have indicated that a digital data signal of 5.73 Mbit/s could be utilized for teletext in the 525-line television system. The Japanese teletext system now being developed employs this bit-rate for transmitting and displaying the signals.     

Modeling Broadcast Teletext Systems for Analysis and Computer Simulation Studies

An isomorphism is derived between a typical bandpass broadcast television system to be used in transmitting teletext data and its complex baseband equivalent representation for use in analysis and computer simulations. The distortions introduced by a multipath channel are discussed. The complex noise process is modeled by a mixture of Gaussian and impulsive noise, and the parameters of the noise model are derived. The video signal-to-noise ratio SNRTVis related to other parameters such as the input noise variance, output noise power, and the carrier-to-noise density ratio. A complete simulation model for broadcast television transmission and reception is shown in block diagram form. The remaining components of the computer simulation model are briefly discussed and references given. These include topics such as amplitude control, computer generation of ensembles of complex impulse responses, simulation of synchronous, quasi-synchronous and envelope detectors, bit slicers, bit synchronizers, error-correcting codes, estimation of error statistics and bit error rates, and adaptive equalization. Validation is also briefly noted with references. Several examples of simulation results are given. Some of the implementation details, simulation results, and a flow diagram of the simulation program are provided. This teletext computer simulation model appears to be the most complete one created to this time and has been used extensively in performance analyses to evaluate new designs and gain insights into design improvements.     

On the Timing Information Disappearance of Digital Transmission Systems

Probability distribution of a timing-wave envelope level in a regenerative repeater, which transmits a random binary sequence, is analyzed. The result obtained is that the probability of timing information disappearance in a repeated line can be disregarded compared with that of failure of a repeater.     

欧洲图文电视标准及ST图文电视方案

介绍了现行的欧洲图文电视标准,以及STMicroeletronics公司的图文电视机芯和相应的软件方案。     

On the Optimality of Multi-User Coordinated Zero-Forcing Beamforming Multicell Systems with Limited Feedback in Interference Channels

Wireless Personal Communications - An efficient multicell coordinated zero-forcing channel feedback scheme is proposed in this paper. The objective of the proposed feedback design is to control the...     

On the Optimality of the ARQ-DDF Protocol

In this correspondence, the performance of the automatic repeat request-dynamic decode and forward (ARQ-DDF) cooperation protocol is analyzed in two distinct scenarios. The first scenario is the multiple access relay channel where a single relay is dedicated to simultaneously help two multiple access users. For this setup, it is shown that the ARQ-DDF protocol achieves the channel's optimal diversity multiplexing tradeoff (DMT). The second scenario is the cooperative vector multiple access channel where two users cooperate in delivering their messages to a destination equipped with two receiving antennas. For this setup, a new variant of the ARQ-DDF protocol is developed where the two users are purposefully instructed not to cooperate in the first round of transmission. Lower and upper bounds on the achievable DMT are then derived. These bounds are shown to converge to the optimal tradeoff as the number of transmission rounds increases.     

On the Speed Tolerance of Certain Classes of Data Transmission Systems

Improved efficiency multilevel partial response systems have recently been discovered. They are superior to conventional partial response systems when operated above the Nyquist signaling rate. This behavior has not as yet been explained and this correspondence gives a concise analysis, which shows the reason for the superior performance.     

图文电视原理简介

本文主要介绍了图文电视系统的基本概念及其工作原理。图文电视是一种新型的电视多工数据广播方式，文中将中文图文电视（CCST）系统规范中的有关技术规定做了简单明了的解释。     

Introduction to Cyclic Replacement Systems

A fundamental and unified treatment of problems akin to the classical Swedish Machine Problem is presented. Section I describes the nature of the systems known as cyclic replacement systems. In Section II pertinent facts about Markov processes are gathered. In Section III, it is shown that a certain class of cyclic systems behave as homogeneous Markov processes. The special class of homogeneous Markov processes known as homogeneous birth and death processes is considered in Section IV. Results of Section IV are applied to some cyclic replacement systems in Section V. In Section VI some systems are treated which cannot be represented as birth and death processes.     

论电力通信系统中的常用光纤传输体系

介绍了密集波分复用(DWDM)与同步数字体系(SDH),根据电力通信系统的特点,分析了在电力系统中的一种常用组网方式:在DWDM上构建SDH体系.同时介绍了多业务传送技术及其在电力通信系统中的应用.     

On the Convergence of Genetic Scheduling Algorithms for Downlink Transmission in Multi-User MIMO Systems

In a multi-user MIMO system using a successive precoding method such as dirty paper coding, it is combinatorially complex to determine the optimal set of users to schedule and the proper order to encode their signals in order to optimize a utility function in a scheduling algorithm. Genetic algorithms represent a fast suboptimal approach to reducing the complexity of the search. In this paper, we build upon prior work that implements scheduling via genetic algorithms. We examine the impact of parameter values within the adaptive mutation rate of the algorithm on its convergence time. We demonstrate that although there is a range of values for the parameters that yields similar near-minimum convergence times, it is nonetheless important to ensure that the parameters are tuned to be within that range. In one case, tuning the parameter values reduces the time of convergence to less than 30% compared to that achievable with the initial parameter values. We also demonstrate that the proper parameter values are dependent on both the number of transmit antennas and the number of users in the pool of users to be scheduled. A simple equation is proposed that is linear in the adaptive mutation parameters to tune the values for different numbers of transmit antennas and users.     

OFDM传输系统同步方案简介

本文研究数字地面电视DVB-T的OFDM传输系统接收端的同步。根据OFDM的原理特点和DVB-T标准,设计同步方案。该方案采用多载波(OFDM)系统时域插在循环保护间隔携带的冗余信息进行粗符号和分数频率偏移估计。该方案利用OFDM系统时域插入的保护间隔前缀所携带的冗余信息,进行粗符号同步和分数频率偏移估计。FFT后,再利用频域插入的连续导频进行整数频偏估计,及利用分散导频通过估计信道冲击响应,实现精符号同步。仿真表明,同步设计在加性高斯白噪声信道能达到最佳性能,在慢衰落Rayleigh信道下也有较好的性能。     

On the Optimal Cyclic Delay Value in Cyclic Delay Diversity

In this paper, we propose a method to determine the optimal cyclic delay value of cyclic delay diversity (CDD) in orthogonal frequency division multiplexing (OFDM) systems. As the cyclic delay value increases, we can get signal to interference and noise ratio (SINR) gain by the diversity effect, while SINR loss increases because of channel estimation errors. If the optimal cyclic delay value obtained by the proposed method is applied to a CDD scheme, we can minimize the required SINR for a given frame error rate (FER) under the above-mentioned trade-off.      

On the Capacity of Ultra Wideband Block Transmission Systems with Narrowband Interference Avoidance

In this letter, the theoretical capacities of single-carrier and multi-carrier block transmission systems that employ narrowband interference avoidance are derived. It is shown that the capacity of an OFDM system that implements active interference cancellation is degraded by approximately one bit per second per Hz at high SNR when 10% of the band is nulled. In contrast, the capacity of a single-carrier system that uses envelope scaling in the time domain to create deep frequency notches is not significantly affected by the nulling process.     

图文电视的现状与发展

本文描述了数据广播的现状,探讨了图文电视的结构和特点及其在中国的发展状况和前景。     

High-Capacity Optical Transmission Systems

The 25 years since the founding of the Journal of Lightwave Technology have seen more than three orders of magnitude increase in the capacity of optical transmission systems. This dramatic increase was brought about by the deployment of WDM and advances in high-speed transmission technologies.     

副载波复用视频光纤传输系统

本文介绍AM-VSB多频道CATV光纤干线传输系统。采用的主要技术有分频段直接光调制技术,波分复用,直接光放大EDFA等。较详细地论述了各部分的工作原理。重点分析了系统的主要性能指标。