Multimedia and multimedia communication: a tutorial

This paper presents, in a tutorial fashion, the important features of multimedia technology. The specific areas addressed are multimedia and compression standards, computer networks, multimedia transport, and some specific applications employed by industry to date. Multimedia and the effective and efficient communication of multimedia using compression and networks are fused together in this tutorial in an attempt to demonstrate the tight coupling which exists between these two interrelated technologies. First, the techniques and properties inherent in both multimedia and compression standards are presented. Then, the important characteristics of the major local and wide area networks are summarized. Next, the communication techniques for the transport of video and video conferencing are discussed. The new strategies employed to connect homes through cable TV and the telephone companies, as well as the new Ethernet technologies, are also described. Finally, some modern applications of multimedia communication derived from the automotive industry are used to describe the use of this technology in design, manufacturing, and sales     

Multimedia communication systems: upper layers in the OSI referencemodel

The structuring, services, and major protocol functions that are required in the upper layers of the OSI reference model in order to support end-to-end multimedia communication, assuming a simple transport service, are examined. It is assumed that variable-bit-rate (VBR) coding techniques will be used in future multimedia systems. Mutual stream synchronization, integral management, and multiparty connections, which appear to be crucial issues in multimedia communication, are addressed. Important implementation and performance issues are discussed     

Analysis of a correlated queue in a communication system

A family of queues is studied for which the service time B_n of customer n and the interarrival time I_n between customers n-1 and n exhibit some sort of proportionality. The focus is on dependencies that arise naturally in the context of communication systems, where the finite speed of the communication links constrains the amount of data that can be received in a given time interval. The simple case of a deterministic proportionality relation between the service time of a customer and its preceding interarrival time is considered. This is extended to allow the addition of an independent, generally distributed overhead to the service time of each customer. Several models that capture the ON-OFF behavior of communication links in packet networks are considered. In all cases, expressions for the delay experienced by a packet in the system are provided. Numerical examples illustrate the impact of dependencies through comparison with less accurate models. The results should be of relevance to environments other than communication as well     

Reliability of a laser communication system

Reliability function of a laser communication system is found with the help of a probability of error bound. Attention is restricted to the special case when the average photon arrivals at the receiver of the communication system is large. This reliability function is a complicated function and depends on number of parameters such as average number of signal photons, average number of noise photons, information rate and the channel capacity. The system reliability function and the corresponding curves can give the idea of system parameters which may be useful for the implementation of an optimum laser communication system.     

Parameter estimation in a multi-user communication system

Many of the previously-developed multiple-access detection algorithms have assumed knowledge of the time delay, the amplitude, and the phase of each user. This paper presents methods of estimating the amplitudes and phases, both when the time delays are known and when the delays are unknown. In neither case are the transmitted bits assumed to be known. The estimators are unbiased and consistent, and each has a computational complexity linear in the number of users. Simulations are provided to demonstrate performance     

直升机卫星通信系统信道模拟与通信实现

针对直升机卫星通信系统中直升机旋翼对通信信道造成的周期性衰落问题,采用射频收发器AD9361模拟了信道周期性衰落模型,基于此模型在现场可编程门阵列(Field Programmable Gate Array,FPGA)上优化并实现了缝隙检测算法.根据信道衰落模型和缝隙检测算法及数据链路速率和带宽的要求,提出了一套直升机...     

An adaptive array in a spread-spectrum communication system

This paper describes the integration of an LMS adaptive array into a pseudonoise (PN) coded biphase modulated communication system. The paper explains how these systems my be combined and presents a systems overview of the interaction between the adaptive array and the signaling waveform. An experimental system is described, and typical performance results are presented. The hybrid system requires only very modest spectrum-spreading ratios, such as 5:1, for the adaptive array to null interference. The combined system provides the interference protection of the adaptive array during the code timing acquisition phase as well as after code lockup.     

Integrated services from high-altitude platforms: a flexible communication system

In this article the provision of integrated services from high-altitude platforms (HAPs) is discussed, and a flexible communication system for HAP-based communications is identified and analyzed, with particular attention to the delivery of broadband services from HAPs to highspeed trains. The high coding gain required by the proposed scenario is achieved through adaptive concatenated coding schemes, while smart antennas operating with adaptive beamforming algorithms are employed at the ground stations. The simulated system performance based on a multi-antenna model of the stratospheric channel is reported, and the use of HAPs in synergy with terrestrial and satellite systems is discussed.     

Analysis of a communication system with imperfect repair

This paper is devoted to the modelling and the calculation of dependability measures of a complex communication system with dormant failure modes and imperfect repair. Steady state availability, interval availability and mean time to failure are evaluated with Markov chain technique. Furthermore, a sensitivity analysis is performed to quantify system specificities. Numerical results are provided.     

Mathematical analysis of a transitional computer communication system

This paper investigates a mathematical model for a computer communication system of two units—a computer and a controller. Each unit has n components, i.e. the computer has an n-processor while the controller has n converters. The amount of change in the computer or controller depends on the change in the components of these two units. These changes bring the system to either a partially failed state or a completely (totally) failed state. Failure rates are assumed to be negative exponential; recovery and repair rates are arbitrary. Various cost-related reliability measures have been studied using the regenerative point technique.     

导航通信系统中频可变增益放大器设计

实现了一个GPS/伽利略双模导航通信系统中频可变增益放大器(中频6MHz,带宽2MHz/中频16MHz,带宽10MHz).增益有4档可调,从16dB至34dB, 每6dB一档.闭环电阻反馈结构保证了高线性度需求.在最高增益模式下,通带波纹小于0.2dB, 输入噪声小于15nV/sqrt(Hz),该放大器同时含有直流失调抑制功能.采用SMIC 0.18μm工艺,1.8V电源电压, 功耗为9mW.该接收机系统已成功流片.     

Implementing a client/server system in Korean organizations:interrelated IT innovation perspective

Since information technologies have become critical to business success as a tool for organizational innovation, successful implementation of information technology (IT) innovation is viewed as one of the most crucial tasks for many organizations. This paper examines the effects of the contextual factors on the implementation of the client/server system as an interrelated IT innovation. The authors clarify the concept of IT innovation by distinguishing between IT innovation object and IT innovation process and provide the conceptual framework for IT innovation process. Four types of IT innovation implementation were classified according to the dimensions of implementation scope and implementation pace. They developed a set of relevant propositions and examined them through multiple case studies following Yin's case-study methodology     

Optimal signalling of demand in a demand-assigned multiple-access communication system

Capacity requirements for multiple-access demand-assigned communication systems are broken down into information, demand and assignment signalling. A simultaneous-transmission scheme for demand signalling greatly reduces the bit rate incurred by polling. More generally, bits required by demand signalling are calculated and shown to be an appreciable part of the total for certain message types.     

STDM加密技术在Android平台通讯中的应用

自Android系统成为时代天骄,越来越多的Android通讯设备融入了人们生活,随之Android平台下通讯环境的安全性成为聚焦点,安全技术也需要在这一新的平台下寻求最佳方案。本文在研究跨平台即时通讯系统的基础上,将基于STDM的数字水印加密技术应用于Android平台图像传输中,并对水印图像进行了攻击测试,实验表明它在水印提取和抗攻击性方面应用性良好。     

一种数字语音通信系统的DSP实现

本文论述了一种甚低频低码率数字通信系统的实现方案,其软件采用混合编程的方法,用DSP实现,给出了整个系统的DSP软硬件调试方法。调试的结果表明,该方案具有很好的可行性和实时性。     

The channel capacity of a fiber optics communication system:perturbation theory

We consider the communication channel given by a fiber optical transmission line. We develop a method to perturbatively calculate the information capacity of a nonlinear channel, given the corresponding evolution equation. Using this technique, we compute the decrease of the channel capacity to the leading order in the perturbative parameter for fiber optics communication systems     

铁路通信系统中移动通信技术的有效应用研究

移动通信技术的使用是铁路通信系统数字化、智能化的标志,铁路通信系统中应用移动通信技术,使得光纤技术与铁路通信进行结合,可以进一步减少铁路通信系统的故障,提升通信系统质量。文章主要针对铁路通信系统中移动通信技术的有效应用进行研究,为完善铁路通信系统提供一定参考。