小容量移动电话系统的实现

本文论述了重庆通信学院研制的一种经济而实用的小容量移动电话系统。采用 DTMF 信号作为多信道共用无线电话系统的信令是一种新方法,这是一个有意义的成功的尝试.该系统特别适用于开设有线电话有困难的企业或事业单位,也适用于农话或用于城市边缘地区作为对市话的延伸.文中较详细的叙述了系统的结构、功能、特点和工作过程,便于需要这种系统的用户选用时参考。     

模拟蜂窝移动电话计费系统的实现

本文介绍了采用ＦｏｘＰｒｏｆｏｒＷｉｎｄｏｗｓ（２．６）数据库处理移动电话脱机计费问题的基本原理和实现方法。一方面读者可知道移动电话各收费项目是如何进行合计的；另一方面可以了解到该系统安装到局域网络上采用的并行处理方法。     

移动电话自动开关机系统的实现

对移动电话自动开关机的实现进行了可行性研究，提出了采用模拟人机通信的方式实现计算机与交换机之间的通信，并设计了自动开关机系统的系统结构和功能，最后介绍了两个重要模块的实现方法。     

GSM移动电话保密常识

谈到数字移动电话安全保密的性能,它主要基于一张用户识别卡,这张卡相信用户也不会陌生,它就是ＳＩＭ卡。在ＧＳＭ系统中,每一个用户都有一张ＩＣ卡,它叫用户识别卡。ＳＩＭ卡中储存有用于用户身份确认所需的信息,并能执行这些与安全保密有关的信息,此外ＳＩＭ卡还存储有与网络和用户有关的管理功能。 ＳＩＭ卡由五部分组成,它们分别是ＣＰＵ、程序存储器（ＲＯＭ）、工作存储器（ＲＡＮ）、数据存储器（ＥＰＲＯＭ）和串行通信单元,这些模块都集成在一个芯程序存储器片上。 ＳＩＭ卡在保证系统的安全保密方面有４种功能： １．使…     

移动通信公众网的主体蜂窝状移动电话系统

近年来,国内外移动通信技术发展迅速,蜂窝状移动电话技术与系统的发展引起世界电信领域的重大关注。蜂窝状移动电话已经是现代通信网中重要的组成部分,移动通信技术涉及的面很广,如无线寻呼、集群通信、无绳电话、卫星移动通信、个人通信等技术,尤其是以蜂窝移动电话技术与系统的发展最为引人注目。     

数字蜂窝式移动电话系统现状与发展

目前在世界上许多国家运营的蜂窝式移动电话系统如北欧四国的 NMT、美国的AMPS、联邦德图的 C 网、英国的 TACS、日本的 NAMTS,我国在北京、上海和广州运营的 TACS 和爱立克森系统都属第一代模拟式移动电话系统。为了满足更多用户的要求,建立符合统一技术标准的系统,欧州许多国家在移动通信专业组(GSM)组织协调下,提出了多种系统方案,即第二代数字蜂窝式移动电话系统试验系统方案。本文对这几种系统,重点对 CD900、S900D,作了全面介绍。并从多址技术、信道编码、语音编码、调制技术以及经济性等方面进行了分析和评估。     

Software-Based Video/Audio Processing for Cellular Phones

Nowadays, most cellular phones are used beyond voice communication. Although the processing power of cellular phones is sufficient for most data applications, it is difficult to play video and audio contents in software because of their computational complexity and lack of basic tools for multimedia processing, so software-based multimedia processing on cellular phones is a challenging issue. Several transcoding methods are introduced to address this issue, but they are mainly of the DCT-domain conversion. Hence, they are only applicable to high-end cellular phones. To develop a solution for low-end and mid-tier cellular phones, we begin this paper by analyzing the complexity of existing video standards to see if it is possible to play them on cellular phones by software. Next, various coding profiles as combinations of subalgorithms are studied, and we select a profile that adapts its complexity to the processing power of cellular phones. Also, an efficient dithering algorithm called out-of-order dithering is developed. We implement the profile with out-of-order dithering in an actual cellular phone software environment and present the performance results. The performance results show that software based video/audio processing is indeed possible on low-end cellular phones.     

联通公司机卡分离的构想与实现

文章介绍了中国联合通信公司推行CDMA机卡分离工作的定位及进展情况,并着重描述了机卡分离的技术规范。     

蜂窝电话定位系统技术与性能分析

近年来,定位技术在许多领域得到了广泛应用,随着蜂窝电话的普及、蜂窝电话定位系统的理论研究与应用开发工作也在不停地进行着,人们提出了多种方案,它们各有特点,需要依据一系列的性能指标对其整体性能进行分析。     

数字蜂窝区移动通信的纠错编码技术

本文对数字蜂窝区移动通信中所采用的纠错技术作简单介绍 ,着重分析了GSM系统中纠错编码技术工作的原理和技术特点。     

蜂房移动通信系统的信道下界

本文提出了蜂房移动通信系统中无三阶互调带宽信道数的下界公式。根据该公式得到最小带宽信道数。本文还给出了实际带宽信道数和无三阶互调信道组。     

多层蜂窝系统的研究及发展

本文首先介绍了多层蜂窝系统的基本概念，然后讨论了多层蜂窝系统的架构，层次间的资源共享以及层次间的切换策略。     

A Video Streaming System for Mobile Phones: Practice and Experience

This paper presents a case of video streaming system for mobile phone which has actually been implemented and deployed for commercial services in CDMA2000 1X cellular phone networks. As the computing environment and the network connection of cellular phones are significantly different from the wired desktop environment, the traditional desktop streaming method is not applicable. Therefore, a new architecture is required to suit the successfully streaming in the mobile phone environment. We have developed a very lightweight video player for use in mobile phone and the related authoring tool for the player. The streaming server has carefully been designed to provide high efficiency, reliability and scalability. Based on a specifically-designed suite of streaming protocol, the server employs an adaptive rate control mechanism which transmits the media packets appropriately into the network according to the change in network bandwidth.Hojung Cha is currently a professor in computer science at Yonsei University, Seoul, Korea. His research interests include multimedia computing system, multimedia communication networks, wireless and mobile communication systems and embedded system software. He received his B.S. and M.S. in computer engineering from Seoul National University, Korea, in 1985 and 1987, respectively. He received his Ph.D. in computer science from the University of Manchester, England, in 1991.Jongmin Lee is a Ph.D. candidiate in computer science at Yonsei University, Seoul, Korea. His research interests include wireless multimedia system, QoS architecture, multimedia communication networks. He received his B.S. and M.S. in computer science from Kwangwoon University in 1999 and 2001, respectively.Jongho Nang is a professor in the Department of Computer Science at Sogang University. He received his B.S. degree from Sogang University, Korea, in 1986 and M.S. and Ph.D. degree from KAIST, in 1988 and in 1992, respectively. His research interests are in the field of multimedia systems, digital video library, and Internet technologies. He is a member of KISS, ACM, and IEEE.Sung-Yong Park is an associate professor in the Department of Computer Science at Sogang University, Seoul, Korea. He received his B.S. degree in computer science from Sogang University, and both the M.S. and Ph.D. degrees in computer science from Syracuse University. From 1987 to 1992, he worked for LG Electronics, Korea, as a research engineer. From 1998 to 1999, he was a research scientist at Telcordia Technologies (formerly Bellcore) where he developed network management software for optical switches. His research interests include high performance distributed computing and systems, operating systems, and multimedia.Jin-Hwan Jeong received the B.S. and M.S. degrees in computer science from Korea University, Seoul, Korea, in 1997, and 1999, respectively. He is currently in Ph.D. course at Korea University. His research interests include video processing for thin devices, multimedia streaming and operating systems.Chuck Yoo received the B.S. degree in electronics engineering from Seoul National University, Seoul, Korea and the M.S. and Ph.D. in computer science in University of Michigan. He worked as a researcher in Sun Microsystems Lab. from 1990 to 1995. He joined the Computer Science and Enginnering Department, Korea University, Seoul, Korea in 1995, where he is currently a professor. His research interests include high performance network, multimedia streaming, and operating systems.Jin-Young Choi received the B.S. degree from Seoul National University, Seoul, Korea, in 1982, the M.S. degree from Drexel University in 1986, and the Ph.D. degree from University of Pennsylvania, in 1993. He is currently a professor of Computer Science and Engineering Department, Korea University, Seoul, Korea. His current research interests are in real-time computing, formal methods, programming languages, process algebras, security, software engineering, and protocol engineering.     

GSM数字蜂窝网及其在中国的进展

本文介绍了 GSM 的技术规范,包括系统结构及主要参数,论述了中国选择 GSM 的关键因素,如频段划分、标准公开、设备商品化等。并介绍了GSM 在中国大发展的第一年,16个省市建网计划概况,展望了 GSM 在中国的前景。     

Scalable Schemes for Call Admission and Handover in Cellular Networks with Multiple Services

The introduction of new service categories withdifferent bandwidth requirements, e.g., data and multimedia, to cellularmobile radio networks makes many of the traditional mechanisms for controlingtraffic unusable orless efficient. The call admission and the handover handling are of the mostsensitive issues in this extension to new services. The performance of allservices includingthe traditional voice and the new services can be dramatically affected ifappropriate schemes are not used. In this paper, we propose call admission andhandover handling schemes for a cellular mobile network that offers twoservice types: voice and data. The data connections are assumed to transmitatdifferent transmission rates that are integer multiples to that of one radiochannel. In the case of congestion, the base station asks the active dataconnections to reduce their transmission rate in order to provide freechannels for the newly arrived request of both service types. This isbasically intended for incoming handover requests. The request will berejected if the transmission rate of the active connections reaches a givenminimum rate. Similar mechanism can also be used for new call arrivals, butsome priority can be given to handovers by setting a higher transmission ratethreshold for the new call rejection. As an extension to the proposedscalability, aqueuing of new calls is also proposed and analyzed. Analytical models werebuilt for the two proposed schemes together with the traditional channelreservation scheme. The effect of different traffic and configurationparameters on the performance measures like the grade of service, blockingprobabilities, and utilization, are studied using the proposed technique.Results show that the proposed schemes provide very good performance and morefairness among the different service types.     

直放站在蜂窝移动通信网中的应用

对直放站的使用可能带来的问题,以及直放站前后向链路参数的设定和直放站前后向放大器的增益调整方法等阐述了看法。