AMBE-2000TM在双路语音编解码器中的应用

AMBE-2000具有话音质量高、编码速率可变、配置灵活等特点,在卫星通信、安全通信、数字移动无线电领域得到了广泛应用。根据关键管脚功能以及时序要求使用4片ABME-2000设计实现了双路话音编解码器,每个AMBE-2000只完成编码或解码功能。为了保证话音质量,采用CD74HC4046A进行编解码时钟的同步设计。设计的双路话音编解码模块经试验验证,话音清晰,满足系统要求。     

SATELLITE-ENHANCED PERSONAL COMMUNICATIONS EXPERIMENTS

Users of future generation wireless information services will have diverse needs for voice, data, and potentially even video communications in a wide variety of circumstances. For users in dense, inner-city areas, low power personal communications services (PCS) technology should be ideal. Vehicular-based users travelling at high speeds will need high-power cellular technology. For users in remote or inaccessible locations, or for applications that are broadcast over a wide geographic area, a satellite technology would be the best choice. Packet data networks provide an excellent solution for users requiring occasional small messages, whereas circuit switched networks provide more economical solutions for larger messages. To provide ubiquitous personal communications service, it is necessary to capitalize on the strength of each wireless technology and network to create one seamless internetwork including both current and future wired and wireless networks. As an initial step in exploring the opportunities afforded by the merging of satellite and terrestrial networks, Bellcore and JPL conducted several experiments. These experiments utilized Bellcore's experimental personal communications system (including several messaging applications with adaptations to wireless networks), NASA's advanced communications technology satellite (ACTS), JPL's ACTS mobile terminal, and various commercial data networks (such as the wireline Internet and the RAM wireless packet data network). Looking at loss of bits, packets and higher layer blocks (over the satellite-terrestrial internetworks with mobile and stationary users under various conditions) our initial results indicate that the communication channel can vary dramatically, even within a single network. We show that these conditions necessitate powerful and adaptive protocols if we are to achieve a seamless internetworking of satellite and terrestrial networks.     

基于TFO的移动话音安全传输应用研究

如何在移动通信系统中建立语音业务的安全数据流透明传输通道,是移动通信系统安全语音方案设计的关键技术。移动通信标准中的TFO技术可以避免核心网侧设备的语音编解码功能,实现语音数据流的端到端透明传输通道。研究了GSM、CDMA等移动通信系统中的TFO协商流程、协商原则,重点分析和研究如何基于TFO实现移动通信安全语音业务的技术,为实现高音质的移动通信安全语音业务打下了良好基础。     

A Reliable Pipeline Protocol for the Message Service of a Land Mobile Satellite Experiment

This paper describes and analyzes a pipeline protocol for the data message communications of MSAT-X, a proposed experimental satellite-based mobile communications network. A demand-assigned multiple access protocol using pure ALOHA for making reservation requests has been developed for MSAT-X under error-free assumptions. Preliminary propagation studies indicate that the shortterm bit error rate of satellite channels in a mobile environment can be as high as 10^-3. Therefore, error-control schemes must be developed to ensure reliable transmissions. In this paper, we propose a retransmission scheme using selective repeat to minimize the end-to-end delay. We also use slotted ALOHA for making reservation requests to increase the overall system throughput. Since the number of channels available for reservation and data channels is essentially fixed for a given voice call blocking probability and a fixed call arrival rate, the analysis presented in this paper is also applicable to the integrated voice and data services of MSAT-X. Various operational scenarios have been investigated.     

An integrated mobile satellite broadcast, paging, communicationsand navigation system

The design of an integrated mobile satellite broadcast, paging, communications, and navigation system is described. Ku-band RadioSat ground stations will broadcast digital audio signals and data packets (including alphanumeric pages and group cells) to mobiles through a satellite to be launched in 1993. Each mobile radio will simultaneously receive L-band digital audio and data broadcasts from the satellite and L-band navigation broadcasts from the Global Positioning Systems (GPS) through a common omnidirectional mobile antenna and receiver front end. RadioSat mobile radios will use GPS broadcasts and differential corrections sent through the satellite to navigate with 2-m accuracy. With optional transmitters, RadioSat mobile radios can support two-way voice and data communications     

基于AMBE2000的高质量窄带语音系统

介绍一种基于AMBE2000的高质量窄带语音系统的硬件设计与实现。该系统使用了DVSI公司开发的AMBE语音芯片,可以在低速率下保持声音自然、语音清晰,并且在选择语音速率和纠错数据配置中提供了高度的灵活性,此外还具有低成本、低功耗等优点。因此,该系统具有广泛的应用前景,可以应用于诸如安全通信、话音多路传输及卫星通讯等多种语音处理的场合。     

移动个人通信的技术进展

简单回顾移动与个人通信的早期历史,依次说明无线蜂窝网的更新换代、语音压缩编码的发展、基站的软件无线电和智能天线,以及地理定位等有关移动通信的主要技术发展进程,最后阐述卫星移动通信的现状。     

基于AMBE-2000的数字语音传输系统

介绍了AMBE-2000的工作原理及其应用,并结合实例给出了数字语音传输系统中AMBE-2000与TLV320AIC10的A/D、D/A接口电路。AMBE-2000是DVSI(Digital Voice System·Inc)公司的语音压缩解压缩芯片,它采用AMBE语音压缩技术,具有语音音质好和编码波特率低、功耗低等优点;TLV320AIC10是TI公司的低功耗∑-Δ型16位A/D、D/A音频接口芯片。应用AMBE-2000的数字语音传输系统可以在低速率下提供优良的语音质量,并能实现全双工、实时语音压缩解压缩功能,因此在卫星通信、移动通信等领域有着广泛的应用。     

Satellite systems for personal communications

A number of industry groups are planning to construct satellite systems that will provide a personal communications service (PCS) (typically voice, data, and fax) to users over small, hand-held, cellular-type telephones. Some of these systems (e.g., Iridium and Globalstar) will be constructed using satellites in low Earth orbit. Two (Ellipso and ICO) will employ medium Earth orbit (3-8-h period), and still others (ACeS and Agrani) will operate from geostationary altitude. The origin and evolution of mobile satellite communications is discussed first, including the Inmarsat system and several land-based mobile satellite systems in operation. The rival approaches to the PCS market are then described, and some of the technical challenges inherent in each are indicated. This paper concludes with speculation on the factors influencing the likelihood of business success for the various PCS systems     

世纪之交看固定与移动两类通信一同快速前进

指出新世纪的通信将是固定与移动两类一同快速发展。先说明有线传输的固定通信网的发展进程。再说明无线移动通信的蜂窝网和卫星系统的情况。最后说明固定与移动两类通信网必将结合前进。     

数据管理中心的原理及应用

在通信行业融合发展的趋势下,人们对通信的要求已不仅限于单一的语音信息交流,更青睐于个性化的综合信息服务,固定与移动的融合,语音、视频和数据的融合等等。这些融合给电信业务带来了深刻变革。要实现新业务的统一规划就需要采用数据管理中心实现数据的集中管理。基于数据管理中心的实现原理,通过业务与控制相分离,能够给用户提供更多更快捷的增值业务,提高业务增长点。     

Voice over IP service and performance in satellite networks

Voice over IP services have emerged as a low-cost alternative to PSTN voice service, and an attractive solution for voice/data integration in public and private networks. Satellite systems, as an integral part of the global communications infrastructure, already have an increasing portion of their capacities used to carry data packets, and with their global coverage and reach to remote areas are well positioned to enable growth of VoIP services. For VoIP over satellite, several issues need to be addressed. These include transmission and quality of service issues, as well as service-related issues such as service creation and customization, support of IN and supplementary services, and seamless integration with the PSTN. While the service-related aspects of VoIP are common to both terrestrial and satellite networks, transport-related issues are different. This article reports performance results of laboratory experiments for evaluating VoIP over satellite under different link and traffic conditions     

移动通信系统从1G到4G的演进

第2代(2G)的数字移动通信由单纯的语音通信转移到提供语音、图像、文字等综合信息的传输,并能无线接入因特网.2G系统的传输速率难以满足人们对移动多媒体信息以及移动数据传输的需求.3G的核心网是从2G演进而来,但并不是传输TCP/IP数据包的最优结构.4G系统将是基于TCP/IP的核心网,混合OFDM和CDMA的无线接入方式,分离的接收、发射基站,基于无线ad hoc网络的结构而非蜂窝结构.     

Satellite systems for personal communications

A number of industrial groups are planning to construct satellite systems to provide personal communications services (typically voice, data, and fax) to users who will employ small, hand-held, cellular-type telephones. Some of these systems (e.g., Iridium and Globalstar) will be constructed using satellites in low Earth orbit. Two (Odyssey and ICO) will employ medium Earth orbit (six-hour period), and still others (ACeS and Agrani) will operate from geostationary altitude. The origin and evolution of mobile satellite communications is discussed first, including the INMARSAT system and several land-based mobile satellite systems in operation. The rival approaches to the personal communications services (PCS) market are then described, and some of the technical challenges inherent in each are indicated. The paper concludes with speculation on the factors influencing the likelihood of business success for the various PCS systems     

20世纪的卫星通信

自本世纪５０年代末人类发射第一颗试验通信卫星以来,卫星通信在技术,通信方式和通信能力等方面都获得巨大进步。在２０世纪即将结束之际,本文作者对固定卫星通信,移动卫星通信,卫星直播等进行了总结性的回顾与介绍,揭示了某些发展趋势。文章最后对太空信息高速公路的描述展示了卫星通信的巨大潜力与美好前景。     

Satellite Scenarios and Technology for the 1990's

Commercial satellite communications continues to undergo changes arising not only from advancing technology but also from new service offerings and regulatory activities. As the communications industry grows more competitive, future directions in satellite communications will become more economically than technologically motivated. This paper addresses the future of satellite communications, emphasizing fixed satellite services but also covering maritime mobile and broadcast satellite services. Following a brief recapping of the past, current services are discussed and future services are projected for the above service categories. A projection is made of the economics of satellite communications systems using gateway and varying degrees of distribution of earth stations, for both INTELSAT VI and future multibeam satellites and the TAT-8 fiber-optic undersea cable. After a brief allusion to systems design considerations, the anticipated technology projections towards the year 2000 for satellite communication services (including satellite antennas, transmitters and receivers, and on-board interconnection subsystems) are presented in some detail. Finally, it is concluded that satellite communications will have a major role in this epoch, and widespread use of low-cost customer premise earth station may justify more sophisticated and more expensive spacecraft.     

Universal broadband mobility target for post-TINA infrastructure:toward the fourth generation

Future universal broadband mobile services present a challenge for telecommunications architectures, control, and management. The focus of the future mobile (fourth) generation vision is turned from capacity to services, from radio to network-wide issues. New types of applications will evolve that should be supported by an adequate programmable intelligent telecommunications infrastructure. A convergence between telecom and datacom networks will happen based on the communications middleware concept, which will provide universal secure connectivity between mobile users and their applications. Actual specifications of TINA-C do not address all such necessary issues. There is a need for technology evolution, enhancement, and integration to meet these new requirements at different levels. The author the concept of the universal broadband mobile telecommunications systems (UBMTS, or simply UBM) described as fourth-generation mobile systems. The UBMTS objective is both to extend mobile user access to the range of broadband services that will exist for broadband integrated services digital network (B-ISDN) users, and to extend the customization of new services related to personal communications systems (PCS) users     

Communications [Technology 1998 analysis and forecast]

The communications industry is rampaging ahead and metamorphosing so rapidly as to defy comprehension. Wireless technology is all over the place-from globe-spanning satellite systems to local-area networks. The Internet, and above all the World Wide Web, race ahead exponentially, burdening the circuit-switched public voice telephone network and stirring a hunger for faster public data networks. Two other areas where events are challenging assumptions fundamental to current nationwide systems are deregulation and privatization. Immense business deals are being negotiated and then renegotiated as competing visions of the future conduce to differing notions of corporate valuation. And pundits can be found all over the media explaining to each other why everyone else has failed to grasp the true meaning and vast implications of the communications revolution. Constantly cited as a major force behind the excitement is the need for multimedia, though it is not always clear what it is, who needs it, and what for. In the communications context, it is simply a way of describing a broadband system that is good at handling both bursty and constant-bit-rate data. Global wireless access, digital cellular radio, a satellite network for Internet access in space, wireless access for fixed subscribers, and making local access easier are discussed     

INNOVATIVE NETWORKING CONCEPTS TESTED ON THE ADVANCED COMMUNICATIONS TECHNOLOGY SATELLITE

This paper describes a program of experiments conducted over the advanced communications technology satellite (ACTS) and the associated T1-VSAT (very small aperture terminal). The experiments were motivated by the commercial potential of low-cost receive-only satellite terminals that can operate in a hybrid network environment, and by the desire to demonstrate frame relay technology over satellite networks. The first experiment tested highly adaptive methods of satellite bandwidth allocation in an integrated voice–data service environment. The second involved comparison of forward error correction (FEC) and automatic-repeat-request (ARQ) methods of error control for satellite communication with emphasis on the advantage that a hybrid architecture provides, especially in the case of multicasts. Finally, the third experiment demonstrated hybrid access to databases and compared the performance of internetworking protocols for interconnecting local area networks (LANs) via satellite. A custom unit termed frame relay access switch (FRACS) was developed by COMSAT Laboratories for these experiments; the preparation and conduct of these experiments involved a total of 20 people from the University of Maryland, the University of Colorado and COMSAT Laboratories, from late 1992 until 1995.