动态多通道卫星话音／数据综合的S—ALOHA性能分析

本文分析了一种新的多通道话音／数据综合ＶＳＡＴ系统的Ｓ－ＡＬＯＨＡ性能，并给出了数值计算结果；从中可秆到该协议既能提供较高的吞吐量，又能有效地减小话音时延，并能协调话音和数据这间对性能要求的差异，文中考虑了Ｓ－ＡＬＯＨＡ中分组达到时间抖动的影响。文中还讨论了话音的重负载的条件下可占用数据通道的动态分配方案，并给出了动态分配的算法。     

HFC网络CDMA时隙ALOHA接入系统性能分析

同步ＣＤＭＡ（Ｓ－ＣＤＭＡ）解决了双向ＨＦＣ系统上行信道的噪声和容量问题,基于Ｓ－ＣＤＭＡ的ＨＦＣ是一代的ＨＦＣ系统,初始接入ＣＤＭＡ终端是采用时隙ＡＬＯＨＡ技术完成接入进程的,把ＣＤＭＡ技术与时隙ＡＬＯＨＡ技术相结合,会使原来的时隙ＡＬＯＨＡ技术的吞吐量得到一定的改善。本文提出了一种ＨＦＣ网络ＣＤＭＡ－时隙ＡＬＯＨＡ接入系统,分析了该系统的吞吐量性能和接入时延性能,并给出了实验结果与分析。     

卫星分组话音／数据扩频时隙ALOHA的性能分析

本文讨论了卫星分组话音／数据综合的扩频时隙ＡＬＯＨＡ的性能，并认为该协议较适合于卫星分组话音／数据综合的通信网中，给出了在扩频多址干扰为改进型高斯分布和某一时隙用户数有限的前提下，系统吞吐量的近似解析表达式和平均时延表达式，这比通常的标准高斯分布和无限用户的假设更精确，模拟说明结果性能是优越的。     

大容量FLASHMEMORY芯片28F032SA及其在心电记录中的应用

介绍ＩＮＴＥＬ公司３２－Ｍｂｉｔ ＦＬＡＳＨ ＭＥＭＯＲＹ芯片２８Ｆ０３２ＳＡ的性能及其用法；给出了２８Ｆ０３２ＳＡ与８０Ｃ１９８单片机的一种接口电路及ＰＬ／Ｍ－９６语言编程示例。     

一种扩频随机多址协议性能分析

本文在时间扩展ＡＬＯＨＡ多址协议的基础上，描述了卫星无线电测定业务（ＲＤＳＳ）中正在研究的一种新的多址协议－扩频ＡＬＯＨＡ多址协议，给出了该协议信道的延迟捕获特性，获得了信道的吞吐容量对延时捕获时间的关系曲线。     

EMX—500交换机系统带数据丢失的原因分析

ＥＭＸ－５００交换机系统带数据丢失的原因分析江苏省徐州邮电局朱小枫ＥＭＸ－５００交换机的系统带最初是由ＭＯＴＯＲＯＬＡ公司提供的，它共有３个组成部分，即ＰＡＴＣＨ，ＳＹＳＧＥＮ（ＳＹＳＴＥＮＧＥＮＡＲＡＴＩＯＮ）和空的ＣＨＡＮＧＥＪＯＵＮＡＬ。前两部...     

一种VSAT数据通信网络报文传输协议的分析

本文描述并分析了一种适用于多信道ＶＳＡＴ卫星数据通信网的报文传输协议，特别是考虑了无线信道误码率对传输协议的影响，分析表明利用Ｓ－ＲＥ－ＡＬＯＨＡ作为预订信道的多址方式及按报文占用数据信道方法可以减小报文传输延时并增加系统吞吐量。     

CDMA随机接入系统与S—ALOHA系统的性能对比分析

传统的Ｓ－ＡＬＤＨＡ随机接入协议用于通信网络，其理论上的极限通过量为３６％，但在这种情况下，系统的时延随着负荷的增加也变得越来越大，因此传统Ｓ－ＡＬＯＨＡ方式不适合于时延要求较高的通信系统，本文通过研究系统在较低负荷的情况发现采用ＣＤＭＡ技术的随机接入方法在占用相同的系统带宽的条件下，可以获得与传统Ｓ＿ＡＬＯＨＡ方式相同的通过量，而时延却大大降低，而且随着ＣＤＭＡ领域抗干扰技术的发展，它的系统性能     

R—S码在ADSL传输中的抗突发噪声性能

文中讨论了ＡＤＳＬ传输环境中的突发噪声问题，重点研究了采用Ｒ－Ｓ码来克服突发噪声的性能，并给出了计算机仿真结果。     

高速LAN/MAN的话音和数据负载控制方案

本文提出在高速光纤局域网和都市网（ＬＡＮ／ＭＡＮ）上动态分配多媒体业务带宽的方法，适用于分布控制通道反馈。根据分组限额，每个数据站独立执行必要的控制功能，话音站随时发送话音。用数学公式解全网门控制排队模型，最后给出仿真结果。     

VSAT卫星通信 第二讲 VSAT卫星通信网──专用网中的佼佼者

本文首先对ＶＳＡＴ卫星通信网的发展概况、系统组成、组网形式等进行了分析和介绍，然后重点介绍了数据ＶＳＡＴ网和话音ＶＳＡＴ网的传输体制、数据ＶＳＡＴ网的通信协议等内容。     

VSAT communications networks-an overview

The very-small-aperture-terminal (VSAT) fixed satellite communication network is a star network in which many dispersed micro terminals attempt to send data in a packet form through a random access/time-division multiple-access (RA/TDMA) satellite channel with transmission delay. The basic concept of the VSAT and its service potential are discussed. Two classes of traffic are addressed, namely business-oriented low-rate-data traffic and bulk data traffic of corporate networks. Satellite access, throughput, and delay are considered. The size of the network population that can be served in an RA/TDMA environment is calculated. User protocols are examined. A typical VSAT business scenario is described     

PMCAP/CDMA协议在语音与数据混合业务中的应用研究

该文将CDMA移动通信系统上行信道中的一种MAC协议PMCAP／CDMA协议应用到语音与数据混合业务的情况，对协议建立数学模型，并对性能进行理论计算和仿真。为了保证对语音请求的优先分配，将PN码集分为语音可用码集，数据可用码集及语音与数据的预防码集。提出了新的动态码集分配方案。仿真表现，该方案较固定码集方案更好地提高了系统的综合性能，而负指数码字分配方案提供了语音与数据性能的很好折衷。     

Next generation multiservice VSAT networks

Very-small-aperture terminal (VSAT) satellite networks have so far been successful in the provision of specific communication services to geographically dispersed users. However, user demands are becoming more complex and VSAT networks are expected to provide a much wider range of services (voice, data and multimedia). This paper investigates how this service integration could be achieved and shows that performance improvements are possible if efficient multi-access protocols and speech compression with voice-activity-detection techniques are used. It also discusses the future role that VSATs could play in the provision of access to the integrated broadband communication network to remote users. It is shown that it could be possible to use VSATs for ATM service provision, but there are limitations on the system's performance from the satellite delay and limited link capacity     

Performance of a Dynamic TDMA System for Mobile Wireless Access

A dynamic TDMA system can utilize voice activityand allow the integration of voice and data traffic.This can be achieved by allocating frequency channelsand time slots on demand. In this approach, upon the arrival of a talkspurt or a data packet,the base station is requested to assign a time slot foreach transmission. Message requests and assignments ofmobile users are carried over a Control channel, while the voice and traffic are transmittedover a Traffic channel. Time slot assignments are madefrom a pool of Traffic channels. A numberof slots in the pool will be shared by voice and data, with voice having priority over data, andthe remaining will be used by data only. Voice slots arereserved for the duration of the talkspurt whereas datapackets are assigned on a per-slot basis. Data packets can be buffered whereas voicetraffic can only tolerate limited delay beyond whichtalkspurts will be clipped off. The Control channeluplink access is based on Slotted Aloha so that mobile users have autonomous access to base stations.This paper presents the performance of the dynamic TDMAsystem outlined here. The analysis aims at assessing thecapacity gained by using voice activity and voice/data integration, in terms of theimpairments introduced to voice quality (e.g., speechclipping and/or delay) and the delays to data packets.The analysis has been based on a discrete time Markov model operating on a frame-by-frame basis thatprovides the joint distribution of the number of activevoice and data users in the system. The analysis alsoevaluates the delays of message requests via the uplink control channel. In evaluating theclipping probability, we combine the impact of both theaccess delays at the control channel as well as theunavailability of time slots in the pool. Performance results indicate that the capacity gain mayexceed 80% and the speech clipping can be kept below 1%.Also, data packets may be transmitted with limiteddelays even when all capacity is allocated for voice users. The proposed approach may be used toenhance the capacity of the existing TDMA cellularsystems and to provide integration of voice and dataservices.     

VSAT Networks—an overview

This paper examines the technology and constraints of very small aperture terminals (VSAT) networks, a special type of wide-area thin-route satellite network that represents a recent innovation in the field of satellite communications. VSAT network architectures suitable for both data and voice communications are studied in this paper. Several issues concerning the frequency of operations, that is, C-band versus Ku-band are examined, and trade-offs between non-spread spectrum and spread spectrum techniques, as well as modulation and multiple access schemes, are considered in detail. Link design examples are given to illustrate the performance of various types of VSAT networks.     

Performance evaluation of a reservation TDMA protocol forvoice/data transmission in personal communication networks withnonindependent channel errors

This paper deals with a random reservation TDMA protocol able to support constant bit-rate services as well as variable bit-rate services. In particular, we consider here the case of voice communications and data transmissions in a fading channel environment with nonindependent errors. Voice terminals are assumed to have higher priority than data terminals, in accessing the shared channel. A suitable analytical approach is proposed in order to evaluate the data and voice subsystem performance. Computer simulations are also shown in order to validate the obtained analytical predictions. The results shown here highlight that the proposed protocol permits an efficient integration of voice and data transmissions in the same wireless network even in the presence of a nonideal transmission channel     

Design and operational issues of VSAT application in ISDN-typenetworks

Advances in satellite technology in the area of very small aperture terminals (VSATs) offer economical data and voice services for corporate networks and rural applications. The authors describe VSAT application and technology with emphasis on analyzing the issues of quality after the sale. The quality and maintenance requirements of the VSAT networks in operation are defined. The reliability, maintainability, and availability calculations for VSAT networks with different topologies are evaluated. Results show that both star and point-to-point VSAT networks are capable of meeting higher availability standards     

一种数话兼容VSAT网络模型及其性能分析

本文提出了并讨论了一种新的数／话兼容ＶＳＡＴ网络实现方案：在不改变ＤＡＭＡ／ＳＣＰＣ这类ＶＳＡＴ系统的主要拓扑结构和通信单元的硬件的情况下只通过更改软件设计而使网络的数／话兼容能力得到较大提高。