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。     

“铱”系统及其业务进展

“铱”（Iridium）系统是美国摩托罗拉公司于1987年提出的一种利用低轨道（LEO）卫星群实现全球个人卫星移动通信的系统，它与现有的通信网相结合，可以实现全球数字化个人通信。“铱”系统区别于其它卫星移动通信系统的特点之一是卫星载有处理器，采用星间交换链路技术，因而，系统的性能极为先进、复杂、投资费用较高。此外，“铱”系统的漫游方案设计解决了卫星网与地面蜂窝网之间以及地面蜂窝网之间的跨协议漫游，这是“铱”系统有别于其它卫星移动通信系统的又一大特点。“铱”系统市场主要定位于国际旅行、商务活动、工业开发、政府…     

2004～2020年我国卫星通信发展目标探讨(下)

到2002年底，我国卫星通信业务发展的基本情况为：(1)卫星固定通信：空间段建设大发展；相应的卫星公用通信网、卫星专用通信网和卫星广播电视传输网得到较好的发展。(2)卫星移动通信：采用静止轨道和便携式用户终端方式的全球卫星移动通信系统运营良好；采用低轨道和手持式用户终端的各     

全球无线通信连通的可能性

１全球连通概述近年来，世界各国的通信建设既有固定通信网，也有移动通信网；或者说，既有有线（铜线、光纤）通信网，也有无线通信网。无线通信网既有专供固定通信用的，也有专供移动通信用的。移动通信主要依靠三类无线通信：无线局域网（WLAN）、城市蜂窝网（2G~3G）和卫星通信（GEO~MEO/LEO）。一般说来，城市蜂窝网主要用于城市，为携带轻便手机的移动用户提供通信便利。低轨（LEO，地球上空N ×100~1000km）卫星通信若能真正实现和开放应用，则对远距对方的用户实现移动通信很有利。静轨（GEO，地球上空36000km）卫星通信则…     

无线移动信息基础结构

本文首先简述无线移动通信结合发展潮流 ,从模拟至数字 ,即将过渡至宽带和多媒体通信。为此 ,全国无线通信网将推广使用异步转移模式。接着 ,本文说明移动信息基础结构包含接入网和骨干网 ,而且无线基台处于接入网边缘 ,提供移动手机的无线接入。最后指出低轨道 /中轨道卫星族对全球个人通信将起重要作用。     

21世纪通信技术发展趋势

文章在开始时对 2 0世纪通信演变过程作简单回顾 ,接着讲到 90年代中期发生的重大转折和国际上对未来通信的重要预测 ,再依次描述 2 1世纪即将形成的通信网结构、光纤传输线路、全光通信网 ,以及蜂窝网和卫星移动通信。最后提出通信建设发展趋势的两个明显标志     

无线局域网的新发展

本文说明近年建立无线局域网的趋向 ,数据速率将从 1Mb /s提高至1 0Mb /s,无线电频段从 91 5MHz升至 2 .4GHz。采用有省电措施的新型网卡 ,依靠直接序列扩频技术和快速数字信号处理器。其载波感测多址接入控制采用碰撞避免代替碰撞检测。提高数据速率的方法主要是正交相移键控结合巴克码位置调制。在较大网区采用接入点结构 ,根据通信质量的实测结果决定交接过程。网区内部地点可使用较高数据速率 ,移动到外围就自动退回低速率。本文扼要讲述无线局域网新发展的一些技术。     

亚洲蜂窝网卫星通信系统新计划

本文先全面说明同步卫星和低 /中轨道移动卫星通信系统的最新动态。其后着重介绍发展中国家利用同步卫星组成区域移动通信系统。文中特别讲到亚洲蜂窝网卫星通信系统和中东的Thuraya卫星移动通信系统。最后指出 ,这种利用同步卫星的区域通信系统与全球低 /中轨道卫星系统相比 ,投资节省 ,管理简便 ,手持机价格和每分钟通话资费都较低廉 ,在发展中国家地区值得提倡。     

移动通信的甚低速率压缩编码技术

移动通信的甚低速率压缩编码技术张煦现时盛行的城市蜂窝网移动电话通信，正从模拟信号过渡至数字信号的型式。到了未来的全球个人通信时代，必然全是数字化移动通信和个人通信的便携机和手持机，通过无线接入电台。这些无线电发信收信设备都是小型的，只具有有限的频带宽...     

浅论卫星移动通信在PCS发展中的作用

个人通信业务（ＰＣＳ）是以实现全球范围的无缝隙通信为目标,要求在任意时间,任何地点均能利用个人通信网络和终端能力,在任何用户之间实现多种业务组合的通信,目前有多家公司推出了各不个同的基于卫星移动通信技术的ＰＣＳ,按卫星高度可分为高轨道,中轨道和低轨道卫星移动通信系统三类。     

迎接新一代通信网来临

参照国际上报道关于数据通信业务量和移动手机数量发展的预测 ,认为在运营竞争、市场扩大和技术引进三方面的推动下 ,现行通信网必将进化为新一代通信网。较详细地描述新一代以数据为重心、分组为基本的核心网轮廓并描绘了第三代无线蜂窝网和移动卫星系统的前景。     

Network and common channel signalling aspects of dynamic satellite constellations

This paper discusses networking issues associated with the provision of L/S-band personal satellite communications. Both the UMTS and IMT-2000 third generation mobile communication concepts have identified the need for a satellite component as part of their overall structure. The work is mostly based on the ESA-developed medium altitude global satellite system (MAGSS-14).¹ It is, therefore, mainly relevant to MEO (medium earth orbit) constellations but most ideas can also be extended to LEO (low earth orbit) constellations. After examining user and service requirements the specific networking issues associated with personal satellite communications are reviewed. A network architecture is then proposed which takes these restrictions into account. Based on this network architecture, network signalling requirements, more specifically those relevant to network common control channels, are estimated.     

高速率无线个人域网(WPAN)

未来的无线通信系统大到覆盖全球的卫星网，小到个人域网。高速无线个人域网（WPAN）工作在不需许可证2.4GHz频段，最高速率可达55Mbit/s。本文阐述了WPAN的基本概念、目标应用以及媒体接入控制（MAC）层与物理层（PHY）的标准情况，还与无线局域网（WLAN）进行了比较。     

LEO satellite communication networks—a routing approach

In the modern world of telecommunications, the concept of wireless global coverage is of the utmost importance. However, real global coverage can only be achieved by satellite systems. Until recently, the satellites were in geostationary orbit and their high altitude could not allow real‐time communication such as cellular networks. The development of LEO satellite networks seems to overcome this limit. However, LEO satellite systems have specific characteristics that need to be taken into account. In the same manner, the TCP/IP standard was developed for terrestrial network. The need is then to come up with a solution that would permit the use of TCP/IP on LEO satellite networks without losing too many packets. The idea is to develop a routing algorithm that maximizes the RTT delays compared to the TCP timer granularity. For that matter, we use an FSA‐based link assignment that simulates the satellite constellation as a fixed network for a predetermined time interval. In this configuration, the problem becomes a static routing problem where an algorithm can find the best solution. Copyright © 2003 John Wiley & Sons, Ltd.     

Efficient dynamic authentication for mobile satellite communication systems without verification table

The mobile satellite system is an important wireless communication system widely used nowadays. The issue of protecting the transmission security in low‐earth‐orbit satellite networks thus becomes more and more critical. It is known that several authentication schemes for satellite communication systems have been proposed to deal with the issue. However, previous protocols either employ complicated public key computation or have to maintain a verification table. In this paper, the author will introduce a new dynamic authentication protocol for mobile satellite communication systems without using a verification table. The comparison results will also show that the proposed scheme has lower computational costs. Copyright © 2014 John Wiley & Sons, Ltd.     

FUTURE MULTIMEDIA COMMUNICATIONS VIA SATELLITE

We are now moving into an era when conventional speech service will expand to full multimedia service offerings. This paper looks at ways in which satellite systems could provide such services in both the mobile as well as the fixed bands and the integration and inter-operability of such systems. Provision of multimedia services by ATM to integrate with an ATM core network is taken as the basis of the future network. Some of the constraints and difficulties of provision of ATM over satellite are discussed as well as some potential solutions for the ATM wireless protocols and network architectures which potentially could provide such services. Finally, some suggestions of how new orbit constellations could help meet these requirements are given. © 1996 by John Wiley & Sons, Ltd.     

Satellite constellation design for 5G wireless networks of mobile communications

Satellite constellation design plays an important role in satellite networks. Network constellation system design can affect the effectiveness of current improvements of the communications link and the management of the entire network. The power requirement of the mobile stations and ground stations is very high in a geostationary Earth orbit communication system, which means the terrestrial terminal is hard to be made handheld for fifth generation mobile communications. The emergence of nongeostationary orbit satellites such as low Earth orbit satellites greatly compensates for the disadvantage of geostationary Earth orbit satellites. Based on the classical constellation design method, the orthogonal circular orbit constellation is proposed. The design objectives considered here are the following: global Earth coverage by low Earth orbit satellites, the duration of continuously covering one mobile station by one satellite is more than 9.57 min, the access satellite link duration time of the mobile station is more than 4.79 min, and the number of satellites and orbits is to be minimum.     

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.