北美数字蜂窝式移动电话系统的新进展

为把握蜂窝移动通信的未来发展趋势，ＴＤＭＡ（时分多址联接）数字蜂窝移动电话系统已在世界范围内逐步建成。根据ＴＩＡ的Ｄ－ＡＭＰＳ标准建立的ＴＤＭＡ数字蜂窝移动电话系统于１９９２年在北美投入运行。为使该系统的功能升级，业已开发出配备一个数字控制信道的Ｄ－ＡＭＰＳ新规范，其主要优势在于新的终端用户性能，通过支持微区来推动蜂窝通信网的演变。在８００ＭＨｚ蜂窝通信频率及ＰＣＳ（个人通信业务）的１８５０ＭＨｚ     

蜂窝式移动电话建网简介

蜂窝式移动电话网已在我国北京、上海、广州等城市相继建立,虽然为时不久,但已经显示了它的优越性,受到了广泛的欢迎,用户发展的速度比预料的要快。目前,国内其它一些城市也正在筹备建设,预计在近年内将会有较快的发展。本文就蜂窝式移动电话网的组成及建网中的相关工作作些介绍,供参考。     

900MHz蜂窝式移动电话系统联网探讨

900MHz蜂窝式移动电话系统的特点是,只要频段和制式相同,就可以将两个或两个以上的系统联接成网路,扩大其服务区域。我国规定了900MHz 频段为890—915MHz 和935—960MHz,频道间隔25kHz,双工收、发频率间隔为45MHz。根据这个规定,同时为了使我国的公用移动通信网能与其他国家和地区的 TACS 系统兼容工作,基本采用了 TACS 标准,这就为建立全国性网路创造了良好的条件。900MHz 蜂窝式移动电话系统,美国的 AMPS 制     

数字移动电话与模拟移动电话

本文介绍了通信市场的电话网，以及移动电话特点。     

大容量蜂窝状公用移动电话系统及其应用

一、概述公用移动通信是在40年代出现的,由于频道不足和技术上的原因,发展一直缓慢.直至七十年代以来,由于大规模集成电路和微电子技术的成熟与发展,使用大型程控电子交换机控制蜂窝结构布局的无线电发射与接收,克服了无线电频率资源有限的缺点,从而大大扩展     

Performance bounds of a multiple-step paging strategy in future universal mobile telecommunication systems

In future mobile telecommunications, due to the huge number of users and the specific functions that support mobility, a significant amount of signaling load will have to be carried by the finite capacity of the radio link. Hence, methods aiming at radio link signaling load reduction are welcome. In this paper we propose and analyze a method that saves paging signaling load by exploiting information related to the terminal location during the most recent interaction between the terminal and the network. The penalty paid is extra processing power and extra paging delays. An analytical model is developed so as to describe the performance versus traffic intensity and mobility conditions. The performance of the proposed paging scheme is investigated, and it is shown that the method operates well even in the worst case, which is the high user mobility conditions. Possible extensions of the method, which exploit information related to the mobility degree of each individual user or information characterizing the mobility conditions in a certain location area, are also proposed.This paper has been partially funded by CEC through the RACE 2066 Mobile Network (MONET) project. The paper does not present the views of the project as a whole, but those of the authors.     

Traffic engineering of combined mobile telephone and dispatch systems

If a server group carrying short-holding-time queued traffic at high blocking probability is combined with another server group carrying normal blocked-calls-cleared traffic at low blocking probability, the resulting mixed group will in many cases operate at an intermediate blocking probability. Thus the mixed group provides better service to the queued traffic, while degrading the service of the cleared traffic. If the random arrival characteristics of the short-holding-time traffic are suitably modified by delaying calls an appropriate time before service, then the grades of service for both types of traffic may be engineered independently. An example of a possible use of this technique of induced delay, the combining of dispatch and mobile-telephone traffic on the same set of radio channels in the High-Capacity Mobile Telecommunications System, is discussed.     

TFT—LCD液晶显示器现状及发展

TFT-LCD显示器具有诸多优点:比普通CRT显示器能够节省大量空间;在重量、耗电等方面,LCD显示器的重量仅为同屏幕尺寸的CRT显示器的1/7左右,耗电量仅为CRT显示器的1/4;同时,LCD显示器有利于使用者的健康,可以说是一种真正意义上的无辐射产品;另外,由于不存在电子束的汇聚问题,LCD显示器不存在几何失真和散焦现象,新一代的LCD还具有不受电磁场的干扰、亮度较高、视角宽广的特点。     

High Altitude Platform Station (HAPS): A Review of New Infrastructure Development for Future Wireless Communications

This paper looks into the relatively new field of high altitude platform stations. HAPS is seen as a ‘middle ground’ between the terrestrial and satellite cases, and aims to exploit of the advantages of both types of system. Since HAPS is such a new field, this paper focuses on the technology behind a HAPS communications system, how this has developed, and compares it to the terrestrial and satellite equivalents. One important area that is being investigated is the applications for which HAPS should be used. This is a critical issue if a significant business case is to be made for HAPS. Worldwide HAPS projects and research issues are also highlighted. Finally, the review concludes with the remarks on the future of HAPS for wireless communications systems.     

手机短信为糖尿病患者进行药学服务的可行性研究

目的探索利用手机短信为糖尿病患者进行药学服务的可行性,为临床药师参与药学服务提供新思路。方法利用手机短信为糖尿病患者进行1周的个体化药学服务,服务内容包括降糖药物的使用及不良反应、血糖的监测方法、低血糖的救治、饮食运动控制、糖尿病的危害与综合治疗、定期复查指标等。1周后进行电话问卷调查,评价此项服务的可行性。结果共入组175例糖尿病患者,完成问卷随访155例,平均综合评分为(96.7±5.6)分。结论利用手机短信为糖尿病患者进行药学服务具有较高的患者认可度和可行性,临床药师可利用这一平台为糖尿病患者进行药学服务。     

Voice transmission quality of mobile satellite communications systems

Recently, a number of commercial digital mobile satellite communications systems have become operational, and the introduction of more systems is imminent. The voice transmission quality of the Inmarsat-aeronautical, Inmarsat-M and Inmarsat-B systems was evaluated and compared with the quality of the Inmarsat-A analogue communication system on the basis of subjective listener opinion assessments. From this evaluation it can be concluded that, under nominal operating conditions, the current generation of digital mobile systems may offer a perceived performance that surpasses that of the older Inmarsat-A analogue system, at least when measured in terms of transmission quality.     

A simple detector for trellis-coded PSK mobile radio systems

A simple detector for a trellis-coded PSK mobile radio system is proposed. A precoder is added to the regular TC-PSK modulator before convolution coding, and a simple one-bit differential detector is used in the receiver. The decision is made symbol by symbol based on the output samples. The bit error rate of this system is evaluated in fast Rayleigh fading characterizing mobile radio channels by numerical integration.     

Parameter estimation validity and relationship robustness: A comparison of telephone and internet survey techniques

With the expansion of telecommunication and online technologies for the purpose of survey administration, the issue of measurement validity has come to the fore. The proliferation of automated audio services and computer-based survey techniques has been matched by a corresponding denigration of the quality of traditional phone survey data, most notably as an outcome of falling response rates. This trend, combined with the introduction of screening technologies and answering machines, represents a barrier to the proper execution of survey research. Whereas the question was once, “can technology-assisted surveys achieve the same level of validity as traditional phone surveys?”, the question now becomes, “what are the relative advantages and disadvantages of technology-assisted and phone surveys?” Each has its own challenges and opportunities, and this paper begins to explore these. The present study provides further insight into the validity of telephone and Internet survey data, and explores whether or not the robustness of relationships between variables varies by survey mode.     

移动互联网与移动电子商务的研发与应用

综述了国际移动互联网的发展概况,阐述了移动电子商务赖以发展的条件,通过与传统互联网及传统电信网的比较,分析了移动互联网的特点,最后,介绍了日本1－Mode成功的经验。     

Interference from mobile satellite systems through terrain scattering

The emerging generation of personal communications satellites, built to communicate with handheld telephone units, will generate power flux on earth that is orders of magnitude higher than that of the present satellite service, and its potential interference with terrestrial-based systems is of concern. It is proposed here that the flux scattered from the ground surface into the antenna main beam and near sidelobes may cause higher interference than direct coupling into the antenna. This mechanism, previously observed in terrestrial systems, may not be mitigated by adaptive nulling techniques, and is less angle-dependent. A simple model is developed, to be used as a computational tool for assessing the interference and its functional dependence on governing parameters. In the absence of proper terrain scattering models, examples are evaluated by borrowing results from interference observed in terrestrial microwave links, which indicate the possible severity of the effect.