欢迎来到麦多课文档分享! | 帮助中心 海量文档,免费浏览,给你所需,享你所想!
麦多课文档分享
全部分类
  • 标准规范>
  • 教学课件>
  • 考试资料>
  • 办公文档>
  • 学术论文>
  • 行业资料>
  • 易语言源码>
  • ImageVerifierCode 换一换
    首页 麦多课文档分享 > 资源分类 > PDF文档下载
    分享到微信 分享到微博 分享到QQ空间

    ITU-R F 1611-2003 Prediction methods for adaptive HF system planning and operation《自适应HF系统规划和操作的预报方法》.pdf

    • 资源ID:791111       资源大小:111.77KB        全文页数:8页
    • 资源格式: PDF        下载积分:10000积分
    快捷下载 游客一键下载
    账号登录下载
    微信登录下载
    二维码
    微信扫一扫登录
    下载资源需要10000积分(如需开发票,请勿充值!)
    邮箱/手机:
    温馨提示:
    如需开发票,请勿充值!快捷下载时,用户名和密码都是您填写的邮箱或者手机号,方便查询和重复下载(系统自动生成)。
    如需开发票,请勿充值!如填写123,账号就是123,密码也是123。
    支付方式: 支付宝扫码支付    微信扫码支付   
    验证码:   换一换

    加入VIP,交流精品资源
     
    账号:
    密码:
    验证码:   换一换
      忘记密码?
        
    友情提示
    2、PDF文件下载后,可能会被浏览器默认打开,此种情况可以点击浏览器菜单,保存网页到桌面,就可以正常下载了。
    3、本站不支持迅雷下载,请使用电脑自带的IE浏览器,或者360浏览器、谷歌浏览器下载即可。
    4、本站资源下载后的文档和图纸-无水印,预览文档经过压缩,下载后原文更清晰。
    5、试题试卷类文档,如果标题没有明确说明有答案则都视为没有答案,请知晓。

    ITU-R F 1611-2003 Prediction methods for adaptive HF system planning and operation《自适应HF系统规划和操作的预报方法》.pdf

    1、 Rec. ITU-R F.1611 1 RECOMMENDATION ITU-R F.1611*Prediction methods for adaptive HF system planning and operation (Questions ITU-R 205/9 and ITU-R 147/9) (2003) The ITU Radiocommunication Assembly, considering a) that the number of adaptive HF systems in operational use is growing, specifically auto

    2、matic link establishment (ALE) systems; b) that Recommendation ITU-R F.1110 specifies the general characteristics of adaptive HF systems, and specifically recognizes that adaptive HF systems make it possible to achieve the following: a higher quality of service by combining the ability to exploit mo

    3、dern radio frequency technology with advanced real-time control software; to reduce transmission times, thereby securing most efficient use of the spectrum, reduced interference between users, and the ability to increase traffic density; c) that ITU has developed an adaptive HF Handbook which descri

    4、bes the nature of adaptive HF systems and their use; d) that frequency-adaptive HF systems are constrained to use the minimum number of active frequency channels in order to limit the potential for interference with other users; e) that Recommendation ITU-R F.1337 recommends that automatic and adapt

    5、ive management schemes be utilized for adaptive HF networks; f) that frequency planning with an accurate HF performance prediction model will reduce the margins over which adaptive HF systems must be designed to adapt, with the result that operational procedures can reduce the potential for interfer

    6、ence, and overall cost may be reduced; g) that Recommendation ITU-R P.533 (and its software program REC533) is the established ITU-R method for HF performance predictions, and is well-suited to be an umbrella for additional (related) prediction methods, some of which are currently used in the contro

    7、l of various quasi-adaptive HF systems and in the design of systems employing forms of ALE; h) that other related prediction methods, such as the IONCAP family of programs, are maintained on the same publicly-available Institute for Telecommunication Sciences (ITS) website as is Recommendation ITU-R

    8、 P.533; *This Recommendation should be brought to the attention of Radiocommunication Study Group 3. 2 Rec. ITU-R F.1611 j) that all methods downloaded from the ITS website (including Recommendation ITU-R P.533, VOACAP and ICEPAC) have input/output methods that can be reconciled with some additional

    9、 effort, recommends 1 that administrations which intend to procure and deploy adaptive HF and ALE systems, based upon the information in Annex 1, should explore the use of HF performance prediction models such as those contained in Recommendation ITU-R P.533 and related models in advance of deployme

    10、nt to establish adaptivity bounds; 2 that the models contained in Recommendation ITU-R P.533, augmented by material such as that contained in the (optional) IONCAP family of programs, are preferred methods for the design of adaptive HF systems and for possible incorporation within software modules f

    11、or real-time adaptation using recognized real-time channel evaluation (RTCE) technologies (i.e. in-band sounders, advanced channel probes, and out-of-band frequency modulated-continuous wave (FM-CW) sounding). Annex 1 Adaptive HF system planning and operation using prediction methods 1 Introduction

    12、The ionospheric channel provides the connectivity for the links in an adaptive HF radio circuit or network. To provide proper utilization of this resource the radio system must operate on the ideal frequency or as close to it as practical. This may be the same frequency for a simplex circuit or two

    13、different but closely related frequencies for a full duplex circuit. Frequency changes will be dictated by the natural cycles of ionospheric propagation; diurnal, seasonal and sunspot variations. Natural or man-made radio interference may dictate unpredicted changes in the operating frequency. Also

    14、solar flares and geomagnetic storms may cause communications disruptions which will also require changes in the operating frequency. For the most part, the frequency adaptive HF radio system will detect link failure, find another usable frequency, bring the link up on the new frequency and re-establ

    15、ish communications without operator intervention. Several things can create intolerable outages even with the most sophisticated adaptive HF radio system. Equipment failure is one that is unavoidable over the life cycle of the system. It can be mitigated by fault detection, backup power supplies and

    16、 equipment redundancy in the system design. However, most disruptions are attributed incorrectly to propagation failure. Only Rec. ITU-R F.1611 3 under the most rare of ionospheric conditions should propagation failure occur. Most cases, where the signal power on any frequency across the band is unu

    17、sable, can be directly traced to improper system design. The areas, which must be considered in the system design, will be discussed in the following paragraphs. Let it suffice to say at this point that the most common areas are: inadequate number of frequencies in the authorization list; underestim

    18、ation of radio noise environment at the receive sites; antenna radiation patterns which do not match the takeoff and arrival angles of the ionospheric channel; and excessive losses in the transmission lines between the transmitter and the transmit antenna or the receiver and its antenna. 2 Frequency

    19、 planning Frequency planning begins early in the design phase of the HF radio system. For frequency adaptive HF radio systems, it is essential that the ionospheric model used for making the frequency predictions include as much knowledge as possible concerning the expected variation of the hourly ma

    20、ximum usable frequency (MUF) about the monthly median value (i.e. the MUF) for each of the probable modes on each link in the proposed radio system. The needed accuracy in the prediction model is directly related to the very low S/Ns required for the sophisticated adaptivity techniques employed in t

    21、he modern radio equipment and their associated modems. We will now outline a sample procedure by which prediction methods can be used to design and operate adaptive HF systems. The discussion in this Annex is based upon the VOACAP procedure that is used within the United States of America administra

    22、tion, having some experience in its application for adaptive HF systems. It is likely that similar procedures could be developed for other methods such as the preferred ITU method, Recommendation ITU-R P.533. At this time the preferred programs in the IONCAP family are VOACAP and ICEPAC, which, alon

    23、g with Recommendation ITU-R 533, are maintained and available at no cost via the Internet from the US Department of Commerce (i.e. http:/elbert.its.bldrdoc.gov/pc-hf/hfwin32.html). The Recommen-dation ITU-R P.533 computer program predicts the monthly median MUF. It currently does not explicitly give

    24、, as an output, the expected distribution of daily MUF values over the days of the month at that hour for the possible modes. In evaluating an adaptive HF system, each link in the radio net needs to be evaluated using a recommended prediction program. (In this example, we specify VOACAP, which belon

    25、gs to the IONCAP family of programs.) These prediction methods were originally developed for non-adaptive systems. However they can be utilized for adaptive system planning. For conventional HF radio links, the optimum working frequency (OWF) would be determined by finding the most reliable frequenc

    26、y at each hour, season and for high and low sunspot activity. However, for frequency adaptive HF radio systems, the highest probable frequency (HPF) needs to be found. This is the frequency which would not be exceeded more than 10% of the days in the month at that hour and sunspot number; whereas th

    27、e OWF is the frequency which is exceeded on 4 Rec. ITU-R F.1611 approximately 90% of the days per month. The frequency adaptive system using ALE should have the capability of operating on frequencies above the monthly median MUF on half of the days per month. The frequency authorization list for suc

    28、h a system should include frequencies above the MUF but not to exceed the HPF. This feature of frequency adaptivity demands the use of accurate prediction programs in the systems design of the radio circuit or network. It is essential in the planning for an adaptive HF radio system that the equipmen

    29、t be designed to work over the full range of usable frequencies including those below the MUF but above the lowest usable frequency (LUF). When possible, the system should operate at the highest usable frequency which permits error-free connectivity. The higher frequencies will experience less atmos

    30、pheric and man-made radio noise and provide higher S/Ns for less transmitter power and antenna gain. By designing the adaptive system to take advantage of the highest possible frequency usage, cost savings can be made in the power capacity of the transmitter and the size of the transmit and receive

    31、antennas. At the same time, it should be recognized that practical circumstances may require operation of individual links at less than optimal frequencies to avoid self-interference or to avoid harmful interference to other users in a shared environment. Frequency predictions provide an a priori ca

    32、pability for assessing groups of sub-optimal channels to provide the best possible system reliability under specified conditions. Also care must be taken in the system design to assure that the signal-plus-noise power delivered to the receiver is meets the sensitivity requirements of the proposed re

    33、ceiver. Another frequency consideration which will be important in the operation of the frequency adaptive system is that the frequency assignment should be several times per day and for seasonal and sunspot number changes. Ideally the frequency sampling should not exceed more than half a dozen freq

    34、uencies at a given time epoch. This allows the adaptive system to perform link establishment more rapidly and reduces the needless interference caused by sounding on useless frequencies. Also a priority of frequency sampling should be established so that during a given time epoch the most reliable f

    35、requency is sampled first in the link establishment process. If there is a frequency which is 90% reliable, then on 27 days out of the month at that hour the system should lock up on that frequency and on the first try. Short term forecasting or now-casting techniques can further assure the success

    36、of finding the best operating frequency in the shortest time possible. The advantage of using predicted frequencies for first priority is that they are more likely to remain stable over the entire hour than a frequency of opportunity found by random sampling of the spectrum. In short, there are two

    37、levels of frequency steering in a frequency adaptive HF system. At the first level, frequency predictions can be used to reduce the range of frequencies to be sampled or sounded in a real-time scenario. The second level of steering is defined by channel properties best derived from sounding or equiv

    38、alent RTCE schemes, supplemented by a knowledge of the expected trends in frequency availability obtained from an appropriate prediction procedure. In-band channel soundings (e.g. ALE sounding), full-band FM-CW soundings (i.e. chirp sounding), or parameters derived from the modulation in use may be

    39、used. (See Chapter 6 of the Handbook on Frequency Rec. ITU-R F.1611 5 adaptive communication systems and networks in the MF/HF bands, on sounding and RTCE technologies.) Still, the use of frequency predictions is essential for the development of requisite lists of the most likely frequencies to be u

    40、sed during the day and night path conditions by an adaptive HF radio system. 3 Power budget The next phase in the design for a frequency adaptive HF radio system is to establish the power budget for each of the ionospheric links in the circuit or network. The power budget may be considered as the me

    41、ans of finding the most cost-efficient design which will permit for acceptable service over the life cycle of the system. Again for adaptive HF system design, performance prediction models with the highest degree of accuracy in modelling the signal and noise variations should be used. Programs shoul

    42、d employ the full statistics of the expected variation in transmission loss by mode and the time variation of the atmospheric and man-made radio noise. The reason for needing this sophistication in the prediction model is that adaptive HF radio systems operate at very low S/Ns. In order to be certai

    43、n that the selected transmitter power and antennas for each of the links are adequate, great care must be taken in the calculation of the time- and frequency-variant signal and the noise power delivered to the receiver. Errors in this design step will result in needless cost in over-design or commun

    44、ications failure when the signal power is below the detection threshold of the receiver. 4 Design process The first step in the design process is to evaluate the predicted required power gain (RPWRG) on each link of the radio circuit or network. It is defined as the additional or excess power, expre

    45、ssed in dB, required to achieve the required S/N at a specified reliability. A value of 0 dB at 90% reliability would mean that the required S/N would be achieved or exceeded 90% of the days of the month at that circuit hour. Generally, the prediction program is set up with an assumed transmitter po

    46、wer of 1 kW and isotropic (0 dBi) antennas. To prevent modes from being considered at unreasonably low take-off or arrival angles, the minimum take-off angle to be considered is set at 3 above the horizon. At this time a revised frequency list (up to 11 frequency bands between 2 and 30 MHz can be sp

    47、ecified in one run of the Recommendation ITU-R P.533 and VOACAP-family of programs) needs to be established for this phase of the system design. The goal is to select frequencies which fall between the lowest usable frequency and the highest probable frequency needed over the hours, seasons and suns

    48、pot numbers representing the expect life cycle of the system. In other words the performance prediction should be made for only those frequencies for which we expect ionospheric support. The LUF is not predicted as such in the IONCAP-family or the Recommendation ITU-R P.533 programs. Instead, the re

    49、liability expected at various frequencies is predicted, which may be compared with the service requirement. (For design purposes the LUF is defined as the lowest frequency which will provide 90% reliability of meeting the required S/N or as approximately 90% of the MUF.) The next step is to decide upon the minimum required S/N density 6 Rec. ITU-R F.1611 ratio needed to allow the adaptive system to provide a minimum acceptable grade of service. The value of the required S/N is not well established this time for adaptive HF radio equipment. However, there are several guidelines w


    注意事项

    本文(ITU-R F 1611-2003 Prediction methods for adaptive HF system planning and operation《自适应HF系统规划和操作的预报方法》.pdf)为本站会员(eastlab115)主动上传,麦多课文档分享仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对上载内容本身不做任何修改或编辑。 若此文所含内容侵犯了您的版权或隐私,请立即通知麦多课文档分享(点击联系客服),我们立即给予删除!




    关于我们 - 网站声明 - 网站地图 - 资源地图 - 友情链接 - 网站客服 - 联系我们

    copyright@ 2008-2019 麦多课文库(www.mydoc123.com)网站版权所有
    备案/许可证编号:苏ICP备17064731号-1 

    收起
    展开