1、 Rec. ITU-R F.1610 1 RECOMMENDATION ITU-R F.1610 Planning, design and implementation of HF fixed service radio systems (Question ITU-R 205/9) (2003) The ITU Radiocommunication Assembly, considering a) the need for HF radiocommunication services; b) that recent developments in HF system techniques ma
2、ke it possible to achieve the following: a higher quality of service by combining the ability to exploit modern signal processing technology with advanced real-time control software; a reduction in transmission times, thereby securing the most efficient use of the spectrum opportunity to decrease in
3、terference between users, and the capability to increase traffic density; c) that ITU-R has developed a Handbook on frequency adaptive communications systems and networks in the MF/HF bands which describes the nature of adaptive HF systems and their use; d) that the performance of the HF system depe
4、nds on the engineering design and planning of the radio installation, recommends 1 that users, who intend to deploy HF systems, should use the information contained in Annex 1 as a guide to planning, system design and implementation. Annex 1 Planning, design and implementation of HF fixed service ra
5、dio systems 1 Introduction High operational flexibility, easy maintenance of equipment requirements make HF system techniques very useful in world communications; this is particularly emphasized in the case of large geographical areas with low density of telegraph, telephone and data traffic. 2 Rec.
6、 ITU-R F.1610 At the present time, the development of modern high capacity means of telecommunications, such as satellites and cables, has allowed a wide part of the RF spectrum between 3 and 30 MHz to be available for telecommunications systems, even while meeting the needs of the mobile services.
7、When the need for a new communications capability between two or more points is first envisioned, and HF radio is suggested as a possible solution, a feasibility study is required to analyse and define the whole system. This study will verify that HF is the appropriate means of communication for the
8、 set of system requirements pending, based on a comparison of technical and operational alternatives, and that the economic aspects for the new HF system are compelling. 2 Definition and analysis of requirements A rigorous analysis of the expectations and requirements for the new system should show
9、whether or not this communication medium is proper for this application. Some of the factors that support the use of HF radio over other means of communication are: distance reliability terrain message traffic requirements message priority requirements estimates solar cycle and available frequency s
10、et adequate sites. A review of the above items will determine if the use of HF radio equipment is appropriate for the proposed application. 2.1 Preliminary system design and feasibility study Once it has been determined that HF is a viable solution to the communications requirement, then a prelimina
11、ry system design and feasibility study must be conducted. The items, which the system engineer must consider, make up the remainder of this item. 2.2 Trunking/routing plans The trunking and routing plans in the design analysis provide information on the number and types of channels needed to interco
12、nnect each of the terminals within the HF system. If the radio system is to be a part of larger network of radios, the implementing engineer will work with the network manager to identify all the stations or nodes to be included in the network as well as their geographical locations. The routing pla
13、ns have to consider the following factors: physical location of each node and the relationship to other nodes in the network, physical obstacles (i.e. mountains, buildings, antenna, etc.) between nodes, equipment located at each node, especially the power and antenna characteristics, Rec. ITU-R F.16
14、10 3 propagation paths between the stations involved, communication interfaces that are connected to each node, characteristics and volume and priority of the communications traffic. 2.3 Frequency plan Planning must begin early in the project to secure an adequate list of frequencies to support each
15、 link in the HF radio system so that uninterrupted operations are possible both day and night, at any time of the year, and throughout the whole 11-year solar cycle. A frequency prediction program such as Recommendation ITU-R P.533 could be used determining frequency requirements in different condit
16、ions. 2.4 Personnel manning requirements To ensure that each station in the network is operated and maintained properly, an analysis of the numbers, training and experience of the personnel that will be required to staff each of the nodes in the network during the required period of service should b
17、e conducted early in the planning process. 2.5 Support requirements The system designer must select a site having adequate access roads, water and electrical power supply, fuel for generators, telephone service, post office, medical facilities, and adequate housing and shopping areas for site person
18、nel. In the vast majority of cases, the radio site will be located near a city or large town, and the support considerations mentioned above, will normally be available. But in a few cases obtaining these services may require special logistics effort. 2.6 Modes of communications required (voice, dat
19、a, and image) The requirement specifications will specify what type(s) of traffic the HF station must be capable of handling. This may be voice only, both voice and data, or may indicate the need to handle other forms of information, such as image, facsimile, or encrypted voice. Each of these types
20、of traffic will indicate additional pieces of equipment that must be considered by the system engineer. 2.7 Required S/N The modes of communications required (i.e. voice, data, etc.) will determine the required S/N. Recommendation ITU-R F.339 can be used to determine what S/N is needed for the requi
21、red grade of service (orderwire quality, marginal commercial grade, or good commercial grade), for the type of signal (analogue, digital). 2.8 Modulation types and data rates Normally this information will be furnished in the system designer with the equipment specifications. Care must be taken to a
22、ssure that equipment interfaced together operates at the same data rates and uses the same modulation types. For HF data transmission Recommendations ITU-R F.763 and ITU-R F.436 have suggestions for different techniques to avoid degradations resulting from the radio channel. 4 Rec. ITU-R F.1610 In t
23、he solution adopted by the ITU-R, a serial to parallel conversion of the high-speed signal (up to 1 200 bit/s) is effectuated giving 6-12 channels, FDM multiplexed. The low modulation rate (50-100 Bd) so obtained for each subchannel makes the digital signal practically free from multipath distortion
24、. At the receiving side a data concentrator restores the original signal characteristics. For higher signal speeds (up to 4 800 bit/s), systems based on differential phase keying with frequency shifted tones are sometimes used. In this case the information is derived from the relative difference of
25、phase between two simultaneously transmitted tones. The multipath effects over the two tones are practically the same, because of the small difference value (about 40 Hz). An alternative technique is to transmit the data in serial form and utilize the adaptive equalizer in the receiver to remove to
26、multipath distortion. HF modems for data rates up to 9 600 bit/s have been developed with these signalling formats. The information is transmitted in analogue or digital form through the radio channel, the transmission types described in this section are defined in Table 1. TABLE 1 Types of modulati
27、on Designator Modulation form Definition CW Continuous wave Defined as a radio wave of constant amplitude and constant frequency. As a modulation form, CW is defined as an interrupted continuous wave, which is on/off, keyed using Morse code AM Amplitude modulation A form of modulation in which the a
28、mplitude of a carrier wave is varied in accordance with some characteristic of the modulating signal FM Frequency modulation Amplitude changes of the modulating signal are used to vary the instantaneous frequency of the carrier wave from its unmodulated value SSB Single sideband A form of amplitude
29、modulation in which the carrier and one sideband are suppressed and the remaining sideband is transmitted. Also designated as USB and LSB, for upper and lower sideband ISB Independent sideband A method of double-sideband transmission in which the information carried by each sideband is different RTT
30、Y Radio teletypewriter A teletypewriter used in a communication system using radio circuits. Mark/space teletypewriter signals are modulated on radio systems either by a two-frequency shift of the carrier wave, called frequency-shift keying (FSK) or by a two-frequency audio signal, called voice freq
31、uency telegraph (VFT) or audio frequency-shift keying (AFSK) Data Binary digital Information that is represented by a code consisting of a sequence of discrete elements. Digital data is produced by teletypewriters, digital facsimile equipment and computer terminals among other sources. The signals a
32、re generally transmitted by digital-to-analog conversion to FSK or phase-shift keying (PSK) Rec. ITU-R F.1610 5 2.9 Required circuit reliability HF circuits are able to provide circuit reliability of 80% (19.2 h/day) to 95% (22.8 h/day). Modern, adaptive equipment such as automatic link establishmen
33、t (ALE) will operate near the high end of the reliability spectrum. 2.10 Terminal facilities required The term terminal facilities are used here to describe all of the physical plant, primary and auxiliary power, and environmental control systems required to support the new HF system. 2.11 Required
34、system lifetime of service The length of time that the new HF system will be expected to be in service will have an impact on the selection of equipment. If the service is only for a short period of time (several months to a few years), it may be possible to operate with transportable or tactical eq
35、uipment. Any longer life expectancy will usually require permanently installed equipment. 2.12 Facilities site requirements Because of the long wavelengths involved with HF operations, large amounts of land are required for HF stations. A simple dipole antenna usually requires at least 0.5 hectares
36、of ground, and a rhombic antenna can require from 2 to 7 hectares. If the new HF system cannot use an existing site, then planning must begin very early in the project to find and acquire a suitable location. Additionally, if operation is contemplated on several circuits or full-duplex operation on
37、one circuit, then various antennas must be separated to prevent co-site interference. This antenna separation compounds the need for additional land. 2.13 Environmental impact assessments Frequently, the construction of an HF radio site, or the upgrade of an existing site, will require environmental
38、 impact assessments. If towers in excess of 50 m are anticipated, or if the site is to be located near an existing airport or heliport, then notification of the aviation authorities is required. 2.14 Required operational date The date that the station is required to be operational (or the new equipm
39、ent is required to be operational) may be given in the original statement of requirements, or it may require negotiation with the operational agency. Some of the major system components may have delayed delivery times, so their delivery schedule should be factored into the plans for an operational d
40、ate. 3 Practical aspects Development of a new or expanded HF radio capability includes more than just the estimates for the equipment. This section contains the direct and indirect project estimates including details about: start-up; equipment; installation. 6 Rec. ITU-R F.1610 3.1 Start-up 3.1.1 Pr
41、oject management estimates Estimates must include direct and indirect labour for the project manager and any staff, for the time spent monitoring and managing the project. Also included are other items, such as travel. 3.1.2 System engineering estimates Estimates must include direct and indirect lab
42、our for the system engineer and any assigned staff, for time spent reviewing the project requirements, and the time devoted to system design work. These estimates may also include other direct items such as travel, printing, drafting, etc. 3.1.3 Real estate/land acquisition estimates If the site for
43、 the new HF station(s) is/are not owned by the operational agency, the site(s) must be acquired through purchase or lease. These acquisition estimates include all estimates associated with the acquiring of the land for the site(s), including the purchase, yearly lease, legal fees, and any taxes that
44、 apply. 3.1.4 Site preparation These include estimates associated with levelling or grading the land, constructing fences, digging trenches for antenna cables, constructing concrete piers for antenna towers. 3.1.5 Construction or modifications to equipment building(s) If the site is a new one, then
45、an equipment building/control facility must be constructed to house the equipment and to provide a place for the sites personnel to operate. If the site is an existing one, then it may be necessary to construct additional rooms for the site building(s) to house the new capability. 3.1.6 Construction
46、 or modifications to the sites primary and auxiliary power system The HF system requires a.c. power, from the local power company grid to run the HF equipment and site to provide support for equipment such as heating, ventilation, and air-conditioning. If the site is an existing one, this power may
47、be already provided, but in many cases the power distribution system may have to be upgraded with larger transformers, and additional circuit breakers. The engineering plan may also call for the installation of an auxiliary power source, such as a gasoline- or diesel-powered electrical power generat
48、or for emergency use. 3.2 Equipment 3.2.1 Equipment in general The estimates of the HF system equipment may or may not be the largest item of the project, depending on how many circuits are required, what power levels the transmitters require and the distances between sites. Equipment is usually pur
49、chased through one supplier or vendor, although it is not uncommon for multiple vendors to support a large contract. The usual process is for the operating agency to notify all qualified vendors of intent to purchase equipment and/or services, Rec. ITU-R F.1610 7 through the request for proposal (RFP). The interested vendors respond to the RFP with their proposed solution to the customers need, and with an estimate. The customer can then choose among several competing solutions, and choose the one that best meets their needs. The vendors, often will pro
