ITU-R P.530-12 地面视距内系统设计要求的传播数据和预测方法

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Rec. ITU-R P.530-12 1

RECOMMENDATION ITU-R P.530-12

Propagation data and prediction methods required for

the design of terrestrial line-of-sight systems

(Question ITU-R 204/3)

(1978-1982-1986-1990-1992-1994-1995-1997-1999-2001-2001-2005-2007)

Scope

This Recommendation provides prediction methods for the propagation effects that should be taken into

account in the design of digital fixed line-of-sight links, both in clear-air and rainfall conditions. It also

provides link design guidance in clear step-by-step procedures including the use of mitigation techniques to

minimize propagation impairments. The final outage predicted is the base for other Recommendations

addressing error performance and availability.

The ITU Radiocommunication Assembly,

considering

a) that for the proper planning of terrestrial line-of-sight systems it is necessary to have

appropriate propagation prediction methods and data;

b) that methods have been developed that allow the prediction of some of the most important

propagation parameters affecting the planning of terrestrial line-of-sight systems;

c) that as far as possible these methods have been tested against available measured data and

have been shown to yield an accuracy that is both compatible with the natural variability of

propagation phenomena and adequate for most present applications in system planning,

recommends

1 that the prediction methods and other techniques set out in Annex 1 be adopted for planning

terrestrial line-of-sight systems in the respective ranges of parameters indicated.

Annex 1

1 Introduction

Several propagation effects must be considered in the design of line-of-sight radio-relay systems.

These include:

– diffraction fading due to obstruction of the path by terrain obstacles under adverse

propagation conditions;

– attenuation due to atmospheric gases;

2 Rec. ITU-R P.530-12

– fading due to atmospheric multipath or beam spreading (commonly referred to as

defocusing) associated with abnormal refractive layers;

– fading due to multipath arising from surface reflection;

– attenuation due to precipitation or solid particles in the atmosphere;

– variation of the angle-of-arrival at the receiver terminal and angle-of-launch at the

transmitter terminal due to refraction;

– reduction in cross-polarization discrimination (XPD) in multipath or precipitation

conditions;

– signal distortion due to frequency selective fading and delay during multipath propagation.

One purpose of this Annex is to present in concise step-by-step form simple prediction methods for

the propagation effects that must be taken into account in the majority of fixed line-of-sight links,

together with information on their ranges of validity. Another purpose of this Annex is to present

other information and techniques that can be recommended in the planning of terrestrial

line-of-sight systems.

Prediction methods based on specific climate and topographical conditions within an

administration’s territory may be found to have advantages over those contained in this Annex.

With the exception of the interference resulting from reduction in XPD, the Annex deals only with

effects on the wanted signal. Some overall allowance is made in § 2.3.6 for the effects of intra-

system interference in digital systems, but otherwise the subject is not treated. Other interference

aspects are treated in separate Recommendations, namely:

– inter-system interference involving other terrestrial links and earth stations in

Recommendation ITU-R P.452,

– inter-system interference involving space stations in Recommendation ITU-R P.619.

To optimize the usability of this Annex in system planning and design, the information is arranged

according to the propagation effects that must be considered, rather than to the physical

mechanisms causing the different effects.

It should be noted that the term “worst month” used in this Recommendation is equivalent to the

term “any month” (see Recommendation ITU-R P.581).

2 Propagation loss

The propagation loss on a terrestrial line-of-sight path relative to the free-space loss (see

Recommendation ITU-R P.525) is the sum of different contributions as follows:

– attenuation due to atmospheric gases,

– diffraction fading due to obstruction or partial obstruction of the path,

– fading due to multipath, beam spreading and scintillation,

– attenuation due to variation of the angle-of-arrival/launch,

– attenuation due to precipitation,

– attenuation due to sand and dust storms.

Each of these contributions has its own characteristics as a function of frequency, path length and

geographic location. These are described in the paragraphs that follow.

Sometimes propagation enhancement is of interest. In such cases it is considered following the

associated propagation loss.

Rec. ITU-R P.530-12 3

2.1 Attenuation due to atmospheric gases

Some attenuation due to absorption by oxygen and water vapour is always present, and should be

included in the calculation of total propagation loss at frequencies above about 10 GHz. The

attenuation on a path of length d (km) is given by:

dBdA aa

= (1)

The specific attenuation γa (dB/km) should be obtained using Recommendation ITU-R P.676.

NOTE 1 – On long paths at frequencies above about 20 GHz, it may be desirable to take into account known

statistics of water vapour density and temperature in the vicinity of the path. Information on water vapour

density is given in Recommendation ITU-R P.836.

2.2 Diffraction fading

Variations in atmospheric refractive conditions cause changes in the effective Earth’s radius or

k-factor from its median value of approximately 4/3 for a standard atmosphere (see

Recommendation ITU-R P.310). When the atmosphere is sufficiently sub-refractive (large positive

values of the gradient of refractive index, low k-factor values), the ray paths will be bent in such a

way that the Earth appears to obstruct the direct path between transmitter and receiver, giving rise

to the kind of fading called diffraction fading. This fading is the factor that determines the antenna

heights.

k-factor statistics for a single point can be determined from measurements or predictions of the

refractive index gradient in the first 100 m of the atmosphere (see Recommendation ITU-R P.453

on effects of refraction). These gradients need to be averaged in order to obtain the effective value

of k for the path length in question, ke. Values of ke exceeded for 99.9% of the time are discussed in

terms of path clearance criteria in the following section.

2.2.1 Diffraction loss dependence on path clearance

Diffraction loss will depend on the type of terrain and the vegetation. For a given path ray

clearance, the diffraction loss will vary from a minimum value for a single knife-edge obstruction to

a maximum for smooth spherical Earth. Methods for calculating diffraction loss for these two cases

and also for paths with irregular terrain are discussed in Recommendation ITU-R P.526. These

upper and lower limits for the diffraction loss are shown in Fig. 1.

The diffraction loss over average terrain can be approximated for losses greater than about 15 dB by

the formula:

dB10/20 1+−= FhAd (2)

where h is the height difference (m) between most significant path blockage and the path trajectory

(h is negative if the top of the obstruction of interest is above the virtual line-of-sight) and F1 is the

radius of the first Fresnel ellipsoid given by:

m17.3= 21

1df

F (3)

with:

f : frequency (GHz)

d : path length (km)

d1 and d2 : distances (km) from the terminals to the path obstruction.

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标签： #设计要求

摘要：

ITU-R P.530-12 是国际电信联盟无线电通信部门发布的核心技术标准，专门针对地面视距内微波通信系统的设计要求，提供详细的传播数据和预测方法。该标准涵盖了衰落、多径效应、雨衰减、大气吸收及折射等关键传播因素，帮助工程师在规划点对点链路时准确评估信号质量与可用性。通过应用ITU-R P.530-12，设计人员可以优化天线高度、频率选择及系统冗余，确保在高频段（如6至86 GHz）的无线传输中克服传播障碍，提升网络可靠性。无论是用于5G回传、固定无线接入还是广播传输，该标准都是实现高效链路预

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