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63 Proceedings of WFMN07, Chemnitz, Germany
WFMN07_II_B3, pp. 63-67 http://archiv.tu-chemnitz.de/pub/2007/0210/
Abstract—The Radiocommunication Sector of the International
Telecommunication Union (ITU) develops Recommendations
providing information and propagation prediction methods for
various telecommunication services. This paper presents the
Recommendations concentrating on the work carried out in ITU
Study Group 3 “Radiowave Propagation”, in particular on
Recommendations for terrestrial point-to-area services, such as
terrestrial broadcasting and land mobile services. The respective
Recommendations cover propagation in the VHF and UHF range,
short range indoor and outdoor services in the frequency range
from 1 to 100 GHz and point-to-multipoint (e.g. WiMAX) services
in the frequency range of 3 to 60 GHz.
Index Terms—field strength prediction, point-to-area services,
propagation curves, radiowave propagation
I. INTRODUCTION
ITU is the leading United Nations agency for information
and communication technologies. As the global focal point for
governments and the private sector, ITU's role in helping the
world communicate spans 3 core sectors: radiocommunication,
standardization and development. ITU also organizes
TELECOM events and was the lead organizing agency of the
World Summit on the Information Society.
ITU is based in Geneva, Switzerland, and its membership
includes 191 Member States and more than 700 Sector
Members and Associates.
II. ITU-R RADIOCOMMUNICATION SECTOR
The mission of the ITU Radiocommunication Sector is,
inter alia, to ensure rational, equitable, efficient and
economical use of the radio-frequency spectrum by all
radiocommunication services and to carry out studies and
adopt recommendations on radiocommunication matters.
The ITU Radiocommunication Sector specializes in
facilitating international collaboration to ensure the rational,
equitable, efficient and economical use of the radio-frequency
spectrum and satellite orbits, by:
- holding World and Regional Radiocommunication
Conferences to expand and adopt Radio Regulations and
Regional Agreements covering the use of the radio-
frequency spectrum;
- establishing ITU-R Recommendations, developed by ITU-R
Study Groups (SG) in the framework set by
Radiocommunication Assemblies, on the technical
characteristics and operational procedures for
radiocommunication services and systems;
- coordinating endeavours to eliminate harmful interference
between radio stations of different countries;
- maintaining the Master International Frequency Register;
and
- offering tools, information and seminars to assist national
radiofrequency spectrum management.
III. ITU-R STUDY GROUPS
The work is organized in Study Groups. More than 1 500
specialists, from telecommunication organizations and
administrations throughout the world, participate in the work
of the Study Groups concerned with:
- drafting technical bases for Radiocommunication
Conferences
- developing Draft Recommendations
- compiling Handbooks
ITU-R Study Groups are established and assigned study
Questions by a Radiocommunication Assembly to prepare
draft Recommendations for approval by ITU Member States.
Compliance with ITU-R Recommendations is not
mandatory. However, since they are developed by well-
respected radiocommunication experts from all over the world,
they enjoy a high reputation and are implemented worldwide,
getting therefore the status of international standards in their
domain of application.
Studies focus on the following:
- efficient use of the spectrum/orbit resource by space and
terrestrial services;
- characteristics and performance of radio systems;
- operation of radio stations;
- radiocommunication aspects of distress and safety matters.
ITU-R Study Groups also carry out preparatory studies for
World and Regional Radiocommunication Conferences. On
the basis of the input material from the Study Groups the
Conference Preparatory Meeting prepares a Report on the
technical, operational and regulatory or procedural matters to
be considered by a given Conference.
ITU Field-strength prediction methods for
terrestrial point-to-area services Rainer Grosskopf
Institut für Rundfunktechnik, Floriansmühlstraße 60, D-80939 München, Germany
64 Proceedings of WFMN07, Chemnitz, Germany
WFMN07_II_B3, pp. 63-67 http://archiv.tu-chemnitz.de/pub/2007/0210/
At present, there are seven Study Groups specializing in the
following areas:
- SG 1 Spectrum management
- SG 3 Radiowave propagation
- SG 4 Fixed-satellite service
- SG 6 Broadcasting services
- SG 7 Science services
- SG 8 Mobile, radiodetermination, amateur and related
satellite services
- SG 9 Fixed service
Subgroups, such as Working Parties (WP) and Task Groups
(TG) are established to study the Questions assigned to the
different Study Groups.
IV. STUDY GROUP 3 – RADIOWAVE PROPAGATION
Chairman: Mr. B. Arbesser-Rastburg (European Space
Agency)
Scope: Propagation of radio waves in ionized and non-
ionized media and the characteristics of radio noise, for the
purpose of improving radiocommunication systems.
The following four Working Parties carry out studies on the
Questions assigned to Study Group 3:
WP 3J - Propagation
fundamentals
Chairman: M. Pontes
(Brazil)
WP 3K - Terrestrial point-
to-area propagation
Chairman: R. Grosskopf
(Germany)
WP 3L - Ionospheric
propagation
Chairman: J. Wang (USA)
WP 3M - Terrestrial point-
to-point and Earth-space
propagation
Chairman: C. Wilson
(Australia)
The principal aim of the Working Parties is to draft
Recommendations in the ITU-R P Series for subsequent
adoption by Study Group 3, and approval by the Member
States. The Working Parties also develop Handbooks, which
provide descriptive and tutorial material, especially useful for
developing countries. A further task of the Working Parties is
to provide, through Study Group 3, propagation information
and advice to other ITU-R Study Groups in their preparation
of the technical bases for Radiocommunication Conferences.
Such information typically concerns identifying relevant
propagation effects and mechanisms, and providing
propagation prediction methods. The predictions are needed
for the design and operation of radiocommunication systems
and services, and also for the assessment of frequency sharing
between them.
V. ITU-R WORKING PARTY 3K – POINT-TO-AREA
PROPAGATION
Chairman: Mr. R. Grosskopf, Germany
WP 3K is responsible for developing prediction methods for
terrestrial point-to-area propagation paths. In the main, these
are associated with
- terrestrial broadcasting and mobile services
- short-range indoor and outdoor communication systems
(e.g. Wireless Local Area Networks)
- point-to-multipoint wireless access systems
In the following an overview is given on the ITU-R
Recommendations in the responsibility of Working Party 3K.
To find the respective Recommendation providing information
for a particular application it is best to look into
Recommendation ITU-R P.1144 “Guide to the application of
the propagation methods of Radiocommunication Study
Group 3”.
WG 3K developed and maintains the Handbook on
Terrestrial Land Mobile Radiowave Propagation. This
Handbook gives the technical basis for predicting radiowave
propagation in terrestrial point-to-point, point-to-area, and
point-to-multipoint mobile networks.
P.528 Propagation curves for aeronautical mobile and
radionavigation services using the VHF, UHF and SHF bands
This Recommendation provides propagation curves for the
above mentioned services. The Recommendation has not been
changed since 1986.
P.1406 Propagation effects relating to terrestrial land mobile
service in the VHF and UHF bands
Basic information is given on:
- Attenuation due to land cover
- Signal strength variability (shadowing, local reflections)
- Delay spread (local and large distance scatterers)
- Antenna effects (height gain, polarisation diversity)
- Portable effects (body loss)
- Temporal variations
VI. VHF AND UHF BANDS
In the VHF and UHF bands, field strength prediction takes
account of the effects of terrain in the vicinity of the
transmitter and receiver, and of the refractive nature of the
atmosphere. Allowance is also made for location variability for
land area coverage prediction with account taken of local
clutter surrounding the receiver. Consideration is also given to
mixed paths crossing both land and sea.
P.1546 Method for point-to-area predictions for terrestrial
services in the frequency range 30 MHz to 3 000 MHz
A consolidated prediction procedure has been developed,
suitable for broadcasting, land mobile, maritime mobile and
certain fixed services (e.g. those using point-to-multipoint
systems), allowing the appropriate values of antenna height
and path distance to be applied. Such a prediction procedure
represents a major tool for the frequency planning of
broadcasting and mobile services, particularly in the range 1-3
GHz, and for coordination when frequency sharing is involved.
This Recommendation provides a path general propagation
prediction method based on propagation curves (Fig.1) for
- Frequencies 100, 600, 2000 MHz
- Effective transmitting/base antenna heights
- Time percentage 50%, 10%, 1%
65 Proceedings of WFMN07, Chemnitz, Germany
WFMN07_II_B3, pp. 63-67 http://archiv.tu-chemnitz.de/pub/2007/0210/
- Land, sea (cold, warm)
Field strength for a certain distance can be achieved by
inter- and/or extrapolation between the respective propagation
curves. Corrections can be calculated for
- receiving/mobile antenna heights
- ground cover types at receiving location
- location percentages (location variability)
- indoor reception (building entry loss)
- site shielding, e.g. terrain clearance angle
Fig.1 Field strength versus distance curve
P.[Path specific] A path specific propagation prediction
method for point-to-area terrestrial services in the VHF and
UHF band
A Draft New Recommendation was drafted in April 2007
providing a path specific propagation prediction method where
a terrain profile is needed. This propagation prediction method
takes account of the following model elements:
- line-of-sight;
- diffraction (embracing smooth-Earth, irregular terrain and
sub-path cases);
- tropospheric scatter;
- anomalous propagation (ducting and layer
reflection/refraction);
- height-gain variation in clutter;
- location variability;
- building entry losses.
The prediction procedure requires two radio-meteorological
parameters to describe the variability of atmospheric
refractivity.
- ∆N (N-units/km), the average radio-refractive index lapse-
rate through the lowest 1 km of the atmosphere, provides
the data upon which the appropriate effective Earth radius
can be calculated for path profile and diffraction obstacle
analysis (Fig. 2).
- N0 (N-units), the sea-level surface refractivity, is used only
by the troposcatter model as a measure of variability of the
troposcatter mechanism (´Fig. 3).
Global maps of ∆N and N0, and data files containing the
digitized maps are available.
Fig. 2 Average annual values ∆N
Fig. 3 Sea-level surface refractivity N0
VII. FREQUENCY RANGE ~1 TO 100 GHZ
At higher frequencies (typically from around 1 to 100 GHz),
the emphasis is on short-range systems, either indoor or
outdoor, as might be used by WLAN and personal mobile
communications.
P.1411 Propagation data and prediction methods for the
planning of short-range outdoor radiocommunication systems
and radio local area networks in the frequency range 300
MHz to 100 GHz
The Recommendation describes the relevant propagation
mechanisms such as reflection, scattering and diffraction
associated with buildings which give rise to effects such as
attenuation and multipath. The latter plays a vital part in the
channel modelling of a radio link, with which an assessment of
performance quality may be obtained. Models are developed
describing different types of environment (urban to rural) and
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66 Proceedings of WFMN07, Chemnitz, Germany
WFMN07_II_B3, pp. 63-67 http://archiv.tu-chemnitz.de/pub/2007/0210/
expressions are developed for quantifying the resulting path
loss.
Environments described in this Recommendation are
categorized solely from the radio propagation perspective.
Radiowave propagation is influenced by the environment, i.e.
building structures and heights, the usage of the mobile
terminal (pedestrian/vehicular) and the positions of the
antennas. Four different environments are identified,
considered to be the most typical, these are urban high-rise,
urban/suburban low-rise, residential and rural.
Different cell types depending on cell radius and typical
position of the base station antenna are defined. Physical
operating environments and the respective propagation
impairments by building heights, trees, traffic and street width
are described, as well as path categories for propagation over
rooftops, along street canyons or for line-of-sight paths. For
these scenarios models are given to evaluate path loss and the
characteristics of multipath, polarization, direction of arrival
and fading.
P.1238 Propagation data and prediction methods for the
planning of indoor radiocommunication systems and radio
local area networks in the frequency range 900 MHz to 100
GHz
Indoor wireless communication services can be
characterized by the following features:
- high/medium/low data rate
- coverage area (e.g. room, floor, building)
- mobile/portable/fixed
- real time/non-real time/quasi-real time
- network topology (e.g. point-to-point, point-to-multipoint,
each-point-to-each-point)
Propagation impairments in an indoor radio channel are
caused mainly by reflection from, and diffraction around,
objects (including walls and floors) within the rooms,
transmission loss through walls, floors and other obstacles,
channelling of energy, especially in corridors at high
frequencies and motion of persons and objects in the room.
These effects give rise to impairments such as path loss,
temporal and spatial variation of path loss, multipath effects
from reflected and diffracted components of the wave and
polarization mismatch due to random alignment of mobile
terminal.
ITU-R P.1238 gives information on path loss calculation
(site general), delay spread models (impulse response,
statistical models, site specific models), effect of polarization
and antenna radiation pattern, effect of building materials,
furnishings and furniture, effect of movement of objects in the
room and angular spread models.
P.[time and spatial profile] The prediction of the time and the
spatial profile for broadband land mobile services using UHF
and SHF bands
This Draft New Recommendation describes empirical
models for time and spatial profiles that are valid for a
frequency range from 0.7 GHz to 9 GHz. It is based on
measurements in both urban and suburban environments.
Broadband mobile systems have a focus to use techniques such
as multi-input-multi-output and adaptive array antenna.
Temporal and spatial profiles of multipath are fundamental
parameters for the study of those new techniques. Those
profiles are also influenced by propagation conditions such as
length and properties of the propagation path.
The delay profile and the arrival angular profile are
fundamental parameters for evaluating the multipath
characteristics. Once the profiles are modelled, multipath
parameters such as delay spread and correlation bandwidth, or
arrival angular spread and spatial correlation distance can be
derived from the profiles.
P.1791 Propagation prediction methods for assessment of the
impact of ultra-wideband devices
This Recommendation provides methods valid for a
frequency range from 1-10 GHz to calculate an ultra-wideband
(UWB) path loss in indoor and outdoor operating
environments for line-of-sight (LoS) and obstructed path
categories and to assess the power received by a conventional
narrow-band receiver from a UWB transmitter.
VIII. POINT-TO-MULTIPOINT
With the growing interest in delivery of broadband services
through local access networks, WP 3K studies the propagation
effects associated with millimetric radio systems (e.g.
operating around 3-60 GHz) used for point-to-multipoint
distribution. The frequency range was recently extended down
to approximately 3 GHz to cover WiMAX.
P.1410 Propagation data and prediction methods required for
the design of terrestrial broadband radio access systems
operating in a frequency range from 3 to 60 GHz
Prediction of area coverage has to address the effects of
buildings, their spatial distribution, attenuation and scattering
from vegetation, and attenuation by rain. Methods to quantify
the relevant propagation effects such as attenuation, and
distortion due to multipath, are a key area of study in WP 3K.
The Recommendation provides methods to calculate area
coverage (building blockage) by ray tracing or statistical
methods, vegetation attenuation, effects of precipitation on
availability (route diversity improvement with 2 base stations)
and propagation channel distortion by frequency selective
vegetation attenuation and multipath from reflections.
IX. FUTURE TASKS
An ongoing important task for Working Party 3K is to
improve existing Recommendations, either based on inputs
from member organisations or through liaisons with other
ITU-R Study Groups requesting for guidance on propagation
problems for new or existing services.
Working Party 3K is progressing toward Recommendations
that allow smooth transitions of propagation predictions:
- from short-path to long-path situations;
- from terrestrial broadcasting and terrestrial mobile to
combined situations;
67 Proceedings of WFMN07, Chemnitz, Germany
WFMN07_II_B3, pp. 63-67 http://archiv.tu-chemnitz.de/pub/2007/0210/
- and from first-order propagation predictions (site general)
to more detailed and accurate predictions (site specific)
based upon terrain and surface features.
It is believed this progression will produce better
Recommendations that will be easier for the service Study
Groups to utilize and provide better results. There is also a
need to extend the frequency range of point-to-area prediction
methods up to approximately 6 GHz for future terrestrial
services.
Another important issue is the development of a new
Recommendation on the effect of objects such as buildings or
vegetation, generally termed “clutter”.
REFERENCES
ITU homepage at http://www.itu.int/ITU-R/ in particular
brochure on ITU-R Study Groups http://www.itu.int/ITU-
R/study-groups/docs/brochure-sg-en.pdf