1. Thailand, Bangkok, 18 – 21 October 2016
ICAO Handbook on Radio Frequency Spectrum Requirements for Civil Aviation
Workshops
Egypt, Cairo, 9 – 13 October 2016
Thailand, Bangkok, 18 – 21 October 2016
Robert Witzen
Loftur Jónasson

2. Introduction Volume I + Spectrum Management
Spectrum strategy - Provides for the long term of current and future spectrum usage of radio systems
ICAO policies on use of aeronautical spectrum to support the ICAO spectrum strategic objectives
ICAO position for future ITU WRC .
Volume II + Frequency Management
ICAO Frequency Assignment Planning
The Handbook Volume I addresses three main areas relating to Spectrum Management.
The first area is:
A description of the spectrum strategy which provides for the long term spectrum use for current and new radio communication and radio-navigation systems for International Civil Aviation. The availability of sufficient spectrum for aviation for air-ground communication and for radio navigation systems is of paramount importance to support in the near and longer future safe and efficient aircraft operations.
Second:
To support the spectrum strategy, ICAO has developed a policy, for each frequency band and for each system operating in any frequency band, the ICAO Policy. These policy statements are approved by Council. The policy statements are used by ICAO to defend the spectrum strategy as and where necessary.
And thirdly:
An ICAO position is developed for any ITU World Radio Communication Conference, to defend ICAO spectrum requirements which are specific to the frequency bands that are being reviewed at that particular WRC. The ICAO position, is developed by the Air Navigation Commission with the assistance from the Frequency Spectrum Management Panel and is expected to be used by States to formulate their views on matters that are discussed during the WRC. Normally, the ICAO position is a detailed sub-set of the total ICAO policy.

3. Vol. I – Overview of spectrum for aviation
This slides provides an overview of the Radio Frequency Spectrum that is allocated for use by aeronautical Radio Communication and Radio Navigation systems. {{
Traditionally the radio frequency spectrum is divided into frequency ranges, each 10 times larger than the previous one.
The two lowest [frequency] ranges shown on this slide, Low and Medium Frequency can be used quite far beyond line of sight, through ground wave propagation. Used for Aeronautical NDBs.
HF is mainly used for oceanic en-route communications. Long distance communications, traditionally rather unreliable.
VHF, here aviation alone uses more spectrum than is available altogether on HF. Very efficient, but any frequencies above HF are good for line of sight only.
UHF, small antennas, efficient, one could say that this is the frequency range that everyone covets. Aviation uses over 20% of the available resources in this range. The Mobile and WiFi industries keep a constant pressure on all possible allocations in this range.
SHF, more suitable for the requirements of high definition radar and satellite. The lower end of this range, including the radio-altimeter and the MLS band, is much coveted for mobile phone, WiFi and mobile satellite.
Aviation uses around 14% of the total available spectrum in the 0 – 16 GHz range, for aeronautical safety purposes.
(Air-Ground communications are shown in Red. Navigation applications are shown in Blue and Radar applications are shown in Green.) }}

4. Vol. II – Frequency assignment planning
Provides for globally harmonized frequency assignment planning criteria and guidance material to support the application of SARPs in Annex 10, Vol. V
Developed in conjunction with the revisions to Annex 10, Vol. V
Developed by the frequency Spectrum Management Panel (FMSP)
Implementation has been agreed through the relevant Regional eANP
Support the development of a frequency assignment plan which encompasses Global and Regional COM lists and the Global Air Navigation Plan
The purpose of the Volume II of the Handbook is to provide globally harmonized frequency assignment planning criteria for aeronautical radio communication and navigation systems.
These criteria facilitate the protection of ICAO standardized systems on a uniform and a Global basis. These criteria (revised compared to what was used in the Regions previously) also introduce flexibility in actual frequency assignment planning and support efficient use of the available spectrum. Volume II of the Handbook incorporates details on (more or less) recent developments on the use of the VHF band – 137 MHz, such as the introduction of 8.33 kHz channel spacing and air/ground data link.
The material in the Handbook Volume II was developed in conjunction with a revision of the SARPS in Annex 10 for VHF air/ground communication systems. Guidance material previously contained in Attachment A to Annex 10, Volume V has now been removed and relocated to the Handbook, Volume II. Additional relevant and more comprehensive material has been accommodated in the Handbook with the intention to not only provide for the revised frequency assignment planning criteria but also to explain how these criteria were developed. The revisions to Annex 10 are were adopted by Council in 2013
In order to provide a global forum for the development of the revised frequency assignment planning criteria for VHF sir-ground communication systems operating in the frequency band – 137 MHz, initially ACP Working Group F was given the task to coordinate and review the planning criteria. This activity is now being continued in the Frequency Spectrum Management Panel (FSMP). The material in the Handbook is an update to the planning criteria currently in use by the ICAO Regions and in this work due account was given to regional differences in the actual use of the frequency band – 137 MHz (e.g. Regional Frequency Allotment Plans).
The frequency assignment planning criteria presented in the Handbook, Volume II update the current criteria used in the ICAO Regions.
The frequency assignment planning criteria in the Handbook (Volume II) support the development of global frequency lists or COM lists (and in particular COM list 3) and a globally harmonized assessment of the compatibility of frequency assignments. One of the elements of the global frequency lists is to facilitate interregional coordination of frequency assignments.
Implementation on a Regional basis of the frequency assignment planning criteria as they are in the Handbook, Volume II, has been agreed through the eANP, as developed for each Region. (Regional ANP, Volume II, Part III (CNS). The eANP stipulates that, for the Aeronautical Mobile Service (AMS), frequencies should be assigned to all VHF aeronautical mobile service (AMS) facilities in accordance with the principles laid out in Annex 10, Volume V and the ICAO Handbook on Radio Frequency Spectrum Requirements for Civil Aviation (Doc. 9718) Volumes I and II, taking into account a number of principles as further identified in the eANP.

5. Vol. II – Frequency assignment planning Chapter 1 – General methodology (1)
General methodology for compatibility analysis
General model for compatibility assessment
Based on:
Protection of desired signal at receiver input
Not to exceed maximum permissible distortion of receiver output signal
The signal level at the receiver input can be calculated as the sum of the Transmitter power, Cable losses, Antenna gain and propagation loss of the radio signal on the path between the transmitter and the receiver. The D/U at the antenna input (or in space) is the same as at the receiver input. The D/U ratio, which is specified by ICAO (Annex 10) guarantees that the receiver performance is not degraded below acceptable limits when the D/U ratio is just met. When the D/U ratio is less than the minimum specified by ICAO, unacceptable distortion may be expected.

6. Vol. II – Frequency assignment planning Chapter 1 – General methodology (2)
Determine the desired signal level at receiver input
Determine the undesired signal level at receiver input
Determine the D/U ratio
If PD and PU are the same, D/U is LD -LU
Chapter 1 contains the general methodology to assess compatibility between the desired communication or navigation frequency and any undesired signal that may potentially cause harmful interference.
For all radio systems in Annex 10, ICAO has established a protection ratio (signals in space) that would provide adequate protection of these systems from harmful interference. These are intra-system protection requirements and cannot be applied when the spectral characteristics of the interfering signal differs from those of the desired signal.
The radio-frequency protection ratios (desired-to-undesired signal ratio) have been developed to ensure that the distortion of the output of an aeronautical communication or navigation receiver does not exceed the operationally acceptable values.
The desired-to-undesired signal ratio is an essential element of the frequency assignment planning criteria. The general model can also be used to establish compatibility requirements, through measurements, when the radio-frequency characteristics differ from the desired input (RF) signal.
The general model allows for the calculation of signal levels (at the antenna or at the receiver input) and to establish separation criteria (geographical or frequency) to be satisfied to protect the desired signal from harmful interference.

7. Vol. II – Frequency assignment planning Radio wave Propagation model
Based on free space propagation
(Re. Recommendation ITU-R P.525)
Propagation model does not accommodate certain phenomena which are difficult to predict such as
Changes in the refractive index of the atmosphere
Ducting
ITU has developed propagation curves for aeronautical communication and navigation systems (Recommendation ITU-R P.528)
Another essential element of the frequency assignment planning criteria is the radio-frequency propagation model that is to be applied. In aviation we normally use the free space propagation model as specified in Recommendation ITU-R P.525.
Propagation of radio waves is affected by the refractive index of the atmosphere and allows VHF frequencies to be received beyond the optical horizon. Radio line of sight normally employs a 4/3 Earth radius to calculate the distance (path) over which the propagation of the (VHF) radio signals can be considered with the free space propagation formulas. This complies with the so-called “standard atmosphere”. In aeronautical frequency assignment planning, variations of the refractive index are not considered. Similarly, temporary propagation phenomena such as ducting is not accommodated in frequency assignment planning.
The ITU has developed a set of aeronautical propagation curves for 125 MHz, 300 MHz, 1200 MHz and 5100 MHz. These may be used for a more precise estimation of the propagation of aeronautical radio frequencies. These curves are based on the IF-77 model and were developed in the late ninteenseventies. They basically apply to temperate regions, that is, between latitudes of about 25 – 55 degrees, north or south.

8. Vol. II – Frequency assignment planning Compatibility criteria for frequency coordination (1)
Frequency assignment planning criteria are to be considered as a generic technical measure to support frequency coordination.
Planning criteria provide for a rather conservative method to assign frequencies without causing harmful interference.
In most cases, a detailed technical analysis may result in reduced geographical separation being required.
Consideration of actual operational use
Frequency assignment planning criteria provide for a general method to achieve compatibility between the desired and potentially interfering (undesired) frequency assignments. A minimal set of technical characteristics is applied to facilitate actual frequency coordination.
Not many details are being used in a compatibility assignment, hence generally resulting in an actual over-protection of the desired frequency.
A detailed technical analysis taking into account the actual e.i.r.p. of both the desired and undesired stations, antenna systems used, effect of the terrain and actual propagation conditions, may in many cases result in reduced minimum required separation distances.

9. Vol. II – Frequency assignment planning Compatibility criteria for frequency coordination (2)
Frequency assignment plans may include frequency assignments which do not meet the planning criteria as agreed by ICAO
In many of such cases these frequency assignments may be considered operationally compatible
consideration of the operational use
absence of interference reports
consideration of the effect of the terrain.
as result of a detailed analysis of the technical characteristics of both the desired and undesired stations
Non-compatible identification in Frequency Finder
does not necessarily imply operational incompatibility
Actual operational use of a frequency assignment may result in interference being acceptable in some parts of the coverage of the desired station.
Separation based on the radio-horizon method, where the undesired station is at or beyond the radio horizon of the desired station is based on the assumption that it is unlikely that two aircraft are at the same time at the maximum height of the coverage or the respective desired and undesired station and at the closest point of the coverage of these stations (Annex 10).
Actual use of frequency assignments that do not meet the minimum ICAO separation criteria may not have resulted in interference reports.

10. Vol. II – Frequency assignment planning Compatibility criteria for frequency coordination (3)
A station that is considered “Not Compatible” because it does not meet the ICAO frequency assignment planning criteria is not, by default, also operationally “Not Compatible” .
Frequency Finder displays geographical areas where interference is predicted to support a more detailed analysis.