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4C/146 (Annex 8)-E
/International Civil Aviation Organization
WORKING PAPER / ACP/WGF 20/WP 18
24/03/09
AERONAUTICAL COMMUNICATIONS PANEL (ACP)
18TH MEETING OF THE WORKING GROUP F
Montreal, Canada, 24 March – 3 April 2009
Agenda Item x:Proposed modification to the work related to the ITU-R methodology for estimation of spectrum requirements of satellite systems operating in the AMS(R)S, under AI 1.7.
Presented by Eric Allaix (DGAC/DSNA) and Tony Azzarelli (European Space Agency)
Prepared by Tony Azzarelli with the help of Catherine Morlet (ESA)
SUMMARYThis document provides an update for the WP4C work on the ITU-R Recommendation for a methodology to derive spectrum requirements of satellite system operating in AMS(R)S.
The revisions try to correct editorial text and also propose to modify the definitions, based on comments made at the last WP4C meeting.
ACTION
The ACP WG-F is invited to consider the changes proposed in this document and prepare an ICAO contribution to the next WP4C, which is relevant to the assessment of aviation requirements and derivation of the information volume required by aviation services within a given airspace region.
Such contribution may also consider a response to the questions and comments made by ITU-R WP4C and sent to ICAO.
Radiocommunication Study Groups /
Source: Document 4C/TEMP/47(Rev.1)
Reference: Documents 4C/89, 125, 131, 138 / Annex 8 to
Document 4C/146-E
20 October 2008
English only
Annex 8 to Working Party 4C Chairman’s Report
Working document towards a PRELIMINARY draft new
Recommendation ITU-R M.[AMS(R)S spectrum]
Methodology for the estimatingon spectrum requirements of satellite systems operating in of the aeronautical mobile-
satellite (R) service spectrum requirements
[Summary]
TBD
[Scope]
TBD
The ITU Radiocommunication Assembly,
considering
a) that aeronautical mobile satellite (Route) service (AMS(R)S) is an essential element of ICAO Communication Navigation and Surveillance (CNS)/Air Traffic Management (ATM) to provide safety and regularity of flight in civil aviation;
b) that AMS(R)S communications for CNS/ATM services are today being provided in the bands 1545-1555MHz and 1646.5-1656.5 MHz under footnote No. 5.357A;
c) that the International Civil Aviation Organization (ICAO) has adopted Standards and Recommended Practices (SARPs) addressing satellite communications with aircraft in accordance with the Convention on International Civil Aviation;
d) that ICAO and other aviation bodies have developed documentation describing the long-term AMS(R)S communication services;
e) that ICAO and other aviation bodies have developed studies and documents for the long-term flight forecast;
f) that existing satellite systems provide AMS(R)S communications and that new satellite systems around the world are being developed to support the long-term AMS(R)S communication requirements,
recognizing
a) that Resolution 222 (Rev.WRC-07) invited ITU-R to study the existing and future spectrum requirements of the AMS(R)S,
recommends
1 that the methodology described in Annex 1 should be used for the estimation of the spectrum requirements of the AMS(R)S communications.
Annex 1
General Introduction to Methodology
In order to estimate the required spectrum for AMS(R)S communications in the framework of Resolution 222 (Rev.WRC-07), the following steps (see figure A1) are envisaged:
(a) Estimation of the AMS(R)S communication needs, described in Annex 2;
(b) AMS(R)S satellite system characteristics (including techniques for efficient use of spectrum) necessary for meeting the needs identified in (a);
(c) Use of the methodology described in Annex 3 and 4 to derive the AMS(R)S spectrum requirements by combining the needs identified in (a) with the satellite communication characteristics identified in (b).
The following conditions should be determined prior to the estimation of the spectrum requirements, e.g.:
– Target year;
– Airspace considered;
– Type of satellite system to be considered.
It is noted that the methodology in this document deals only on a single satellite system basis covering a given region of the world.
Figure A1
Methodology to derive spectrum requirements for AMS(R)S
Annex 2
Aviation communication needs
Aeronautical communication needs will depend on the aggregated information volume throughput (i.e. the total aggregated data and voice requirements) for all aircraft in a certain airspace region and over at a given certain time. In order to estimate these communication needs, knowledge of the following is required:
• flight movements over the area of interest;
• communication needs on a per-aircraft basis.
A2.1 Flight movements
Information on flight movements is required to evaluate the number of aircraft located within a given area (e.g. airspace region) at any given time. The information can be based on the actual air traffic statistics, and/or on forecasts of future traffic over a given certain airspace region. Such statistics are normally compilesd by the relevant aviation authorities, e.g. Eurocontrol for the European reagion.
A2.2 Communication needs of a single aircraft
The AMS(R)S communication needs of a single aircraft will in general depend from several factors, such as the airspace scenarioregion, operational concept, air traffic services provided overfor each different aircraft flight phase and position.
Identification and quantitative characterization of these communication needs is a complex matter and has been considered by different aviation bodies. For example, the ICAO Aeronautical Communication Panel (ACP) has recommended as guidance for the assessment of future communication requirements the “Communications Operating Concept and Requirements for the Future Radio System, Version 2 (COCR V2)”, developed by Eurocontrol and FAA. COCR V2 describes in detail the aviation communication services required by of aeach single aircraft in different each air space domains and flight phases, and is would be a suitable basis for the purpose of the assessment described in this document.
A2.3 Communication needs of multiple aircrafts
The cumulative communication needs over a given airspace area region and a given time frame can be obtained by combining the information on flight movements in that area and time frame (section A2.1) with the information on the communication needs of a single aircraft (section A2.2).
This Annex describes two methods of performing the combination of the above information. One method is based on a simulation approach (See section A2.3.1) and the other on a Peak Instantaneous Aircraft Count (PIAC) approach (See section A2.3.2). The difference between these two methods occurs at in the level of inputsdata required, i.e. one considers a flight by flight and time iterated communication simulation and the other relies on estimation of the maximum number of aircraft over a given airspace regionin view and the average communication rate information volume per aircraft.
A2.3.1 Simulation method
The simulation method relies on the simulation of flight movements over a given airspace region S (see Fig. A2 below) and for each flight the communications needs are simulated based on the COCR V2 requirements.
With this approach the following steps are performed, first to determine the instantaneous information volume over small airspace cells (S; e.g. 1º´1º) this has been defined as the Required Information Volume (RIV) and secondly over a larger area (e.g. either S or the area of a spot beam ) determine the Maximum Information Volume (MIV) from the RIVs. It is the MIV, as we will see, that drives the spectrum requirements for AMS(R)S.
Figure A2: Definition of airspace region S, unit area DS and spot beam area s.
Required Information VolumeThroughput (RIVT)
Given any airspace region area S subdivided into smaller cells S, the “Required Information Throughput” (RIVT) over the cell DS is defined as the instantaneous totalcumulative information volumethroughput at time t , aggregated over of all the N aircraft flying within DS. RIVT is a function of time, and of the airspace area S,. and the communication requirements per each flight. It can be calculated as follows:
RIVT(t; DS) = ∑ (i = 1 .. n) Ri(t; DS) (1)
where n is the number of aircraft transmitting at time t in area DS, with n = n(t; DS)
Ri(t; DS) is the data throughput (bps) generated by the ith aircraft at time t.
The individual simulated Ri(t; DS) can be easily derived from the COCR V2.
In general, n = n(t; S) ≤ N
This can be simplified further by assuming that all the throughputs are at the same channel data rate R (Mbit/s), i.e.:
RIT(t; S) = R ∙ n(t;S) (2)
where the data rate R depends only on the AMS(R)S communication needs of a single aircraft. This can be easily derived from the information throughput per aircraft (for example derived from the COCR V2) where the maximum value is selected, thereby ensuring that all of the AMS(R)S communications defined in the information throughput per aircraft are transmitted appropriately when required.
Figure A32 below shows how the RITV is derived.
Figure A32
Calculation of the RITRIV over a given airspace area DS
Maximum Information VolumeThroughput (MIVT)
Given a smaller airspace region area ss (for example the coverage of a satellite spot beam which has been divided into smaller cells ΔSk) within the area S under study (see Fig. A2), it is possible to calculate the total RIV in this smaller airspace region ss , i.e. RIV(t; ss), by integrating the individual RIV(t; ΔSk) functions over such area, i.e.:
RIV(t; ss) = ∑k RIV(t; ΔSk) , " ΔSk Í ss (2)
With this we derive
From this RIV(t; ss) irspace region,and thus we can define a new parameter called Tthe “Maximum Information VolumeThroughput” (MIVT) is defined as the maximum value of the RIV(t; ss)T(t;S) over the time interval of observation and over the area of interest ss, i.e.: (see also Eq. 2):
MIVT(Sss) = max(t) RIVT(t;Sss) (3)
= R max(t) n(t;S)
= R nmax
Where nmax is the maximum over the time period of the n(t; S).
Hence the MIVT((ssS) represents the peak information volumethroughput requirement over area the airspace region ssS during the interval for which RIVT has is been derived. This value will in all effect occur at the busiest time within the time interval of interest.
From the The MIVT we can then derive can be used as an input to calculate the overall spectrum needs over f area the airspace region ssS, when for example ss S is served by a single satellite beam, or even a cluster of beams for which frequency reuse is not possible.
In some cases ss = S, which is the case where either a single satellite beam serves the area S, or even a cluster of beams that cannot reuse frequencies over area S.
This MIV parameter will be used in Annex 3 and Annex 4 as input to the methodology to derive the spectrum requirements.
It is from the MIT that the spectrum requirements within airspace area S can be derived, and this will be seen in Annex 3 and Annex 4.
In general, if area S is the union of two non-overlapping areas S1 and S2, the following relations apply:
RIT(t;S) = RIT(t;S1) + RIT(t;S2) (4)
and
MIT(S) ≤ MIT(S1) + MIT(S2) (5)
RIT of unit area DSkAdditional Remarks
As mentioned above, MIVT(ssS) can be used as an input to calculate the spectrum requirements of an area airspace region ssS entirely contained within a single satellite beam, or a cluster of beams where frequency reuse is not possible.
Similarly, when an area is served by a large number of spot beams and thus it may be possible to reuse frequencies, then we would repeat the above calculations deriving several MIVs (e.g. for each spot beam). In Annex 3 the methodology to derive the overall spectrum requirements for AMS(R)S uses such generic approach.with known area ss, the respective MIT(ss) can be used as inputs to the process that calculates the spectrum requirements seen in Annex 3.
When the spot beam architecture is not known a priori and/or when several different beam arrangements are under consideration, it may not be possible to identify which MIT value(s) would be required as input(s) for the spectrum calculation. In such cases, it can be convenient to subdivide S in “small” areas DSk (that are areas significantly smaller than any of the potential spot beams) and calculate RIT (t; DSk) for each of the small areas DSk. (See Figure A3).
Figure A3
Area S, unit area DS and spot beam area (s)
Once the RIT(t; DSk) have been calculated for each of the DSk in the given area S, they can then be used to obtain the MIT for any given spot beam ss of interest, as follows:
MIT (ss) = max(t) RIT(t;ss) (6)
where:
RIT(t; ss) = ∑k RIT(t; ΔSk) , " ΔSk Í ss (7)
A2.3.2 PIAC method
The PIAC (Peak Instantaneous Aircraft Count) is defined as the maximum, over a specified period, of the instantaneous count of aircraft present over a given airspace regionarea S, i.e.:
PIAC (S) = max(t) N(t; S) (8)
= Nmax
where N(t;S) is the total number of aircraft flying over the airspace region S at time t
Nmax is the maximum of the N(t; S).
The information on flight movements is captured in a single parameter, i.e. the PIAC itself. The information on the communication needs of the aircraft is also captured by a single parameter, i.e. the average communication throughput volume r (S) per aircraft in a specified duration and within a given airspace S.
From the knowledge of the flight phases (section A2.1), it is possible to derive the average communication throughput volume per aircraft r(S), over a given region of airspace S, in a specified duration. This is done as follows: if each of the communication profile per flight can be written generically as R(t; S), then its time average can be expressed as:
r (S) = average(t) R(t; S) (9)
This can be either derived by simulations, or by statistical approach.
Hence, given PIAC(S) and r(S), the Maximum Information VolumeThroughput PIAC (MIVTPIAC) is then simply calculated as:
MIVTPIAC(S) = PIAC(S) · r(S) (10)
In general, if MIVTSIM is defined by the MIVT derived with the simulation approach of section A2.3.1, then it is easy to show that MIVTPIAC(S) and MIVTSIM(S) are very similar to each other, to the extent that they might be almost equal.
Estimation of the PIAC and r(S) for AMS(R)S communications
The procedures to estimate the MIVTPIAC(S) defined above is based on the estimation of the PIAC and the average data rate r(S), for AMS(R)S communications in a specific airspace (S) and in the year (Y) to be considered.