ACP/WGF 19/WP 12 International Civil Aviation Organization 09/09/08
WORKING PAPER
AERONAUTICAL COMMUNICATIONS PANEL (ACP)
19TH MEETING OF THE WORKING GROUP F
Montreal, Canada, 15 – 19 May 2008
Agenda Item x : Calculation of Aviation Communications Needs for AI 1.7
Proposed Aviation Parameters for Methodology to estimate required spectrum for the AMS(R)S communications
Presented by Tony Azzarelli (European Space Agency) Document supported by the following organizations: ANFR, CNES, DECEA/Brazil, DGAC/France, HCAA/Greece, JCAB/Japan, TAS/France
SUMMARY The ITU-R under AI 1.7 (WRC-11) will be estimating the current and future spectrum requirements for AMS(R)S satellite systems. This paper proposes that the aviation inputs to this process are estimated by the aviation community and then presented to ITU-R WP4C for the subsequent calculation of aviation spectrum under this AI.
ACTION It is proposed that: (1) WGF approves the process of calculation of the aviation communication throughout over a given region as given in this document;
(2) Proposes that ICAO sends this document to the next WP4C meeting, proposing that the aviation communications needs estimated with the process given in this document are accepted by WP4C as an input for the estimation of the aviation spectrum requirements under AI 1.7, and also ask WP4C for comments;
(3) WGF asks the aviation community to contribute in the estimation of the aviation communication throughput in different region of the world.
(31 pages) 051e4c35306321ec6199a4ed523b7f51.docproposed changes to AI 1.7 position ACP/WGF 19 WP12 2 3 ACP/WGF 18/WP-12
Proposed Aviation Parameters for Methodology to estimate required spectrum for the AMS(R)S communications
ITU-R WP4C has proposed to work on a methodology to estimate the spectrum requirements of AMS(R)S under AI 1.7 of WRC-11, ICAO is requested to contribute to these activities under ITU-R Res. 222 (WRC-07).
This document is proposing elements that ICAO ACP WGF could contribute to support the work of WP4C.
1. Elements to estimate spectrum requirements for AMS(R)S In order to estimate the required spectrum for AMS(R)S communications as requested by ITU-R Res. 222 (WRC-07), the following steps are suggested:
(a) ICAO ACP WGF: Identifies the aeronautical communication needs and provides these requirements to the ITU-R WP4C;
(b) ITU-R WP4C: Identifies and proposes the satellite system characteristics necessary for implementing aeronautical safety communication services (including techniques for efficient use of spectrum);
(c) ITU-R WP4C: Proposes a methodology to combine the aeronautical communication needs in (a) with the satellite communication characteristics in (b) to derive the required spectrum for AMS(R)S under WRC-11 AI 1.7.
This document proposes a way to identify, derive and propose the aeronautical communication needs as above in task (a).
2. Identification of the aeronautical communication needs Aeronautical communication needs will depend on the aggregate information throughput accumulated over all aircraft in a certain region and a certain instant of time. These can be estimated by: the flight movements over a certain airspace; and the communication needs per single aircraft or flight basis. ACP/WGF 19 WP12 4
2.1 Flight Movements To identify the aeronautical communication needs it is necessary to evaluate the number of aircraft occupation within a certain airspace area. This can be derived based on the actual air traffic statistics, or by predicting, the future flight movements over a certain region1. For example, to provide usable data for a satellite system, the model could considers areas of airspace units smaller than the typical spot beam area, e.g. air space of 1 deg by 1 deg. For example, Figure 1 below shows the concept above on the aircraft count (called Peak Instantaneous Aircraft Count (PIAC), i.e. the maximum of the instantaneous number of aircraft), counted over a period of 1 day for each and per each 1 deg by 1 deg cell areas over Europe.
Figure 1: Example of Peak Instantaneous Aircraft Count (PIAC) calculated for each 1deg by 1 deg area cells (forecast year 2025)
2.2 Communication needs of a single aircraft In addition to the flight movements, we also need to consider aviation communication needs on a single aircraft basis via a satellite infrastructure, which will depend on the aircraft flight phase and its position, as for example shown in Figure 2.
1 For example in Europe these are found in documentation developed by Eurocontrol, i.e. http://www.EUROCONTROL.int/statfor/gallery/content/public/forecasts/Doc216%20LTF06%20Report %20v1.0.pdf 5 ACP/WGF 18/WP-12
This is a complex matter and has been considered by different aviation bodies. For example Eurocontrol and FAA have developed the “Communications Operating Concept and Requirements for the Future Radio System, Version 2 (COCR V2)”, which is considered by ICAO/ACP as the basis of the Future Communication Infrastructure system concept. COCR V2 describes in details the aviation communication services of a single aircraft in different air space domains and flight phases, thus is a good basis to use for the proposed elements of this document.
cruise
arrival departure flight path / phases
at airport at airport
Amount of data From one flight
airport departure cruise arrival airport
time
begin end
Figure 2: Qualitative example of communications for a single flight through different domain and flight phases
2.3 Combining flight movements with communication needs In this section we address the cumulative aviation needs over a given area and a given time frame. This is obtained from the combinations of the flight movements as we have seen in section 2.1 above with the communication needs as we have seen in section 2.2 above.
This document proposes two ways of estimating aviation communication traffic by combing (1) flight movement data with (2) communication throughout per aircraft per flight. These two methods are very similar and are described in the Annex.
2.3.1 Simulation Approach Method The general model provided in the Annex can be summarized by the following Figure 3, where, for each individual flight movement over the given airspace area, the instantaneous ACP/WGF 19 WP12 6 communications destined to be served by a satellite infrastructure are aggregated at each time step to provide the total instantaneous information throughput over the given area. The aggregated information throughput, called Required Information Throughput (RIT), is given in the bottom plot of Figure 3, and it is a function of time t and space s, i.e. RIT(t, s). The bandwidth requirements are then driven by the maximum of the RIT, called Maximum Information Throughput (MIT), and it is from this that WP4C can derive the spectrum requirement of a satellite infrastructure covering the area s.
Because satellite systems can employ spot beams, the MIT must be provided on a beam by beam basis and since the spot beams are not known a-priory then it is possible to calculate the MIT a-posteriory by: a. giving the RIT in areas S smaller than a typical spot beam area ; b. and then aggregating the RIT(t; S) over the area .
flight - 1
time
flight - 2
time
... flight - i
time
...
flight - N
time
Total instantaneous throughput
time
00:00 24:00 Figure 3: Calculation of the total information throughput over a service area and over the busiest day of the year. 7 ACP/WGF 18/WP-12
2.3.2 PIAC Approach
The Annex also describes a method to estimate the aviation communication needs over a given airspace. This method combines also the (1) flight movement data with (2) communication throughput per aircraft in a different way. This is based on: - the average communication throughput per aircraft, calculated over a given period of time (e.g. one hour, or over a flight duration), in terms of throughput (Mbps), i.e. r; - the peak instantaneous aircraft count (PIAC), i.e. the maximum number of aircraft over a given airspace at the peak time of the day.
With this method the MIT over a given airspace s is derived as MIT = r · PIAC. In order to consider satellite systems which employ spot beams to cover a given airspace, their geometry has to be known by the aviation community in order to calculate the MIT.
It is noted however that the MITSIM calculate through the simulation approach and the MITPIAC calculate with the PIAC approach can be shown to be very similar and possibly equal to each other.
3. Conclusion It is requested that this document is sent to the next meeting of ITU-R WP4C (29 Sep - 8 Oct 2008) as an ICAO input document, proposing ITU-R WP4C to take into account this document for its methodology and also to ask ITU-R WP4C for feedback and comments. . ACP/WGF 19 WP12 8
ANNEX: AVIATION COMMUNICATION NEEDS USABLE FOR ITU-R WP4C
1. INTRODUCTION
The WRC-07 through Resolution 222 and AI 1.7 for WRC-11 has requested the ITU- R to ensure long-term spectrum availability and access to spectrum necessary to meet requirements for the AMS(R)S. The last WP4C meeting 26 March-3 April 2008 has detailed a work plan for this AI 1.7 and work has started at the last ACP WGF meeting to seek aviation consensus for such work.
Part of the WP4C plan is to study existing and future spectrum requirements for AMS(R)S on a worldwide basis and for this a general methodology is required. To do so, it is necessary to identify aviation communication needs and combine these with the satellite communication systems characteristics, in order to compute the amount of required spectrum. Figure 1 shows the concept of such process.
Satellite system parameters
Aviation communication needs Methodology to Methodology to derive AMS(R)S derive AMS(R)S spectrum spectrum requirements for requirements for WRC-11 A.I. 1.7 WRC-11 A.I. 1.7
Total bandwidth Total bandwidth requirements for requirements for AI 1.7 AI 1.7 9 ACP/WGF 18/WP-12
Figure 1: Methodology to Derive Spectrum Requirements for AI 1.7 WRC-11 10 ACP/WGF 19 WP12
Due to the different nature and complexity of the inputs and their derivation, this document proposes that is produced by the two different parties involved, i.e.:
o ICAO provides the Aviation communication needs;
o ITU-R provides the Satellite system parameters and the methodology to calculate the spectrum for the AMS(R)S communications.
Hence, the establishment of a clear way to derive the AMS(R)S spectrum requirements by WP4C demands a systematic process to compile the above two inputs separately.
Consequently, the process proposed is as follows: 1. Firstly, the aviation communication needs are compiled and transformed into aviation communication parameters (i.e. the required information throughput (RIT) within a specific airspace), which are independent of satellite communication technology; 2. Secondly, the above aviation communication parameters are combined with the satellite technology characteristics (e.g. the physical layer), in order to derive the satellite ATM bandwidth requirement for the AI 1.7. The advantage of this method of work is that aviation matters, which are independent of the telecommunication technology, are derived separately from the satellite ones, which are specific to the technology used. This allows the aviation experts to concentrate on aviation issues and satellite systems experts to concentrate on the technological aspects, each one contributing with the best of their knowledge. 11 ACP/WGF 18/WP-12
Deriving Aviation Communication Needs Communication needs per flight Flight movement information Information throughput per flight
Combine Combine
information throughput information throughput
Figure 2: The process to derive Aviation Communication Needs
2. DERIVATION OF AVIATION COMMUNICATIONS NEEDS
This process can be easily understood by looking at Figure 2 above as we will describe below.
2.1.1 Input 1: Communication traffic profile per flight (CTPF)
Types of ATM Services and Signals
Since the aim of the ITU-R WRC-11 AI 1.7 is to consider the requirements of a future AMS(R)S system offering Air Traffic Management (ATM) services, it is under these auspices that the aviation communication needs are based.
The ATM communication services are classified into several groups, for example:
Air Traffic Services (ATS), which are dependant on the “flight phase” the aircraft is currently in, e.g. cruising, landing, departure.
Aeronautical Operational Control (AOC) services, which are concerned with the “safety and regularity of a flight”; and, 12 ACP/WGF 19 WP12
Network Management (NET) services, i.e. signals necessary to support ATS and AOC communications, by establishing and maintaining connections between an aircraft and the ATM ground network.
In addition we may also have signals inherent to the access protocol which may add additional throughput requirements, e.g.:
Protocol related signalling, i.e. signalling exchanged between peer entities inherent to the protocols used (e.g. acknowledgements (ACK) of the upper layers protocol stack).
As the transmission of these above messages depends on the position of the aircraft during its flight, the different flight conditions (e.g. regularity of flight) and the environment (e.g. flight phases) where the aircraft is operating need to be known.
Additionally, and most importantly, this part specifies the expected aviation needs for different types of ATM messages at different time scales in the future. For example in Europe and North America the future is characterised by two phases, i.e.:
the first of which (between 2005-2020) is characterised by a widely used voice communication and few data services; and,
the second one (from 2020 onwards) by mainly automatic data communication services, with voice as backup.
Both of these types of communications (voice and data) are characterised by certain aviation requirements (such as type of message, minimum delay, amount of data transfer and number of transmission instances), which will depend on the position and properties of the concerned aircraft. 13 ACP/WGF 18/WP-12
For this, in Europe the “Communications Operating Concept and Requirements for the Future Radio System, Version 2”, a document (also known as COCR V2) of EUROCONTROL and FAA2, is used. Also ICAO as adopted COCR V2 as the methodology to study future communication needs.
Selecting services served by a satellite infrastructure
Since the overall aviation communication needs can be served by both a terrestrial system as well as by a satellite system, it is at this level of the process that a decision is taken on which services will be served by satellite and/or by terrestrial. Hence this CTPF input will represent the aviation communication needs served via a satellite system.
CTPF Table
The CTPF can be organised as a Table format ordered by aviation service types (voice and data), which will be served by a satellite system covering the given airspace area. We have seen above an example of the types of messages related to the aviation services (e.g. ATS, AOC, NET).
Hence for each type of service, the CTPF table will have elements like:
Type of service, e.g. AOC, ATS, NET;
Type of aircraft;
Flight phase, e.g. airport, take-off or landing, cruising;
Number of instances transmitted during a given flight phase;
Probability of transmission during a given flight phase;
Amount of data transfer D and time latency constraints T;
The message throughput or data rate R = D / T (bps, or kbps).
2 COCR V2 is available at http://nasarchitecture.faa.gov/nas/downloads/home.cfm. 14 ACP/WGF 19 WP12
The CPTF table will be used below to derive the information throughput per aircraft per flight.
2.1.2 Information Throughput per Aircraft per Flight (ITAF)
The Information Throughput per Aircraft per Flight (ITAF), is the required information exchanged between an aircraft and the ground (via a satellite link) in different flight phases and at different operational conditions. This can be derived from the above CTPF Table and could also be organized in a table or tabular format for each flight type (for example dependant on the flight duration).
In Figure 3 below a qualitative example of the communication needs of a single flight is shown. Here it is seen that at each flight phase (departure, cruise and arrival) there are different communication needs and also that the traffic is bursty in nature.
The next step is to aggregate the ITAF requirements over all the aircraft present within a certain region. To do so it is required to understand more about the flight movements as presented in Input 2 below. 15 ACP/WGF 18/WP-12
cruise
arrival departure flight path / phases
at airport at airport
Amount of data in one flight
airport departure cruise arrival airport
time
begin end
Figure 3: Qualitative example (not realistic) of communications for a single flight through different domain and flight phases.
2.2 Input 2: Flight Movements and Forecast
In order to have appropriate parameters to design satellite communication systems, it is necessary to identify the flight movements over a given region (for example see Fig. 4 below).
Such data is normally available from airlines and aviation bodies in the form, for example, of flights between two cities, time of departure, flight duration, airline name, and so on.
Additionally, it is also necessary to estimate future flight movements which can be derived by applying forecast analysis (based for example on economical factors, airport growth) on present flight movements. 16 ACP/WGF 19 WP12
For example in Europe, Eurocontrol compiles flight forecast on a short, medium and long-term basis. In such case the long-term flight movements are based on a 20 year look ahead forecast3.
Flight 1
Flight N
Flight i Flight 2
Figure 4: Example of flights movements over a given time period.
2.3 Aviation Communication Needs: Output Data
Given the above inputs it is possible to derive the aggregate aviation communication needs over a given areas of airspace in two different methods.
One method described below in section 2.3.1. uses a simulation approach and one other method in section 2.3.2 uses a PIAC approach.
3http://www.EUROCONTROL.int/statfor/gallery/content/public/forecasts/Doc216%20LTF06%20 Report%20v1.0.pdf 17 ACP/WGF 18/WP-12
Both methods are now described.
2.3.1 Simulation Approach: Required Information Throughput (RIT) and Maximum Information Throughput
Given a certain aviation area S, the future flight movements derived above and the Information Throughput per Aircraft per Flight (ITAF) can be combined and aggregated to produce the total aviation throughput over such area and for any time t. It is important that these two inputs are consistent in time and space, i.e. that they apply for the same year and the same aviation area S.
The throughput so derived is here called the “required information throughput” (RIT) and it is defined as follows.
RIT over aviation area S
The RIT over a given region of the world (i.e. an aviation region S) and a certain period of time in the future (i.e. the busiest day of a certain year) is a function of time and it is equal to the aggregate throughput at time t (derived from the ITAF table) of each individual aircraft flying within region S (derived from the flight movements). This can be written as RIT (t; S) and the calculation is exposed in Fig. 6 below and the Attachment. This is done in such a way that it considers the flight phases and flight domains (see Fig. 3) applied to each flight (see Fig. 6) and then aggregated the individual communications events as shown at the bottom of Figure 6. From the attachment we can see that RIT can be expressed as
RIT(t; s) = (i = 1 .. N) Di,s(t; TITAF, TFM) (Eq. 1)
Where Di,s is the throughput (Mbps) of each individual aircraft (the throughput defined in table TITAF) present in the region s at time t and N being the total number of aircraft in the table TFM. If we consider that the transmitting aircraft at any given time t is less than the total number of aircraft in the table TFM, then Eq. 1 can be 18 ACP/WGF 19 WP12 simplified by using n(t; S) < N and also using the data throughput Ri(t;s) of the services (defined in TITAF) transmitted by each of those aircraft. Thus simplifying the Eq. 1 as:
RIT(t; s) = (i = 1 .. n) Ri,s(t;s) (Eq. 2)
This can be simplified further by assuming that all the throughputs are at the same data rate R (Mbps), thus we can write Eq. 2 as:
RIT(t; s) = R n(t;s) (Eq. 3)
where as we said above, n(t;s) is the number of aircraft transmitting a service in region s at time t.
RIT over air space unit S
Since a future satellite system may employ spot beams of area (not known a- priory), the process here explained proposes also to derive the RIT at a compatible air space unit S < , (see Fig. 5).
For this, before calculating the RIT at S, the aviation area S has to be subdivided into these smaller areas. When this is done the RIT is calculated for each of these areas S. Also the RIT (t; S) can be calculated with the same process described above.
Maximum Information Throughput (MIT)
The maximum value of the RIT(t;S), here called the Maximum Information Throughput, i.e. MIT(S), represent the peak throughput requirement over the whole of region S. This value will happen at the busiest time of the day and can be used to calculate the overall spectrum needs of the aviation region S when covered by a single satellite beam. 19 ACP/WGF 18/WP-12
The Attachment gives a formulation for the calculation of the RIT and the MIT.
Use of the RIT(t; S)
The output from the process above is the RIT(t;S), for all the S of the given area S. The RIT (t; S) have to be used very carefully, because their maximum value (which determines the spectrum requirement for each S) will happen at different time of the day.
For a multi-spot beam satellite coverage the MIT per each spot beam area must be calculated. For this reason the RIT(t; ) = k RIT(t; Sk), Sk , of the spot beam area has to be derived for the calculation of the MIT(), but since the spot beam is unknown a-priory all that can be provided to the WP4C is the RIT (t; S) and then WP4C methodology has to consider the use of the RIT (t; S) for each satellite spot beam.
Spot beam area (s) Aviation Area (S)
Airspace Unit (DS)
Figure 5: Airspace area S, air space unit S and spot beam area () 20 ACP/WGF 19 WP12
flight - 1
time
flight - 2
time
... flight - i
time
...
flight - N
time
Total instantaneous throughput
time
00:00 24:00
Figure 6: Calculation of the Required Information Throughput (RIT) envelope over a given aviation area.
2.3.2 PIAC Approach: Maximum Information Throughput
It is also possible to combine the flight movements and communication needs per aircraft using the peak instantaneous aircraft count (PIAC) and the average communications needs per aircraft over a given flight duration, this is described here. The flight duration should be selected in a reasonable manner to avoid peak throughput values during the estimation process. 21 ACP/WGF 18/WP-12
The process explained in Figure 1 still applies, except that now the “combination” between (1) flight movements and (2) information throughput per flight is done differently. This is described below in Figure 7.
Flight Communication movement needs per flight information
Average information PIAC throughput per a/c
*
Maximum information Maximum information throughput (MIT) throughput (MIT)
Figure 7: PIAC approach
For this it is seen that the same inputs of section 2.3.1 are also used for this second calculation process, i.e.:
1. Communication traffic profile per flight (CTPF);
2. Flight Movements, except that the processing and use of this data will result in the estimation of the PIAC, which expresses the maximum over a 24 hour period of the instantaneous count of aircraft in a given airspace S and the average communication throughput per aircraft per flight.
The calculation method is such that: 22 ACP/WGF 19 WP12
MITPIAC(s) = PIAC(s) · r(s) (Eq. 4)
Where, PIAC(s) is the PIAC over a given airspace s and r(s) is the average communication throughput per aircraft per flight (over a given period of time, e.g. one hour or a flight duration).
It is also worth nothing that the MITPIAC is equal (or in most cases similar in value) to the MITSIM, and we will find this in the Attachment.
Both of these values are now calculated.
Derivation of PIAC
The PIAC is the maximum over a 24 hour period of the instantaneous count of aircraft present over a given airspace area s, i.e.:
PIAC (s) = max(t) {N(t; s)} (Eq. 5)
where the N(t;s) = sum of all aircraft flying in areas s at time t. This can be derived by simulations or by statistical approach.
Derivation of the average communication throughput per aircraft per flight
From the knowledge of the flight phases (section 2.2), it is possible to derive the average communication throughput per aircraft per flight over a given region of airspace s, in a specified duration 23 ACP/WGF 18/WP-12
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) } (Eq. 6)
This can also be derived by simulations, or by statistical approach.
2.3.3 Output to WP4C
From the above, the Aviation Communications Needs over a given airspace can be expressed with the total communication throughput (Mbps), which can be estimated using different approaches, i.e. either through a simulation approach (section 2.3.1) or through a PIAC approach (section 2.3.2). Hence the output of the process can be either:
(1) with the simulation approach:
RIT(t; S), for a multisport beam coverage;
MIT(S) = max(t) {RIT(t;S)}, for a single beam coverage.
(2) with the PIAC Approach:
MITPIAC(s), for a single beam coverage.
2.4 Uplink and Dowlink
Finally, it is noted that the above process has to be done for both the uplink and downlink since the air traffic requirements could be different. 24 ACP/WGF 19 WP12
3. CONCLUSIONS
This paper proposes a generic methodology to derive aviation communication needs which are useful for the ITU-R WP4C to then derive the bandwidth requirement for AI 1.7.
The process exposed is generic and can be used for different aviation airspace of the Earth and for different regional aviation requirements.
The outputs of this process can be derived by different processes, i.e.:
(1) a simulation approach for which WP4C should require the RIT for each of the airspace units S, i.e. RIT(t; S), with S belonging to the given airspace area S and at each time unit t (1 second) and then derive a beam by beam MIT() to derive a beam by beam bandwidth needs.
(2) a PIAC approach, for which WP4C should required the MITPIAC(s) for each airspace, satellite beam, or for the overall region S.
Either of these two outputs will represent the aviation communication needs over a given region of airspace and when given to WP4C then can be used to calculate the aviation spectrum requirements.
It is proposed here to discuss and agree this process at the WGF 19 th meeting and asks ICAO to input a technical paper to the next ITU-R WP4C (29 Sep to 10 Oct 2008). Such paper from ICAO will also ask ITU-R WP4C for comments and feedback on this process.
The intent then is to make specific calculation of these parameters before the ITU-R WP4C April 2009 meeting. 25 ACP/WGF 18/WP-12
Attachment: Simulation approach to derivation of the Required Information Throughput and the Maximum Information Throughput
In terms of a quantitative analysis the RIT and the MIT are derived below.
Definitions:
RIT (t; s) : Required Information Throughput;
MIT(s) : Maximum Information Throughput
s : the given airspace of interest (e.g. s=S);
t : time (in steps t of 1 second);
TFM : table of the flight movements (FM);
N : the total number of flights (or aircraft) in TFM;
TITAF : table of the flight communications needs from the CPTF;
Di,S(t; TITAF, TFM) : Individual data throughput of the i-th flight path contained in region s, at time t, which is a function of
the two tables TFM and TITAF.
Hence the Required Information Throughput at time t, over the region s and at the given busiest day of the year, is calculated as:
RIT(t; s) = (i = 1 .. N) Di,s(t; TITAF, TFM) (Eq. A1)
which is a sum over all the data throughputs Di at that specific time t and for that i- th flight:
Di,s(t; TITAF, TFM) = pi,s(t; TFM) di,s(t; TITAF) (Eq. A2) 26 ACP/WGF 19 WP12
Where:
1, if the i-th flight in TFM at time t is in inside region s and transmitting an aviation service
pi,s(t; TFM) = (Eq. A3)
0, otherwise
and di,s(t; TITAF) is the data rate Ri(in bps) at time t of the communication service in table TITAF, associated to the i-th flight in region s, and which is also a function of the flight characteristics and the service being transmitted.
One could assume that the data rate of the aviation services are all the same value, i.e. Ri = R i, and that the required data is being transmitted for a period of time Ti. This is a valid assumption as the aviation services would have to then be transmitted over the same aircraft equipment and thus over the same data rate. We take here R as the maximum data rate from all of the aviation services.Hence this will simplify the RIT calculation of Eq. A3 above, i.e.:
RIT(t; s) = R (i = 1 .. n) pi(t-ti, Ti; s) (Eq. A4)
= R n(t; s)
With n=n(t; s) being the number of aircraft in region s and transmitting an aviation service at time t. The functions pi(t-ti, Ti; s) is a door function representing the transmission of the service at data rate R and active between the time period ti and ti+Ti. Ti being the period associated with the transmission of the specific aviation service.
The above formulas are what in essence is shown in Figure 6 above and Figure 8Error: Reference source not found below gives a logical software block diagram 27 ACP/WGF 18/WP-12 implementation of the software for the calculation of the Required Information Throughput.
The Maximum Information Throughput (MIT)
The maximum value of the RIT over the 24 hours period and over an area s covered by a satellite spot beam provides the maximum throughput requirements of that area. This may be required in certain cases (e.g. for each satellite spot beam) to calculate the spectrum requirements over a given area s and equals to:
MIT (s) = max (t = tin to tend) { RIT (t; s) } (Eq. A5)
= R max {n(t; s)}
with n=n(t; s) being the number of aircraft in region s and transmitting an aviation service at time t.
We will show here that the above MIT (defined in section 2.2, call it MITSIM) and the
MITPIAC (defined in section 2.3) are actually the same, i.e.:
MITSIM(s) = R max { n(t;s) } MITPIAC(s) = r(s) PIAC(s)
This is done as follows:
MITSIM(s) = maxt { RIT(t;s) }
= maxt {i=1..n(t;s) Ri(t;s)}
Where:
Ri are data throughput of the i-th aircraft at time t;
n(t;s) number of aircraft transmitting in airspace s. 28 ACP/WGF 19 WP12
= maxt {j=1..N(t;s) Rj (t;s) pj(t;s)}
Where:
n(t;s) was substituted by N(t;s)= total number of aircraft in s; and:
introduce pj(t;s) such that = 1 if the aircraft is transmitting and 0 if not.
= maxt {[N(t;s)/N(t;s)] j=1..N(t;s) Rj (t;s) pj(t;s)}
= maxt {N(t;s)[1/N(t;s) j=1..N(t;s) Rj (t;s) pj(t;s) ]}
Where:
1/N(t;s) j=1..N(t;s) Rj (t;s) pj(t;s) ] = E[R·p](t;s) = r(t;s) i.e. it represents the estimated value or average value of the Ri over all the aircraft present in S at time t, i.e.:
= maxt {N(t) r(t;s) }
= maxt {N(t)} · maxt {r(t;s) }
We assume that the maxt {r(t;s) } is also equal to the maximum value of the time average of the Ri(t;s) (thus assume the process if ergodic, i.e. time average and space average can be interchanged), and maxt {N(t;s) }=PIAC, thus we can write:
= PIAC · r(s)
= MITPIAC(s)
Which proves that MITPIAC = MITSIM. 29 ACP/WGF 18/WP-12 30 ACP/WGF 19 WP12
Set initial parameters: - t = 0, tend = 24:00:00 i = 0 - input TFM, TITAF - D(t)=0, t - set region s Simulate i-th flight movements in TFM - set other parameters
no flight In s ?
yes
Determine which service is active for flight i
no Service active?
yes
Select service data throughput di from TITAF
D (t) = D (t) + di
i = i+1
no i = N ?
yes
t = t + Dt
no tend ? yes Output : RIT (t) = D (t)
End, or next s
Figure 8: Logical block-diagram for the calculation of the 31 ACP/WGF 18/WP-12
Required Information Throughput (RIT)