INTERNATIONAL CIVIL AVIATION ORGANIZATION
MIDDLE EAST OFFICE
FIFTEENTH MEETING OF THE AERONAUTICAL COMMUNICATION PANEL WORKING GROUP F
(ACP WG-F/15)
(Cairo, 7 – 13 June 2006)
Agenda Item 5: AM(R)S spectrum requirement
SPECTRUM RESSOURCE MODEL ANDPROJECTED SPECTRUM REQUIREMENTS
(Presented by the Eurocontrol Agency)
SummaryAviation needs additional allocations for developing applications based on new operational concepts and applications, to cope with increase in air traffic and to relieve the present congestion for the voice service in the VHF band. This paper determines the spectrum requirements necessary for the safety and regularity of flight applications in different airspace.
This paper presents
- the aviation model based on the ITU M1390 methodology to calculate the necessary spectrum resource
- an estimation of the provision and the variability of the spectrum resource as functions of operational requirement and technical constraints.
The meeting:
-notes that a model is available for the aviation scenario to calculate the spectrum resource in a shared RF environment
-reviews the assumptions and the parameters being used for the calculation of the spectrum resource, especially
- Technology efficiency (NSC)
- Adjustment factor which includes compatibility, deployment and safety issues
- Deployment scenario of communication requirement into radio bands
1.Introduction
Industryis confronted with a growing need to deploy new efficient radio technologies. That is especially true for the aviation industry while in addition of that will have to renovate and maintain legacy technologies which have proven safe for aircraft operation.
In this context prediction of future spectrum resource is a fundamental element of technology deployment strategy and scenarios.
At the international telecommunication Union (ITU), the agenda item 1.6 for the next WRC 2007 is for “Consideration of the frequency range between 108 MHz and 6 GHz for new aeronautical applications” as detailed in WRC 2003 resolution 414.
The aim of this paper is to support discussion to select which portions of the considered bands are necessary to deploy the aeronautical Future Communication systems.
2.METHODOLOGY
Assumption and methodologies are described in the following documents:
- ITU M1390 methodology
- FAA/EUROCONTROL COCR document, version 0.9
- PT3 (05) 016 Aeronautical Mobile Spectrum Model
- PT3 (05) 017 Brief on applied methodology to calculate AM®S bandwidth requirement
- PT3 (05) 018 Presentation on bandwidth calculation model
To determine the required spectrum it is necessary for aviation to quantify future communication capacity throughput and to apply a suitable model that converts the throughput into RF bandwidth requirement.
The model includes two main steps.
1)The ITU- R M1390 describes a model which has been used by the mobile phone community to calculate their projected spectrum resource in “clean” radio band. The first step is to calculate the spectrum resource based on the ITU M1390 methodology.
2)The possible band options being already occupied; there is a need to adjust the result of the first step by considering the effect of other constraints such as sharing the same band with the existing radio services.
The algorithm of the calculation is deterministic. Because of many uncertainties on the input parameters and on the assumptions, the projected spectrum resource for the future communication system in the year 2030 can not be exactly determined.The calculation of the sensitivity of the spectrum resource as a function of the input parameters is processed within a 3rd step “statistical model”
2.11ST STEP: INDEPENDENT FROM RF ENVIRONMENT
Operational requirements-Aircraft Traffic
-Airspace modelling
-Communication throughput
and performance
/ SPECTRUM
RESOURCE
MODEL
(1st STEP) / Spectrum Resource in a
“clean” band
2.1.1Input parameters
Operational requirements
-Aircraft Traffic: The current aircraft traffic and projected traffic including un- manned aircraft.
-Airspace modelling: The organisation of the airspace in Terminal area (TMA), airport and en route sectors will remain.
-Communication throughputand performance: The throughput is calculated in transmitted bit per second. According the performance a message can be transmitted with a certain delay and with a certain quality expressed in bit error rate
Technical choices
-Technology
The technology for the future communication systems is being assessed among several on-the-shelf candidates. According ITU M 1390, the technologyis characterized by its “Net System Capability”, which is a measure of how much RF bandwidth is required to transmit a given amount of data in a radio cell taking into account the effect of the adjacent cells of the radio network.
The NSC represents the capability per Hz of the overall communication system to transmit data. It incorporates the frequency separation criteria between transmitters and receivers and the frequency reuse capability between radio cells. The NSC is expressed in
Radio Characteristic-Propagation
-Intra system separation criteria
-Frequency reuse factor
Data Rate Characteristic
-Useful data rate
-Overhead data rate / NET SYSTEM
CAPABILITY (NSC)
CALCULATION / NSC
-Mapping the radio network topology over service volume
The COCR document calculates the throughput requirement according 2 approaches. The calculation for aircraft to aircraft communications is based on air transmission which gives a volume similar to the volume offered by a radio cell. The calculation for air-ground communication is based on a sector, i.e. a single controller position.
As the air-air communication throughput is largely predominant, a radio cell coincidesfor the spectrum resource calculation with the service volume defined in the COCR.
2.1.2Process
In accordance with standard mobile network design, it is usual to size a radio network from its peak cell or busiest sector.
Spectrum provision for all the communication system can be seen as the quotient of the maximum throughput (Mb/s) in a radio cell (calculated in the highest density area) by the NSC.
Bw: Total necessary Bandwidth (MHz)
T : Throughput per sector (Mb/s)
Nsc: Net system Capability of the total communication system ()
2.22ND STEP: INTEGRATING DEPLOYMENT AND RF CONSTRAINTS
Historically, the ITU M-1390 methodology has been developed and used for determining the 3G spectrum requirement in ITU, assuming a “clean” spectrum is available. The ITU M-1390 recommendation predicts an adjustment factor for more complex deployment scenario, for example when the new system has to share the band with another system. This section is to model this “adjustment factor” for the aviation case.
Deployment Constraint-Transition
-Safety / RF Environment
-Multiple Bands
-Propagation
-Compatibility
Spectrum Resource
In “clean” band / ADJUSTED
SPECTRUM
MODEL
(2nd STEP) / Adjusted Spectrum Resource
in VHF, L and C bands
2.2.1Input parameters
- Spectrum resource in non occupied band: calculated from “Step1 Model”
- Deployment Constraint
-Transition: There is a need to preserve the existing spectrum provision for the aviation legacy systems as it will continue to be used for specific applications (such as the voice controller-pilot exchange in the 118-137 MHz band).
-Safety : Scenarios of communications deployment retain redundancy for the most time critical applications
- RF Environment
- Multiple bands: the VHF band, L-band and the C-band were proposed in the ICAO and later in ITU for the newest communication applications.
- Propagation: The C-band is better suited for “airport” applications due to the important attenuation in case of rain fall.
-RF Compatibility
The candidate bands envisaged for new aeronautical applications are already occupied by existing services. These services will not be decommissioned or re-farmed in other bands. The targeted bands being already loaded, the new communication system will have to operate on a wider spectrum. This will be especially true in order to mitigate aircraft co-site compatibility issues. The “adjustment factor” can be given by the overhead of an existing aviation communication system in the real RF environment compared to the capability of the same system in a “clean” spectrum band.
2.2.2Process
The “unconstrained” spectrum resource calculated from step1 is multiplied by the adjustment factor. The spectrum resource is spitted between the identified bands taking into account the deployment and propagation constraints of each band.
2.33RD STEP: STATISTICAL MODEL
Constraints-Net System Capability Nsc, ∆ Nsc
-Adjustment Factor F, ∆F
Operational requirements
-throughput : T, ∆T / STATISTICAL
MODEL
(3rd STEP) / Bw, ∆Bw per band
For each band considered
Bw, ∆Bw : Total necessary Bandwidth and variation (MHz)for the considered band
T, ∆T : throughput and variation per sector (Mb/s)
F, ∆F: Adjustment factor and variation for the considered band
Nsc, ∆ Nsc: Net system Capability and variation()
3.ASSUMPTIONS, INPUT PARAMETER VALUES AND RESULTS
3.11ST STEP: MODEL INDEPENDENT FROM RF ENVIRONMENT
3.1.1Communication throughput:
The communications throughput is calculated from on air traffic scenarios achieved from studies and statistics performed by EUROCONTROL and FAA. The communication traffic has been calculated using a queuing model to take into account that simultaneous messages can be served with a delay not exceeding the necessary time performance. The findings of the joint EUROCONTROL/FAA action are available in the COCR (Communication Operating Concept and Requirement) document. The version used for this paper is the version 0.9 from November 2005.
Service area / Capacity throughput per radio cell Mbit/sAirport area (note) / 1,56
TMA area / 1,62
En route area / 1,19
Note: this line describes only the airport requirement as defined in the COCR. Additional requirement is foreseen for airport surface applications
3.1.2Technology
Different technologies have been analysed to determine what net system capability (NSC) can be achieved for the aviation case. The analysis has been done for different data rates (from 2.4 Kbit/s up to 307.2 Kbit/s) and for different frequency reuse scheme.
The range of the NSC have been found as follows:
Class Name / Low data rates / High data ratesLow / 0.04 / 0.1
Medium / 0.07 / 0.2
High / 0.1 / 0.3
The class “Low” represents systems that are either suffering from high interference (for example systems with small cells and high flying aircraft) or are dimensioned to cover large areas with limited capacity (For example CDMA systems that are used with low data rates in a noise limited environment). The class “Medium” represents systems where cell range and capacity is balanced whereas the class “High” represents a high spectrum efficient system such those in existing 2D environment or the best one that could be selected for the aviation communication system.
For the calculation the highest NSC for low data rate type of applications has been used that is to say 0.1.
Service area / NSCAirport area / 0.1
TMA area / 0.1
En route area / 0.1
3.1.3Result step 1
Service area / “Unconstrained” spectrum (MHz)Airport area (note) / 15,6
TMA area / 16,2
En route area / 11,9
Total / 43,7
Note: this line describes only the airport requirement as defined in the COCR. Additional requirement is foreseen for airport surface applications
3.22ND STEP: INTEGRATING DEPLOYMENT AND RF CONSTRAINTS
3.2.1Adjustment factor
Method
To precisely determine the adjustment factor at the horizon 2030, in-depth analyses are necessary
-on deploying and decommissioning of the legacy systems in the considered bands
-on electro magnetic compatibility between the existing and the legacy systems in the considered bands
Theses analyses are not possible for the moment as deployment and/or decommissioning plans and technology choice are not available with the necessary details and certainties.
Simplified approaches to determine the adjustment factor are:
-Interpolate what could the spectrum requirement when an already deployed technology (such as the VDL in the VHF band or the UAT in the L-band) is used for transmitting all the communication throughput
-Calculate the portion of spectrum which is not used
-Calculate the portion of time where the legacy system is not transmitting
Findings are as follows:
BAND / Adjustment factor[112] -118 MHz / 2
118 – 137 MHz / N/A
960-[1164] MHz / 2.5
[5000]-5150 MHz / 2
3.2.2Deployment Constraint
A single band allocation can not fulfil the communication requirement. For an adjustment factor between 2and 2.5, the total spectrum provision is approximately 100 MHz, which is beyond the offered capacity by any portion of bands considered in ITU.
Scenarios of communications deployment are as follows:
BAND / AIRSPACE / APPLICATIONS / THROUGHPUT[112] -118 MHz / Airport, TMA, En route / As the BW is limited this band is essentially for core traffic message. This band is used for flexibility and safety: facilitate transition and backup, could be a future or legacy system. / 10 %
118 – 137 MHz / Airport, TMA, En route / Pilot-controller voice exchange will remain in this band. This band is saturated. It is predicted that through technology enhancement (8.33 kHz spacing) this band will be sufficient up to 2030 for voice but with no extra capacity for data exchange / 0 %
960-[1164] MHz / TMA, En route, [Airport] / This band is for TMA/en route traffic. Flexibility should be provided to accommodate also (limited) airport type of communications for flexibility and safety reasons / 100% of TMA + En route
5000]-5150 MHz / Airport / This band is essentially for surface communications (the ANLE system based on 802.16e technology) and the airport requirement identified in the COCR. Part of the bands 5000-5010 and/or 5010-5030 MHz can be used if compatibility with RNSS is proven. / 100 % Airport
3.2.3Step2 Results
BAND / Unconstrained spectrum (MHz) / Adjustment factor / Spectrum in “Real” environment (MHz)[112] -118 MHz / 4,37 / 2 / 9
118 – 137 MHz / 19 / N/A / 19
960-[1164] MHz / 28,1 / 2.5 / 70
5091-5150 MHz
[5000-5030] MHz / 15.6 / 2 / 31 (note)
Note: this value does not include surface airport, security or aeronautical telemetry requirement.
3.3STEP 3: STATISTICAL DISTRIBUTION
3.3.1Input parameters and variation
The value of the input parameters are estimated within a confidence interval of 0.95
Service area / ThrougputT,∆T (Mb/s) / Net System Capability
Nsc,∆Nsc
Airport area / 1.56 , +/- 10% / 0.1 , +/- 0.06
TMA area / 1.62 , +/- 10% / 0.1 ,+/-0.06
En route area / 1.19 , +/- 10% / 0.1 ,+/-0.06
Adjustment / factor / F, ∆F
Service area / VHF band / L-band / C-band
Airport area / 2 , +/- 1 / N/A / 2, +/- 1
TMA area / 2 , +/- 1 / 2.5 , +/- 1 / N/A
En route area / 2 , +/- 1 / 2.5 , +/- 1 / N/A
3.3.2Result: “Real” Spectrum Resource
The calculation being made with 3 independent variables with 0.95 of confidence , the result has a confidence interval of 0.953 = 0.86
Band / proportion of total throughput / RF requirement MHzMean / Min / Max
[112] -118 MHz / 10 % / 9 / 3 / 36
118 – 137 MHz / 0 % / N/A
960-[1164] MHz / 100% of TMA and En route / 70 / 26 / 270
5091-5150 MHz
[5000-5030] MHz / 100% of airport (note) / 31 / 14 / 107
Note: this value does not include surface airport, security or aeronautical telemetry requirement.
3.3.3Statistical cumulative distribution of the spectrum resource
3.3.4VHF band: Statistical cumulative distribution of the spectrum resource
L-band: Statistical cumulative distribution of the spectrum resource
C band: Statistical cumulative distribution of the spectrum resource
4.Conclusions
The paper presents a methodology to calculate spectrum provision. The model requires many inputs than can not be exactly predicted for 2030.
The model showsthat the spectrum provision is very sensitive to the variation of these inputs.
It is necessary than the aviation community reviews the assumptions and parameters documented in this paper. The most sensitive ones are:
- Airport communication requirement: While the COCR document describes thoroughly the airport communication requirement when the aircraft is on the air or is going to land on/off, the specific communication requirements at the airport surface is not available
- Deployment scenario of communication requirement into radio bands
- Technology efficiency (NSC)
- Adjustment factor which includes compatibility, deployment and safety issues
1