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 AND PROJECTED SPECTRUM
REQUIREMENTS
(Presented by the Eurocontrol Agency)
Summary
Aviation 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
o the aviation model based on the ITU M1390 methodology to calculate the necessary
spectrum resource
o an estimation of the provision and the variability of the spectrum resource as
functions of operational requirement and technical constraints.
Recommendation
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
o Technology efficiency (NSC)
o Adjustment factor which includes compatibility, deployment and safety issues
o Deployment scenario of communication requirement into radio bands
Provides the airport surface requirement in order to complete the model
1
1.
INTRODUCTION
Industry is 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
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”
2.1
1ST STEP: INDEPENDENT FROM RF ENVIRONMENT
Technical choices
- technology
- Mapping radio network over
airspace
Operational requirements
-
Aircraft Traffic
Airspace modelling
Communication throughput
and performance
SPECTRUM
RESOURCE
MODEL
(1st STEP)
3
Spectrum Resource in a
“clean” band
2.1.1
Input parameters
Operational requirements
- Aircraft Traffic: The current aircraft traffic and projected traffic including unmanned aircraft.
- Airspace modelling: The organisation of the airspace in Terminal area (TMA),
airport and en route sectors will remain.
- Communication throughput and 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 technology is 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
bit / s
in
Hz
4
Radio Characteristic
- Propagation
- Intra system separation criteria
- Frequency reuse factor
Data Rate Characteristic
- Useful data rate
- Overhead data rate
NET SYSTEM
NSC
CAPABILITY (NSC)
CALCULATION
-
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 airground communication is based on a sector, i.e. a single controller position.
As the air-air communication throughput is largely predominant, a radio cell coincides for
the spectrum resource calculation with the service volume defined in the COCR.
2.1.2
Process
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 
T
Nsc
Bw :
T:
Total necessary Bandwidth (MHz)
Throughput per sector (Mb/s)
Nsc:
Net system Capability of the total communication system (
5
bit / s
)
Hz
2.2
2ND 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
ADJUSTED
In “clean” band
SPECTRUM
Adjusted Spectrum Resource
in VHF, L and C bands
MODEL
(2nd STEP)
2.2.1
Input 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.
6
- 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.
2.2.2
Process
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.
2.3
3RD STEP: STATISTICAL MODEL
Constraints
- Net System Capability Nsc, ∆ Nsc
- Adjustment Factor F, ∆F
Operational requirements
- throughput : T, ∆T
STATISTICAL
MODEL
(3rd STEP)
For each band considered
Bw 
TxF
Nsc
7
Bw, ∆Bw per band
Bw, ∆Bw :
T, ∆T :
F, ∆F:
Nsc, ∆ Nsc:
Total necessary Bandwidth and variation (MHz) for the considered band
throughput and variation per sector (Mb/s)
Adjustment factor and variation for the considered band
bit / s
Net system Capability and variation (
)
Hz
3.
ASSUMPTIONS, INPUT PARAMETER VALUES AND RESULTS
3.1
1ST STEP: MODEL INDEPENDENT FROM RF ENVIRONMENT
3.1.1
Communication 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/s
Airport 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
3.1.2
Technology
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
Medium
High
Low data rates
bit / s
Hz
High data rates
0.04
0.07
0.1
0.1
0.2
0.3
8
bit / s
Hz
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
3.1.3
NSC
bit / s
Hz
Airport area
TMA area
En route area
0.1
0.1
0.1
Service area
Airport area (note)
TMA area
En route area
Total
“Unconstrained”
spectrum (MHz)
15,6
16,2
11,9
43,7
Result step 1
Note: this line describes only the airport requirement as defined in the COCR.
Additional requirement is foreseen for airport surface applications
3.2
2ND STEP: INTEGRATING DEPLOYMENT AND RF CONSTRAINTS
3.2.1
Adjustment 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
9
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
[112] -118 MHz
118 – 137 MHz
960-[1164] MHz
Adjustment factor
2
N/A
2.5
[5000]-5150 MHz
2
3.2.2
Deployment Constraint
A single band allocation can not fulfil the communication requirement. For an adjustment
factor between 2 and 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:
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BAND
AIRSPACE
APPLICATIONS
[112] -118 Airport, TMA, As the BW is limited this band is
MHz
En route
essentially for core traffic message.
This band is used for flexibility and
safety: facilitate transition and backup,
could be a future or legacy system.
118 – 137 Airport, TMA, Pilot-controller voice exchange will
MHz
En route
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
960TMA,
En This band is for TMA/en route traffic.
[1164]
route, [Airport] Flexibility should be provided to
MHz
accommodate also (limited) airport
type of communications for flexibility
and safety reasons
5000]Airport
This band is essentially for surface
5150 MHz
communications (the ANLE system
based on 802.16e technology) and
the airport requirement identified in
the COCR. Part of the bands 50005010 and/or 5010-5030 MHz can be
used if compatibility with RNSS is
proven.
3.2.3
THROUGHPUT
10 %
0%
100% of TMA +
En route
100 % Airport
Step 2 Results
BAND
[112] -118 MHz
118 – 137 MHz
960-[1164] MHz
5091-5150 MHz
[5000-5030] MHz
Unconstrained
spectrum (MHz)
4,37
19
28,1
Adjustment
factor
2
N/A
2.5
Spectrum in “Real”
environment (MHz)
9
19
70
15.6
2
31 (note)
Note: this value does not include surface airport, security or aeronautical
telemetry requirement.
3.3
STEP 3: STATISTICAL DISTRIBUTION
11
3.3.1
Input parameters and variation
The value of the input parameters are estimated within a confidence interval of
0.95
Service area
Througput
T,∆T (Mb/s)
Airport area
1.56 , +/- 10%
TMA area
1.62 , +/- 10%
En route area 1.19 , +/- 10%
Adjustment
Service area
Airport area
TMA area
En route area
3.3.2
factor
VHF band
2 , +/- 1
2 , +/- 1
2 , +/- 1
Net System Capability
bit / s
Nsc,∆Nsc
Hz
0.1 , +/- 0.06
0.1 , +/-0.06
0.1 , +/-0.06
F, ∆F
L-band
N/A
2.5 , +/- 1
2.5 , +/- 1
C-band
2, +/- 1
N/A
N/A
Result: “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 MHz
Mean
Min
Max
10 %
9
3
36
0%
N/A
70
26
270
31
14
107
[112] -118 MHz
118 – 137 MHz
960-[1164] MHz
100% of TMA and En route
5091-5150 MHz
[5000-5030] MHz 100% of airport (note)
Note: this value does not include surface airport, security or aeronautical
telemetry requirement.
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3.3.3
Statistical cumulative distribution of the spectrum resource
3.3.4
VHF band: Statistical cumulative distribution of the spectrum resource
10% of
communication
throughput
Probability
(x < Bw)
100%
86%
50%
7%
3
9
36
Bw(MHz)
L-band: Statistical cumulative distribution of the spectrum resource
Probability
(x < Bw)
100% of TMA
and en route
100%
86%
50%
7%
26
70
270
13
Bw(MHz)
C band: Statistical cumulative distribution of the spectrum resource
Probability
(x < Bw)
100% of airport
(without surface)
100%
86%
50%
7%
14
4.
31
107
Bw(MHz)
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 shows that 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:
o
o
o
o
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
14