Analysis of Flight Data for Airborne Networks Design

2 CHAPTER 1. INTRODUCTION
lot of more infotainment's potentiality: Internet access for www applications
and e-mail are the main failures for today's infotainment.
Also telemedicine is important for medical assistance, since that a video
link to medical experts on ground could be the way to save lifes and avoid

ight's interruptions.
On the other hand, half of the airlines' passengers are business travelers
and over 70% of them is carrying a mobile computers and over 80% a mobile
phone [3]. These business travelers need to use their own equipment to con-
nect to the terrestrial network, while the other passengers can use on board
equipments (for instance terminals in seats).
Each category has its specic requirements that can be schematized in
qualitative manner as below:
 availability in terms of 
ight duration
 data rate requirements
 delay, delay jitter and BER limits (user-oriented Quality of Service)
 (in-
ight) oce
 specic protocols and data formats
Solutions in order to provide the possibility of communication from a 
ying
airplane to terrestrial networks can be divided in two main great categories.
The rst is the traditional approach and nowadays provided in experimental
tests. The second is the novel approach, object of this thesis. This novel
approach is completely new, therefore both no documentation and no bibliog-
raphy exist (even if U.S. AirForce developed and still develops a connectivity
system based on the idea of Airborne Networks, but both the approach and
the goal are dierent).
Satellite Networking Communication is the rst approach. Satellites
moving around the Earth on geostationary orbits are used to collect the sig-
nals from airplanes and then re-direct them to a base station on the Earth
surface. This base station is responsible to route the communication in the
terrestrial network. Just three satellites in geostationary orbits can achieve
the requirement of covering the entire Earth surface, as well as every aiplane
can see a geostationary satellite. Therefore the use of satellites solves the
problem of guaranting the connectivity for the entire 
ight duration by ensur-
ing surface connectivity coverage, and provides a continuous communication.
However, satellites are single point of failure, propagation delay time caused
by the great distances of the satellite orbites is hight, as well as the latency
time to esatblish a connection. Moreover the cost of satellite communication
is extremely high. This last is the main limit in large-scale usage.
Airborne Networking Communication is the second approach. Com-
munication from a 
ying airplane is routed just among the other 
ying air-
planes untill it can reach a base station at an airport. Therefore base sta-
tions at airports work as access points between the terrestial network and the
network formed among the 
ying airplane. This solution has the advantage
of no-use of other devices except airplanes, the communication can achieve
higher data rate, the costs are reduced in sensible manner. On the other side,
CHAPTER 1. INTRODUCTION 3
a problem is the coverage of the entire 
ight duration (an amount of 
ight
population should be probably to required) while the management of the re-
sulting airborne network has to be extremely accurate. It's obvious notice
that this solution can't provide the entire coverage of the Earth surface: as
a consequence, for instance, when an airplane is 
ying above the oceans only
the satellite communication can be used.
A key point is that the scenario can be limited by considering only the com-
munication between an airplane and the other in both directions or to/from
the terrestrian network and by avoiding a coverage-type of communication.
It means that each airplane is only a possible source or destination point of
communication and nothing else. In other words, each airplane doesn't work
like a base station that manages all the communication that exists around it
and so it doesn't cover the entire communication space around itself.
The idea of Airborne Networking approach can have a comparison with a
military solution developed by U.S. AirForce in conjunction with important
worldwide Telecommunications and Aircraft Company, like Boeing. However,
this military solution has a compeltely dierent goal: it aims to provide sur-
face connectivity (hence Earth coverage-type connectivity) among all actors
in a war theatre by using an integrated communication system composed by
satellites at top level and Airborne Networks al lower level.
In the next section, some aspects of the novel approach Airborne Network-
ing Communication are brie
y introducted.
1.1 What Airborne Networks means?
As already written, the idea of Airborne Networks was thinked in order to
overcome some limitations of the Satellite Networking solutions.
Airborne Networking aims to bypass the use of satellites by using only
the existing 
ying airplanes. A communication path has to be founded and
ensured at each time from the reference airplane (source of communication)
in such manner that communication can reach an airport and continue on
terrestrial networks. Communication paths between the reference airplane
and the nearest possible airport can be direct or with several hops. These
hops are the other airplanes 
ying at that time.
All these actors (reference airplanes, hop airplanes and airports) can be
considered nodes of a network. From the consideration that the airplanes
are 
ying at high speed, they change their positions at each time in sensible
manner and the communication paths need to be founded-established-ensured
from all the 
ying airplanes at each moment or at least in a fraction of the
setup connection time. Therefore the resulting network is a very highly time-
variant type of network. Since this network consists of xed access points
(the airports) with many highly mobile internal nodes (the airplines), it could
belong to the highly time-variant mobile wireless mesh network family.
This thesis investigates the possibility to design and create Airborne Net-
works. It tries to solve the problem of establishing communication paths, it
analyzes the results coming out by simulating dierent 
ight population sce-
4 CHAPTER 1. INTRODUCTION
narios and it tries to propose a network architecture as well as the routing
protocol that best satises the network requirements.
In order to solve the main problem of Airborne Networks, the Flight Cov-
erage Problem, two subproblems can be recognized: a Localization Problem
and a Routing Problem. The rst subproblem refers to localize at each time
the entire population of 
ying airplanes in order to search and then establish
a communication path starting from the reference airplane, while the sec-
ond ones refers to ensure an ecient and fast as well as reliable delivery of
communication data. In this feasibility study, the considerations on Airborne
Networks come out from analyzing the results of simulations of a Localiza-
tion Software based on Airlines database data. Instead, in the real case, the
localization of the 
ying airplanes can be achieved by using the responses of

ooding messages leaving from each airplane in order to known the position
of its neighbors.
In this thesis the simulations are done by considering the Italian Airspace.
In fact, the original idea was to have a continuous interaction and exchange
of informations with the ocial entity that has the responsibility to manage
the Italian air network, the ENAV S.p.A. Company. Failing a responce from
ENAV Company in terms of useful documentation and airplanes' route data,
the entire work has been done by the author itself with the supervision of the
readers.
An important consideration: the choice of Italian Airpace as example can
be seen as a limitation but it isn't a weakness since each national airspace is
governed by national rules that are standardized and hence similar to each
other. Moreover, at further level, international rules govern the interdepen-
dence and the coordination of the national rules. Therefore the considerations
made by considering only the Italian Airspace, can be well applied on all the
other national airspaces as well as on them international/continental airspace.
Just an attention: the considerations re
ects the 
ight population density.
Therefore the density of two airspaces needs to be similar if one want to main-
tain the same considerations. However, the choice of the reference airspace
scenario has an important impact on the choice among the approaches to solve
the problem of providing Air Communication (for instance, satellite network-
ing approach is the only one that can be used when an airplane is 
ying above
oceans).
Respect to client services, two type of communication can be provided
with this solution: real time communication or delay-tolerant communication
in the case that it's temporaraly impossible to establish a communication path.
1.2 Thesis Structure
This work is structured in parts and chapters in the following manner.
Part I covers the Reference Scenario, that is the Aviation Space and 
ying
airplanes.
 In Chapter 2, the reference scenario is explained in order to understand
CHAPTER 1. INTRODUCTION 5
the 
ight terminology, the 
ight policy and the reference standards as
well as the route directions and the complexity of the problem. The
following characteristics need to be keeped in mind: (i) free space, (ii)
very high mobility and very highly time-variant communication network.
 In Chapter 3 the Italian Airspace is presented as practical example of
scenario. Static maps that show the real coverage of the Italian Air
Network are reported, with the highlighting of the routes and of the
diameter of the areas with no surface coverage, since no airplanes 
y
above them. Some useful but general informations on the 
ight policy
have been founded on-line on ENAV web site http://www.enav.it.
`
Part II covers Use of Satellites to provide connectivity.
 In Chapter 4, the traditional Satellite Networking approach is explained
in the most important aspects in order to give parameters and terms of
comparison with the novel approach that is the object of this thesis.
 since the Satellite approach is the only one that nowadays has been
implemented and tested in real experimental solutions, some of these
practical technologies are brie
y reported in Chapter 5.
Part III covers Airborne Networking Communication.
 An introduction to the Flight Coverage Problem of Airborne Networking
is topic of Chapter 6.
 All the airplanes need to be localized at each time in order to know
their position and to understand if they can be nodes of a communi-
cation path. The Localization Software applied on Airline Companies'
databases, that solves this Localization Problem in this feasibility study,
is topic of Chapter 7. The main functions of the software are explained
as well as its potentialities, its weakness points and its future improve-
ments. Also the underlying issues that are specic to the informatic
choices are considered, like the software language and the informatic re-
sources. Instructions and background requirements are also reported.
The software has been written in Python language and the MySQL
Database Platform has been choosen for the management of database
aspects. The design and realization of the software is an original work
of the author.
 The analysis of Software Simulations applied on dierent 
ight popula-
tion in the Italian Airspace is reported and explained in Chapter 8 with
the help of histograms and charts.
 The Routing Problem is the topic of Chapter 9. A good routing proto-
col is essential to manage the delivering of the data. The protocol needs
to consider and match the characteristics of this particular highly time-
variant network. The analysis of the results of the Localization Software
helps to understand which protocol can be suitable for this type of net-
work. It's easy to predict that Routing Protocols belonging to the Mobile
Ad-Hoc or Wieless Mesh Networks families are the best candidates as
Airborne Networking Routing Protocol.
 Chapter 10 presents a conclusive discussion about Airborne Network-
ing with some Architecture Design and Routing Protocols proposals, by
6 CHAPTER 1. INTRODUCTION
considering the general aspects, the results of Localization Software sim-
ulations as well as routing potocols analysis of Part II. Open Issues and
Future Aspects are also introducted and addressed.
Appendix A covers U.S. AirForce Airborne Networking solution. This so-
lution is dierent, in spite of the same name, from that is topic of this thesis,
both in terms of connectivity type and architecture design: but can be a good
term of comparison. U.S. Airborne Network is explained in detail, as well as
how is dierent from Airborne Networking and not suitable to satisfy our goal.
Part I
Reference Scenario: the case
of Italian Airspace
7
Chapter 2
General Aspects
In this chapter, all main informations in order to understand a particular
scenario as the Aviation Space is, are explained in details [12] [11].
2.1 Airspace Authorities
Generally, Air Trac Control (ATC) involves communication with air-
crafts to help maintain separation - that is, the authority responsible for the air
trac control, ensures that aircrafts are suciently far enough apart horizon-
tally or vertically for no risk of collision. Controllers may coordinate position
reports provided by pilots, or in high trac areas they may use RADAR to
see aircraft positions. ATC is especially important for aircraft 
ying under
Instrument Flight Rules (IFR), where they may be in weather conditions that
do not allow the pilots to see other aircrafts. However, in very high-trac
areas, especially near major airports, aircraft 
ying under Visual Flight Rules
(VFR) are also required to follow instructions from ATC.
In addition to separation from other aircrafts, ATC may provide weather
advisories, terrain separation, navigation assistance, and other services to pi-
lots, depending on their workload.
Summarizing, ATC aims to satisfy these goals:
 prevent collision among aircrafts
 prevent collision between aircrafts and obstructions on the airports' ma-
neuvering area
 speed up and keep in order the air trac 
ow
And it consists of the following services:
 Airport Control Service, provided by a TWR (Control Tower). It
consists of procedures to manage the 
ight in aerodrome zones.
 Approach Control Service, provided by a TWR, or by an ACC (Area
Control Centre) when it's necessery or preferable group all the control
services under the same authority, or by a separated authority APP. It
consists of procedures to manage the 
ight in the appoach phase.
 Area Control Service, provided by an ACC. It consists of procedures
to manage the 
ight in the cruising phase.
9
10 CHAPTER 2. GENERAL ASPECTS
In order to reach the goals, an ATC must:
 have informations about the movements of each 
ights, that is the 
ight
plans or any variation of it.
 determine based on the received informations, the relative positions of
all the aircrafts among each other.
 issue authorizations and informations (through messages called NO-
TAM ) in order to aim the already explained goals.
 coordinate the authorizations with other authorities every time an air-
craft could con
ict against a trac 
ow controlled by those authorities.
Figure 2.1 shows an example in the Italian Airspace of the dierent services
provided by the ATC.
Figure 2.1: ATC services
2.2 The concept of Flight
The term 
ight means a portion of airspace constructed upon conventional
points of intersection. The airway consists both by the nominal route and the
portion of airspace around it as airway's protection area. The nominal route
is dened by a magnetic orientation.
Aircrafts can 
y based on two type of 
ight rules:
 IFR. Instrumental Flight Rules re a set of regulations and procedures for

ying aircraft whereby navigation and obstacle clearance is maintained
with reference to aircraft instruments only
 VFR. With Visual Flight Rules, the pilot is ultimately responsible for
navigation, obstacle clearance and trac separation using the see-and-
avoid concept.
In generalized sense, a 
ight consists in the following 
ight phases:
CHAPTER 2. GENERAL ASPECTS 11
1. on-ground (standing)
2. taxiway
3. take-o
4. ascending
5. cruising
6. course changes
7. descending
8. waiting loops
9. landing
Every airplane that wants to 
y has rst to submit a 
ight plan to ATC
Authority. In the follow, it's presented how ATC works in the dierent phases.
The Control Tower (TWR-Aerodrome Control Service) guarantees safety
to the aircraft on the airport and its vicinity. The Ground Controller is respon-
sible of controlling aircraft ground movement, from the moment of departure
from their gate and while taxiing. Then the Ground Controller hands the

ight over to the Tower Controller: this gives to the aircraft the authorization
to take o so that a safety distance from all the other aircraft is guaranteed.
The Approach Control Service (APP) is responsible for routing aircraft
just airborne, allowing them to climb to join an airway.
The handling of the 
ight passes then to the Area Control Center (ACC),
whose duty is to harmonize each aircraft entrance and exit from the consistent
trac 
owing along inside the airways. Aircrafts are assigned dierent 
ight
levels and they are given trajectories to follow, so that they always remain
apart from one another until they will be passed again to the APP. FL 0
(Flight level zero) corresponds to the pressure level of 1 atmosphere. So FL
1 corresponds to 100 foot/30m of altitude, FL 10 means 1000 foot/300m and
so on. The dierent 
ight levels are separated by 1 interval of pressure that
corresponds to 500 foot.
This last will handle each airplane's approach establishing the correct se-
quence and will lead them since they leave the airways to begin their descent
till they line up with the runway. Once the aircraft is established on the land-
ing path and has the airport in sight, the control of the 
ight is passed to
the control tower of destination which controls the aircraft up to its gate. An
airplane 
ies at 900 KM/H or 600 NM/H as cruise speed, while it is landing
the speed decreases till 150 NM/H.
In table 2.1, a brief list of abbreviations used in aeronautic terminology is
reported:
2.3 Time and Positioning Standard
2.3.1 The UTC as Time Standard
In aviation, the UTC (Universal Time Coordinated) is used as standard of
time. UTC is a time standard based on International Atomic Time (TAI) with
leap seconds added at irregular intervals to compensate for the Earth's slowing
rotation. Leap seconds are used to allow UTC to closely track UT1, which
means solar time at the Royal Observatory, Greenwich. The International
Atomic Time (TAI) is a coordinate time scale tracking notional proper time