Satellite Segment Roadmap
Satellite
segment options for WirelessCabin have been studied. To this end, we have taken
the perspective of a designer whose task is to develop a tailored satellite
system for global aeronautical applications. System design, capacity and market
issues for a global satellite system to serve commercial aeronautical broadband
communications (AirCom) are considered in this
approach.
First,
the integrated global system design approach has been further developed in
top-down manner, as presented in Figure 1 Single blocks such as spectrum
issues, market and business case options, aeronautical channel implications and
airborne terminal antenna design have been investigated and summarized at a
lesser level of detail, for reasons of completeness, whereas
w constellation and coverage issues,
w methodology and numerical treatment of the capacity dimensioning process, and
w revenue estimation and market opportunities
have
been further developed and discussed in detail, forming the core of the work and
of the related final Deliverable D6 ‘Satellite Market Opportunity
Report’.
Figure 1: Capacity dimensioning steps within the system design process
Due to
their crucial relevance in the considered global scenario, satellite
constellation and coverage issues have been investigated in detail. The notion
of ‘effective elevation’, or ‘virtual horizon’ from the
perspective of a cruising aircraft has been introduced, see Figure 2, in order
to evaluate the effective coverage limitations particularly of GEO satellites
at higher latitudes.
Figure 2: Illustration of relevant
angles concerning aircraft-satellite visibility
Considering
the basic GEO vs. non-GEO option, we have concluded with the following
outcomes:
w For the near-term future and any evolutionary approach towards aeronautical multimedia communications, a broadband network based on geostationary satellites seems to be the first option. At least predecessor systems and/or services are available today that are mainly based on GEO satellite transponders. An outstanding candidate is the upcoming Inmarsat B-GAN system.
w The main critical issues in a GEO system are the coverage deficiencies at higher latitudes and the extreme antenna steering requirements at lowest elevation angles (i.e. again highest latitudes), and this in the light of the important near-polar flight routes in the northern hemisphere.
w With an appropriate non-GEO (LEO, MEO, or HEO) satellite constellation coverage with clearly higher elevation angles could be realized in near-polar regions. Moreover, potential system capacity limitations and latency for real-time communications could be reduced. On the other hand, besides system costs, especially networking complexity tends to increase while moving to lower orbits; satellite handover will become a major issue.
w Besides global coverage, availability and reliability are also particularly crucial for an integrated satellite AirCom/ATM approach. In light of this, constellation systems may also gain interest by a constellation design for multiple visibility.
w Among the non-geostationary candidates a MEO solution is the most promising alternative to a GEO system. A MEO system can be regarded as a somewhat reasonable trade-off between (i) coverage/elevation statistics provided, (ii) system complexity, costs and resource utilization (better than LEO), and (iii) moderate latency, acceptable also for real-time services (a significant drawback for HEO here).
As an outcome of all these investigations, consequently a set of useful candidate GEO and MEO constellations has been derived to serve as reference constellations for further numerical studies. These include Inmarsat B-GAN (GEO), Galileo*, a slight variation of the original Galileo MEO constellation and another reference MEO constellation called MEONET.
A key issue in setting up a mid- to long-term satellite segment roadmap for global aeronautical WirelessCabin services is the estimation of aggregate capacity requirements over both geographic location and time, and extraction of the worst case thereof. Capacity demand figures are essential input to
w satellite system planning and design;
w business model studies addressing the market/revenue potential and the cost analysis.
This work
has defined a generic approach to this issue, as illustrated in Figure 3, which
essentially combines the processing of numerical data with scalable and
parametric modelling elements. The top-down implementation of the shown
components in an integrated software tool has been completed and used for
numerical performance evaluation.
Figure 3: Capacity requirements estimation approach.
Finally,
by applying straightforward service pricing assumptions, the expected revenues
from passenger telephone and Internet services offered on
As a
summary of work, some reference results are displayed in the following figures
and tables.
Figure 4: Number of airplanes vs.
satellite and time
|
|
MEONET |
Galileo* |
B-GAN |
|||||||||
|
|
Criterion 1 |
Criterion 2 |
Criterion 1 |
Criterion 2 |
Criterion 1 |
Criterion 2 |
||||||
|
|
in |
out |
in |
out |
in |
out |
in |
out |
in |
out |
in |
out |
|
Mbps |
51.4 |
17.2 |
39.5 |
13.2 |
39.8 |
13.3 |
19.7 |
6.6 |
56.1 |
18.7 |
45.3 |
15.1 |
Table 1: Worst-case gross capacity requirements per footprint (criterion 1: maximum elevation satellite;
criterion 2: maximum visibility satellite)
. 
Table 2: Estimated
daily and yearly revenues (in Euro) for