Attachment Attachment 1

This document pretains to SES-MOD-20190212-00172 for Modification on a Satellite Earth Station filing.

IBFS_SESMOD2019021200172_1625826

Viasat, Inc.

                                          Attachment 1

                                     Technical Description

                The technical parameters and specifications for the earth stations in motion
(ESIMs), models Mantarray M40 and GM40, authorized under Call Sign E180006, were
provided in the application for new license File No. SES-LIC-20180123-00055. In connection
with this request to modify the license to allow operations in 18.8-19.3 GHz, 28.6-29.1 GHz and
27.5-28.35 GHz band segments, Viasat demonstrates that the operations will be compatible with
the other services authorized in these bands. For ease of reference, Viasat includes technical
descriptions of the network and the ESIM terminals relevant to the sharing discussions

Network

                The M40 and GM40 ESIM antennas operate in the same ViaSat-2 Ka-band
network, using the same frequencies and access method, as residential customers using the fixed
VSAT equipment authorized under call sign E170088. In addition to supporting residential
customers, this satellite network also incorporates the functions necessary to support mobility
into the management functions of the Afterburner multi-frequency time division multiple access
(MF-TDMA) waveform technology operating on the network. The network allows the aircraft to
fly across the service area and seamlessly switch from spot beam to spot beam within the current
operational satellite and to switch between satellites as coverage dictates. The transmitted bursts
from the ESIMs use the same return link channels as used by the residential terminals and
represent just another burst out of many on any given return channel frequency.

               Because the Afterburner architecture employs adaptive coding and modulation,
the terminals could transmit at any code and modulation point within the library of available
choices. The available symbol rates are 5 mega-symbols per second, or megabaud (MBd),
10 MBd, 20 MBd, 40 MBd, 80 MBd, 160 MBd, and 320 MBd.

                 The Afterburner architecture is designed to operate at the lowest power density
modulation and code point that allows the link to close. The network employs adaptive power
control and reduces power when conditions permit, keeping the Es/No margin at 1 dB or less
above the intended operating point. When the modem has sufficient excess transmit capability, it
will automatically switch to the next higher symbol rate and increase data rate, keeping the
e.i.r.p. density at the minimum. This further reduces the likelihood that the system will impact
traffic on other satellites.

Antenna and Pointing Accuracy

                 The Mantarray antenna is a low profile waveguide horn array. The same
Mantarray mechanically steered waveguide horn array antenna aperture is used for both earth
stations in this application. The Mantarray M40 uses a 4 W PA and is capable of operating over
the 28.1-30 GHz band. The Global Mantarray, or GM40, earth station antenna is the second-
generation Mantarray. This earth station has a power amplifier output of 31.6 W and is capable
of operating over the 27.5-30 GHz range. The “40” designation in the Mantarray M40 and
Mantarray GM40 model name reflects the number of feed horns across the width of the aperture.
The aperture retains the same 5:1 width to height ratio.


Viasat, Inc.



               As the GM40 and the M40 share the same Mantarray aperture design, they have
the same antenna pattern, and the principal differences between the two earth stations are power
output and tuning range. Due to its lower PA output power and higher loss between the PA and
aperture, the M40 antenna is capable of operating only over a limited number of the available
Afterburner symbol rates, whereas the GM40 with its higher power output supports the full range
symbol rates used with the ViaSat-2 Afterburner waveform. Because the higher power of the
GM40 is spread over a wider bandwidth than the M40 at the higher symbol rates, the resulting
EIRP density of the GM40 is the same or less than the M40 in clear sky conditions.

               The maximum clear sky e.i.r.p. density for the M40 uses the 5 MBd rate and for
the GM40 is the 80 MBd rate. For both antennas, this results in the same 12.5 dBW/4 kHz
maximum e.i.r.p. density. However, nominally, the earth stations use either the next step higher
symbol rate—10 MBd for the M40 and 160 MBd or 320 MBd for the GM40 as conditions
permit, with the 5 MBd and 80 MBd symbol rates being used primarily in beam edge of
coverage conditions. In the case of the GM40, the remaining lower symbol rates are used only
when links are degraded to mitigate the effects of rain and atmospheric conditions.

               Both versions of the Mantarray antenna will be fuselage mounted typically as
depicted in Figure 1 and will be covered by a radome.1

                The terminal is directed toward the intended satellite by the antenna control unit
(ACU), which receives input data from the inertial reference unit (IRU) that is part of the
avionics navigation system of the aircraft. This input includes information, such as the current
latitude, longitude, altitude, pitch, roll and yaw. The antenna control unit uses this information to
calculate the initial pointing angles for the antenna to the desired satellite. Once the required
pointing angles have been determined, the ACU drives the antenna to the desired position and
the modem seeks to acquire the receive signal from the satellite. When the signal is received and
the modem is able to properly identify and demodulate the carrier, the antenna enters a closed
loop tracking mode.




1
       The same radome may also house a receive-only antenna for DBS satellite TV services.
       The DBS satellite receive-only antenna and service are not associated with, or part of,
       this application.


                                                 2


Viasat, Inc.




                        Figure 1 – Typical Antenna Mounting Location

                 By performing closed loop tracking, the ACU is able to properly account for any
installation alignment differences between the IRU / airframe and antenna, as well as bending of
the aircraft body on the ground or in flight. The antenna system also incorporates local rate gyros
to mitigate latency between the IRU and the Mantarray ACU and further improve pointing
accuracy.

Antenna Patterns

                Viasat incorporates by reference the antenna patterns provided in the original
license application for these earth stations (see File No. SES-LIC-20180123-00055, Exhibit B).
The antenna patterns generated by the Mantarray antenna differ from those typically encountered
when considering circular or mildly elliptical reflector type antennas. The patterns are
characterized by a narrow main beam and a line of sidelobes in the azimuth axis, a wide main
beam and line of sidelobes in the elevation axis, and relatively low amplitude sidelobes
elsewhere. Figure 2 depicts an X-Y view of the azimuth and elevation patterns when looking
directly into the boresight of the antenna. The figure illustrates the lobes that exceed the Section
25.138 mask in some respects.

                Notably, there are four grating lobes in the transmit antenna patterns that are well
removed from the main lobe. These grating lobes are present at the geostationary satellite orbital
(GSO) arc only for a limited range of skew angles centered around approximately 25º of skew.
The location and amplitude of the grating lobes is a function of transmit frequency and typically
are between 25 and 35 degrees off axis from the main lobe. A 25-degree skew cut pattern
showing the magnitude of these grating lobes is also included in Exhibit B. While the amplitude
of these grating lobes when operating at the highest clear sky e.i.r.p. is as much as 5 dB above
the 25.138 off-axis e.i.r.p. density mask, the location of these lobes with respect to the GSO arc
is such that the lobes do not intersect the GSO arc except when the aircraft is located in a limited
number of geographic areas. Viasat has analyzed the potential impact to the spacecraft at the
affected locations and found the actual level of interference to be minimal—less than 2% DT/T at


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Viasat, Inc.


the nominal symbol rate of 160 MBd, and less than 4% DT/T at the lowest clear sky symbol rate
of 80 MBd, in the case of the GM40.

                Figure 2 depicts the grating lobes as viewed looking into the boresight of the
antenna. The three colored dotted lines represent the GSO arc from the perspective of the
terminal at three different geographic locations: Red is Carlsbad, CA, Green is Denver, CO, and
Blue is Germantown, MD. The dots on each line represent satellites along the GSO arc at two
degree longitude increments.




                                             Figure 2

                 The only GSO satellites potentially affected by the grating lobes are the DirecTV
satellites operating at the 99º -103º WL nominal orbital locations and are 29-33 degrees away
from ViaSat-2. Viasat has coordinated the operation of the Mantarray M40 and GM40 antennas
with this satellite operator. In any event, these satellites do not operate in the 18.8-19.3 GHz,
28.6-29.1 GHz or 27.5-28.35 GHz frequencies that are the subject of this modification
application.

               Because the width of the main lobe of the antenna increases between the azimuth
and elevation axes as the antenna is rotated around the boresight, the alignment of the major axis
of the antenna with the GSO must be considered. As the geographic location of the aircraft
moves away in longitude from the longitude of the satellite (69.9º for ViaSat-2), the GSO arc
appears skewed with respect to the local horizon of the AES antenna. This skew angle is also



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Viasat, Inc.

affected by the banking of the aircraft while in flight. Viasat has evaluated the worst-case skew
angle within the operational service area of the AES antenna and determined it to be less than 50
degrees. The Mantarray antenna is fully compliant in the main lobe with the 25.138(a) mask for
the GSO arc up to a skew angle of 60 degrees. Accordingly, the Mantarray antenna control unit
monitors the skew and bank angle, and will automatically reduce power or inhibit transmissions
if the combination of bank angle and geographic skew would result in exceeding the authorized
or coordinated EIRP density at any applicable adjacent orbital locations. The current license
includes a condition that requires Viasat to cease transmissions if the antenna-to-GSO skew
angle exceeds 60 degrees and the off-axis EIRP spectral density emissions risk harmful
interference to a GSO space station. This condition also would protect any GSO spacecraft
operating in the additional proposed frequencies.

NGSO Sharing Analysis

                Viasat conducted an interference analysis for the various NGSO systems that
participated in the recent Ka band processing round to demonstrate compatibility with these
systems. This analysis is consistent with that provided and approved by the Commission in the
original license application (SES- LIC-20180123-00055) to demonstrate that the M40 and GM40
earth stations could operate without causing harmful interference into these NGSO systems
authorized or pending in the bands in which GSO FSS is designated as primary. When the
original application was filed, the Commission had not yet adopted service rules for ESIMs as an
application of the FSS in the Ka band, and out of an abundance of caution, Viasat requested a
waiver as needed to allow ESIM operations. Therefore, Viasat provided a compatibility analysis
demonstrating that ESIMs operated based on a waiver could protect NGSO systems. Thus, the
same analysis is applicable in the 28.6-29.1 GHz band, where GSO ESIMs must protect NGSO
operations, which are designated as primary.

               Of these NGSO systems, the technical parameters of both Mantarray antennas are
within the scope of Viasat’s existing coordination agreement with OneWeb, and Space Norway
does not have coverage over the license area.

                Analyses were performed for Audacy, Boeing, Karousel, Leosat, O3b, Theia,
Telesat, and SpaceX using the information in the Schedule S and technical narratives of the
applications of the NGSO operators and using the technical characteristics of the Mantarray from
this application including the antenna pattern with grating lobes. The analysis for each system
was conducted using the Visualyse Pro analysis software available from Transfinite Systems Ltd.

                In the software simulation, an ESIM was placed at the center of the NGSO’s
receiving beam next to a presumed gateway earth station of the NGSO system. The orbit of the
NGSO was propagated over a 30 day period while the ESIM transmitted using a typical duty
cycle, as required to support commercial aircraft services in order to generate I/N statistic over
time.2 While parked aircraft are technically temporary-fixed earth stations, not ESIMs, the
emissions are the same as if the aircraft were flying a holding pattern around the NGSO gateway
station. This simulation was performed to develop worst-case I/N and interference statistics.


2
       Due to the large number of similar orbital planes, the SpaceX simulation was only run for
       24 hours.


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   Viasat, Inc.

                  When the aircraft are in flight, they will normally transit through a typical NGSO
   receiving beam in a relatively short period of time. A nominal cruising speed of 250 m/s
   represents a cruising speed of 560 miles (902 km) per hour. Accordingly, an aircraft typically
   spends less than an hour in any given NGSO receiving beam. To simulate the effects of an
   ESIM transiting an NGSO receiving beam, an ESIM was configured in the simulation to travel
   between two points on either side of the receiving beam. The ESIM then was then flown forth
   and back repeatedly throughout the simulation duration.

                   While long- and short-term interference criteria have not yet been established for
   these NGSO systems, a reasonable benchmark to check for the presence of interference is the 6%
   DT/T coordination trigger. This value is equivalent to an I/N of -12.2 dB and represents an
   increase in the noise floor of the receiver of just 0.25 dB. In the case of GSO networks, this is
   also the long-term criterion for interference from an adjacent satellite network that could be
   received 100% of the time. So, if received I/N levels are less than the -12.2 dB, coordination is
   not required in the case of GSOs. If received I/N is greater than -12.2, but only for brief intervals
   and for a very small percentage of time, the brief noise floor increases are generally considered
   short-term interference, which are typically acceptable.

                   The results show that for the NGSO system most sensitive to the elevation beam
   of the Mantarray, the time statistics for percent of time less than -12 dB I/N increases from
   99.995% to 99.9994%, and the worst case I/N is reduced 3 dB in this scenario where the aircraft
   is flying at normal cruising speeds through the receiving beam. This is as reasonably expected
   because the aircraft is not in the beam full time, and when it is in the beam, it is not always at the
   beam center when transmitting. Received interference is reduced by the roll-off of the receiving
   beam pattern over the coverage area.


                   Table 2: Simulation Results for the Various NGSO systems

                                                                           Total
                   -12.2 dB                  % of time                   Exceeded                    Separation
                     I/N                     meeting       Worst I/N        (s) /       Longest        Angle
System            Exceeded      % Time       -12.2 dB        (dB)         month         Event (s)      (deg)
Audacy                No              0        100.000        -60.00          0            0             NA
Boeing                No              0        100.000        -19.00          0            0              6
Karousel              No              0        100.000        -23.00          0            0             20
Leosat               Yes       0.000965        99.9990         -2.72         26            1              7
O3b                  Yes       0.000116        99.9999         -1.13          3            1             7.6
SpaceX               Yes       0.000579        99.9994         -4.68         15            1             22
Telesat              Yes       0.000270        99.9997         -6.70          8            1            11.9
Theia
Holdings            Yes        0.000154        99.9998          -7.46        4              1               10

                   These simulations use a single ESIM in either the stationary or moving scenarios,
   which is a realistic representation of the actual operation of a larger number of ESIM terminals in
   the entire network, because these networks use MF-TDMA as described below. As described


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Viasat, Inc.

above, the ViaSat-2 GSO satellite network employs MF-TDMA as an access method for the
various residential user terminals and for the ESIMs accessing the satellite. In a time-division
multiple access system, only one station may transmit on a given frequency and polarization
within a beam at a given time. Each station transmits for a brief time and then another station
transmits and so on. There may be gaps or pauses between transmissions depending upon
network loading, but two stations never transmit on the same frequency at the same time.

                In the case of multi-frequency TDMA, a given station may dynamically change
frequencies as directed by the network controller and transmit on frequency A for burst 1,
frequency B for burst 2, and so on, or the station may transmit on frequency A for burst 1 and
burst 2, and remain on that frequency indefinitely—choice of frequency allocation and time slots
are up to the network management system. As with the residential earth stations which operate
under E170088, regardless of how many aircraft are flying through the same ViaSat-2 beam at a
given time, only one earth station, residential or ESIM, will transmit on the same return link
channel frequency at a time. Therefore, having a single ESIM in the simulation co-located with
an NGSO gateway 24/7 is representative of the highest possible interfering power because no
two earth stations, and certainly no two aircraft, will burst at the same time and aggregate their
energy. Thus, the I/N recorded in the simulation for an aircraft in the beam center of the NGSO
receiving beam represents the highest expected at any time

               While ViaSat-2 has many beams, these beams have a frequency and polarization
reuse pattern such that it is unlikely that any two adjacent beams which might fall inside the area
of a given NGSO receiving beam will be both co-frequency and co-polarization. While there
maybe be two ESIMs transmitting, one in one ViaSat-2 beam and one in the other ViaSat-2
beam, the two ESIMs will not be operating on the same frequency and polarization due to the
frequency reuse pattern of ViaSat-2. Therefore, it is very unlikely that transmissions from
adjacent ViaSat-2 beams will result in the aggregation of interference into the receiving beam of
an NGSO satellite.

                Lastly, as described above, while only a single ESIM may transmit at any given
time, multiple ESIMs may transmit one after the other, effectively increasing the percentage of
time interference is received on a given frequency—this does not, however, increase the I/N, just
the percentage of time in which it might occur. With the exception of operation near airports,
ESIMs are generally well distributed throughout a satellite receiving beam. The alignment
between the Mantarray antenna on each aircraft and the NGSO satellite will be different give the
various geographic locations of the ESIMs. Accordingly, even though multiple stations may
burst one after the other in a receiving beam, the elevation beam of each ESIM will not align
with the NGSO satellite and some of those bursts will not contribute toward effectively
increasing the duty cycle. As noted in Table 2 above, several NGSO systems have worst case
I/N values much lower than -12 dB I/N, and where a NGSO network’s worst case I/N is -12 dB
or greater, the percentage of time for a single aircraft is very low—in the region of < 99.999% of
the time. In those cases, even a theoretical hundredfold increase in the number of aircraft
transmitting one after the other still only raises the likelihood of hitting a -12 dB I/N to < 99.9%
of the time.

                 In addition, the ESIMs operate under control of a Network Management System
(NMS) that coordinates the real-time operations of the TDMA scheduler for each beam on the
satellite, cease transmission commands can be sent to individual earth stations for the duration of



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Viasat, Inc.

the brief period when the separation angle identified below falls below the specified minimum as
calculated by the NMS using data from Space Track or the NGSO operators.

UMFUS Sharing Analysis

                  The GM40 antenna will operate across the 27.5-28.35 GHz band, and the M40
antenna will operate only in the 28.1-28.35 GHz portion of this band. To assess compatibility
with the UMFUS in the 27.5-28.35 GHz band, an analysis was performed using Visualyse to
determine the power flux density (PFD) at a 10 m reference height above ground level from an
aircraft flying at 10,000 ft above ground level.

                 The analysis considered an aircraft flying at 10,000 ft above ground level rather
than an aircraft operating on the ground because Viasat is not seeking authority to operate below
10,000 ft in the UMFUS band. Communications below 10,000 ft, on the ground, and at the gate
will be conducted in 28.35-29.1 GHz and 29.5-30 GHz bands.

                 The Visualyse analysis uses the measured GM40 antenna pattern assumes the
maximum antenna input power of 31.6 W is being applied across one of several operating
symbol rates from 5 MBd to 320 MBd. The aircraft in the simulation is set to fly at 10,000 ft
above ground level directly over a reference antenna located at 10 m above ground level. The
flight starts approximately 230 km away from the airport and flies at 250 knots until it passes
over the airport and continues until it is approximately 230 km away in the other direction. The
operating elevation angle from the aircraft to the satellite is 43.6 degrees. As the aircraft is
flying at 10,000 ft, the UMFUS PFD reference antenna is always below the aircraft and
accordingly the angle downward from the aircraft toward the UMFUS PFD reference is always
negative and ranges from -1.8 degrees relative to the horizon to -89 degrees as the aircraft passes
over the top of the reference antenna on the ground and back up to -1.8 degrees at the end of the
simulation run. The total off-axis angle is the difference of the elevation angle towards the
satellite (43.6 degrees) minus the angle downward toward the UMFUS reference antenna (-1.8 to
-89 degrees), or 45.4 to 132.6 degrees.

                The simulation takes into consideration fuselage attenuation (airframe blockage)
according to Figure 3 and normal path and atmospheric losses but does not assume any clutter
losses between the aircraft and the antenna on the ground. At long distances, fuselage
attenuation is minimal but path loss is higher. At closer distances, the downward angle toward
the UMFUS PFD reference angle on the ground increases, as does the related fuselage
attenuation. As the airplane banks in flight the amount of fuselage attenuation varies but at no
point during the simulation run does the PFD exceed the -77.6 dBm/(m2 * MHz) limit at the
reference antenna location on the ground.

                                             Figure 3
                 Fuselage Attenuation (Aircraft Shielding) from Report ITU-R M.2221




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Viasat, Inc.
                                                                       Fuselage Attenuation
                                                45

                                                40

                                                35

                                                30

                                                25




                             Attenuation (dB)
                                                20

                                                15

                                                10

                                                 5

                                                 0

                                                 -5

                                                -10
                                                      0   20   40   60       80      100      120   140   160   180
                                                                     off-axis orientation (deg)




                Table 3 shows the values taken from the Visualyse simulation at a snapshot of
the point when the worst-case PFD value at the 5G reference measurement location occurred in
the simulation. The maximum observed PFD value was -123.2 dBW/(m2 * MHz), which is 15.4
dB below the -77.6 dBm/(m2 * MHz) limit in 25.136.

               Table 3: Visualyse simulation snapshot results

    Aero ESIM
    Antenna Input power                                                    31.6               W
    Modulated bandwidth                                                     5.0               MHz
    Input power density                                                     8.0               dBW/MHz
    Antenna on-axis gain                                                   40.0               dBi
    Antenna relative gain toward 5G                                       -59.1               dB
    Antenna off-axis gain toward 5G                                       -19.1               dBi
    EIRP density toward 5G                                                -11.1               dBW/MHz
    Path and atm loss toward 5G                                           127.5               dB
    Fuselage attenuation                                                   35.0               dB
    Power density at 5G ref location                                     -173.6               dBW/MHz
    Gain of m2 area                                                        50.5               dB/m2
    Power flux density at 5G ref loc                                     -123.2               dBW/(m2*MHz)
    Power flux density at 5G ref loc                                      -93.2               dBW/(m2*MHz)

                The analysis shows that the PFD limit for protection of UMFUS stations will be
met even at the highest potential operational EIRP density for the GM-40 which normally will
only be used in rain faded conditions. The nominal operational EIRP density in clear sky
conditions is an additional 12 dB lower, providing additional margin.




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Document Created: 0880-04-26 00:00:00
Document Modified: 0880-04-26 00:00:00

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