MP-IST-209-1760.pdf — page 9

F. Discussion
The Wi-Fi results illustrate the degradation in performance
when moving from static to dynamic environments, especially
in terms of bitrate and packet loss. UDP is particularly
sensitive to motion. In the TCP tests, 19.1 Mbit/s was obtained
with static communication.
The Wi-Fi-RAD-MAVLink-Bridge performs well in short-
range and moving conditions, with limited impact from move-
ment. However, distance significantly degrades performance,
particularly in bidirectional communication and UDP mode,
where packet loss becomes a significant issue, especially at 47
meters. The Raspberry Pi and GCS computer antennas have
an omnidirectional radiation diagram. Looking at a similar
example in a UAV configuration in [30], it’s clear that having a
directional antenna with a tracker on the GCS would increase
the range of a RAD-MAVLink-Bridge configuration. In the
TCP tests, 57.6 Mbit/s was obtained with static communica-
tion.
Analysing the results of P/PRC-535, maybe only one UGV
can be supported on the communication channel with this con-
figuration. This is because the Raspberry Pi has a bottleneck
on the communication channel, and because there is no traffic
control, the channel prioritises sending UDP. This proves to
be a problem, as it is more critical for the system to send an
Friendly Force Information (FFI) XMl than a HEARTBEAT
message. In the TCP tests, 574 bit/s was obtained with static
communication; in the UDP tests, 5.01 Kbit/s was obtained
with static communication.
After analyzing the results of the TR5000H tests, it can be
seen that this configuration can support one more UGV on the
communication channel. The TR5000H controls traffic since
it does not let UDP occupy all the capacity. More throughput
is used for TCP packets, which can be explained by the fact
that TCP packets are larger, so more throughput is used for
this transmission. One more time, the Raspberry Pi had a bot-
tleneck in the communication channel. In the TCP tests, 3.50
Kbit/s was obtained with static communication; in the UDP
tests, 2.49 Kbit/s was obtained with static communication. This
can be seen in the Table 2.
TABLE 2: Comparison of P/PRC-525 and TR5000H.
Radio
Transmission Rate
TCP: 574 bit/s
P/PRC-525
UDP: 5.01 Kbit/s
TCP: 3.50 Kbit/s
TR5000H
UDP: 2.49 Kbit/s
V. CONCLUSIONS
In this study, the first architecture for integrating UxVs
into the BMS was developed. It was possible to drive a
UGV without the need for specific autopilot hardware such as
Pixhawk line or Ardupilot Mega. Made integrations in BMS
developed for future exercises with entities outside the Army
using UxVs, such as ARmy Technological EXperimentation
(ARTEX), and data regarding the throughput required to drive
a UGV, different network architectures, and limitations of the
used hardware.
As for the Wi-Fi network tests, given that a communication
architecture was being used with relatively low-quality image
transmission and a relatively long position sending interval (10
seconds), it was noticeable that even in conditions with less
available bandwidth, it was possible to establish communica-
tion with the UGV. When there was less signal available, the
first thing that failed was the video transmission, with some
cuts in the image.
As for the tests with Wi-Fi-RAD-MAVLink-Bridge, it was
possible to observe that at short distances, it was possible
to command and control the UGV. However, the signal was
considerably degraded after about 40 meters. This configu-
ration is interesting for short distances and can be extended
using directional antennas. It can be applied as an alternative
to another radio communication mode, focussing on short
distances.
It was possible to communicate using military radios, as
only MAVLink HEARTBEAT and GPS RAW INT messages
and FFI XML were sent. Ideally, the frequency at which the
messages are sent should be adjusted considering the available
bandwidth, and the application itself, in the case of the P/PRC
525, would have to control the traffic. The TR5000H was
advantageous in almost all the tests. It performs automatic
traffic control and allows a parallel communication mode,
where data and voice can be sent simultaneously on two
channels, thus advantageous over the P/PRC-525.
It would be important to be more extensive in terms of the
test scenarios and frequencies used, but each test carried out
in Pac¸o de Arcos took a long time, leaving some interesting
configurations untested. The development that has been made
and the connection to the Mission Planner makes it possible
to drive a UGV with autopilot hardware using waypoints;
in a configuration like this, military radios would only be
necessary, as there would be no need to send video or control
commands.
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STO-MP-IST-209 
1760 - 9 
Integration of a Commercial 
Unmanned Vehicle into the Army Communications System