Presentation of the paper "AN IMPLEMENTATION OF SOFTWARE DEFINED RADIOS FOR FEDERATED AEROSPACE NETWORKS" at the 8th International Workshop on Satellite Constellations and Formation Flying, 8 - 10 June, TUD, Delft

1. AN IMPLEMENTATION OF
SOFTWARE DEFINED RADIOS FOR
FEDERATED AEROSPACE NETWORKS:
INFORMING SATELLITE IMPLEMENTATIONS USING AN
INTER-BALLOON COMMUNICATIONS EXPERIMENT
Rustam Akhtyamov, Ignasi Lluch, Hripsime Matevosyan, Dominik Knoll, Udrivolf Pica,
Marco Lisi and Alessandro Golkar
June 2015

2. Outline
2
1. Problem background;
2. Experimental Approach;
3. Experimental campaign results;
4. Limitations and future work;
5. Conclusions
June 2015

3. Background: FSS needs
3
FSS concept requires a single, unique
and universal TT&C transponder that
can be reusable for the maximum
number of spacecraft designs with the
minimum recurring cost
June 2015
Federated Satellites Systems (FSS) are
networks of spacecraft trading previously
inefficiently allocated and unused
resources: downlink bandwidth, storage,
processing power, and instrument time

4. 4
Background: Software defined radio (SDR)
technology
Tailored solutions Commercial off-the-shelf
solutions (COTS)
RF coverage custom from 70 MHz – 6 GHz already today
HDLs VHDL, Verilog VHDL, Verilog
graphical
programming
environments
- GNU Radio, Simulink, LabVIEW
Examples
SDR TT&C Transponder,
developed under ESA ARTES
Program
USRP N210, developed
by Ettus Research
June 2015

5. Goal and objectives of the work
5
Goal
To understand the performance of a Commercial Off The Shelf (COTS)
Software Defined Radio (SDR) system as a key technology for Federated
Satellite Systems (FSS).
In particular: what is the performance of such communications system in a
near-space environment?
Specific objectives
1.Demonstrate the operations of COTS SDRs and single-board computers in
environments with characteristics out of industrial range;
2. Experimentally characterize the long range performance of such system;
3.Demonstrate Federated Satellite Systems concept on a High Altitude
Balloon (HAB) network flight.
June 2015

6. Experimental set-up
6June 2015
HAB2
32 km
Ceiling
Altitude
5 element Yagi on Celestron tracking mount
Ping for status/ Receive broadcasts
HAB1
3kg platforms
6,6 m/s
Ascent Rate
Each HAB broadcasts its telemetry data comprising coordinates, altitude, time, and
relays data from the other HAB upon receiving.
Tracking
Ground
Station (GS)
2 Stratospheric Balloons (HABs)

7. Ground Station structure
7June 2015
All electronics were covered by a foam box for protection. The GS
antenna is a 5 element Yagi mounted on an azimuth – elevation
tracking mount.
Tracking Laptop
Matlab
BladeRF
Software
Defined Radio
USB
RF amplifier
RF switch
Coax
Coax
TTL
5V
24V
5V
Receiver Laptop
GNU Radio
Power
BUS
Lithium Polymer
11.1V 4000 mAh
Electronics deck mounted on tripod
CELESTRON AUTOMATED TRIPOD
Manual command
USB to com

8. Tracking Ground Station
8
External and internal views of the Tracking Ground Station

9. HAB payload structure
9June 2015
Raspberry Pi 2
BladeRF
Software
Defined
RadioArduino
MEGA2560
USB
RF
amplifier
Power
BUS
GPS
GSM
Gyroscope,
Compass,
Barometer,
Thermometer
I2C
UART
UART
RF
switch
GoPRO
Independent Recovery System
(SPOT)
Coax
Coax
TTL
Auxiliary
USB
battery
Lithium Polymer
11.1V 5500 mAh
Structure:
Double deck detachable
Electronics support
5V
12V
5V
24V
5V
UART
Sensor bus
Communications subsystem

10. HAB payload: mounting desk view
10
The inferior (left) and superior (right) decks of the HAB platforms

11. HAB payload: foam container view
11
Foam container for electronics and ground metal plane

12. Communications module structure
12June 2015
• An RF 20-500MHZ 1.5W power
amplifier is used for signal
amplification.
• In order to operate with a single
antenna, the RPi2 controls an
absorptive SPDT Solid State RF
Switch ZFSWA2-63DR+ that
connects the TX and RX ports of
BladeRF to the omnidirectional
antenna.
• The RF chain is completed with
a ground metal base plate of
350x350 mm, which is required
for the omnidirectional
monopole
BladeRF SDR
USB
Coax
Coax
TTL
RPi2
RF switch
RF
amp

13. Communications protocol (pure ALOHA)
ID
{9 bytes}
DATA (Time; Lat; Long; Alt)
{21..52 bytes}
Secondary ID
{10 bytes}
Retransmitted data
(ping confirmation)
{27..61 bytes}
13
BladeRF
RF Front End
PC / RPi2
USB 3.0
RF
IF
RF
IF
LNA
RF amp
RX
TX
A
D
A
D
FPGA
•Data rate
conversion
•Timing
GNU Radio
Signal Processing
• Synchronization
• Modulation
• Demodulation
Bash script
Structure of the message generated by Bash script
June 2015

14. Communications protocol (pure ALOHA)
14
Time profile of operations
1..5 s – reading data from the
Sensor Bus, forming messages
2 s – TX script initialization
8 s – TX script execution
2 s – RX script initialization
8…23 s – RX script execution
Bash script flow diagram
June 2015

15. GNU Radio flow graphs
15
Transmitter script
File Source  Packet Encoder  GMSK Mod  Polyphase Synthesizer  Sink
Receiver script
Source  Xlating FIR Filter  GMSK Demod  Packet Decoder  File Sink
June 2015

16. Radio link parameters
Central Frequency, Hz 446043750
Bandwidth, Hz 12500
Modulation GMSK
Data rate 3.3 kbps
Power, W 0.5
16
Expected range > 100 km
June 2015

17. 17June 2015
• Two HABs were
launched in Moscow
Region on April, 21st;
• Maximum altitudes
were 32 and 31 km;
• Flight durations were
2:29:17 and 2:40:24;
• Flight ground distances
were 104 and 95 km.
Experimental campaign

18. Experimental campaign: general results
• HAB2 was tracked by GS during the whole flight;
• HAB2(TX)-GS and HAB2(TX)-HAB1(RX) radio links were
operational till the landing (loss of direct line of sight);
• HAB1(TX)-GS radio link was operational for 15 minutes,
because of cable misconnection. However data were
recovering through HAB1(TX)-HAB2(RX) radio link for 45
minutes, thanks to Federated approach;
• I/Q data were recorded on the ground and on balloons.
18June 2015

19. Experimental campaign: radio links
19
HAB2 (TX) – HAB1 (RX) link:
Operational as predicted
Max distance – 16 km
BER – 0,3
HAB2(TX) – GS link:
Operational as predicted
Max distance – 90 km
BER – 0,63
HAB1(TX) – HAB2(RX) link:
Misbehavior
Max distance – 4 km
HAB1(TX) – GS link:
Misbehavior
Max distance – 11 km
June 2015
Antenna pointing
error

20. Known Limitations
• Russian Federation Radio Regulation law;
• GNU Radio bugs;
• Absence of an internal clock in RPi2;
• Selected Protocol limitations;
• Insertion losses of cables and adapters.
20June 2015

21. Future work
21
This work paves the way to future research in COTS SDR to realize Software
Defined Networks:
June 2015
• VHDL-based communications
protocols (higher utilization of
BladeRF FPGA).
• the evolution of the code written in
GNU Radio to enhance the usage of
embedded systems.
An improvement of the current communications protocol is required:
• An upgrade to Slotted ALOHA • Internet Protocol could be adapted
and implemented.
These upgrades would increase the channel utilization and give the
possibility to add more nodes into the system. In order to increase the
reliability and agility of the tracking system, it should be fully automated

22. Conclusions
22
1. Despite frequency band and power limitation, the designed
system based upon Nuand's BladeRF and single-board
computer RPi2 can establish radio links at more than 90km
distance with a margin larger than 10 dB.
2. We experimentally demonstrated that our Federated
Approach substantially increased the resilience of the
ad-hoc network. In our case it increased time of
operations by a factor of three.
3. Our experimental system can be evolved to implement
mobile ad-hoc networks on small satellites.
June 2015

23. 23
I would like to thank our MONSTER team!
MObile Networking for Space Technology Experimental Research
June 2015

24. 24
Thank you!
June 2015

25. Backup slides
25June 2015

26. Flight Profiles of HAB1 and HAB2
26June 2015

27. 27
Myriad-RF UmTRXZepto-SDR
HackRF USRP B210 BladeRF
COTS SDRs
June 2015

28. COTS SDRs comparison
HackRF
bladeRF USRP
x40 x115 B100 Starter B200 B210
Radio Spectrum
30 MHz – 6
GHz
300 MHz – 3.8 GHz
50 MHz –
2.2 GHz [1]
50MHz –
6 GHz
Bandwidth 20 MHz 28 MHz 16 MHz [2] 61.44 MHz [3]
Duplex Half Full Full Full 2x2 MIMO
Sample Size
(ADC/DAC)
8 bit 12 bit
12 bit /
14 bit
12 bit
Sample Rate
(ADC/DAC)
20 Msps 40 Msps
64 Msps /
128 Msps
61.44 Msps
Interface
(Speed)
USB 2 HS
(480 megabit)
USB 3 (5 gigabit)
USB 2 HS
(480 megabit)
USB 3
(5 gigabit)
FPGA Logic
Elements
CPLD 40k 115k 25k 75k 150k
Microcontroller LPC43XX Cypress FX3 Cypress FX2 Cypress FX3
Open Source Everything
HDL + Code
Schematics
HDL + Code
Schematics
Host Code [5]
Availability January 2014 Now Now Now
Cost $300 [6] $420 $650 $675 $675 $1100
28June 2015

29. RF switch
29
Absorptive SPDT Solid State RF Switch ZFSWA2-63DR+
June 2015

30. Compliance with Russian Radio regulations
(SCRF protocol #05-10)
30
Frequency 446-446.1 MHz
RF power < 0.5 W
Level of side lobes < 0.25 μW
June 2015