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

Outline

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1. Problem background;

2. Experimental Approach;

3. Experimental campaign results;

4. Limitations and future work;

5. Conclusions

June 2015

Background: FSS needs

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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

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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

Goal and objectives of the work

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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

Experimental set-up

6 June 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)

Ground Station structure

7 June 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

Tracking Ground Station

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External and internal views of the Tracking Ground Station

HAB payload structure

9 June 2015

Raspberry Pi 2 BladeRF Software Defined Radio Arduino

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

HAB payload: mounting desk view

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The inferior (left) and superior (right) decks of the HAB platforms

HAB payload: foam container view

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Foam container for electronics and ground metal plane

Communications module structure

12 June 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

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}

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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

Communications protocol (pure ALOHA)

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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

GNU Radio flow graphs

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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

Radio link parameters

Central Frequency, Hz 446043750 Bandwidth, Hz 12500

Modulation GMSK Data rate 3.3 kbps Power, W 0.5

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Expected range > 100 km

June 2015

17 June 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

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.

18 June 2015

Experimental campaign: radio links

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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

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.

20 June 2015

Future work

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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

Conclusions

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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

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

June 2015

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Thank you!

June 2015

Backup slides

25 June 2015

Flight Profiles of HAB1 and HAB2

26 June 2015

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Myriad-RF UmTRX Zepto-SDR

HackRF USRP B210 BladeRF

COTS SDRs

June 2015

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

28 June 2015

RF switch

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Absorptive SPDT Solid State RF Switch ZFSWA2-63DR+

June 2015

Compliance with Russian Radio regulations (SCRF protocol #05-10)

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Frequency 446-446.1 MHz RF power < 0.5 W Level of side lobes < 0.25 μW

June 2015