open source software defined radio platform for gnss … open source sdr platform for gn… · x...

Open Source Software Defined

Radio Platform for GNSS

Recording, Simulation and

Tracking

Alison Brown

NAVSYS Corporation

Colorado Springs, CO

www.navsys.com

ION GNSS+ 2013

Session E3: Software Receivers September 19, 2013

http://www.navsys.com/

Steps for Building an SDR

GNSS Signal Simulator

• Step 1. Install GNU Radio Companion

Open Source software

• Step 2. Purchase GRC compatible SDR

that covers GNSS frequency bands

• Step 3. Configure GRC to record and

playback GNSS signals into GPS UE

• Step 4. Build simulated GRC files using

Signal Architect and playback to GPS UE

2

3

GNU Radio Overview • GNU Radio is a free & open-source software development

toolkit (http://gnuradio.org)

• Designed to be used with low-cost external RF hardware to

create SDRs

• Widely used in academic & industry labs

• GNU Radio Companion (GRC) is a graphical tool for

developers to easily create signal flow graphs and generate

flow-graph source code











4

BEIDOU BEIDOU AND GALILEO BEIDOU, GPS AND GALILEO GLONASS GPS GALILEO

GNSS Frequency Bands

5 1.16 to 1.61 GHz

BEIDOU B1I

1561.098 MHz

GPS+GALILEO L1

1575.42 MHz

GLONASS L1

16.02 MHz

GPS L2

1227.6 MHz

GNU Radio Compatible SDRs

• Ettus USRP™ family ($675+)

• B100+WBX (50 MHz-2.2 GHz, 8 Msps)

• N210+WBX (50 MHz-2.2 GHz,

25Msps, 2x2 MIMO)

• www.ettus.com

• Nuand blade RF ($420)

• X40 (300 MHz-3.8 GHz,

40 Msps, 2x2 MIMO)

• www.nuand.com

6











7

System Architecture

Windows / Linux Computer

· Garmin eMap· Novatel DL4-plus· Rockwell Collins DAGR· Etc.

GPS UE

Software Defined Radio

· Ettus USRP N210· Nuand bladeRF· Etc.

DSF to BINSignal

ArchitectSoftware

ScenarioPlan

GNURadio Companion

Ethernetor USB

Coax

DIG

ITA

LA

NA

LOG

8

Single band w/ GNU Radio Companion

Ethernet data rate

supports up to 25 Msps

16 bit I/Q data

Dual-Band System Architecture



GUE

Software Defined Radio 1


SignalArchitectSoftware

ScenarioPlan

NAVSYSMultibandExpansionSoftware

Ethernet / USB

Coax

DIG

ITA

LA

NA

LOG

MIMO Cable

https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&docid=pPoDj4dQonuDXM&tbnid=nTg62EVPGj35kM:&ved=0CAUQjRw&url=https%3A%2F%2Fwww.ettus.com%2Fproduct%2Fdetail

s%2FUN210-KIT&ei=mdw5UoqeK9PS2wWQ1oHoBw&bvm=bv.52288139,d.b2I&psig=AFQjCNHYKJ0N4ukewINUUUD9idHiLspa7g&ust=1379610128847728

SDR 2(slave)

9

Dual band with GNU Radio Companion & Ettus MIMO

- Limited to two radios

- All data on one computer

- Clock / PPS shared over MIMO cable

- Per-radio data bandwidth is halved

Multiband System Architecture



GPS UE

Software Defined Radio 1


SDR 2

. . .

SDR N

SignalArchitectSoftware

ScenarioPlan

NAVSYSMultibandExpansionSoftware

Shared Clock / PPS

Ethernet / USB

Coax

DIG

ITA

LA

NA

LOG

Coax

https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&docid=pPoDj4dQonuDXM&tbnid=nTg62EVPGj35kM:&ved=0CAUQjRw&url=https%3A%2F%2Fwww.ettus.com%2Fproduct%2Fdetail

s%2FUN210-KIT&ei=mdw5UoqeK9PS2wWQ1oHoBw&bvm=bv.52288139,d.b2I&psig=AFQjCNHYKJ0N4ukewINUUUD9idHiLspa7g&ust=1379610128847728

. . .

10

Multi band with NAVSYS Multiband Expansion Software

- Unlimited radios by using

multiple Computers

- Allows multiple computers to

… share data load

- Clock / PPS split externally

- Full per-radio bandwidth

…now available

11

GRC Dual-Band (MIMO)

Record/Playback Flow Graph

Multiband Approach Comparison

12

• With GNURadio & MIMO

• Easy setup

• All GNURadio Companion GUI and functionality

• Limit of 2 radios with ethernet limiting data to 25 Msps, 16

bit I+Q (100 MBps)

• All data flow through one computer

• Windows or Linux

• With NAVSYS Multiband Expansion Software

• Must manually split clock and PPS

• Command line interface

• Unlimited radios, full per-radio bandwidth with DAC bit

compression to reduce ethernet bandwidth usage

• Unlimited computers to share data load

• Currently Linux only – Windows version in development

Sample Dual-Band Implementation

• MIMO Example (<= 25 Msps)

• Left radio: L1, 4Msps (C/A)

• Right radio: L2, 20Msps (P)

• Dual band GRC output is

directed over Ethernet to

each radio

• NAVSYS Multiband Expansion

SW Example

• Left radio: L1, 25 Msps

(C/A+P+M’)

• Right radio: L2, 25 Msps

(P+M’)

• Single band I/Q output is

directed over Ethernet to

each radio from multiple

host computers

• Dual radio record and

playback simulation setup

13

Single band, L1-C/A on Garmin GPS III

Record & Playback Example

14

Dual band, L1-C/A and L2-P(Y) carrier phase on

NovAtel DL4-plus


15

Dual band, L1-C/A and L1-GLONASS on

NovAtel FlexPak G2-V1G


16



• Step 1. Install GNU Radio Companion Open

Source software

• Step 2. Purchase GRC compatible SDR that

covers GNSS frequency bands





17

GNSS Signal Architect

Software • Trajectory generation from Google Earth

(KML) or NMEA file

• Almanac file used to define SVs

• User defines mask angle, CN0 and GNSS

signals/codes to be generated

• Generates simulated IQ data files at each

GNSS frequency for GRC playback into

SDRs

18

GNSS Signal Architect Operation

• Generates simulated IQ data files for playback

through GNU Radio into SDRs

• IQ datafile is read from disk by GRC software

and sent to SDR for playback at RF

1) User selects the

simulation parameters

and trajectory

2) IQ datafile is created

using GNSS Signal

Architect Software

3) IQ datafile is

stored on disk

on GNURadio

Host Computer

4) IQ datafile is read from

disk by GRC software and

sent to USRP N210 for

playback at RF

Signal

Design

Signal

Creation

Signal

Archiving

Signal

Generation

RF Signal

Generation

19

GNSS Signal Architect

Simulator Software GUI

20

Signal Architect Features

21

Base Version

Interfaces with any GNU Radio Capable SDR

GPS Scenario Generation (Static and Dynamic)

GPS L1 Record / Playback + C/A code simulation

Real-time RF Signal Visualization

Multi-Core Processing to speed signal generation

Upgrades

Multiband Expansion Software (included with multi-frequency generation)

GLONASS(civil codes)

GPS Military P+M’ (L1 and L2)

BeiDou, Galileo and QZSS (in development)

Single band, Dynamic L1-C/A on Novatel DL4-plus

Simulated Scenario Example

Dynamic real world track recorded as

NMEA file using vehicle and used to

generate repeatable Signal Architect

scenario file to play back through GNU

Radio; Can also programmatically

generate precise NMEA/KML files

using any available software package

Dual band, Static L1-P and L2-P on Rockwell

Collins DAGR

Simulated Scenario Example

Simulated GRC Jammer Option

24

25

Advantages of Open Source

SDRs for GNSS Simulation • Inexpensive hardware for signal generation from

multiple Gnu Radio SDR vendors

• Intuitive signal flow generation using open source

Gnu Radio Companion interface

• Flexible upgrade path for multi-frequency/multi-

code generation

• Upgrade option with GNSS Toolbox Matlab source

code allows customized GNSS signal simulation

Backup

Ettus USRP Product Line

Model DB Slots Host

Intf

Max

BW

(MS/s)

DAC ADC MIMO CPU Codes

N200 1TX/1RX GigE 50 16-bit, 400

MSPS

14-bit, 100

MSPS Yes n/a

All

supported

N210 1TX/1RX GigE 50 16-bit, 400

MSPS

14-bit, 100

MSPS Yes n/a

All

supported

E100* 1TX/1RX Emb. 8 14-bit, 128

MSPS

12-bit, 64

MSPS No

OMAP

3730

All,

except P

E110* 1TX/1RX Emb. 8 14-bit, 128

MSPS

12-bit, 64

MSPS No

OMAP

3730

All,

except P

USRP1 2TX/2RX USB

2.0 16

14-bit, 128

MSPS

12-bit, 64

MSPS Yes n/a

All,

except P

B100 1TX/1RX USB

2.0 16

14-bit, 128

MSPS

12-bit, 64

MSPS No n/a

All,

except P

27

- Supported codes are currently: L1-C/A, L1-P, L1-GLONASS, and L2-P

- Future release: BeiDou

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