CS434/534: GNU Radio

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GNU Radio
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Outline

• What is GNU Radio?
• Basic Concepts
• Developing Applications

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What is GNU Radio?

• Software toolkit for signalprocessing
• Software radio construction
• Rapid development
• USRP (Universal Software Radio Peripheral)
• Hardware frontend for sendingand receiving
  waveforms

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GNU Radio Components
Hardware Frontend
Host Computer
RF Frontend (Daugtherboard)
ADC/DAC and Digital Frontend (USRP)
GNU Radio Software
http//mobiledevices.kom.aau.dk/fileadmin/mobilede
vices/teaching/software_testing/Gnu_radio_lecture.
pdf
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GNU Radio Software

• Opensource software (GPL)
• Don't know how something works? Take a look!
• Existing examples 802.11b(Wi-Fi), ATSC (HDTV),
  OFDM, DBPSK, DQPSK
• Features
• Extensive library of signal processing
  blocks(C/ and assembly)
• Python environment for composing blocks (flow
  graph)

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GNU Radio Hardware

• Sends/receives waveforms
• USRP Features
• USB 2.0 interface (480Mbps)
• FPGA (customizable)
• 64Msps Digital to Analog converters
• 128Msps Analog to Digital converteres
• Daughterboards for different frequency ranges
• Available Daughterboard
• 400-500Mhz, 800-1000Mhz, 1150-1450Mhz,
  1.5-2.1Ghz, 2.3-2.9Ghz

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GNU Radio Hardware Schematic
Host Computer
RX/TXDaughterboard
ADC/DAC
FPGA
USB Interface
http//mobiledevices.kom.aau.dk/fileadmin/mobilede
vices/teaching/software_testing/Gnu_radio_lecture.
pdf
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Outline

• What is GNU Radio?
• Basic Concepts
• Developing Applications

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Basics Blocks

• Signal Processing Block
• Accepts 0 or more input streams
• Produces 0 or more output streams
• Source No input
• noise_source,signal_source,usrp_source
• Sink No outputs
• audio_alsa_sink,usrp_sink

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Basics Data Streams

• Blocks operate on streams of data

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Basics Data Types

• Blocks operate on certain data types
• char, short, int, float, complex
• Vectors
• Input Signature
• Data types for input streams
• Output Signature
• Data types for output streams

Two streamsof float
One streamof complex
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Basics Flow Graph

• Blocks composed as a flow graph
• Data stream flowing from sources to sinks

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Example OFDM Synchronizer
http//gnuradio.org/trac/raw-attachment/wiki/Wirel
ess/gr_ofdm.pdf
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GNU Radio Companion
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GNU Radio Companion (Cont'd)

• GNU Radio Companion
• Design flow graphsgraphically
• Generate runnable code
• Demonstration

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Outline

• What is GNU Radio?
• Basic Concepts
• Developing Applications

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Development Architecture
PythonApplication developmentFlow graph
construction

• Python
• Application management (e.g., GUI)
• Flow graph construction
• Non-streaming code (e.g., MAC-layer)
• C
• Signal processing blocks
• Certain routines also coded in assembly
• Why is the hybrid structure?

CSignal processing blocks
http//mobiledevices.kom.aau.dk/fileadmin/mobilede
vices/teaching/software_testing/Gnu_radio_lecture.
pdf
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Dial Tone Example
!/usr/bin/env python from gnuradio import
gr from gnuradio import audio from
gnuradio.eng_option import eng_option from
optparse import OptionParser class
my_top_block(gr.top_block) def
__init__(self) gr.top_block.__init__(self
) parser OptionParser(option_classeng_
option) parser.add_option("-O",
"--audio-output", type"string", default"",
help"pcm output device
name. E.g., hw0,0") parser.add_option("-
r", "--sample-rate", type"eng_float",
default48000,
help"set sample rate to RATE (48000)")
(options, args) parser.parse_args () if
len(args) ! 0 parser.print_help()
raise SystemExit, 1
sample_rate int(options.sample_rate)
ampl 0.1 src0 gr.sig_source_f
(sample_rate, gr.GR_SIN_WAVE, 350, ampl)
src1 gr.sig_source_f (sample_rate,
gr.GR_SIN_WAVE, 440, ampl) dst
audio.sink (sample_rate, options.audio_output)
self.connect (src0, (dst, 0))
self.connect (src1, (dst, 1)) if __name__
'__main__' try my_top_block().run()
except KeyboardInterrupt pass
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Dial Tone Example (1)
from gnuradio import gr from gnuradio import
audio from gnuradio.eng_option import
eng_option from optparse import OptionParser
Import modules from GNU Radio library
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Dial Tone Example (2)
class my_top_block(gr.top_block) def
__init__(self) gr.top_block.__init__(self
)
Define container for Flow Graph gr.top_block
class maintains thegraph
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Dial Tone Example (3)
Define and parse command-line options
parser OptionParser(option_classeng_op
tion) parser.add_option("-O",
"--audio-output", type"string", default"",
help"pcm output device
name. E.g., hw0,0") parser.add_option("-
r", "--sample-rate", type"eng_float",
default48000,
help"set sample rate to RATE (48000)")
(options, args) parser.parse_args () if
len(args) ! 0 parser.print_help()
raise SystemExit, 1
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Dial Tone Example (4)
Create and connect signal processing blocks
sample_rate int(options.sample_rate)
ampl 0.1 src0 gr.sig_source_f
(sample_rate, gr.GR_SIN_WAVE, 350, ampl)
src1 gr.sig_source_f (sample_rate,
gr.GR_SIN_WAVE, 440, ampl) dst
audio.sink (sample_rate, options.audio_output)
self.connect (src0, (dst, 0))
self.connect (src1, (dst, 1))
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Dial Tone Example (5)
Run the flow graph when the program is executed
if __name__ '__main__' try
my_top_block().run() except
KeyboardInterrupt pass
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Useful Links

• Homepage (download, more links, etc)
• http//gnuradio.org/trac/
• More comprehensive tutorial
• http//gnuradio.org/trac/wiki/Tutorials/WritePytho
  nApplications
• Available Signal Processing Blocks
• http//gnuradio.org/doc/doxygen/hierarchy.html
• GNU Radio Mailing List Archives
• http//www.gnu.org/software/gnuradio/mailinglists.
  html
• CGRAN 3rd Party GNU Radio Apps
• https//www.cgran.org/
• OFDM Implementation Presentation
• http//gnuradio.org/trac/wiki/Wireless

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Backup
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Creating Your Own Block

• Basics
• A block is a C class
• Typically derived from gr_block or gr_sync_block
  class
• Three components
• my_block_xx.h Block definition
• my_block_xx.cc Block implementation
• my_block_xx.i Python bindings (SWIG interface)

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Block Definition
include ltgr_sync_block.hgt class
my_block_cc typedef boostshared_ptrltcs434_my_b
lock_ccgt cs434_my_block_cc_sptr cs434_my_block_c
c_sptr cs434_make_my_block_cc() class
my_block_cc public gr_sync_block private uns
igned int d_count friend cs434_my_block_cc_sptr
cs434_make_my_block_cc() cs434_my_block_cc()
public int work(int noutput_items,
gr_vector_const_void_star input_items,
gr_vector_void_star output_items)
Create instances of block
Method for processing input streams andproducing
output streams
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Block Implementation (1)
ifdef HAVE_CONFIG_H include "config.h" endif
include ltmy_block_cc.hgt include
ltgr_io_signature.hgt cs434_my_block_cc_sptr
cs434_make_my_block_cc() return
cs434_my_block_cc_sptr(new cs434_my_block_cc())
cs434_my_block_cccs434_my_block_cc()
gr_sync_block("my_block_cc", gr_make_io_signatu
re(1, 1, sizeof(gr_complex)), gr_make_io_signat
ure(1, 1, sizeof(gr_complex))), d_count(0)
Helper method to create block
Define input and output signatures
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Block Implementation (2)
int cs434_my_block_ccwork(int
noutput_items, gr_vector_const_void_star
input_items, gr_vector_void_star
output_items) const gr_complex in (const
gr_complex)input_items0 gr_complex out
(gr_complex)output_items0 memcpy(out, in,
sizeof(out) noutput_items) for (int i 0
i lt noutput_items i) fprintf(stderr,
"u\tlt.6f, .6fgt\n", d_count, ini.real(),
ini.imag()) return noutput_items
Copy input stream to output stream
Echo samples stderr
Return number of items processed
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SWIG Interface
Condensed copy of block definition (in header
file)
GR_SWIG_BLOCK_MAGIC(cs434, my_block_cc) cs434_my
_block_cc_sptr cs434_make_my_block_cc() class
cs434_my_block_cc public gr_sync_block private
cs434_my_block_cc()
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Outline

• What is GNU Radio?
• Basic Concepts
• Developing Applications
• HW2 Introduction

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HW2 Overview

• Implement MAC layer for a wireless device
• Link-layer header
• Carrier-sensing and backoff
• Link-layer acknowledgments
• Template code at
• https//www-net.cs.yale.edu/svn/courses/cs434/spri
  ng09/hw4/gr-cs434-hw4/