mpsk
DESCRIPTION
M-PSKTRANSCRIPT
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IntroductionDigital Modulation Study
Hands-on MPSK
Digital Modulation Primer
using GNU Radio
Thomas W. Rondeau
2014-02-13
Thomas W. Rondeau Digital Modulation Primer using GNU Radio
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IntroductionDigital Modulation Study
Hands-on MPSK
Download Materials
http://www.trondeau.com/gr-tutorial
Use examples for version 3.7
Presentation PDF
Case Study materials
GNU Radio apps to run examples.
Links to source code for analysis.
Data �le for �rst case study.
Images of expected output.
Exercises.
Thomas W. Rondeau Digital Modulation Primer using GNU Radio
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IntroductionDigital Modulation Study
Hands-on MPSK
Sources and Sinks (quick review)
sources_and_sinks.grc
Demonstration of using multiple sources to create a noisy sinewave and multiple sinks to view it in di�erent domains.
Thomas W. Rondeau Digital Modulation Primer using GNU Radio
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IntroductionDigital Modulation Study
Hands-on MPSK
Sources and Sinks (quick review)
sources_and_sinks.grc - Output
Showing PSD, spectrogram, and time domain of the noisysignal.
Thomas W. Rondeau Digital Modulation Primer using GNU Radio
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IntroductionDigital Modulation Study
Hands-on MPSK
Complex Numbers
z(t) = x(t)cos(2πf (t)t + φ(t)) + jy(t)sin(2πf (t)t + φ(t))
z(t) = c(t)e−j2πf (t)t+φ(t)
Information can be encoded in c(t), f (t), and φ(t).
Thomas W. Rondeau Digital Modulation Primer using GNU Radio
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IntroductionDigital Modulation Study
Hands-on MPSK
Complex Numbers: Polar Plots
Thomas W. Rondeau Digital Modulation Primer using GNU Radio
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IntroductionDigital Modulation Study
Hands-on MPSK
Modulating & Transmitting a Signal
mpsk_stage1.grc
Using a pre-build PSK modulator block from GNU Radio.
Thomas W. Rondeau Digital Modulation Primer using GNU Radio
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IntroductionDigital Modulation Study
Hands-on MPSK
Modulating & Transmitting a Signal
Thomas W. Rondeau Digital Modulation Primer using GNU Radio
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IntroductionDigital Modulation Study
Hands-on MPSK
The Received Signal
mpsk_stage2.grc
We can simulate a channel model with noise, frequency andtiming o�sets, and multipath.
Thomas W. Rondeau Digital Modulation Primer using GNU Radio
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IntroductionDigital Modulation Study
Hands-on MPSK
The Received Signal
Signal captured using a multipath channel with some AWGNnoise and timing o�set. No frequency o�set was used.
Thomas W. Rondeau Digital Modulation Primer using GNU Radio
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IntroductionDigital Modulation Study
Hands-on MPSK
After Timing Recovery
mpsk_stage3.grc
We use a control loop algorithm to �nd the right sampling timeto �x clock mismatches between the transmitter and receiver.
Thomas W. Rondeau Digital Modulation Primer using GNU Radio
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IntroductionDigital Modulation Study
Hands-on MPSK
After Timing Recovery
Showing a no-noise situation to illustrate ISI (self-interference)issues in the received signal before timing recovery andmatched �ltering.
Thomas W. Rondeau Digital Modulation Primer using GNU Radio
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IntroductionDigital Modulation Study
Hands-on MPSK
After Timing Recovery - With Noise
Even with noise, we can still recover the proper timing.
Thomas W. Rondeau Digital Modulation Primer using GNU Radio
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IntroductionDigital Modulation Study
Hands-on MPSK
Multipath in Brief
Multipath channels result from a signal bouncing o� objectsand hitting the receiver at di�erent times and with di�erentphases.
Thomas W. Rondeau Digital Modulation Primer using GNU Radio
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IntroductionDigital Modulation Study
Hands-on MPSK
E�ects of Multipath
mpsk_multipath.grc
This simulation allows us to adjust the multipath channel asthough we are adjusting a stereo's equalizer. (SA:multipath_sim.grc)
Thomas W. Rondeau Digital Modulation Primer using GNU Radio
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IntroductionDigital Modulation Study
Hands-on MPSK
Equalizing Multipath
Cartoon showing signal corrupted by multipath. Equalizer triesto invert the multipath so that the combination is a �atfrequency response.
Thomas W. Rondeau Digital Modulation Primer using GNU Radio
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IntroductionDigital Modulation Study
Hands-on MPSK
Equalizing Multipath
mpsk_stage4.grc
Using the constant modulus algorithm (CMA) blind equalizeris used here to correct multipath distortion.
Thomas W. Rondeau Digital Modulation Primer using GNU Radio
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IntroductionDigital Modulation Study
Hands-on MPSK
Equalizing Multipath
Note the similarity between the time-synchronized and �lteredoutput with multipath and the ISI of the signal before thematched �lter with no multipath.
Thomas W. Rondeau Digital Modulation Primer using GNU Radio
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IntroductionDigital Modulation Study
Hands-on MPSK
Equalizing Multipath
Equalization working with noise.
Thomas W. Rondeau Digital Modulation Primer using GNU Radio
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IntroductionDigital Modulation Study
Hands-on MPSK
Phase O�set Correction
mpsk_stage5.grc
The transmitter and receiver work o� di�erent clocks, so therewill be a frequency and phase o�set. We need to correct forany small frequency and phase o�sets.
Thomas W. Rondeau Digital Modulation Primer using GNU Radio
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IntroductionDigital Modulation Study
Hands-on MPSK
After Phase O�set Correction
Left �gure shows a rotate constellation. The Costas Loopblock �xes the o�set.
Thomas W. Rondeau Digital Modulation Primer using GNU Radio
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IntroductionDigital Modulation Study
Hands-on MPSK
After Phase O�set Correction - With Noise
Again, robust to AWGN.
Thomas W. Rondeau Digital Modulation Primer using GNU Radio
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IntroductionDigital Modulation Study
Hands-on MPSK
Using captured DQPSK data
mod01-intro/data/dqpsk_capture.32fc
Symbol rate of 1 Msps
Di�erential QPSK
RRC �lter with alpha=0.35
Captured with ~100 kHz frequency o�set
Use scripts/rx_data.grc to experiment
Thomas W. Rondeau Digital Modulation Primer using GNU Radio