diff options
Diffstat (limited to 'gnuradio-examples/python/digital-bert')
| -rw-r--r-- | gnuradio-examples/python/digital-bert/Makefile.am | 33 | ||||
| -rw-r--r-- | gnuradio-examples/python/digital-bert/README | 62 | ||||
| -rwxr-xr-x | gnuradio-examples/python/digital-bert/benchmark_rx.py | 164 | ||||
| -rwxr-xr-x | gnuradio-examples/python/digital-bert/benchmark_tx.py | 111 | ||||
| -rw-r--r-- | gnuradio-examples/python/digital-bert/receive_path.py | 116 | ||||
| -rw-r--r-- | gnuradio-examples/python/digital-bert/transmit_path.py | 62 |
6 files changed, 548 insertions, 0 deletions
diff --git a/gnuradio-examples/python/digital-bert/Makefile.am b/gnuradio-examples/python/digital-bert/Makefile.am new file mode 100644 index 000000000..886033792 --- /dev/null +++ b/gnuradio-examples/python/digital-bert/Makefile.am @@ -0,0 +1,33 @@ +# +# Copyright 2008 Free Software Foundation, Inc. +# +# This file is part of GNU Radio +# +# GNU Radio is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation; either version 3, or (at your option) +# any later version. +# +# GNU Radio is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with GNU Radio; see the file COPYING. If not, write to +# the Free Software Foundation, Inc., 51 Franklin Street, +# Boston, MA 02110-1301, USA. +# + +include $(top_srcdir)/Makefile.common + +EXTRA_DIST = \ + benchmark_rx.py \ + benchmark_tx.py \ + receive_path.py \ + transmit_path.py + +ourdatadir = $(exampledir)/digital-bert +ourdata_DATA = $(EXTRA_DIST) + +MOSTLYCLEANFILES = *.pyc *.pyo *~ diff --git a/gnuradio-examples/python/digital-bert/README b/gnuradio-examples/python/digital-bert/README new file mode 100644 index 000000000..74d85b703 --- /dev/null +++ b/gnuradio-examples/python/digital-bert/README @@ -0,0 +1,62 @@ +BERT testing example scripts + + +benchmark_tx.py + +This sets up a BPSK transmitter that is modulated with a pseudorandom +sequence of bits. The PN code is generated by sending an all 1s +sequence through a 7-bit scrambler. The transmitter performs the BPSK +modulation, then passes the complex baseband waveform through a +root-raised-cosine filter and onto the USRP. + +The --sps parameter controls how many baseband samples per symbol +are created and passed through the RRC filter, prior to going to the +USRP over the USB for interpolation to the final DAC rate. + +The baseband bit rate is controlled by -r or --rate. This value, when +multiplied by the --sps parameter, must result in valid interpolation +rate for the USRP. For example, if the baseband rate is 250k bits/sec, +and the samples per symbol is 4, then the final rate is 1M samples/sec, +which results in an interpolation rate of 128. The valid interpolation +rates for the USRP are multiples of 4 between 16 and 512. + +Finally, the RRC excess bandwidth may be specified by --excess-bw. +(See ./benchmark_tx.py -h for additional parameters.) + + +benchmark_rx.py + +This sets up a BPSK receiver to demodulate the received waveform. It +accepts a similar set of parameters as the transmitter, except that one +specifies the USRP decimation rate desired. The resulting sample stream +rate must be an integral number of baseband symbols. For example, the +parameters corresponding to the above transmitter would be to use a +decimation rate of 8 (32 sps), 16 (16 sps), 32 (8 sps), 64, (4 sps), or +128 (2 sps). The lower the USRP decimation, the more CPU is required to +demodulate the signal, so not all valid decimation rates will work. + +The baseband signal from the USRP is first passed through an AGC to +establish an average power of 1.0. It is then passed through a matched +filter (another RRC), a Costas phase-locked loop, and an M&M bit timing +recovery loop. The resulting constellation has an SNR estimation probe +attached, and is then sliced into a bit stream. + +The recovered bits are then passed through a 7-bit descrambler. If +there are no channel errors, the all 1s sequence is recovered. In the +event of a channel error, there will be a 0 in the bit stream for each +feedback tap in the descrambler. In this case, the CCSDS descrambler is +using 3 feedback taps. + +Finally, the signal is passed into a bit density measurement probe. The +channel BER is measured by dividing the 0s density by three. This +measurement is inaccurate at high BER rates (>10%) as the error 0s +begin to overlap. + +The benchmark script will, once per second, output the mean symbol power, +the average noise variance, the estimated SNR, and the average BER. + +NOTE: The particular SNR estimator used is inaccurate below about 7dB, +and will report erroneously high values even for random noise. + +There are a variety of Costas and M&M loop parameters one can adjust. +See ./benchmark_rx.py -h for the full set. diff --git a/gnuradio-examples/python/digital-bert/benchmark_rx.py b/gnuradio-examples/python/digital-bert/benchmark_rx.py new file mode 100755 index 000000000..96bf7fa12 --- /dev/null +++ b/gnuradio-examples/python/digital-bert/benchmark_rx.py @@ -0,0 +1,164 @@ +#!/usr/bin/env python +# +# Copyright 2008 Free Software Foundation, Inc. +# +# This file is part of GNU Radio +# +# GNU Radio is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation; either version 3, or (at your option) +# any later version. +# +# GNU Radio is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with GNU Radio; see the file COPYING. If not, write to +# the Free Software Foundation, Inc., 51 Franklin Street, +# Boston, MA 02110-1301, USA. +# + +from gnuradio import gr, eng_notation, usrp +from optparse import OptionParser +from gnuradio.eng_option import eng_option +from receive_path import receive_path +import gnuradio.gr.gr_threading as _threading +import sys, time + +n2s = eng_notation.num_to_str + +class status_thread(_threading.Thread): + def __init__(self, tb): + _threading.Thread.__init__(self) + self.setDaemon(1) + self.tb = tb + self.done = False + self.start() + + def run(self): + while not self.done: + print "Magnitude: %5.3f Variance: %5.3f Estimated SNR: %4.1f dB BER: %g" % ( + tb.mag(), tb.var(), tb.snr(), tb.ber()) + try: + time.sleep(1.0) + except KeyboardInterrupt: + self.done = True + +class rx_bpsk_block(gr.top_block): + def __init__(self, options): + + gr.top_block.__init__(self, "rx_mpsk") + + print "USRP decimation rate", options.decim_rate + + # Create a USRP source at desired board, sample rate, frequency, and gain + self._setup_usrp(options.which, + options.decim_rate, + options.rx_subdev_spec, + options.freq, + options.gain) + + # Create the BERT receiver + if_rate = self._usrp.adc_rate()/options.decim_rate + self._receiver = receive_path(if_rate, + options.rate, + options.excess_bw, + options.costas_alpha, + options.costas_beta, + options.costas_max, + options.mm_gain_mu, + options.mm_gain_omega, + options.mm_omega_limit) + + self.connect(self._usrp, self._receiver) + + + def _setup_usrp(self, which, decim, subdev_spec, freq, gain): + self._usrp = usrp.source_c(which=which, decim_rate=decim) + if subdev_spec is None: + subdev_spec = usrp.pick_rx_subdevice(self._usrp) + self._subdev = usrp.selected_subdev(self._usrp, subdev_spec) + mux = usrp.determine_rx_mux_value(self._usrp, subdev_spec) + self._usrp.set_mux(mux) + tr = self._usrp.tune(0, self._subdev, freq) + if not (tr): + print "Failed to tune to center frequency!" + else: + print "Center frequency:", n2s(freq) + if gain is None: + g = self._subdev.gain_range(); + gain = float(g[0]+g[1])/2.0 + self._subdev.set_gain(gain) + print "RX d'board:", self._subdev.side_and_name() + + def snr(self): + return self._receiver.snr() + + def mag(self): + return self._receiver.signal_mean() + + def var(self): + return self._receiver.noise_variance() + + def ber(self): + return self._receiver.ber() + +def get_options(): + parser = OptionParser(option_class=eng_option) + parser.add_option("-w", "--which", type="int", default=0, + help="select which USRP (0, 1, ...) (default is %default)", + metavar="NUM") + parser.add_option("-R", "--rx-subdev-spec", type="subdev", default=None, + help="select USRP Rx side A or B (default=first one with a daughterboard)") + parser.add_option("-f", "--freq", type="eng_float", default=None, + help="set frequency to FREQ", metavar="FREQ") + parser.add_option("-g", "--gain", type="eng_float", default=None, + help="set Rx gain (default is mid-point)") + parser.add_option("-r", "--rate", type="eng_float", default=250e3, + help="Select modulation symbol rate (default=%default)") + parser.add_option("-d", "--decim-rate", type="int", default=8, + help="Select USRP decimation rate (default=%default)") + parser.add_option("", "--excess-bw", type="eng_float", default=0.35, + help="Select RRC excess bandwidth (default=%default)") + parser.add_option("", "--costas-alpha", type="eng_float", default=0.2, + help="set Costas loop 1st order gain, (default=%default)") + parser.add_option("", "--costas-beta", type="eng_float", default=0.01, + help="set Costas loop 2nd order gain, (default=%default)") + parser.add_option("", "--costas-max", type="eng_float", default=0.005, + help="set Costas loop max freq (rad/sample) (default=%default)") + parser.add_option("", "--mm-gain-mu", type="eng_float", default=0.2, + help="set M&M loop 1st order gain, (default=%default)") + parser.add_option("", "--mm-gain-omega", type="eng_float", default=0.01, + help="set M&M loop 2nd order gain, (default=%default)") + parser.add_option("", "--mm-omega-limit", type="eng_float", default=0.005, + help="set M&M max timing error, (default=%default)") + + + (options, args) = parser.parse_args() + if len(args) != 0: + parser.print_help() + sys.exit(1) + + if options.freq == None: + print "You must supply a frequency with -f or --freq" + sys.exit(1) + + return (options, args) + + +if __name__ == "__main__": + (options, args) = get_options() + + tb = rx_bpsk_block(options) + + print "\n*** SNR estimator is inaccurate below about 7dB" + print "*** BER estimator is inaccurate above about 10%\n" + updater = status_thread(tb) + + try: + tb.run() + except KeyboardInterrupt: + updater.done = True + updater = None diff --git a/gnuradio-examples/python/digital-bert/benchmark_tx.py b/gnuradio-examples/python/digital-bert/benchmark_tx.py new file mode 100755 index 000000000..1778a74b5 --- /dev/null +++ b/gnuradio-examples/python/digital-bert/benchmark_tx.py @@ -0,0 +1,111 @@ +#!/usr/bin/env python +# +# Copyright 2008 Free Software Foundation, Inc. +# +# This file is part of GNU Radio +# +# GNU Radio is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation; either version 3, or (at your option) +# any later version. +# +# GNU Radio is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with GNU Radio; see the file COPYING. If not, write to +# the Free Software Foundation, Inc., 51 Franklin Street, +# Boston, MA 02110-1301, USA. +# + +from gnuradio import gr, eng_notation, usrp +from gnuradio.eng_option import eng_option +from optparse import OptionParser +from transmit_path import transmit_path +import sys + +_dac_rate = 128e6 + +n2s = eng_notation.num_to_str + +class tx_bpsk_block(gr.top_block): + def __init__(self, options): + gr.top_block.__init__(self, "tx_mpsk") + + self._transmitter = transmit_path(options.sps, + options.excess_bw, + options.amplitude) + + if_rate = options.rate*options.sps + interp = int(_dac_rate/if_rate) + + print "Modulation:", n2s(options.rate), "bits/sec" + print "TX IF rate:", n2s(if_rate), "samples/sec" + print "USRP interpolation:", interp + print "DAC amplitude:", options.amplitude + + self._setup_usrp(options.which, + interp, + options.tx_subdev_spec, + options.freq) + + self.connect(self._transmitter, self._usrp) + + + def _setup_usrp(self, which, interp, subdev_spec, freq): + self._usrp = usrp.sink_c(which=which, interp_rate=interp) + if subdev_spec is None: + subdev_spec = usrp.pick_tx_subdevice(self._usrp) + self._usrp.set_mux(usrp.determine_tx_mux_value(self._usrp, subdev_spec)) + self._subdev = usrp.selected_subdev(self._usrp, subdev_spec) + tr = usrp.tune(self._usrp, self._subdev._which, self._subdev, freq) + if not (tr): + print "Failed to tune to center frequency!" + else: + print "Center frequency:", n2s(freq) + gain = float(self._subdev.gain_range()[1]) # Max TX gain + self._subdev.set_gain(gain) + self._subdev.set_enable(True) + print "TX d'board:", self._subdev.side_and_name() + + +def get_options(): + parser = OptionParser(option_class=eng_option) + parser.add_option("-w", "--which", type="int", default=0, + help="select which USRP (0, 1, ...) default is %default", + metavar="NUM") + parser.add_option("-T", "--tx-subdev-spec", type="subdev", default=None, + help="select USRP Tx side A or B (default=first one with a daughterboard)") + parser.add_option("-f", "--freq", type="eng_float", default=None, + help="set frequency to FREQ", metavar="FREQ") + parser.add_option("-a", "--amplitude", type="eng_float", default=2000, + help="set Tx amplitude (0-32767) (default=%default)") + parser.add_option("-r", "--rate", type="eng_float", default=250e3, + help="Select modulation symbol rate (default=%default)") + parser.add_option("", "--sps", type="int", default=2, + help="Select samples per symbol (default=%default)") + parser.add_option("", "--excess-bw", type="eng_float", default=0.35, + help="Select RRC excess bandwidth (default=%default)") + + (options, args) = parser.parse_args() + if len(args) != 0: + parser.print_help() + sys.exit(1) + + if options.freq == None: + print "Must supply frequency as -f or --freq" + sys.exit(1) + + return (options, args) + +if __name__ == "__main__": + (options, args) = get_options() + + tb = tx_bpsk_block(options) + + try: + tb.run() + except KeyboardInterrupt: + pass diff --git a/gnuradio-examples/python/digital-bert/receive_path.py b/gnuradio-examples/python/digital-bert/receive_path.py new file mode 100644 index 000000000..84ff32916 --- /dev/null +++ b/gnuradio-examples/python/digital-bert/receive_path.py @@ -0,0 +1,116 @@ +# +# Copyright 2008 Free Software Foundation, Inc. +# +# This file is part of GNU Radio +# +# GNU Radio is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation; either version 3, or (at your option) +# any later version. +# +# GNU Radio is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with GNU Radio; see the file COPYING. If not, write to +# the Free Software Foundation, Inc., 51 Franklin Street, +# Boston, MA 02110-1301, USA. +# + +from gnuradio import gr, eng_notation +import math + +n2s = eng_notation.num_to_str + +class receive_path(gr.hier_block2): + def __init__(self, + if_rate, # Incoming sample rate + symbol_rate, # Original symbol rate + excess_bw, # RRC excess bandwidth, typically 0.35-0.5 + costas_alpha, # Costas loop 1st order gain, typically 0.01-0.2 + costas_beta, # Costas loop 2nd order gain, typically alpha^2/4.0 + costas_max, # Costas loop max frequency offset in radians/sample + mm_gain_mu, # M&M loop 1st order gain, typically 0.001-0.2 + mm_gain_omega, # M&M loop 2nd order gain, typically alpha^2/4.0 + mm_omega_limit, # M&M loop max timing error + ): + + gr.hier_block2.__init__(self, "receive_path", + gr.io_signature(1, 1, gr.sizeof_gr_complex), # Input signature + gr.io_signature(0, 0, 0)) # Output signature + + sps = int(if_rate/symbol_rate) + print "IF sample rate:", n2s(if_rate) + print "Symbol rate:", n2s(symbol_rate) + print "Samples/symbol:", sps + print "RRC bandwidth:", excess_bw + + # Create AGC to scale input to unity + self._agc = gr.agc_cc(1e-5, 1.0, 1.0, 1.0) + + # Create RRC with specified excess bandwidth + taps = gr.firdes.root_raised_cosine(1.0, # Gain + sps, # Sampling rate + 1.0, # Symbol rate + excess_bw, # Roll-off factor + 11*sps) # Number of taps + + self._rrc = gr.fir_filter_ccf(1, taps) + + # Create a Costas loop frequency/phase recovery block + + print "Costas alpha:", costas_alpha + print "Costas beta:", costas_beta + print "Costas max:", costas_max + + self._costas = gr.costas_loop_cc(costas_alpha, # PLL first order gain + costas_beta, # PLL second order gain + costas_max, # Max frequency offset rad/sample + -costas_max, # Min frequency offset rad/sample + 2) # BPSK + + # Create a M&M bit synchronization retiming block + mm_mu = 0.5 + mm_omega = sps + + print "MM gain mu:", mm_gain_mu + print "MM gain omega:", mm_gain_omega + print "MM omega limit:", mm_omega_limit + + self._mm = gr.clock_recovery_mm_cc(mm_omega, # Initial samples/symbol + mm_gain_omega, # Second order gain + mm_mu, # Initial symbol phase + mm_gain_mu, # First order gain + mm_omega_limit) # Maximum timing offset + + # Add an SNR probe on the demodulated constellation + self._snr_probe = gr.probe_mpsk_snr_c(10.0/symbol_rate) + self.connect(self._mm, self._snr_probe) + + # Slice the resulting constellation into bits. + # Get inphase channel and make decision about 0 + self._c2r = gr.complex_to_real() + self._slicer = gr.binary_slicer_fb() + + # Descramble BERT sequence. A channel error will create 3 incorrect bits + self._descrambler = gr.descrambler_bb(0x8A, 0x7F, 7) # CCSDS 7-bit descrambler + + # Measure BER by the density of 0s in the stream + self._ber = gr.probe_density_b(1.0/symbol_rate) + + self.connect(self, self._agc, self._rrc, self._costas, self._mm, + self._c2r, self._slicer, self._descrambler, self._ber) + + def snr(self): + return self._snr_probe.snr() + + def signal_mean(self): + return self._snr_probe.signal_mean() + + def noise_variance(self): + return self._snr_probe.noise_variance() + + def ber(self): + return (1.0-self._ber.density())/3.0 diff --git a/gnuradio-examples/python/digital-bert/transmit_path.py b/gnuradio-examples/python/digital-bert/transmit_path.py new file mode 100644 index 000000000..47b6ab229 --- /dev/null +++ b/gnuradio-examples/python/digital-bert/transmit_path.py @@ -0,0 +1,62 @@ +#!/usr/bin/env python +# +# Copyright 2008 Free Software Foundation, Inc. +# +# This file is part of GNU Radio +# +# GNU Radio is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation; either version 3, or (at your option) +# any later version. +# +# GNU Radio is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with GNU Radio; see the file COPYING. If not, write to +# the Free Software Foundation, Inc., 51 Franklin Street, +# Boston, MA 02110-1301, USA. +# + +from gnuradio import gr +from math import pi, log10 +import cmath + +class transmit_path(gr.hier_block2): + """ + This transmits a BERT sequence of bits using filtered BPSK and + outputs the complex baseband waveform. + """ + def __init__(self, + sps, # Samples per symbol + excess_bw, # RRC filter excess bandwidth (typically 0.35-0.5) + amplitude # DAC output level, 0-32767, typically 2000-8000 + ): + + gr.hier_block2.__init__(self, "transmit_path", + gr.io_signature(0, 0, 0), # Input signature + gr.io_signature(1, 1, gr.sizeof_gr_complex)) # Output signature + + # Create BERT data bit stream + self._bits = gr.vector_source_b([1,], True) # Infinite stream of ones + self._scrambler = gr.scrambler_bb(0x8A, 0x7F, 7) # CCSDS 7-bit scrambler + + # Map to constellation + self._constellation = [-1+0j, 1+0j] + self._mapper = gr.chunks_to_symbols_bc(self._constellation) + + # Create RRC with specified excess bandwidth + taps = gr.firdes.root_raised_cosine(sps*amplitude, # Gain + sps, # Sampling rate + 1.0, # Symbol rate + excess_bw, # Roll-off factor + 11*sps) # Number of taps + + self._rrc = gr.interp_fir_filter_ccf(sps, # Interpolation rate + taps) # FIR taps + + # Wire block inputs and outputs + self.connect(self._bits, self._scrambler, self._mapper, self._rrc, self) + |