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   1 #
   2 # Copyright 2005,2006,2007,2009 Free Software Foundation, Inc.
   3 #
   4 # This file is part of GNU Radio
   5 #
   6 # GNU Radio is free software; you can redistribute it and/or modify
   7 # it under the terms of the GNU General Public License as published by
   8 # the Free Software Foundation; either version 3, or (at your option)
   9 # any later version.
  10 #
  11 # GNU Radio is distributed in the hope that it will be useful,
  12 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 # GNU General Public License for more details.
  15 #
  16 # You should have received a copy of the GNU General Public License
  17 # along with GNU Radio; see the file COPYING.  If not, write to
  18 # the Free Software Foundation, Inc., 51 Franklin Street,
  19 # Boston, MA 02110-1301, USA.
  20 #
  21
  22 # See gnuradio-examples/python/digital for examples
  23
  24 """
  25 differential QPSK modulation and demodulation.
  26 """
  27
  28 from gnuradio import gr, gru, modulation_utils
  29 from math import pi, sqrt
  30 import psk
  31 import cmath
  32 from pprint import pprint
  33
  34 # default values (used in __init__ and add_options)
  35 _def_samples_per_symbol = 2
  36 _def_excess_bw = 0.35
  37 _def_gray_code = True
  38 _def_verbose = False
  39 _def_log = False
  40
  41 _def_costas_alpha = 0.01
  42 _def_timing_alpha = 0.100
  43 _def_timing_beta = 0.010
  44 _def_timing_max_dev = 1.5
  45
  46
  47 # /////////////////////////////////////////////////////////////////////////////
  48 #                           DQPSK modulator
  49 # /////////////////////////////////////////////////////////////////////////////
  50
  51 class dqpsk2_mod(gr.hier_block2):
  52
  53     def __init__(self,
  54                  samples_per_symbol=_def_samples_per_symbol,
  55                  excess_bw=_def_excess_bw,
  56                  gray_code=_def_gray_code,
  57                  verbose=_def_verbose,
  58                  log=_def_log):
  59         """
  60         Hierarchical block for RRC-filtered QPSK modulation.
  61
  62         The input is a byte stream (unsigned char) and the
  63         output is the complex modulated signal at baseband.
  64
  65         @param samples_per_symbol: samples per symbol >= 2
  66         @type samples_per_symbol: integer
  67         @param excess_bw: Root-raised cosine filter excess bandwidth
  68         @type excess_bw: float
  69         @param gray_code: Tell modulator to Gray code the bits
  70         @type gray_code: bool
  71         @param verbose: Print information about modulator?
  72         @type verbose: bool
  73         @param debug: Print modualtion data to files?
  74         @type debug: bool
  75         """
  76
  77         gr.hier_block2.__init__(self, "dqpsk2_mod",
  78                                 gr.io_signature(1, 1, gr.sizeof_char),       # Input signature
  79                                 gr.io_signature(1, 1, gr.sizeof_gr_complex)) # Output signature
  80
  81         self._samples_per_symbol = samples_per_symbol
  82         self._excess_bw = excess_bw
  83         self._gray_code = gray_code
  84
  85         if not isinstance(samples_per_symbol, int) or samples_per_symbol < 2:
  86             raise TypeError, ("sbp must be an integer >= 2, is %d" % samples_per_symbol)
  87
  88         ntaps = 11 * samples_per_symbol
  89
  90         arity = pow(2,self.bits_per_symbol())
  91
  92         # turn bytes into k-bit vectors
  93         self.bytes2chunks = \
  94           gr.packed_to_unpacked_bb(self.bits_per_symbol(), gr.GR_MSB_FIRST)
  95
  96         if self._gray_code:
  97             self.symbol_mapper = gr.map_bb(psk.binary_to_gray[arity])
  98         else:
  99             self.symbol_mapper = gr.map_bb(psk.binary_to_ungray[arity])
 100
 101         self.diffenc = gr.diff_encoder_bb(arity)
 102
 103         rot = .707 + .707j
 104         rotated_const = map(lambda pt: pt * rot, psk.constellation[arity])
 105         self.chunks2symbols = gr.chunks_to_symbols_bc(rotated_const)
 106
 107         # pulse shaping filter
 108         self.rrc_taps = gr.firdes.root_raised_cosine(
 109             self._samples_per_symbol, # gain  (sps since we're interpolating by sps)
 110             self._samples_per_symbol, # sampling rate
 111             1.0,                      # symbol rate
 112             self._excess_bw,          # excess bandwidth (roll-off factor)
 113             ntaps)
 114
 115         self.rrc_filter = gr.interp_fir_filter_ccf(self._samples_per_symbol, self.rrc_taps)
 116
 117         if verbose:
 118             self._print_verbage()
 119
 120         if log:
 121             self._setup_logging()
 122
 123         # Connect & Initialize base class
 124         self.connect(self, self.bytes2chunks, self.symbol_mapper, self.diffenc,
 125                      self.chunks2symbols, self.rrc_filter, self)
 126
 127     def samples_per_symbol(self):
 128         return self._samples_per_symbol
 129
 130     def bits_per_symbol(self=None):   # staticmethod that's also callable on an instance
 131         return 2
 132     bits_per_symbol = staticmethod(bits_per_symbol)      # make it a static method.  RTFM
 133
 134     def _print_verbage(self):
 135         print "\nModulator:"
 136         print "bits per symbol:     %d" % self.bits_per_symbol()
 137         print "Gray code:           %s" % self._gray_code
 138         print "RRS roll-off factor: %f" % self._excess_bw
 139
 140     def _setup_logging(self):
 141         print "Modulation logging turned on."
 142         self.connect(self.bytes2chunks,
 143                      gr.file_sink(gr.sizeof_char, "tx_bytes2chunks.dat"))
 144         self.connect(self.symbol_mapper,
 145                      gr.file_sink(gr.sizeof_char, "tx_graycoder.dat"))
 146         self.connect(self.diffenc,
 147                      gr.file_sink(gr.sizeof_char, "tx_diffenc.dat"))
 148         self.connect(self.chunks2symbols,
 149                      gr.file_sink(gr.sizeof_gr_complex, "tx_chunks2symbols.dat"))
 150         self.connect(self.rrc_filter,
 151                      gr.file_sink(gr.sizeof_gr_complex, "tx_rrc_filter.dat"))
 152
 153     def add_options(parser):
 154         """
 155         Adds QPSK modulation-specific options to the standard parser
 156         """
 157         parser.add_option("", "--excess-bw", type="float", default=_def_excess_bw,
 158                           help="set RRC excess bandwith factor [default=%default] (PSK)")
 159         parser.add_option("", "--no-gray-code", dest="gray_code",
 160                           action="store_false", default=_def_gray_code,
 161                           help="disable gray coding on modulated bits (PSK)")
 162     add_options=staticmethod(add_options)
 163
 164
 165     def extract_kwargs_from_options(options):
 166         """
 167         Given command line options, create dictionary suitable for passing to __init__
 168         """
 169         return modulation_utils.extract_kwargs_from_options(dqpsk2_mod.__init__,
 170                                                             ('self',), options)
 171     extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)
 172
 173
 174 # /////////////////////////////////////////////////////////////////////////////
 175 #                           DQPSK demodulator
 176 #
 177 # Differentially coherent detection of differentially encoded qpsk
 178 # /////////////////////////////////////////////////////////////////////////////
 179
 180 class dqpsk2_demod(gr.hier_block2):
 181
 182     def __init__(self,
 183                  samples_per_symbol=_def_samples_per_symbol,
 184                  excess_bw=_def_excess_bw,
 185                  costas_alpha=_def_costas_alpha,
 186                  timing_alpha=_def_timing_alpha,
 187                  timing_max_dev=_def_timing_max_dev,
 188                  gray_code=_def_gray_code,
 189                  verbose=_def_verbose,
 190                  log=_def_log):
 191         """
 192         Hierarchical block for RRC-filtered DQPSK demodulation
 193
 194         The input is the complex modulated signal at baseband.
 195         The output is a stream of bits packed 1 bit per byte (LSB)
 196
 197         @param samples_per_symbol: samples per symbol >= 2
 198         @type samples_per_symbol: float
 199         @param excess_bw: Root-raised cosine filter excess bandwidth
 200         @type excess_bw: float
 201         @param costas_alpha: loop filter gain
 202         @type costas_alphas: float
 203         @param timing_alpha: timing loop alpha gain
 204         @type timing_alpha: float
 205         @param timing_max: timing loop maximum rate deviations
 206         @type timing_max: float
 207         @param gray_code: Tell modulator to Gray code the bits
 208         @type gray_code: bool
 209         @param verbose: Print information about modulator?
 210         @type verbose: bool
 211         @param debug: Print modualtion data to files?
 212         @type debug: bool
 213         """
 214
 215         gr.hier_block2.__init__(self, "dqpsk2_demod",
 216                                 gr.io_signature(1, 1, gr.sizeof_gr_complex), # Input signature
 217                                 gr.io_signature(1, 1, gr.sizeof_char))       # Output signature
 218
 219         self._samples_per_symbol = samples_per_symbol
 220         self._excess_bw = excess_bw
 221         self._costas_alpha = costas_alpha
 222         self._timing_alpha = timing_alpha
 223         self._timing_beta = _def_timing_beta
 224         self._timing_max_dev=timing_max_dev
 225         self._gray_code = gray_code
 226
 227         if samples_per_symbol < 2:
 228             raise TypeError, "sbp must be >= 2, is %d" % samples_per_symbol
 229
 230         arity = pow(2,self.bits_per_symbol())
 231
 232         # Automatic gain control
 233         self.agc = gr.agc2_cc(0.6e-1, 1e-3, 1, 1, 100)
 234         #self.agc = gr.feedforward_agc_cc(16, 2.0)
 235
 236         self._costas_beta  = 0.25 * self._costas_alpha * self._costas_alpha
 237         # Allow a frequency swing of +/- half of the sample rate
 238         fmin = -0.5
 239         fmax = 0.5
 240
 241         self.clock_recov = gr.costas_loop_cc(self._costas_alpha,
 242                                              self._costas_beta,
 243                                              fmax, fmin, arity)
 244
 245         # symbol timing recovery with RRC data filter
 246         nfilts = 32
 247         ntaps = 11 * samples_per_symbol*nfilts
 248         taps = gr.firdes.root_raised_cosine(nfilts, nfilts, 1.0/float(self._samples_per_symbol), self._excess_bw, ntaps)
 249         self.time_recov = gr.pfb_clock_sync_ccf(self._samples_per_symbol,
 250                                                 self._timing_alpha,
 251                                                 taps, nfilts, nfilts/2, self._timing_max_dev)
 252         self.time_recov.set_beta(self._timing_beta)
 253
 254         # Perform Differential decoding on the constellation
 255         self.diffdec = gr.diff_phasor_cc()
 256
 257         # find closest constellation point
 258         rot = 1
 259         rotated_const = map(lambda pt: pt * rot, psk.constellation[arity])
 260         self.slicer = gr.constellation_decoder_cb(rotated_const, range(arity))
 261
 262         if self._gray_code:
 263             self.symbol_mapper = gr.map_bb(psk.gray_to_binary[arity])
 264         else:
 265             self.symbol_mapper = gr.map_bb(psk.ungray_to_binary[arity])
 266
 267         # unpack the k bit vector into a stream of bits
 268         self.unpack = gr.unpack_k_bits_bb(self.bits_per_symbol())
 269
 270         if verbose:
 271             self._print_verbage()
 272
 273         if log:
 274             self._setup_logging()
 275
 276         # Connect
 277         self.connect(self, self.agc,
 278                      self.clock_recov,
 279                      self.time_recov,
 280                      self.diffdec, self.slicer, self.symbol_mapper, self.unpack, self)
 281
 282     def samples_per_symbol(self):
 283         return self._samples_per_symbol
 284
 285     def bits_per_symbol(self=None):   # staticmethod that's also callable on an instance
 286         return 2
 287     bits_per_symbol = staticmethod(bits_per_symbol)      # make it a static method.  RTFM
 288
 289     def _print_verbage(self):
 290         print "\nDemodulator:"
 291         print "bits per symbol:     %d"   % self.bits_per_symbol()
 292         print "Gray code:           %s"   % self._gray_code
 293         print "RRC roll-off factor: %.2f" % self._excess_bw
 294         print "Costas Loop alpha:   %.2e" % self._costas_alpha
 295         print "Costas Loop beta:    %.2e" % self._costas_beta
 296         print "Timing alpha gain:   %.2f" % self._timing_alpha
 297         print "Timing beta gain:    %.2f" % self._timing_beta
 298         print "Timing max dev:      %.2f" % self._timing_max_dev
 299
 300     def _setup_logging(self):
 301         print "Modulation logging turned on."
 302         self.connect(self.pre_scaler,
 303                      gr.file_sink(gr.sizeof_gr_complex, "rx_prescaler.dat"))
 304         self.connect(self.agc,
 305                      gr.file_sink(gr.sizeof_gr_complex, "rx_agc.dat"))
 306         self.connect(self.rrc_filter,
 307                      gr.file_sink(gr.sizeof_gr_complex, "rx_rrc_filter.dat"))
 308         self.connect(self.clock_recov,
 309                      gr.file_sink(gr.sizeof_gr_complex, "rx_clock_recov.dat"))
 310         self.connect(self.time_recov,
 311                      gr.file_sink(gr.sizeof_gr_complex, "rx_time_recov.dat"))
 312         self.connect(self.diffdec,
 313                      gr.file_sink(gr.sizeof_gr_complex, "rx_diffdec.dat"))
 314         self.connect(self.slicer,
 315                      gr.file_sink(gr.sizeof_char, "rx_slicer.dat"))
 316         self.connect(self.symbol_mapper,
 317                      gr.file_sink(gr.sizeof_char, "rx_gray_decoder.dat"))
 318         self.connect(self.unpack,
 319                      gr.file_sink(gr.sizeof_char, "rx_unpack.dat"))
 320
 321     def add_options(parser):
 322         """
 323         Adds modulation-specific options to the standard parser
 324         """
 325         parser.add_option("", "--excess-bw", type="float", default=_def_excess_bw,
 326                           help="set RRC excess bandwith factor [default=%default] (PSK)")
 327         parser.add_option("", "--no-gray-code", dest="gray_code",
 328                           action="store_false", default=_def_gray_code,
 329                           help="disable gray coding on modulated bits (PSK)")
 330         parser.add_option("", "--costas-alpha", type="float", default=_def_costas_alpha,
 331                           help="set Costas loop alpha value [default=%default] (PSK)")
 332         parser.add_option("", "--gain-alpha", type="float", default=_def_timing_alpha,
 333                           help="set timing symbol sync loop gain alpha value [default=%default] (GMSK/PSK)")
 334         parser.add_option("", "--gain-beta", type="float", default=_def_timing_beta,
 335                           help="set timing symbol sync loop gain beta value [default=%default] (GMSK/PSK)")
 336         parser.add_option("", "--timing-max-dev", type="float", default=_def_timing_max_dev,
 337                           help="set timing symbol sync loop maximum deviation [default=%default] (GMSK/PSK)")
 338     add_options=staticmethod(add_options)
 339
 340     def extract_kwargs_from_options(options):
 341         """
 342         Given command line options, create dictionary suitable for passing to __init__
 343         """
 344         return modulation_utils.extract_kwargs_from_options(
 345             dqpsk2_demod.__init__, ('self',), options)
 346     extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)
 347
 348
 349 #
 350 # Add these to the mod/demod registry
 351 #
 352 modulation_utils.add_type_1_mod('dqpsk2', dqpsk2_mod)
 353 modulation_utils.add_type_1_demod('dqpsk2', dqpsk2_demod)