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   1 #
   2 # Copyright 2005,2006,2007 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 BPSK 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 = 0.1
  42 _def_gain_mu = None
  43 _def_mu = 0.5
  44 _def_omega_relative_limit = 0.005
  45
  46
  47 # /////////////////////////////////////////////////////////////////////////////
  48 #                             DBPSK modulator
  49 # /////////////////////////////////////////////////////////////////////////////
  50
  51 class dbpsk_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 differential BPSK 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 baud >= 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 log: Log modulation data to files?
  74         @type log: bool
  75         """
  76
  77         gr.hier_block2.__init__(self, "dbpsk_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(self._samples_per_symbol, int) or self._samples_per_symbol < 2:
  86             raise TypeError, ("sbp must be an integer >= 2, is %d" % self._samples_per_symbol)
  87
  88         ntaps = 11 * self._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         self.chunks2symbols = gr.chunks_to_symbols_bc(psk.constellation[arity])
 104
 105         # pulse shaping filter
 106         self.rrc_taps = gr.firdes.root_raised_cosine(
 107             self._samples_per_symbol,   # gain (samples_per_symbol since we're
 108                                         # interpolating by samples_per_symbol)
 109             self._samples_per_symbol,   # sampling rate
 110             1.0,                        # symbol rate
 111             self._excess_bw,            # excess bandwidth (roll-off factor)
 112             ntaps)
 113         self.rrc_filter = gr.interp_fir_filter_ccf(self._samples_per_symbol,
 114                                                    self.rrc_taps)
 115
 116         # Connect
 117         self.connect(self, self.bytes2chunks, self.symbol_mapper, self.diffenc,
 118                      self.chunks2symbols, self.rrc_filter, self)
 119
 120         if verbose:
 121             self._print_verbage()
 122
 123         if log:
 124             self._setup_logging()
 125
 126
 127     def samples_per_symbol(self):
 128         return self._samples_per_symbol
 129
 130     def bits_per_symbol(self=None):   # static method that's also callable on an instance
 131         return 1
 132     bits_per_symbol = staticmethod(bits_per_symbol)      # make it a static method.  RTFM
 133
 134     def add_options(parser):
 135         """
 136         Adds DBPSK modulation-specific options to the standard parser
 137         """
 138         parser.add_option("", "--excess-bw", type="float", default=_def_excess_bw,
 139                           help="set RRC excess bandwith factor [default=%default]")
 140         parser.add_option("", "--no-gray-code", dest="gray_code",
 141                           action="store_false", default=True,
 142                           help="disable gray coding on modulated bits (PSK)")
 143     add_options=staticmethod(add_options)
 144
 145     def extract_kwargs_from_options(options):
 146         """
 147         Given command line options, create dictionary suitable for passing to __init__
 148         """
 149         return modulation_utils.extract_kwargs_from_options(dbpsk_mod.__init__,
 150                                                             ('self',), options)
 151     extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)
 152
 153
 154     def _print_verbage(self):
 155         print "\nModulator:"
 156         print "bits per symbol:     %d" % self.bits_per_symbol()
 157         print "Gray code:           %s" % self._gray_code
 158         print "RRC roll-off factor: %.2f" % self._excess_bw
 159
 160     def _setup_logging(self):
 161         print "Modulation logging turned on."
 162         self.connect(self.bytes2chunks,
 163                      gr.file_sink(gr.sizeof_char, "tx_bytes2chunks.dat"))
 164         self.connect(self.symbol_mapper,
 165                      gr.file_sink(gr.sizeof_char, "tx_graycoder.dat"))
 166         self.connect(self.diffenc,
 167                      gr.file_sink(gr.sizeof_char, "tx_diffenc.dat"))
 168         self.connect(self.chunks2symbols,
 169                      gr.file_sink(gr.sizeof_gr_complex, "tx_chunks2symbols.dat"))
 170         self.connect(self.rrc_filter,
 171                      gr.file_sink(gr.sizeof_gr_complex, "tx_rrc_filter.dat"))
 172
 173
 174 # /////////////////////////////////////////////////////////////////////////////
 175 #                             DBPSK demodulator
 176 #
 177 #      Differentially coherent detection of differentially encoded BPSK
 178 # /////////////////////////////////////////////////////////////////////////////
 179
 180 class dbpsk_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                  gain_mu=_def_gain_mu,
 187                  mu=_def_mu,
 188                  omega_relative_limit=_def_omega_relative_limit,
 189                  gray_code=_def_gray_code,
 190                  verbose=_def_verbose,
 191                  log=_def_log):
 192         """
 193         Hierarchical block for RRC-filtered differential BPSK demodulation
 194
 195         The input is the complex modulated signal at baseband.
 196         The output is a stream of bits packed 1 bit per byte (LSB)
 197
 198         @param samples_per_symbol: samples per symbol >= 2
 199         @type samples_per_symbol: float
 200         @param excess_bw: Root-raised cosine filter excess bandwidth
 201         @type excess_bw: float
 202         @param costas_alpha: loop filter gain
 203         @type costas_alphas: float
 204         @param gain_mu: for M&M block
 205         @type gain_mu: float
 206         @param mu: for M&M block
 207         @type mu: float
 208         @param omega_relative_limit: for M&M block
 209         @type omega_relative_limit: float
 210         @param gray_code: Tell modulator to Gray code the bits
 211         @type gray_code: bool
 212         @param verbose: Print information about modulator?
 213         @type verbose: bool
 214         @param debug: Print modualtion data to files?
 215         @type debug: bool
 216         """
 217
 218         gr.hier_block2.__init__(self, "dbpsk_demod",
 219                                 gr.io_signature(1, 1, gr.sizeof_gr_complex), # Input signature
 220                                 gr.io_signature(1, 1, gr.sizeof_char))       # Output signature
 221
 222         self._samples_per_symbol = samples_per_symbol
 223         self._excess_bw = excess_bw
 224         self._costas_alpha = costas_alpha
 225         self._mm_gain_mu = gain_mu
 226         self._mm_mu = mu
 227         self._mm_omega_relative_limit = omega_relative_limit
 228         self._gray_code = gray_code
 229
 230         if samples_per_symbol < 2:
 231             raise TypeError, "samples_per_symbol must be >= 2, is %r" % (samples_per_symbol,)
 232
 233         arity = pow(2,self.bits_per_symbol())
 234
 235         # Automatic gain control
 236         scale = (1.0/16384.0)
 237         self.pre_scaler = gr.multiply_const_cc(scale)   # scale the signal from full-range to +-1
 238         #self.agc = gr.agc2_cc(0.6e-1, 1e-3, 1, 1, 100)
 239         self.agc = gr.feedforward_agc_cc(16, 2.0)
 240
 241         # RRC data filter
 242         ntaps = 11 * samples_per_symbol
 243         self.rrc_taps = gr.firdes.root_raised_cosine(
 244             1.0,                      # gain
 245             self._samples_per_symbol, # sampling rate
 246             1.0,                      # symbol rate
 247             self._excess_bw,          # excess bandwidth (roll-off factor)
 248             ntaps)
 249         self.rrc_filter=gr.interp_fir_filter_ccf(1, self.rrc_taps)
 250
 251         # symbol clock recovery
 252         if not self._mm_gain_mu:
 253             self._mm_gain_mu = 0.1
 254
 255         self._mm_omega = self._samples_per_symbol
 256         self._mm_gain_omega = .25 * self._mm_gain_mu * self._mm_gain_mu
 257         self._costas_beta  = 0.25 * self._costas_alpha * self._costas_alpha
 258         fmin = -0.1
 259         fmax = 0.1
 260
 261         self.receiver=gr.mpsk_receiver_cc(arity, 0,
 262                                          self._costas_alpha, self._costas_beta,
 263                                          fmin, fmax,
 264                                          self._mm_mu, self._mm_gain_mu,
 265                                          self._mm_omega, self._mm_gain_omega,
 266                                          self._mm_omega_relative_limit)
 267
 268         # Do differential decoding based on phase change of symbols
 269         self.diffdec = gr.diff_phasor_cc()
 270
 271         # find closest constellation point
 272         rot = 1
 273         rotated_const = map(lambda pt: pt * rot, psk.constellation[arity])
 274         self.slicer = gr.constellation_decoder_cb(rotated_const, range(arity))
 275
 276         if self._gray_code:
 277             self.symbol_mapper = gr.map_bb(psk.gray_to_binary[arity])
 278         else:
 279             self.symbol_mapper = gr.map_bb(psk.ungray_to_binary[arity])
 280
 281         # unpack the k bit vector into a stream of bits
 282         self.unpack = gr.unpack_k_bits_bb(self.bits_per_symbol())
 283
 284         if verbose:
 285             self._print_verbage()
 286
 287         if log:
 288             self._setup_logging()
 289
 290         # Connect and Initialize base class
 291         self.connect(self, self.pre_scaler, self.agc, self.rrc_filter, self.receiver,
 292                      self.diffdec, self.slicer, self.symbol_mapper, self.unpack, self)
 293
 294     def samples_per_symbol(self):
 295         return self._samples_per_symbol
 296
 297     def bits_per_symbol(self=None):   # staticmethod that's also callable on an instance
 298         return 1
 299     bits_per_symbol = staticmethod(bits_per_symbol)      # make it a static method.  RTFM
 300
 301     def _print_verbage(self):
 302         print "\nDemodulator:"
 303         print "bits per symbol:     %d"   % self.bits_per_symbol()
 304         print "Gray code:           %s"   % self._gray_code
 305         print "RRC roll-off factor: %.2f" % self._excess_bw
 306         print "Costas Loop alpha:   %.2e" % self._costas_alpha
 307         print "Costas Loop beta:    %.2e" % self._costas_beta
 308         print "M&M mu:              %.2f" % self._mm_mu
 309         print "M&M mu gain:         %.2e" % self._mm_gain_mu
 310         print "M&M omega:           %.2f" % self._mm_omega
 311         print "M&M omega gain:      %.2e" % self._mm_gain_omega
 312         print "M&M omega limit:     %.2f" % self._mm_omega_relative_limit
 313
 314     def _setup_logging(self):
 315         print "Modulation logging turned on."
 316         self.connect(self.pre_scaler,
 317                          gr.file_sink(gr.sizeof_gr_complex, "rx_prescaler.dat"))
 318         self.connect(self.agc,
 319                      gr.file_sink(gr.sizeof_gr_complex, "rx_agc.dat"))
 320         self.connect(self.rrc_filter,
 321                      gr.file_sink(gr.sizeof_gr_complex, "rx_rrc_filter.dat"))
 322         self.connect(self.receiver,
 323                      gr.file_sink(gr.sizeof_gr_complex, "rx_receiver.dat"))
 324         self.connect(self.diffdec,
 325                      gr.file_sink(gr.sizeof_gr_complex, "rx_diffdec.dat"))
 326         self.connect(self.slicer,
 327                     gr.file_sink(gr.sizeof_char, "rx_slicer.dat"))
 328         self.connect(self.symbol_mapper,
 329                      gr.file_sink(gr.sizeof_char, "rx_symbol_mapper.dat"))
 330         self.connect(self.unpack,
 331                      gr.file_sink(gr.sizeof_char, "rx_unpack.dat"))
 332
 333     def add_options(parser):
 334         """
 335         Adds DBPSK demodulation-specific options to the standard parser
 336         """
 337         parser.add_option("", "--excess-bw", type="float", default=_def_excess_bw,
 338                           help="set RRC excess bandwith factor [default=%default] (PSK)")
 339         parser.add_option("", "--no-gray-code", dest="gray_code",
 340                           action="store_false", default=_def_gray_code,
 341                           help="disable gray coding on modulated bits (PSK)")
 342         parser.add_option("", "--costas-alpha", type="float", default=None,
 343                           help="set Costas loop alpha value [default=%default] (PSK)")
 344         parser.add_option("", "--gain-mu", type="float", default=_def_gain_mu,
 345                           help="set M&M symbol sync loop gain mu value [default=%default] (GMSK/PSK)")
 346         parser.add_option("", "--mu", type="float", default=_def_mu,
 347                           help="set M&M symbol sync loop mu value [default=%default] (GMSK/PSK)")
 348         parser.add_option("", "--omega-relative-limit", type="float", default=_def_omega_relative_limit,
 349                           help="M&M clock recovery omega relative limit [default=%default] (GMSK/PSK)")
 350     add_options=staticmethod(add_options)
 351
 352     def extract_kwargs_from_options(options):
 353         """
 354         Given command line options, create dictionary suitable for passing to __init__
 355         """
 356         return modulation_utils.extract_kwargs_from_options(
 357                  dbpsk_demod.__init__, ('self',), options)
 358     extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)
 359 #
 360 # Add these to the mod/demod registry
 361 #
 362 modulation_utils.add_type_1_mod('dbpsk', dbpsk_mod)
 363 modulation_utils.add_type_1_demod('dbpsk', dbpsk_demod)