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   1 #
   2 # Copyright 2005,2006 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 2, 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 import Numeric
  33 from pprint import pprint
  34
  35 # default values (used in __init__ and add_options)
  36 _def_samples_per_symbol = 2
  37 _def_excess_bw = 0.35
  38 _def_gray_code = True
  39 _def_verbose = False
  40 _def_log = False
  41
  42 _def_costas_alpha = 0.1
  43 _def_gain_mu = None
  44 _def_mu = 0.5
  45 _def_omega_relative_limit = 0.005
  46
  47
  48 # /////////////////////////////////////////////////////////////////////////////
  49 #                             DBPSK modulator
  50 # /////////////////////////////////////////////////////////////////////////////
  51
  52 class dbpsk_mod(gr.hier_block):
  53
  54     def __init__(self, fg,
  55                  samples_per_symbol=_def_samples_per_symbol,
  56                  excess_bw=_def_excess_bw,
  57                  gray_code=_def_gray_code,
  58                  verbose=_def_verbose,
  59                  log=_def_log):
  60         """
  61         Hierarchical block for RRC-filtered differential BPSK modulation.
  62
  63         The input is a byte stream (unsigned char) and the
  64         output is the complex modulated signal at baseband.
  65
  66         @param fg: flow graph
  67         @type fg: flow graph
  68         @param samples_per_symbol: samples per baud >= 2
  69         @type samples_per_symbol: integer
  70         @param excess_bw: Root-raised cosine filter excess bandwidth
  71         @type excess_bw: float
  72         @param gray_code: Tell modulator to Gray code the bits
  73         @type gray_code: bool
  74         @param verbose: Print information about modulator?
  75         @type verbose: bool
  76         @param log: Log modulation data to files?
  77         @type log: bool
  78         """
  79
  80         self._fg = fg
  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         fg.connect(self.bytes2chunks, self.symbol_mapper, self.diffenc,
 118                    self.chunks2symbols, self.rrc_filter)
 119
 120         if verbose:
 121             self._print_verbage()
 122
 123         if log:
 124             self._setup_logging()
 125
 126         # Initialize base class
 127         gr.hier_block.__init__(self, self._fg, self.bytes2chunks, self.rrc_filter)
 128
 129     def samples_per_symbol(self):
 130         return self._samples_per_symbol
 131
 132     def bits_per_symbol(self=None):   # static method that's also callable on an instance
 133         return 1
 134     bits_per_symbol = staticmethod(bits_per_symbol)      # make it a static method.  RTFM
 135
 136     def add_options(parser):
 137         """
 138         Adds DBPSK modulation-specific options to the standard parser
 139         """
 140         parser.add_option("", "--excess-bw", type="float", default=_def_excess_bw,
 141                           help="set RRC excess bandwith factor [default=%default]")
 142         parser.add_option("", "--no-gray-code", dest="gray_code",
 143                           action="store_false", default=True,
 144                           help="disable gray coding on modulated bits (PSK)")
 145     add_options=staticmethod(add_options)
 146
 147     def extract_kwargs_from_options(options):
 148         """
 149         Given command line options, create dictionary suitable for passing to __init__
 150         """
 151         return modulation_utils.extract_kwargs_from_options(dbpsk_mod.__init__,
 152                                                             ('self', 'fg'), options)
 153     extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)
 154
 155
 156     def _print_verbage(self):
 157         print "\nModulator:"
 158         print "bits per symbol:     %d" % self.bits_per_symbol()
 159         print "Gray code:           %s" % self._gray_code
 160         print "RRC roll-off factor: %.2f" % self._excess_bw
 161
 162     def _setup_logging(self):
 163         print "Modulation logging turned on."
 164         self._fg.connect(self.bytes2chunks,
 165                          gr.file_sink(gr.sizeof_char, "tx_bytes2chunks.dat"))
 166         self._fg.connect(self.symbol_mapper,
 167                          gr.file_sink(gr.sizeof_char, "tx_graycoder.dat"))
 168         self._fg.connect(self.diffenc,
 169                          gr.file_sink(gr.sizeof_char, "tx_diffenc.dat"))
 170         self._fg.connect(self.chunks2symbols,
 171                          gr.file_sink(gr.sizeof_gr_complex, "tx_chunks2symbols.dat"))
 172         self._fg.connect(self.rrc_filter,
 173                          gr.file_sink(gr.sizeof_gr_complex, "tx_rrc_filter.dat"))
 174
 175
 176 # /////////////////////////////////////////////////////////////////////////////
 177 #                             DBPSK demodulator
 178 #
 179 #      Differentially coherent detection of differentially encoded BPSK
 180 # /////////////////////////////////////////////////////////////////////////////
 181
 182 class dbpsk_demod(gr.hier_block):
 183
 184     def __init__(self, fg,
 185                  samples_per_symbol=_def_samples_per_symbol,
 186                  excess_bw=_def_excess_bw,
 187                  costas_alpha=_def_costas_alpha,
 188                  gain_mu=_def_gain_mu,
 189                  mu=_def_mu,
 190                  omega_relative_limit=_def_omega_relative_limit,
 191                  gray_code=_def_gray_code,
 192                  verbose=_def_verbose,
 193                  log=_def_log):
 194         """
 195         Hierarchical block for RRC-filtered differential BPSK demodulation
 196
 197         The input is the complex modulated signal at baseband.
 198         The output is a stream of bits packed 1 bit per byte (LSB)
 199
 200         @param fg: flow graph
 201         @type fg: flow graph
 202         @param samples_per_symbol: samples per symbol >= 2
 203         @type samples_per_symbol: float
 204         @param excess_bw: Root-raised cosine filter excess bandwidth
 205         @type excess_bw: float
 206         @param costas_alpha: loop filter gain
 207         @type costas_alphas: float
 208         @param gain_mu: for M&M block
 209         @type gain_mu: float
 210         @param mu: for M&M block
 211         @type mu: float
 212         @param omega_relative_limit: for M&M block
 213         @type omega_relative_limit: float
 214         @param gray_code: Tell modulator to Gray code the bits
 215         @type gray_code: bool
 216         @param verbose: Print information about modulator?
 217         @type verbose: bool
 218         @param debug: Print modualtion data to files?
 219         @type debug: bool
 220         """
 221
 222         self._fg = fg
 223         self._samples_per_symbol = samples_per_symbol
 224         self._excess_bw = excess_bw
 225         self._costas_alpha = costas_alpha
 226         self._mm_gain_mu = gain_mu
 227         self._mm_mu = mu
 228         self._mm_omega_relative_limit = omega_relative_limit
 229         self._gray_code = gray_code
 230
 231         if samples_per_symbol < 2:
 232             raise TypeError, "samples_per_symbol must be >= 2, is %r" % (samples_per_symbol,)
 233
 234         arity = pow(2,self.bits_per_symbol())
 235
 236         # Automatic gain control
 237         scale = (1.0/16384.0)
 238         self.pre_scaler = gr.multiply_const_cc(scale)   # scale the signal from full-range to +-1
 239         #self.agc = gr.agc2_cc(0.6e-1, 1e-3, 1, 1, 100)
 240         self.agc = gr.feedforward_agc_cc(16, 2.0)
 241
 242         # RRC data filter
 243         ntaps = 11 * samples_per_symbol
 244         self.rrc_taps = gr.firdes.root_raised_cosine(
 245             1.0,                      # gain
 246             self._samples_per_symbol, # sampling rate
 247             1.0,                      # symbol rate
 248             self._excess_bw,          # excess bandwidth (roll-off factor)
 249             ntaps)
 250         self.rrc_filter=gr.interp_fir_filter_ccf(1, self.rrc_taps)
 251
 252         # symbol clock recovery
 253         if not self._mm_gain_mu:
 254             self._mm_gain_mu = 0.1
 255
 256         self._mm_omega = self._samples_per_symbol
 257         self._mm_gain_omega = .25 * self._mm_gain_mu * self._mm_gain_mu
 258         self._costas_beta  = 0.25 * self._costas_alpha * self._costas_alpha
 259         fmin = -0.025
 260         fmax = 0.025
 261
 262         self.receiver=gr.mpsk_receiver_cc(arity, 0,
 263                                          self._costas_alpha, self._costas_beta,
 264                                          fmin, fmax,
 265                                          self._mm_mu, self._mm_gain_mu,
 266                                          self._mm_omega, self._mm_gain_omega,
 267                                          self._mm_omega_relative_limit)
 268
 269         # Do differential decoding based on phase change of symbols
 270         self.diffdec = gr.diff_phasor_cc()
 271
 272         # find closest constellation point
 273         rot = 1
 274         rotated_const = map(lambda pt: pt * rot, psk.constellation[arity])
 275         self.slicer = gr.constellation_decoder_cb(rotated_const, range(arity))
 276
 277         if self._gray_code:
 278             self.symbol_mapper = gr.map_bb(psk.gray_to_binary[arity])
 279         else:
 280             self.symbol_mapper = gr.map_bb(psk.ungray_to_binary[arity])
 281
 282         # unpack the k bit vector into a stream of bits
 283         self.unpack = gr.unpack_k_bits_bb(self.bits_per_symbol())
 284
 285         if verbose:
 286             self._print_verbage()
 287
 288         if log:
 289             self._setup_logging()
 290
 291         # Connect and Initialize base class
 292         self._fg.connect(self.pre_scaler, self.agc, self.rrc_filter, self.receiver,
 293                          self.diffdec, self.slicer, self.symbol_mapper, self.unpack)
 294         gr.hier_block.__init__(self, self._fg, self.pre_scaler, self.unpack)
 295
 296     def samples_per_symbol(self):
 297         return self._samples_per_symbol
 298
 299     def bits_per_symbol(self=None):   # staticmethod that's also callable on an instance
 300         return 1
 301     bits_per_symbol = staticmethod(bits_per_symbol)      # make it a static method.  RTFM
 302
 303     def _print_verbage(self):
 304         print "\nDemodulator:"
 305         print "bits per symbol:     %d"   % self.bits_per_symbol()
 306         print "Gray code:           %s"   % self._gray_code
 307         print "RRC roll-off factor: %.2f" % self._excess_bw
 308         print "Costas Loop alpha:   %.2e" % self._costas_alpha
 309         print "Costas Loop beta:    %.2e" % self._costas_beta
 310         print "M&M mu:              %.2f" % self._mm_mu
 311         print "M&M mu gain:         %.2e" % self._mm_gain_mu
 312         print "M&M omega:           %.2f" % self._mm_omega
 313         print "M&M omega gain:      %.2e" % self._mm_gain_omega
 314         print "M&M omega limit:     %.2f" % self._mm_omega_relative_limit
 315
 316     def _setup_logging(self):
 317         print "Modulation logging turned on."
 318         self._fg.connect(self.pre_scaler,
 319                          gr.file_sink(gr.sizeof_gr_complex, "rx_prescaler.dat"))
 320         self._fg.connect(self.agc,
 321                          gr.file_sink(gr.sizeof_gr_complex, "rx_agc.dat"))
 322         self._fg.connect(self.rrc_filter,
 323                          gr.file_sink(gr.sizeof_gr_complex, "rx_rrc_filter.dat"))
 324         self._fg.connect(self.receiver,
 325                          gr.file_sink(gr.sizeof_gr_complex, "rx_receiver.dat"))
 326         self._fg.connect(self.diffdec,
 327                          gr.file_sink(gr.sizeof_gr_complex, "rx_diffdec.dat"))
 328         self._fg.connect(self.slicer,
 329                         gr.file_sink(gr.sizeof_char, "rx_slicer.dat"))
 330         self._fg.connect(self.symbol_mapper,
 331                          gr.file_sink(gr.sizeof_char, "rx_symbol_mapper.dat"))
 332         self._fg.connect(self.unpack,
 333                          gr.file_sink(gr.sizeof_char, "rx_unpack.dat"))
 334
 335     def add_options(parser):
 336         """
 337         Adds DBPSK demodulation-specific options to the standard parser
 338         """
 339         parser.add_option("", "--excess-bw", type="float", default=_def_excess_bw,
 340                           help="set RRC excess bandwith factor [default=%default] (PSK)")
 341         parser.add_option("", "--no-gray-code", dest="gray_code",
 342                           action="store_false", default=_def_gray_code,
 343                           help="disable gray coding on modulated bits (PSK)")
 344         parser.add_option("", "--costas-alpha", type="float", default=None,
 345                           help="set Costas loop alpha value [default=%default] (PSK)")
 346         parser.add_option("", "--gain-mu", type="float", default=_def_gain_mu,
 347                           help="set M&M symbol sync loop gain mu value [default=%default] (GMSK/PSK)")
 348         parser.add_option("", "--mu", type="float", default=_def_mu,
 349                           help="set M&M symbol sync loop mu value [default=%default] (GMSK/PSK)")
 350         parser.add_option("", "--omega-relative-limit", type="float", default=_def_omega_relative_limit,
 351                           help="M&M clock recovery omega relative limit [default=%default] (GMSK/PSK)")
 352     add_options=staticmethod(add_options)
 353
 354     def extract_kwargs_from_options(options):
 355         """
 356         Given command line options, create dictionary suitable for passing to __init__
 357         """
 358         return modulation_utils.extract_kwargs_from_options(
 359                  dbpsk_demod.__init__, ('self', 'fg'), options)
 360     extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)
 361 #
 362 # Add these to the mod/demod registry
 363 #
 364 modulation_utils.add_type_1_mod('dbpsk', dbpsk_mod)
 365 modulation_utils.add_type_1_demod('dbpsk', dbpsk_demod)