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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 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 = 0.15
  42 _def_gain_mu = None
  43 _def_mu = 0.5
  44 _def_omega_relative_limit = 0.005
  45
  46
  47 # /////////////////////////////////////////////////////////////////////////////
  48 #                           DQPSK modulator
  49 # /////////////////////////////////////////////////////////////////////////////
  50
  51 class dqpsk_mod(gr.hier_block):
  52
  53     def __init__(self, fg,
  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 fg: flow graph
  66         @type fg: flow graph
  67         @param samples_per_symbol: samples per symbol >= 2
  68         @type samples_per_symbol: integer
  69         @param excess_bw: Root-raised cosine filter excess bandwidth
  70         @type excess_bw: float
  71         @param gray_code: Tell modulator to Gray code the bits
  72         @type gray_code: bool
  73         @param verbose: Print information about modulator?
  74         @type verbose: bool
  75         @param debug: Print modualtion data to files?
  76         @type debug: bool
  77         """
  78
  79         self._fg = fg
  80         self._samples_per_symbol = samples_per_symbol
  81         self._excess_bw = excess_bw
  82         self._gray_code = gray_code
  83
  84         if not isinstance(samples_per_symbol, int) or samples_per_symbol < 2:
  85             raise TypeError, ("sbp must be an integer >= 2, is %d" % samples_per_symbol)
  86
  87         ntaps = 11 * samples_per_symbol
  88
  89         arity = pow(2,self.bits_per_symbol())
  90
  91         # turn bytes into k-bit vectors
  92         self.bytes2chunks = \
  93           gr.packed_to_unpacked_bb(self.bits_per_symbol(), gr.GR_MSB_FIRST)
  94
  95         if self._gray_code:
  96             self.symbol_mapper = gr.map_bb(psk.binary_to_gray[arity])
  97         else:
  98             self.symbol_mapper = gr.map_bb(psk.binary_to_ungray[arity])
  99
 100         self.diffenc = gr.diff_encoder_bb(arity)
 101
 102         rot = .707 + .707j
 103         rotated_const = map(lambda pt: pt * rot, psk.constellation[arity])
 104         self.chunks2symbols = gr.chunks_to_symbols_bc(rotated_const)
 105
 106         # pulse shaping filter
 107         self.rrc_taps = gr.firdes.root_raised_cosine(
 108             self._samples_per_symbol, # gain  (sps since we're interpolating by sps)
 109             self._samples_per_symbol, # sampling rate
 110             1.0,                      # symbol rate
 111             self._excess_bw,          # excess bandwidth (roll-off factor)
 112             ntaps)
 113
 114         self.rrc_filter = gr.interp_fir_filter_ccf(self._samples_per_symbol, self.rrc_taps)
 115
 116         if verbose:
 117             self._print_verbage()
 118
 119         if log:
 120             self._setup_logging()
 121
 122         # Connect & Initialize base class
 123         self._fg.connect(self.bytes2chunks, self.symbol_mapper, self.diffenc,
 124                          self.chunks2symbols, self.rrc_filter)
 125         gr.hier_block.__init__(self, self._fg, self.bytes2chunks, self.rrc_filter)
 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._fg.connect(self.bytes2chunks,
 143                          gr.file_sink(gr.sizeof_char, "tx_bytes2chunks.dat"))
 144         self._fg.connect(self.symbol_mapper,
 145                          gr.file_sink(gr.sizeof_char, "tx_graycoder.dat"))
 146         self._fg.connect(self.diffenc,
 147                          gr.file_sink(gr.sizeof_char, "tx_diffenc.dat"))
 148         self._fg.connect(self.chunks2symbols,
 149                          gr.file_sink(gr.sizeof_gr_complex, "tx_chunks2symbols.dat"))
 150         self._fg.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(dqpsk_mod.__init__,
 170                                                             ('self', 'fg'), 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 dqpsk_demod(gr.hier_block):
 181
 182     def __init__(self, fg,
 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 DQPSK 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 fg: flow graph
 199         @type fg: flow graph
 200         @param samples_per_symbol: samples per symbol >= 2
 201         @type samples_per_symbol: float
 202         @param excess_bw: Root-raised cosine filter excess bandwidth
 203         @type excess_bw: float
 204         @param costas_alpha: loop filter gain
 205         @type costas_alphas: float
 206         @param gain_mu: for M&M block
 207         @type gain_mu: float
 208         @param mu: for M&M block
 209         @type mu: float
 210         @param omega_relative_limit: for M&M block
 211         @type omega_relative_limit: float
 212         @param gray_code: Tell modulator to Gray code the bits
 213         @type gray_code: bool
 214         @param verbose: Print information about modulator?
 215         @type verbose: bool
 216         @param debug: Print modualtion data to files?
 217         @type debug: bool
 218         """
 219
 220         self._fg = fg
 221         self._samples_per_symbol = samples_per_symbol
 222         self._excess_bw = excess_bw
 223         self._costas_alpha = costas_alpha
 224         self._mm_gain_mu = gain_mu
 225         self._mm_mu = mu
 226         self._mm_omega_relative_limit = omega_relative_limit
 227         self._gray_code = gray_code
 228
 229         if samples_per_symbol < 2:
 230             raise TypeError, "sbp must be >= 2, is %d" % samples_per_symbol
 231
 232         arity = pow(2,self.bits_per_symbol())
 233
 234         # Automatic gain control
 235         scale = (1.0/16384.0)
 236         self.pre_scaler = gr.multiply_const_cc(scale)   # scale the signal from full-range to +-1
 237         #self.agc = gr.agc2_cc(0.6e-1, 1e-3, 1, 1, 100)
 238         self.agc = gr.feedforward_agc_cc(16, 2.0)
 239
 240         # RRC data filter
 241         ntaps = 11 * samples_per_symbol
 242         self.rrc_taps = gr.firdes.root_raised_cosine(
 243             1.0,                      # gain
 244             self._samples_per_symbol, # sampling rate
 245             1.0,                      # symbol rate
 246             self._excess_bw,          # excess bandwidth (roll-off factor)
 247             ntaps)
 248         self.rrc_filter=gr.interp_fir_filter_ccf(1, self.rrc_taps)
 249
 250         if not self._mm_gain_mu:
 251             sbs_to_mm = {2: 0.050, 3: 0.075, 4: 0.11, 5: 0.125, 6: 0.15, 7: 0.15}
 252             self._mm_gain_mu = sbs_to_mm[samples_per_symbol]
 253
 254         self._mm_omega = self._samples_per_symbol
 255         self._mm_gain_omega = .25 * self._mm_gain_mu * self._mm_gain_mu
 256         self._costas_beta  = 0.25 * self._costas_alpha * self._costas_alpha
 257         fmin = -0.025
 258         fmax = 0.025
 259
 260         self.receiver=gr.mpsk_receiver_cc(arity, pi/4.0,
 261                                           self._costas_alpha, self._costas_beta,
 262                                           fmin, fmax,
 263                                           self._mm_mu, self._mm_gain_mu,
 264                                           self._mm_omega, self._mm_gain_omega,
 265                                           self._mm_omega_relative_limit)
 266
 267         # Perform Differential decoding on the constellation
 268         self.diffdec = gr.diff_phasor_cc()
 269
 270         # find closest constellation point
 271         rot = 1
 272         rotated_const = map(lambda pt: pt * rot, psk.constellation[arity])
 273         self.slicer = gr.constellation_decoder_cb(rotated_const, range(arity))
 274
 275         if self._gray_code:
 276             self.symbol_mapper = gr.map_bb(psk.gray_to_binary[arity])
 277         else:
 278             self.symbol_mapper = gr.map_bb(psk.ungray_to_binary[arity])
 279
 280         # unpack the k bit vector into a stream of bits
 281         self.unpack = gr.unpack_k_bits_bb(self.bits_per_symbol())
 282
 283         if verbose:
 284             self._print_verbage()
 285
 286         if log:
 287             self._setup_logging()
 288
 289         # Connect & Initialize base class
 290         self._fg.connect(self.pre_scaler, self.agc, self.rrc_filter, self.receiver,
 291                          self.diffdec, self.slicer, self.symbol_mapper, self.unpack)
 292         gr.hier_block.__init__(self, self._fg, self.pre_scaler, self.unpack)
 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 2
 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._fg.connect(self.pre_scaler,
 317                          gr.file_sink(gr.sizeof_gr_complex, "rx_prescaler.dat"))
 318         self._fg.connect(self.agc,
 319                          gr.file_sink(gr.sizeof_gr_complex, "rx_agc.dat"))
 320         self._fg.connect(self.rrc_filter,
 321                          gr.file_sink(gr.sizeof_gr_complex, "rx_rrc_filter.dat"))
 322         self._fg.connect(self.receiver,
 323                          gr.file_sink(gr.sizeof_gr_complex, "rx_receiver.dat"))
 324         self._fg.connect(self.diffdec,
 325                          gr.file_sink(gr.sizeof_gr_complex, "rx_diffdec.dat"))
 326         self._fg.connect(self.slicer,
 327                          gr.file_sink(gr.sizeof_char, "rx_slicer.dat"))
 328         self._fg.connect(self.symbol_mapper,
 329                          gr.file_sink(gr.sizeof_char, "rx_gray_decoder.dat"))
 330         self._fg.connect(self.unpack,
 331                          gr.file_sink(gr.sizeof_char, "rx_unpack.dat"))
 332
 333     def add_options(parser):
 334         """
 335         Adds modulation-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=_def_costas_alpha,
 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] (PSK)")
 346         parser.add_option("", "--mu", type="float", default=_def_mu,
 347                           help="set M&M symbol sync loop mu value [default=%default] (PSK)")
 348     add_options=staticmethod(add_options)
 349
 350     def extract_kwargs_from_options(options):
 351         """
 352         Given command line options, create dictionary suitable for passing to __init__
 353         """
 354         return modulation_utils.extract_kwargs_from_options(
 355             dqpsk_demod.__init__, ('self', 'fg'), options)
 356     extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)
 357
 358
 359 #
 360 # Add these to the mod/demod registry
 361 #
 362 modulation_utils.add_type_1_mod('dqpsk', dqpsk_mod)
 363 modulation_utils.add_type_1_demod('dqpsk', dqpsk_demod)