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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/gmsk2 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 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 = None
  43 _def_gain_mu = 0.03
  44 _def_mu = 0.05
  45 _def_omega_relative_limit = 0.005
  46
  47
  48 # /////////////////////////////////////////////////////////////////////////////
  49 #                           DQPSK modulator
  50 # /////////////////////////////////////////////////////////////////////////////
  51
  52 class dqpsk_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 QPSK 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 symbol >= 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 debug: Print modualtion data to files?
  77         @type debug: 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(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._fg.connect(self.bytes2chunks, self.symbol_mapper, self.diffenc,
 125                          self.chunks2symbols, self.rrc_filter)
 126         gr.hier_block.__init__(self, self._fg, self.bytes2chunks, self.rrc_filter)
 127
 128     def samples_per_symbol(self):
 129         return self._samples_per_symbol
 130
 131     def bits_per_symbol(self=None):   # staticmethod that's also callable on an instance
 132         return 2
 133     bits_per_symbol = staticmethod(bits_per_symbol)      # make it a static method.  RTFM
 134
 135     def _print_verbage(self):
 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, "bytes2chunks.dat"))
 144         self._fg.connect(self.symbol_mapper,
 145                          gr.file_sink(gr.sizeof_char, "graycoder.dat"))
 146         self._fg.connect(self.diffenc,
 147                          gr.file_sink(gr.sizeof_char, "diffenc.dat"))
 148         self._fg.connect(self.chunks2symbols,
 149                          gr.file_sink(gr.sizeof_gr_complex, "chunks2symbols.dat"))
 150         self._fg.connect(self.rrc_filter,
 151                          gr.file_sink(gr.sizeof_gr_complex, "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._gain_mu = gain_mu
 225         self._mu = mu
 226         self._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, 1.0)
 239
 240         # Costas loop (carrier tracking)
 241         if self._costas_alpha is None:   # If no alpha value was specified by the user
 242             alpha_dir = {2:0.075, 3:0.09, 4:0.09, 5:0.095, 6:0.10, 7:0.105}
 243             self._costas_alpha = alpha_dir[self._samples_per_symbol]
 244
 245         costas_order = 4
 246         # The value of beta is now set to be underdamped; this value can have a huge impact on the
 247         # performance of QPSK. Set to 0.25 for critically damped or higher for underdamped responses.
 248         beta = .35 * self._costas_alpha * self._costas_alpha
 249         self.costas_loop = gr.costas_loop_cc(self._costas_alpha, beta, 0.02, -0.02, costas_order)
 250
 251         # RRC data filter
 252         ntaps = 11 * samples_per_symbol
 253         self.rrc_taps = gr.firdes.root_raised_cosine(
 254             self._samples_per_symbol, # gain
 255             self._samples_per_symbol, # sampling rate
 256             1.0,                      # symbol rate
 257             self._excess_bw,          # excess bandwidth (roll-off factor)
 258             ntaps)
 259
 260         self.rrc_filter=gr.fir_filter_ccf(1, self.rrc_taps)
 261
 262         # symbol clock recovery
 263         omega = self._samples_per_symbol
 264         gain_omega = .25 * self._gain_mu * self._gain_mu
 265         self.clock_recovery=gr.clock_recovery_mm_cc(omega, gain_omega,
 266                                                     self._mu, self._gain_mu,
 267                                                     self._omega_relative_limit)
 268
 269         self.diffdec = gr.diff_phasor_cc()
 270         #self.diffdec = gr.diff_decoder_bb(arity)
 271
 272         # find closest constellation point
 273         rot = 1
 274         #rot = .707 + .707j
 275         rotated_const = map(lambda pt: pt * rot, psk.constellation[arity])
 276         #print "rotated_const = %s" % rotated_const
 277
 278         self.slicer = gr.constellation_decoder_cb(rotated_const, range(arity))
 279
 280         if self._gray_code:
 281             self.symbol_mapper = gr.map_bb(psk.gray_to_binary[arity])
 282         else:
 283             self.symbol_mapper = gr.map_bb(psk.ungray_to_binary[arity])
 284
 285
 286         # unpack the k bit vector into a stream of bits
 287         self.unpack = gr.unpack_k_bits_bb(self.bits_per_symbol())
 288
 289         if verbose:
 290             self._print_verbage()
 291
 292         if log:
 293             self._setup_logging()
 294
 295         # Connect & Initialize base class
 296         self._fg.connect(self.pre_scaler, self.agc, self.costas_loop,
 297                          self.rrc_filter, self.clock_recovery,
 298                          self.diffdec, self.slicer, self.symbol_mapper,
 299                          self.unpack)
 300         gr.hier_block.__init__(self, self._fg, self.pre_scaler, self.unpack)
 301
 302     def samples_per_symbol(self):
 303         return self._samples_per_symbol
 304
 305     def bits_per_symbol(self=None):   # staticmethod that's also callable on an instance
 306         return 2
 307     bits_per_symbol = staticmethod(bits_per_symbol)      # make it a static method.  RTFM
 308
 309     def _print_verbage(self):
 310         print "bits per symbol = %d"         % self.bits_per_symbol()
 311         print "Gray code = %s"               % self._gray_code
 312         print "RRC roll-off factor = %.2f"   % self._excess_bw
 313         print "Costas Loop alpha = %.5f"     % self._costas_alpha
 314         print "M&M symbol sync gain = %.5f"  % self._gain_mu
 315         print "M&M symbol sync mu = %.5f"    % self._mu
 316         print "M&M omega relative limit = %.5f" % self._omega_relative_limit
 317
 318
 319     def _setup_logging(self):
 320         print "Modulation logging turned on."
 321         self._fg.connect(self.pre_scaler,
 322                          gr.file_sink(gr.sizeof_gr_complex, "prescaler.dat"))
 323         self._fg.connect(self.agc,
 324                          gr.file_sink(gr.sizeof_gr_complex, "agc.dat"))
 325         self._fg.connect(self.costas_loop,
 326                          gr.file_sink(gr.sizeof_gr_complex, "costas_loop.dat"))
 327         self._fg.connect((self.costas_loop,1),
 328                          gr.file_sink(gr.sizeof_gr_complex, "costas_error.dat"))
 329         self._fg.connect(self.rrc_filter,
 330                          gr.file_sink(gr.sizeof_gr_complex, "rrc_filter.dat"))
 331         self._fg.connect(self.clock_recovery,
 332                          gr.file_sink(gr.sizeof_gr_complex, "clock_recovery.dat"))
 333         self._fg.connect((self.clock_recovery,1),
 334                         gr.file_sink(gr.sizeof_gr_complex, "clock_recovery_error.dat"))
 335         self._fg.connect(self.diffdec,
 336                          gr.file_sink(gr.sizeof_gr_complex, "diffdec.dat"))
 337         self._fg.connect(self.slicer,
 338                          gr.file_sink(gr.sizeof_char, "slicer.dat"))
 339         self._fg.connect(self.symbol_mapper,
 340                          gr.file_sink(gr.sizeof_char, "gray_decoder.dat"))
 341         self._fg.connect(self.unpack,
 342                          gr.file_sink(gr.sizeof_char, "unpack.dat"))
 343
 344     def add_options(parser):
 345         """
 346         Adds modulation-specific options to the standard parser
 347         """
 348         parser.add_option("", "--excess-bw", type="float", default=_def_excess_bw,
 349                           help="set RRC excess bandwith factor [default=%default] (PSK)")
 350         parser.add_option("", "--no-gray-code", dest="gray_code",
 351                           action="store_false", default=_def_gray_code,
 352                           help="disable gray coding on modulated bits (PSK)")
 353         parser.add_option("", "--costas-alpha", type="float", default=None,
 354                           help="set Costas loop alpha value [default=%default] (PSK)")
 355         parser.add_option("", "--gain-mu", type="float", default=_def_gain_mu,
 356                           help="set M&M symbol sync loop gain mu value [default=%default] (PSK)")
 357         parser.add_option("", "--mu", type="float", default=_def_mu,
 358                           help="set M&M symbol sync loop mu value [default=%default] (PSK)")
 359     add_options=staticmethod(add_options)
 360
 361     def extract_kwargs_from_options(options):
 362         """
 363         Given command line options, create dictionary suitable for passing to __init__
 364         """
 365         return modulation_utils.extract_kwargs_from_options(
 366             dqpsk_demod.__init__, ('self', 'fg'), options)
 367     extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)
 368
 369
 370 #
 371 # Add these to the mod/demod registry
 372 #
 373 modulation_utils.add_type_1_mod('dqpsk', dqpsk_mod)
 374 modulation_utils.add_type_1_demod('dqpsk', dqpsk_demod)