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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 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 = 0.15
  43 _def_gain_mu = None
  44 _def_mu = 0.5
  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 "\nModulator:"
 137         print "bits per symbol:     %d" % self.bits_per_symbol()
 138         print "Gray code:           %s" % self._gray_code
 139         print "RRS roll-off factor: %f" % self._excess_bw
 140
 141     def _setup_logging(self):
 142         print "Modulation logging turned on."
 143         self._fg.connect(self.bytes2chunks,
 144                          gr.file_sink(gr.sizeof_char, "tx_bytes2chunks.dat"))
 145         self._fg.connect(self.symbol_mapper,
 146                          gr.file_sink(gr.sizeof_char, "tx_graycoder.dat"))
 147         self._fg.connect(self.diffenc,
 148                          gr.file_sink(gr.sizeof_char, "tx_diffenc.dat"))
 149         self._fg.connect(self.chunks2symbols,
 150                          gr.file_sink(gr.sizeof_gr_complex, "tx_chunks2symbols.dat"))
 151         self._fg.connect(self.rrc_filter,
 152                          gr.file_sink(gr.sizeof_gr_complex, "tx_rrc_filter.dat"))
 153
 154     def add_options(parser):
 155         """
 156         Adds QPSK modulation-specific options to the standard parser
 157         """
 158         parser.add_option("", "--excess-bw", type="float", default=_def_excess_bw,
 159                           help="set RRC excess bandwith factor [default=%default] (PSK)")
 160         parser.add_option("", "--no-gray-code", dest="gray_code",
 161                           action="store_false", default=_def_gray_code,
 162                           help="disable gray coding on modulated bits (PSK)")
 163     add_options=staticmethod(add_options)
 164
 165
 166     def extract_kwargs_from_options(options):
 167         """
 168         Given command line options, create dictionary suitable for passing to __init__
 169         """
 170         return modulation_utils.extract_kwargs_from_options(dqpsk_mod.__init__,
 171                                                             ('self', 'fg'), options)
 172     extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)
 173
 174
 175 # /////////////////////////////////////////////////////////////////////////////
 176 #                           DQPSK demodulator
 177 #
 178 # Differentially coherent detection of differentially encoded qpsk
 179 # /////////////////////////////////////////////////////////////////////////////
 180
 181 class dqpsk_demod(gr.hier_block):
 182
 183     def __init__(self, fg,
 184                  samples_per_symbol=_def_samples_per_symbol,
 185                  excess_bw=_def_excess_bw,
 186                  costas_alpha=_def_costas_alpha,
 187                  gain_mu=_def_gain_mu,
 188                  mu=_def_mu,
 189                  omega_relative_limit=_def_omega_relative_limit,
 190                  gray_code=_def_gray_code,
 191                  verbose=_def_verbose,
 192                  log=_def_log):
 193         """
 194         Hierarchical block for RRC-filtered DQPSK demodulation
 195
 196         The input is the complex modulated signal at baseband.
 197         The output is a stream of bits packed 1 bit per byte (LSB)
 198
 199         @param fg: flow graph
 200         @type fg: flow graph
 201         @param samples_per_symbol: samples per symbol >= 2
 202         @type samples_per_symbol: float
 203         @param excess_bw: Root-raised cosine filter excess bandwidth
 204         @type excess_bw: float
 205         @param costas_alpha: loop filter gain
 206         @type costas_alphas: float
 207         @param gain_mu: for M&M block
 208         @type gain_mu: float
 209         @param mu: for M&M block
 210         @type mu: float
 211         @param omega_relative_limit: for M&M block
 212         @type omega_relative_limit: float
 213         @param gray_code: Tell modulator to Gray code the bits
 214         @type gray_code: bool
 215         @param verbose: Print information about modulator?
 216         @type verbose: bool
 217         @param debug: Print modualtion data to files?
 218         @type debug: bool
 219         """
 220
 221         self._fg = fg
 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, "sbp must be >= 2, is %d" % 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         if not self._mm_gain_mu:
 252             sbs_to_mm = {2: 0.050, 3: 0.075, 4: 0.11, 5: 0.125, 6: 0.15, 7: 0.15}
 253             self._mm_gain_mu = sbs_to_mm[samples_per_symbol]
 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 = -0.025
 259         fmax = 0.025
 260
 261         self.receiver=gr.mpsk_receiver_cc(arity, pi/4.0,
 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         # Perform Differential decoding on the constellation
 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 & Initialize base class
 291         self._fg.connect(self.pre_scaler, self.agc, self.rrc_filter, self.receiver,
 292                          self.diffdec, self.slicer, self.symbol_mapper, self.unpack)
 293         gr.hier_block.__init__(self, self._fg, self.pre_scaler, self.unpack)
 294
 295     def samples_per_symbol(self):
 296         return self._samples_per_symbol
 297
 298     def bits_per_symbol(self=None):   # staticmethod that's also callable on an instance
 299         return 2
 300     bits_per_symbol = staticmethod(bits_per_symbol)      # make it a static method.  RTFM
 301
 302     def _print_verbage(self):
 303         print "\nDemodulator:"
 304         print "bits per symbol:     %d"   % self.bits_per_symbol()
 305         print "Gray code:           %s"   % self._gray_code
 306         print "RRC roll-off factor: %.2f" % self._excess_bw
 307         print "Costas Loop alpha:   %.2e" % self._costas_alpha
 308         print "Costas Loop beta:    %.2e" % self._costas_beta
 309         print "M&M mu:              %.2f" % self._mm_mu
 310         print "M&M mu gain:         %.2e" % self._mm_gain_mu
 311         print "M&M omega:           %.2f" % self._mm_omega
 312         print "M&M omega gain:      %.2e" % self._mm_gain_omega
 313         print "M&M omega limit:     %.2f" % self._mm_omega_relative_limit
 314
 315     def _setup_logging(self):
 316         print "Modulation logging turned on."
 317         self._fg.connect(self.pre_scaler,
 318                          gr.file_sink(gr.sizeof_gr_complex, "rx_prescaler.dat"))
 319         self._fg.connect(self.agc,
 320                          gr.file_sink(gr.sizeof_gr_complex, "rx_agc.dat"))
 321         self._fg.connect(self.rrc_filter,
 322                          gr.file_sink(gr.sizeof_gr_complex, "rx_rrc_filter.dat"))
 323         self._fg.connect(self.receiver,
 324                          gr.file_sink(gr.sizeof_gr_complex, "rx_receiver.dat"))
 325         self._fg.connect(self.diffdec,
 326                          gr.file_sink(gr.sizeof_gr_complex, "rx_diffdec.dat"))
 327         self._fg.connect(self.slicer,
 328                          gr.file_sink(gr.sizeof_char, "rx_slicer.dat"))
 329         self._fg.connect(self.symbol_mapper,
 330                          gr.file_sink(gr.sizeof_char, "rx_gray_decoder.dat"))
 331         self._fg.connect(self.unpack,
 332                          gr.file_sink(gr.sizeof_char, "rx_unpack.dat"))
 333
 334     def add_options(parser):
 335         """
 336         Adds modulation-specific options to the standard parser
 337         """
 338         parser.add_option("", "--excess-bw", type="float", default=_def_excess_bw,
 339                           help="set RRC excess bandwith factor [default=%default] (PSK)")
 340         parser.add_option("", "--no-gray-code", dest="gray_code",
 341                           action="store_false", default=_def_gray_code,
 342                           help="disable gray coding on modulated bits (PSK)")
 343         parser.add_option("", "--costas-alpha", type="float", default=_def_costas_alpha,
 344                           help="set Costas loop alpha value [default=%default] (PSK)")
 345         parser.add_option("", "--gain-mu", type="float", default=_def_gain_mu,
 346                           help="set M&M symbol sync loop gain mu value [default=%default] (PSK)")
 347         parser.add_option("", "--mu", type="float", default=_def_mu,
 348                           help="set M&M symbol sync loop mu value [default=%default] (PSK)")
 349     add_options=staticmethod(add_options)
 350
 351     def extract_kwargs_from_options(options):
 352         """
 353         Given command line options, create dictionary suitable for passing to __init__
 354         """
 355         return modulation_utils.extract_kwargs_from_options(
 356             dqpsk_demod.__init__, ('self', 'fg'), options)
 357     extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)
 358
 359
 360 #
 361 # Add these to the mod/demod registry
 362 #
 363 modulation_utils.add_type_1_mod('dqpsk', dqpsk_mod)
 364 modulation_utils.add_type_1_demod('dqpsk', dqpsk_demod)