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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 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 = 0.1
  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_block2):
  52     def __init__(self,
  53                  samples_per_symbol=_def_samples_per_symbol,
  54                  excess_bw=_def_excess_bw,
  55                  gray_code=_def_gray_code,
  56                  verbose=_def_verbose,
  57                  log=_def_log):
  58         """
  59         Hierarchical block for RRC-filtered QPSK modulation.
  60
  61         The input is a byte stream (unsigned char) and the
  62         output is the complex modulated signal at baseband.
  63
  64         @param samples_per_symbol: samples per symbol >= 2
  65         @type samples_per_symbol: integer
  66         @param excess_bw: Root-raised cosine filter excess bandwidth
  67         @type excess_bw: float
  68         @param gray_code: Tell modulator to Gray code the bits
  69         @type gray_code: bool
  70         @param verbose: Print information about modulator?
  71         @type verbose: bool
  72         @param debug: Print modualtion data to files?
  73         @type debug: bool
  74         """
  75
  76         gr.hier_block2.__init__(self, "dqpsk_mod",
  77                                 gr.io_signature(1,1,gr.sizeof_char),       # Input signature
  78                                 gr.io_signature(1,1,gr.sizeof_gr_complex)) # Output signature
  79
  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         # Connect components
 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     def samples_per_symbol(self):
 127         return self._samples_per_symbol
 128
 129     def bits_per_symbol(self=None):   # staticmethod that's also callable on an instance
 130         return 2
 131     bits_per_symbol = staticmethod(bits_per_symbol)      # make it a static method.  RTFM
 132
 133     def _print_verbage(self):
 134         print "\nModulator:"
 135         print "bits per symbol = %d" % self.bits_per_symbol()
 136         print "Gray code = %s" % self._gray_code
 137         print "RRS roll-off factor = %f" % self._excess_bw
 138
 139     def _setup_logging(self):
 140         print "Modulation logging turned on."
 141         self.connect(self.bytes2chunks, gr.file_sink(gr.sizeof_char, "tx_bytes2chunks.dat"))
 142         self.connect(self.symbol_mapper, gr.file_sink(gr.sizeof_char, "tx_symbol_mapper.dat"))
 143         self.connect(self.diffenc, gr.file_sink(gr.sizeof_char, "tx_diffenc.dat"))
 144         self.connect(self.chunks2symbols, gr.file_sink(gr.sizeof_gr_complex, "tx_chunks2symbols.dat"))
 145         self.connect(self.rrc_filter, gr.file_sink(gr.sizeof_gr_complex, "tx_rrc_filter.dat"))
 146
 147     def add_options(parser):
 148         """
 149         Adds QPSK modulation-specific options to the standard parser
 150         """
 151         parser.add_option("", "--excess-bw", type="float", default=_def_excess_bw,
 152                           help="set RRC excess bandwith factor [default=%default] (PSK)")
 153         parser.add_option("", "--no-gray-code", dest="gray_code",
 154                           action="store_false", default=_def_gray_code,
 155                           help="disable gray coding on modulated bits (PSK)")
 156     add_options=staticmethod(add_options)
 157
 158
 159     def extract_kwargs_from_options(options):
 160         """
 161         Given command line options, create dictionary suitable for passing to __init__
 162         """
 163         return modulation_utils.extract_kwargs_from_options(dqpsk_mod.__init__,
 164                                                             ('self', 'fg'), options)
 165     extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)
 166
 167
 168 # /////////////////////////////////////////////////////////////////////////////
 169 #                           DQPSK demodulator
 170 #
 171 # Differentially coherent detection of differentially encoded qpsk
 172 # /////////////////////////////////////////////////////////////////////////////
 173
 174 class dqpsk_demod(gr.hier_block2):
 175
 176     def __init__(self,
 177                  samples_per_symbol=_def_samples_per_symbol,
 178                  excess_bw=_def_excess_bw,
 179                  costas_alpha=_def_costas_alpha,
 180                  gain_mu=_def_gain_mu,
 181                  mu=_def_mu,
 182                  omega_relative_limit=_def_omega_relative_limit,
 183                  gray_code=_def_gray_code,
 184                  verbose=_def_verbose,
 185                  log=_def_log):
 186         """
 187         Hierarchical block for RRC-filtered DQPSK demodulation
 188
 189         The input is the complex modulated signal at baseband.
 190         The output is a stream of bits packed 1 bit per byte (LSB)
 191
 192         @param samples_per_symbol: samples per symbol >= 2
 193         @type samples_per_symbol: float
 194         @param excess_bw: Root-raised cosine filter excess bandwidth
 195         @type excess_bw: float
 196         @param costas_alpha: loop filter gain
 197         @type costas_alphas: float
 198         @param gain_mu: for M&M block
 199         @type gain_mu: float
 200         @param mu: for M&M block
 201         @type mu: float
 202         @param omega_relative_limit: for M&M block
 203         @type omega_relative_limit: float
 204         @param gray_code: Tell modulator to Gray code the bits
 205         @type gray_code: bool
 206         @param verbose: Print information about modulator?
 207         @type verbose: bool
 208         @param debug: Print modualtion data to files?
 209         @type debug: bool
 210         """
 211
 212         gr.hier_block2.__init__(self, "dqpsk_demod",
 213                                 gr.io_signature(1,1,gr.sizeof_gr_complex), # Input signature
 214                                 gr.io_signature(1,1,gr.sizeof_char))       # Output signature
 215
 216         self._samples_per_symbol = samples_per_symbol
 217         self._excess_bw = excess_bw
 218         self._costas_alpha = costas_alpha
 219         self._mm_gain_mu = gain_mu
 220         self._mm_mu = mu
 221         self._mm_omega_relative_limit = omega_relative_limit
 222         self._gray_code = gray_code
 223
 224         if samples_per_symbol < 2:
 225             raise TypeError, "sbp must be >= 2, is %d" % samples_per_symbol
 226
 227         arity = pow(2,self.bits_per_symbol())
 228
 229         # Automatic gain control
 230         scale = (1.0/16384.0)
 231         self.pre_scaler = gr.multiply_const_cc(scale)   # scale the signal from full-range to +-1
 232         self.agc = gr.feedforward_agc_cc(16, 2.0)
 233
 234         # RRC data filter
 235         ntaps = 11 * samples_per_symbol
 236         self.rrc_taps = gr.firdes.root_raised_cosine(
 237             1.0,                      # gain
 238             self._samples_per_symbol, # sampling rate
 239             1.0,                      # symbol rate
 240             self._excess_bw,          # excess bandwidth (roll-off factor)
 241             ntaps)
 242         self.rrc_filter=gr.interp_fir_filter_ccf(1, self.rrc_taps)
 243
 244         # symbol clock recovery
 245         self._mm_omega = self._samples_per_symbol
 246         self._mm_gain_omega = .25 * self._mm_gain_mu * self._mm_gain_mu
 247         self._costas_beta  = 0.25 * self._costas_alpha * self._costas_alpha
 248         fmin = -0.01
 249         fmax = 0.01
 250
 251         self.receiver=gr.mpsk_receiver_cc(arity, pi/4.0,
 252                                          self._costas_alpha, self._costas_beta,
 253                                          fmin, fmax,
 254                                          self._mm_mu, self._mm_gain_mu,
 255                                          self._mm_omega, self._mm_gain_omega,
 256                                          self._mm_omega_relative_limit)
 257
 258         # Perform Differential decoding on the constellation
 259         self.diffdec = gr.diff_phasor_cc()
 260
 261         # find closest constellation point
 262         rot = 1
 263         rotated_const = map(lambda pt: pt * rot, psk.constellation[arity])
 264         self.slicer = gr.constellation_decoder_cb(rotated_const, range(arity))
 265
 266         if self._gray_code:
 267             self.symbol_mapper = gr.map_bb(psk.gray_to_binary[arity])
 268         else:
 269             self.symbol_mapper = gr.map_bb(psk.ungray_to_binary[arity])
 270
 271         # unpack the k bit vector into a stream of bits
 272         self.unpack = gr.unpack_k_bits_bb(self.bits_per_symbol())
 273
 274         # Connect and Initialize base class
 275         self.connect(self, self.pre_scaler, self.agc, self.rrc_filter, self.receiver, self.diffdec,
 276                      self.slicer, self.symbol_mapper, self.unpack, self)
 277
 278         if verbose:
 279             self._print_verbage()
 280
 281         if log:
 282             self._setup_logging()
 283
 284     def samples_per_symbol(self):
 285         return self._samples_per_symbol
 286
 287     def bits_per_symbol(self=None):   # staticmethod that's also callable on an instance
 288         return 2
 289     bits_per_symbol = staticmethod(bits_per_symbol)      # make it a static method.  RTFM
 290
 291     def _print_verbage(self):
 292         print "\nDemodulator:"
 293         print "bits per symbol:     %d"   % self.bits_per_symbol()
 294         print "Gray code:           %s"   % self._gray_code
 295         print "RRC roll-off factor: %.2f" % self._excess_bw
 296         print "Costas Loop alpha:   %.2e" % self._costas_alpha
 297         print "Costas Loop beta:    %.2e" % self._costas_beta
 298         print "M&M mu:              %.2f" % self._mm_mu
 299         print "M&M mu gain:         %.2e" % self._mm_gain_mu
 300         print "M&M omega:           %.2f" % self._mm_omega
 301         print "M&M omega gain:      %.2e" % self._mm_gain_omega
 302         print "M&M omega limit:     %.2f" % self._mm_omega_relative_limit
 303
 304     def _setup_logging(self):
 305         print "Demodulation logging turned on."
 306         self.connect(self.pre_scaler, gr.file_sink(gr.sizeof_gr_complex, "rx_prescaler.dat"))
 307         self.connect(self.agc, gr.file_sink(gr.sizeof_gr_complex, "rx_agc.dat"))
 308         self.connect(self.rrc_filter, gr.file_sink(gr.sizeof_gr_complex, "rx_rrc_filter.dat"))
 309         self.connect(self.receiver, gr.file_sink(gr.sizeof_gr_complex, "rx_receiver.dat"))
 310         self.connect(self.diffdec, gr.file_sink(gr.sizeof_gr_complex, "rx_diffdec.dat"))
 311         self.connect(self.slicer, gr.file_sink(gr.sizeof_char, "rx_slicer.dat"))
 312         self.connect(self.symbol_mapper, gr.file_sink(gr.sizeof_char, "rx_symbol_mapper.dat"))
 313         self.connect(self.unpack, gr.file_sink(gr.sizeof_char, "rx_unpack.dat"))
 314
 315     def add_options(parser):
 316         """
 317         Adds modulation-specific options to the standard parser
 318         """
 319         parser.add_option("", "--excess-bw", type="float", default=_def_excess_bw,
 320                           help="set RRC excess bandwith factor [default=%default] (PSK)")
 321         parser.add_option("", "--no-gray-code", dest="gray_code",
 322                           action="store_false", default=_def_gray_code,
 323                           help="disable gray coding on modulated bits (PSK)")
 324         parser.add_option("", "--costas-alpha", type="float", default=None,
 325                           help="set Costas loop alpha value [default=%default] (PSK)")
 326         parser.add_option("", "--gain-mu", type="float", default=_def_gain_mu,
 327                           help="set M&M symbol sync loop gain mu value [default=%default] (PSK)")
 328         parser.add_option("", "--mu", type="float", default=_def_mu,
 329                           help="set M&M symbol sync loop mu value [default=%default] (PSK)")
 330     add_options=staticmethod(add_options)
 331
 332     def extract_kwargs_from_options(options):
 333         """
 334         Given command line options, create dictionary suitable for passing to __init__
 335         """
 336         return modulation_utils.extract_kwargs_from_options(
 337             dqpsk_demod.__init__, ('self', 'fg'), options)
 338     extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)
 339
 340
 341 #
 342 # Add these to the mod/demod registry
 343 #
 344 modulation_utils.add_type_1_mod('dqpsk', dqpsk_mod)
 345 modulation_utils.add_type_1_demod('dqpsk', dqpsk_demod)