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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 QAM256 modulation and demodulation.
  26 """
  27
  28 from gnuradio import gr, gru, modulation_utils
  29 from math import pi, sqrt
  30 import qam
  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 = None
  42 _def_gain_mu = 0.03
  43 _def_mu = 0.05
  44 _def_omega_relative_limit = 0.005
  45
  46
  47 # /////////////////////////////////////////////////////////////////////////////
  48 #                           QAM256 modulator
  49 # /////////////////////////////////////////////////////////////////////////////
  50
  51 class qam256_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         """
  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(qam.binary_to_gray[arity])
  98         else:
  99             self.symbol_mapper = gr.map_bb(qam.binary_to_ungray[arity])
 100
 101         self.diffenc = gr.diff_encoder_bb(arity)
 102
 103         rot = 1.0
 104         print "constellation with %d arity" % arity
 105         rotated_const = map(lambda pt: pt * rot, qam.constellation[arity])
 106         self.chunks2symbols = gr.chunks_to_symbols_bc(rotated_const)
 107
 108         # pulse shaping filter
 109         self.rrc_taps = gr.firdes.root_raised_cosine(
 110             self._samples_per_symbol, # gain  (sps since we're interpolating by sps)
 111             self._samples_per_symbol, # sampling rate
 112             1.0,                      # symbol rate
 113             self._excess_bw,          # excess bandwidth (roll-off factor)
 114             ntaps)
 115
 116         self.rrc_filter = gr.interp_fir_filter_ccf(self._samples_per_symbol, self.rrc_taps)
 117
 118         if verbose:
 119             self._print_verbage()
 120
 121         if log:
 122             self._setup_logging()
 123
 124         # Connect & Initialize base class
 125         self._fg.connect(self.bytes2chunks, self.symbol_mapper, self.diffenc,
 126                          self.chunks2symbols, self.rrc_filter)
 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):   # staticmethod that's also callable on an instance
 133         return 8
 134     bits_per_symbol = staticmethod(bits_per_symbol)      # make it a static method.  RTFM
 135
 136     def _print_verbage(self):
 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, "bytes2chunks.dat"))
 145         self._fg.connect(self.symbol_mapper,
 146                          gr.file_sink(gr.sizeof_char, "graycoder.dat"))
 147         self._fg.connect(self.diffenc,
 148                          gr.file_sink(gr.sizeof_char, "diffenc.dat"))
 149         self._fg.connect(self.chunks2symbols,
 150                          gr.file_sink(gr.sizeof_gr_complex, "chunks2symbols.dat"))
 151         self._fg.connect(self.rrc_filter,
 152                          gr.file_sink(gr.sizeof_gr_complex, "rrc_filter.dat"))
 153
 154     def add_options(parser):
 155         """
 156         Adds QAM 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(qam256_mod.__init__,
 171                                                             ('self', 'fg'), options)
 172     extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)
 173
 174
 175 # /////////////////////////////////////////////////////////////////////////////
 176 #                           QAM256 demodulator
 177 #
 178 # /////////////////////////////////////////////////////////////////////////////
 179
 180 class qam256_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         # do this
 194         pass
 195
 196     def bits_per_symbol(self=None):   # staticmethod that's also callable on an instance
 197         return 8
 198     bits_per_symbol = staticmethod(bits_per_symbol)      # make it a static method.  RTFM
 199
 200 #
 201 # Add these to the mod/demod registry
 202 #
 203 # NOT READY TO BE USED YET -- ENABLE AT YOUR OWN RISK
 204 #modulation_utils.add_type_1_mod('qam256', qam256_mod)
 205 #modulation_utils.add_type_1_demod('qam256', qam256_demod)