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   1 #!/usr/bin/env python
   2 #
   3 # Copyright 2004,2005,2006 Free Software Foundation, Inc.
   4 #
   5 # This file is part of GNU Radio
   6 #
   7 # GNU Radio is free software; you can redistribute it and/or modify
   8 # it under the terms of the GNU General Public License as published by
   9 # the Free Software Foundation; either version 2, or (at your option)
  10 # any later version.
  11 #
  12 # GNU Radio is distributed in the hope that it will be useful,
  13 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 # GNU General Public License for more details.
  16 #
  17 # You should have received a copy of the GNU General Public License
  18 # along with GNU Radio; see the file COPYING.  If not, write to
  19 # the Free Software Foundation, Inc., 51 Franklin Street,
  20 # Boston, MA 02110-1301, USA.
  21 #
  22
  23 import math
  24 from gnuradio import gr
  25 from gnuradio import audio
  26 from gnuradio.eng_option import eng_option
  27 from optparse import OptionParser
  28
  29 class ofdm_receiver(gr.hier_block):
  30     def __init__(self, fg, fft_length, symbol_length, snr):
  31         self.input = gr.add_const_cc(0) # Kluge that goes away with hier_block2
  32
  33         self.fg = fg
  34
  35         cpsize = symbol_length - fft_length;
  36
  37         SNR = 10.0**(snr/10.0)
  38         rho = SNR / (SNR + 1.0)
  39
  40         # ML Sync
  41
  42         # Energy Detection from ML Sync
  43
  44         # Create a delay line
  45         delayline = [0.0 for i in range(fft_length+1)]
  46         delayline[fft_length] = 1.0
  47         self.delay = gr.fir_filter_ccf(1,delayline)
  48         self.fg.connect(self.input, self.delay)
  49
  50         # magnitude squared blocks
  51         self.magsqrd1 = gr.complex_to_mag_squared()
  52         self.magsqrd2 = gr.complex_to_mag_squared()
  53         self.adder = gr.add_ff()
  54
  55         moving_sum_taps = [rho/2 for i in range(cpsize)]
  56         self.moving_sum_filter = gr.fir_filter_fff(1,moving_sum_taps)
  57
  58         self.fg.connect(self.input,self.magsqrd1)
  59         self.fg.connect(self.delay,self.magsqrd2)
  60         self.fg.connect(self.magsqrd1,(self.adder,0))
  61         self.fg.connect(self.magsqrd2,(self.adder,1))
  62         self.fg.connect(self.adder,self.moving_sum_filter)
  63
  64
  65         # Correlation from ML Sync
  66         self.conjg = gr.conjugate_cc();
  67         self.mixer = gr.multiply_cc();
  68
  69         movingsum2_taps = [1.0 for i in range(cpsize)]
  70         self.movingsum2 = gr.fir_filter_ccf(1,movingsum2_taps)
  71
  72
  73         # Correlator data handler
  74         self.c2mag = gr.complex_to_mag()
  75         self.angle = gr.complex_to_arg()
  76         self.fg.connect(self.input,(self.mixer,1))
  77         self.fg.connect(self.delay,self.conjg,(self.mixer,0))
  78         self.fg.connect(self.mixer,self.movingsum2,self.c2mag)
  79         self.fg.connect(self.movingsum2,self.angle)
  80
  81         # ML Sync output arg, need to find maximum point of this
  82         self.diff = gr.sub_ff()
  83         self.fg.connect(self.c2mag,(self.diff,0))
  84         self.fg.connect(self.moving_sum_filter,(self.diff,1))
  85
  86         #ML measurements input to sampler block and detect
  87         nco_sensitivity = 1.0/fft_length
  88         self.f2c = gr.float_to_complex()
  89         self.sampler = gr.ofdm_sampler(fft_length,symbol_length)
  90         self.pkt_detect = gr.peak_detector_ff(0.2, 0.25, 30, 0.0001)
  91         self.dpll = gr.dpll_ff(float(symbol_length),0.01)
  92         self.sample_and_hold = gr.sample_and_hold_ff()
  93         self.nco = gr.frequency_modulator_fc(nco_sensitivity)
  94         self.inv = gr.multiply_const_ff(-1)
  95         self.sigmix = gr.multiply_cc()
  96
  97         # Mix the signal with an NCO controlled by the sync loop
  98         self.fg.connect(self.input, (self.sigmix,0))
  99         self.fg.connect(self.nco, (self.sigmix,1))
 100         self.fg.connect(self.sigmix, (self.sampler,0))
 101
 102         sample_trigger = 0
 103         if sample_trigger:
 104             # for testing
 105             peak_null = gr.null_sink(gr.sizeof_float)
 106             data = 640*[0,]
 107             data[639] = 1
 108             peak_trigger = gr.vector_source_f(data, True)
 109
 110             self.fg.connect(self.pkt_detect, peak_null)
 111             self.fg.connect(peak_trigger, self.f2c, (self.sampler,1))
 112             self.fg.connect(peak_trigger, (self.sample_and_hold,1))
 113
 114         # use the sync loop values to set the sampler and the NCO
 115         # self.diff = theta
 116         # self.angle = epsilon
 117
 118         self.fg.connect(self.diff, self.pkt_detect)
 119         use_dpll = 1
 120         if not sample_trigger:
 121             if use_dpll:
 122                 self.fg.connect(self.pkt_detect, self.dpll,self.f2c, (self.sampler,1))
 123                 self.fg.connect(self.dpll, (self.sample_and_hold,1))
 124             if not use_dpll:
 125                 self.fg.connect(self.pkt_detect, self.f2c, (self.sampler,1))
 126                 self.fg.connect(self.pkt_detect, (self.sample_and_hold,1))
 127
 128         self.fg.connect(self.angle, (self.sample_and_hold,0))
 129         self.fg.connect(self.sample_and_hold, self.inv, self.nco)
 130
 131
 132         if 0:
 133             self.fg.connect(self.diff, gr.file_sink(gr.sizeof_float, "theta_f.dat"))
 134             self.fg.connect(self.angle, gr.file_sink(gr.sizeof_float, "epsilon_f.dat"))
 135             if use_dpll:
 136                 self.fg.connect(self.dpll, gr.file_sink(gr.sizeof_float, "dpll_pulses.dat"))
 137             if sample_trigger:
 138                 self.fg.connect(peak_trigger, gr.file_sink(gr.sizeof_float, "peaks_f.dat"))
 139             else:
 140                 self.fg.connect(self.pkt_detect, gr.file_sink(gr.sizeof_float, "peaks_f.dat"))
 141
 142             self.fg.connect(self.sample_and_hold, gr.file_sink(gr.sizeof_float, "sample_and_hold_f.dat"))
 143             self.fg.connect(self.nco, gr.file_sink(gr.sizeof_gr_complex, "nco_c.dat"))
 144             self.fg.connect(self.input, gr.file_sink(gr.sizeof_gr_complex, "input_c.dat"))
 145             self.fg.connect(self.sigmix, gr.file_sink(gr.sizeof_gr_complex, "output_c.dat"))
 146
 147         gr.hier_block.__init__(self, fg, self.input, self.sampler)