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   1 #!/usr/bin/env python
   2 #
   3 # Copyright 2007 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
  26 class ofdm_sync(gr.hier_block):
  27     def __init__(self, fg, fft_length, cp_length, snr):
  28         self.fg = fg
  29
  30         self.input = gr.add_const_cc(0)
  31
  32         SNR = 10.0**(snr/10.0)
  33         rho = SNR / (SNR + 1.0)
  34         symbol_length = fft_length + cp_length
  35
  36         # ML Sync
  37
  38         # Energy Detection from ML Sync
  39
  40         # Create a delay line
  41         self.delay = gr.delay(gr.sizeof_gr_complex, fft_length)
  42         self.fg.connect(self.input, self.delay)
  43
  44         # magnitude squared blocks
  45         self.magsqrd1 = gr.complex_to_mag_squared()
  46         self.magsqrd2 = gr.complex_to_mag_squared()
  47         self.adder = gr.add_ff()
  48
  49         moving_sum_taps = [rho/2 for i in range(cp_length)]
  50         self.moving_sum_filter = gr.fir_filter_fff(1,moving_sum_taps)
  51
  52         self.fg.connect(self.input,self.magsqrd1)
  53         self.fg.connect(self.delay,self.magsqrd2)
  54         self.fg.connect(self.magsqrd1,(self.adder,0))
  55         self.fg.connect(self.magsqrd2,(self.adder,1))
  56         self.fg.connect(self.adder,self.moving_sum_filter)
  57
  58
  59         # Correlation from ML Sync
  60         self.conjg = gr.conjugate_cc();
  61         self.mixer = gr.multiply_cc();
  62
  63         movingsum2_taps = [1.0 for i in range(cp_length)]
  64         self.movingsum2 = gr.fir_filter_ccf(1,movingsum2_taps)
  65
  66         # Correlator data handler
  67         self.c2mag = gr.complex_to_mag()
  68         self.angle = gr.complex_to_arg()
  69         self.fg.connect(self.input,(self.mixer,1))
  70         self.fg.connect(self.delay,self.conjg,(self.mixer,0))
  71         self.fg.connect(self.mixer,self.movingsum2,self.c2mag)
  72         self.fg.connect(self.movingsum2,self.angle)
  73
  74         # ML Sync output arg, need to find maximum point of this
  75         self.diff = gr.sub_ff()
  76         self.fg.connect(self.c2mag,(self.diff,0))
  77         self.fg.connect(self.moving_sum_filter,(self.diff,1))
  78
  79         #ML measurements input to sampler block and detect
  80         nco_sensitivity = 1.0/fft_length
  81         self.f2c = gr.float_to_complex()
  82         self.sampler = gr.ofdm_sampler(fft_length,symbol_length)
  83         self.pk_detect = gr.peak_detector_fb(0.2, 0.25, 30, 0.0005)
  84         self.sample_and_hold = gr.sample_and_hold_ff()
  85         self.nco = gr.frequency_modulator_fc(nco_sensitivity)
  86         self.inv = gr.multiply_const_ff(-1)
  87         self.sigmix = gr.multiply_cc()
  88
  89         # Mix the signal with an NCO controlled by the sync loop
  90         self.fg.connect(self.input, (self.sigmix,0))
  91         self.fg.connect(self.nco, (self.sigmix,1))
  92         self.fg.connect(self.sigmix, (self.sampler,0))
  93
  94         # use the sync loop values to set the sampler and the NCO
  95         #     self.diff = theta
  96         #     self.angle = epsilon
  97
  98         self.fg.connect(self.diff, self.pk_detect)
  99         use_dpll = 1
 100
 101         fixed_timing = 0
 102         if fixed_timing:
 103             # Use a fixed trigger point instead of sync block
 104             peak_null = gr.null_sink(gr.sizeof_char)
 105             data = 640*[0,]
 106             data[639] = 1
 107             peak_trigger = gr.vector_source_b(data, True)
 108
 109             self.fg.connect(self.pk_detect, peak_null)
 110             self.fg.connect(peak_trigger, (self.sampler,1))
 111             self.fg.connect(peak_trigger, (self.sample_and_hold,1))
 112         else:
 113             self.dpll = gr.dpll_bb(float(symbol_length),0.01)
 114             if use_dpll:
 115                 self.fg.connect(self.pk_detect, self.dpll)
 116                 self.fg.connect(self.dpll, (self.sampler,1))
 117                 self.fg.connect(self.dpll, (self.sample_and_hold,1))
 118             else:
 119                 self.fg.connect(self.pk_detect, (self.sampler,1))
 120                 self.fg.connect(self.pk_detect, (self.sample_and_hold,1))
 121
 122         self.fg.connect(self.angle, (self.sample_and_hold,0))
 123         self.fg.connect(self.sample_and_hold, self.inv, self.nco)
 124
 125         if 1:
 126             self.fg.connect(self.diff, gr.file_sink(gr.sizeof_float, "theta_f.dat"))
 127             self.fg.connect(self.angle, gr.file_sink(gr.sizeof_float, "epsilon_f.dat"))
 128             if fixed_timing:
 129                 self.fg.connect(peak_trigger, gr.file_sink(gr.sizeof_char, "peaks_b.dat"))
 130             else:
 131                 self.fg.connect(self.pk_detect, gr.file_sink(gr.sizeof_char, "peaks_b.dat"))
 132                 if use_dpll:
 133                     self.fg.connect(self.dpll, gr.file_sink(gr.sizeof_char, "dpll_b.dat"))
 134
 135             self.fg.connect(self.sigmix, gr.file_sink(gr.sizeof_gr_complex, "sigmix_c.dat"))
 136             self.fg.connect(self.sampler, gr.file_sink(gr.sizeof_gr_complex*fft_length, "sampler_c.dat"))
 137             self.fg.connect(self.sample_and_hold, gr.file_sink(gr.sizeof_float, "sample_and_hold_f.dat"))
 138             self.fg.connect(self.nco, gr.file_sink(gr.sizeof_gr_complex, "nco_c.dat"))
 139             self.fg.connect(self.input, gr.file_sink(gr.sizeof_gr_complex, "input_c.dat"))
 140
 141         gr.hier_block.__init__(self, fg, self.input, self.sampler)