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https://github.com/jhshi/openofdm.git
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735 lines
26 KiB
Python
735 lines
26 KiB
Python
#!/usr/bin/env python
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import os
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import numpy as np
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import cmath
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import collections
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import itertools
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import array
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import math
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from cStringIO import StringIO
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import commpy.channelcoding.convcode as cc
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from wltrace import dot11
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LONG_PREAMBLE_TXT =\
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"""
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0 -0.078 0.000 40 0.098 -0.026 80 0.062 0.062 120 -0.035 -0.151
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1 0.012 -0.098 41 0.053 0.004 81 0.119 0.004 121 -0.122 -0.017
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2 0.092 -0.106 42 0.001 -0.115 82 -0.022 -0.161 122 -0.127 -0.021
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3 -0.092 -0.115 43 -0.137 -0.047 83 0.059 0.015 123 0.075 -0.074
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4 -0.003 -0.054 44 0.024 -0.059 84 0.024 0.059 124 -0.003 0.054
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5 0.075 0.074 45 0.059 -0.015 85 -0.137 0.047 125 -0.092 0.115
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6 -0.127 0.021 46 -0.022 0.161 86 0.001 0.115 126 0.092 0.106
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7 -0.122 0.017 47 0.119 -0.004 87 0.053 -0.004 127 0.012 0.098
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8 -0.035 0.151 48 0.062 -0.062 88 0.098 0.026 128 -0.156 0.000
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9 -0.056 0.022 49 0.037 0.098 89 -0.038 0.106 129 0.012 -0.098
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10 -0.060 -0.081 50 -0.057 0.039 90 -0.115 0.055 130 0.092 -0.106
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11 0.070 -0.014 51 -0.131 0.065 91 0.060 0.088 131 -0.092 -0.115
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12 0.082 -0.092 52 0.082 0.092 92 0.021 -0.028 132 -0.003 -0.054
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13 -0.131 -0.065 53 0.070 0.014 93 0.097 -0.083 133 0.075 0.074
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14 -0.057 -0.039 54 -0.060 0.081 94 0.040 0.111 134 -0.127 0.021
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15 0.037 -0.098 55 -0.056 -0.022 95 -0.005 0.120 135 -0.122 0.017
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16 0.062 0.062 56 -0.035 -0.151 96 0.156 0.000 136 -0.035 0.151
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17 0.119 0.004 57 -0.122 -0.017 97 -0.005 -0.120 137 -0.056 0.022
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18 -0.022 -0.161 58 -0.127 -0.021 98 0.040 -0.111 138 -0.060 -0.081
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19 0.059 0.015 59 0.075 -0.074 99 0.097 0.083 139 0.070 -0.014
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20 0.024 0.059 60 -0.003 0.054 100 0.021 0.028 140 0.082 -0.092
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21 -0.137 0.047 61 -0.092 0.115 101 0.060 -0.088 141 -0.131 -0.065
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22 0.001 0.115 62 0.092 0.106 102 -0.115 -0.055 142 -0.057 -0.039
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23 0.053 -0.004 63 0.012 0.098 103 -0.038 -0.106 143 0.037 -0.098
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24 0.098 0.026 64 -0.156 0.000 104 0.098 -0.026 144 0.062 0.062
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25 -0.038 0.106 65 0.012 -0.098 105 0.053 0.004 145 0.119 0.004
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26 -0.115 0.055 66 0.092 -0.106 106 0.001 -0.115 146 -0.022 -0.161
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27 0.060 0.088 67 -0.092 -0.115 107 -0.137 -0.047 147 0.059 0.015
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28 0.021 -0.028 68 -0.003 -0.054 108 0.024 -0.059 148 0.024 0.059
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29 0.097 -0.083 69 0.075 0.074 109 0.059 -0.015 149 -0.137 0.047
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30 0.040 0.111 70 -0.127 0.021 110 -0.022 0.161 150 0.001 0.115
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31 -0.005 0.120 71 -0.122 0.017 111 0.119 -0.004 151 0.053 -0.004
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32 0.156 0.000 72 -0.035 0.151 112 0.062 -0.062 152 0.098 0.026
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33 -0.005 -0.120 73 -0.056 0.022 113 0.037 0.098 153 -0.038 0.106
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34 0.040 -0.111 74 -0.060 -0.081 114 -0.057 0.039 154 -0.115 0.055
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35 0.097 0.083 75 0.070 -0.014 115 -0.131 0.065 155 0.060 0.088
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36 0.021 0.028 76 0.082 -0.092 116 0.082 0.092 156 0.021 -0.028
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37 0.060 -0.088 77 -0.131 -0.065 117 0.070 0.014 157 0.097 -0.083
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38 -0.115 -0.055 78 -0.057 -0.039 118 -0.060 0.081 158 0.040 0.111
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39 -0.038 -0.106 79 0.037 -0.098 119 -0.056 -0.022 159 -0.005 0.120
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"""
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SHORT_PREAMBLE_TXT =\
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"""
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16 0.046 0.046 56 0.046 0.046 96 0.046 0.046 136 0.046 0.046
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17 -0.132 0.002 57 0.002 -0.132 97 -0.132 0.002 137 0.002 -0.132
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18 -0.013 -0.079 58 -0.079 -0.013 98 -0.013 -0.079 138 -0.079 -0.013
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19 0.143 -0.013 59 -0.013 0.143 99 0.143 -0.013 139 -0.013 0.143
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20 0.092 0.000 60 0.000 0.092 100 0.092 0.000 140 0.000 0.092
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21 0.143 -0.013 61 -0.013 0.143 101 0.143 -0.013 141 -0.013 0.143
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22 -0.013 -0.079 62 -0.079 -0.013 102 -0.013 -0.079 142 -0.079 -0.013
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23 -0.132 0.002 63 0.002 -0.132 103 -0.132 0.002 143 0.002 -0.132
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24 0.046 0.046 64 0.046 0.046 104 0.046 0.046 144 0.046 0.046
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25 0.002 -0.132 65 -0.132 0.002 105 0.002 -0.132 145 -0.132 0.002
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26 -0.079 -0.013 66 -0.013 -0.079 106 -0.079 -0.013 146 -0.013 -0.079
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27 -0.013 0.143 67 0.143 -0.013 107 -0.013 0.143 147 0.143 -0.013
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28 0.000 0.092 68 0.092 0.000 108 0.000 0.092 148 0.092 0.000
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29 -0.013 0.143 69 0.143 -0.013 109 -0.013 0.143 149 0.143 -0.013
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30 -0.079 -0.013 70 -0.013 -0.079 110 -0.079 -0.013 150 -0.013 -0.079
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31 0.002 -0.132
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"""
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LONG_PREAMBLE = dict()
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for idx, i, q in zip(*(iter(LONG_PREAMBLE_TXT.split()),)*3):
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LONG_PREAMBLE[int(idx)] = complex(float(i), float(q))
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LONG_PREAMBLE = [LONG_PREAMBLE[i] for i in sorted(LONG_PREAMBLE.keys())]
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SHORT_PREAMBLE = dict()
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for idx, i, q in zip(*(iter(SHORT_PREAMBLE_TXT.split()),)*3):
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idx = int(idx)
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if idx >= 16 and idx <= 31:
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SHORT_PREAMBLE[idx-16] = complex(float(i), float(q))
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SHORT_PREAMBLE = [SHORT_PREAMBLE[i] for i in sorted(SHORT_PREAMBLE.keys())]
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# Table 78 - Rate-dependent parameters
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RATE_PARAMETERS = {
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# rate : (n_bpsc, n_cbps, n_dbps),
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6: (1, 48, 24),
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9: (1, 48, 36),
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12: (2, 96, 48),
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18: (2, 96, 72),
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24: (4, 192, 96),
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36: (4, 192, 144),
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48: (6, 288, 192),
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54: (6, 288, 216),
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}
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HT_MCS_PARAMETERS = {
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0: (1, 52, 26),
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1: (2, 104, 52),
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2: (2, 104, 78),
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3: (4, 208, 104),
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4: (4, 208, 156),
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5: (6, 312, 208),
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6: (6, 312, 234),
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7: (6, 312, 260),
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}
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PILOT_SUBCARRIES = [-21, -7, 7, 21]
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PHASE_SCALE = 256
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# 802.11a/g
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SUBCARRIERS = range(-26, 0) + range(1, 27)
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FFT_MAPPING = dict((c, c if c > 0 else 64 + c) for c in SUBCARRIERS)
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LTS_REF = dict(
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zip(SUBCARRIERS,
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[1, 1, -1, -1, 1, 1, -1, 1, -1, 1, 1, 1, 1, 1, 1, -1, -1, 1, 1,
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-1, 1, -1, 1, 1, 1, 1, 1, -1, -1, 1, 1, -1, 1, -1, 1, -1, -1, -1,
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-1, -1, 1, 1, -1, -1, 1, -1, 1, -1, 1, 1, 1, 1]))
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polarity = [1, 1, 1, 1, -1, -1, -1, 1, -1, -1, -1, -1, 1, 1, -1, 1, -1, -1, 1,
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1, -1, 1, 1, -1, 1, 1, 1, 1, 1, 1, -1, 1, 1, 1, -1, 1, 1, -1, -1, 1,
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1, 1, -1, 1, -1, -1, -1, 1, -1, 1, -1, -1, 1, -1, -1, 1, 1, 1, 1, 1,
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-1, -1, 1, 1, -1, -1, 1, -1, 1, -1, 1, 1, -1, -1, -1, 1, 1, -1, -1,
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-1, -1, 1, -1, -1, 1, -1, 1, 1, 1, 1, -1, 1, -1, 1, -1, 1, -1, -1,
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-1, -1, -1, 1, -1, 1, 1, -1, 1, -1, 1, 1, 1, -1, -1, 1, -1, -1, -1,
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1, 1, 1, -1, -1, -1, -1, -1, -1, -1]
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RATE_BITS = {
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'1101': 6,
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'1111': 9,
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'0101': 12,
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'0111': 18,
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'1001': 24,
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'1011': 36,
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'0001': 48,
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'0011': 54,
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}
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# 802.11n
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HT_SUBCARRIERS = range(-28, 0) + range(1, 29)
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HT_FFT_MAPPING = dict((c, c if c > 0 else 64 + c) for c in HT_SUBCARRIERS)
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# append 1 for negative sub carriers, -1 for positive sub carriers
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HT_LTS_REF = dict(
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zip(HT_SUBCARRIERS,
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[1, 1, 1, 1, -1, -1, 1, 1, -1, 1, -1, 1, 1, 1, 1, 1, 1, -1, -1,
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1, 1, -1, 1, -1, 1, 1, 1, 1, 1, -1, -1, 1, 1, -1, 1, -1, 1, -1,
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-1, -1, -1, -1, 1, 1, -1, -1, 1, -1, 1, -1, 1, 1, 1, 1, -1,
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-1]))
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def to_hex(n, n_bits):
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return hex((n + (1<<n_bits)) % (1<<n_bits))
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class ChannelEstimator(object):
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"""
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Frequency offset correction and channel equalization.
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"""
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def __init__(self, samples):
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# samples[0] is the first sample of STS/L-STS
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self.samples = samples
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self.ht = False
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self.subcarriers = SUBCARRIERS
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self.fft_mapping = FFT_MAPPING
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self.short_gi = False
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self.fix_freq_offset()
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assert len(self.lts_samples) == 128
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lts1 = self.do_fft(self.lts_samples[:64])
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lts2 = self.do_fft(self.lts_samples[64:128])
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# print '[RAW LTS] (%s)' % (self.samples[160+32:160+32+4])
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for i in range(0):
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print '[%d] (%d, %d) -> (%d, %d) phase: %f (diff: %d)' %\
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(i,
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int(self.samples[192+i].real),
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int(self.samples[192+i].imag),
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int(self.lts_samples[i].real),
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int(self.lts_samples[i].imag),
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cmath.phase(self.lts_samples[i]),
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int((cmath.phase(self.lts_samples[i])-cmath.phase(samples[192+i]))*PHASE_SCALE),
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)
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self.gain = dict((c, (lts1[c]+lts2[c])/2*LTS_REF[c])
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for c in self.subcarriers)
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self.idx = 0
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self.polarity = itertools.cycle(polarity)
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def next_symbol(self):
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if self.short_gi:
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symbol = self.do_fft(self.data_samples[self.idx+8:self.idx+72])
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self.idx += 72
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else:
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symbol = self.do_fft(self.data_samples[self.idx+16:self.idx+80])
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self.idx += 80
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# remove randomness of pilot carriers
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p = self.polarity.next()
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if not self.ht:
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polarity = [p, p, p, -p]
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else:
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polarity = [p*p1 for p1 in self.ht_polarity]
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self.ht_polarity.rotate(-1)
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# print '[POLARITY] %d: %s' % (p, polarity)
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for c, p in zip(PILOT_SUBCARRIES, polarity):
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symbol[c] *= p
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# Correct Residual Carrier Frequency Offset
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prod_sum = 0
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for c in PILOT_SUBCARRIES:
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prod = symbol[c].conjugate()*self.gain[c]
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prod_sum += prod
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beta = cmath.phase(prod_sum)
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print "[PILOT OFFSET] %f (%d)" % (beta, int(beta*PHASE_SCALE))
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carriers = []
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for c in self.subcarriers:
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if c in PILOT_SUBCARRIES:
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continue
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symbol[c] *= cmath.exp(complex(0, beta))
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symbol[c] /= self.gain[c]
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carriers.append(symbol[c])
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return carriers
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def switch_ht(self):
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"""
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Switch to HT channel estimator.
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"""
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self.ht = True
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self.subcarriers = HT_SUBCARRIERS
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self.fft_mapping = HT_FFT_MAPPING
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ht_sts = self.data_samples[self.idx:self.idx+80]
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self.idx += 80
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ht_offset = cmath.phase(sum([ht_sts[i].conjugate()*ht_sts[i+16]
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for i in range(len(ht_sts)-16)]))/16
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print '[HT OFFSET] %f (%d)' % (ht_offset, int(ht_offset*PHASE_SCALE))
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ht_offset = 0
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self.data_samples = [c*cmath.exp(complex(0, -n*ht_offset))
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for n, c in enumerate(self.data_samples[self.idx:])]
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self.idx = 0
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ht_lts = self.do_fft(self.data_samples[self.idx+16:self.idx+80])
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self.idx += 80
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self.gain = dict((c, ht_lts[c]*HT_LTS_REF[c]) for c in self.subcarriers)
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self.ht_polarity = collections.deque([1, 1, 1, -1])
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def do_fft(self, samples):
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assert len(samples) == 64, len(samples)
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freq = np.fft.fft(samples)
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return dict((c, freq[self.fft_mapping[c]]) for c in self.subcarriers)
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def fix_freq_offset(self):
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sts = self.samples[80:160]
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lts = self.samples[160+32:160+160]
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coarse_offset = cmath.phase(sum([sts[i]*sts[i+16].conjugate()
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for i in range(len(sts)-16)]))/16
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print '[COARSE OFFSET] %f (%d)' % (coarse_offset, int(coarse_offset*PHASE_SCALE))
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# coarse_offset = 0
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# coarse correction
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lts = [c*cmath.exp(complex(0, n*coarse_offset))
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for n, c in enumerate(lts)]
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fine_offset = cmath.phase(sum([lts[i]*lts[i+64].conjugate()
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for i in range(len(lts)-64)]))/64
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print '[FINE OFFSET] %f (%d)' % (fine_offset, int(fine_offset*PHASE_SCALE))
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fine_offset = 0
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self.lts_samples = [c*cmath.exp(complex(0, n*fine_offset))
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for n, c in enumerate(lts)]
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self.freq_offset = coarse_offset + fine_offset
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print '[FREQ OFFSET] %f (%d)' % (self.freq_offset, int(self.freq_offset*PHASE_SCALE))
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self.data_samples = [c*cmath.exp(complex(0, n*self.freq_offset))
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for n, c in enumerate(self.samples[320:], start=128)]
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class Demodulator(object):
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QAM16_MAPPING = {
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0b00: -3,
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0b01: -1,
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0b11: 1,
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0b10: 3,
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}
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QAM64_MAPPING = {
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0b000: -7,
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0b001: -5,
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0b011: -3,
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0b010: -1,
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0b110: 1,
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0b111: 3,
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0b101: 5,
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0b100: 7,
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}
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def __init__(self, rate=6, mcs=0, ht=False):
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if (not ht and rate in [6, 9]) or (ht and mcs == 0):
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# BPSK
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self.scale = 1
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self.bits_per_sym = 1
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self.cons_points = np.array([complex(-1, 0), complex(1, 0)])
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elif (not ht and rate in [12, 18]) or (ht and mcs in [1, 2]):
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# QPSK
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self.scale = 1
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self.bits_per_sym = 2
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self.cons_points = np.array(
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[complex(-1, -1), complex(-1, 1),
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complex(1, -1), complex(1, 1)]
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)
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elif (not ht and rate in [24, 36]) or (ht and mcs in [3, 4]):
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# 16-QAM
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self.scale = 3
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self.bits_per_sym = 4
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self.cons_points = np.array(
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[complex(self.QAM16_MAPPING[i >> 2],
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self.QAM16_MAPPING[i & 0b11]) for i in range(16)])
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elif (not ht and rate in [48, 54]) or (ht and mcs in [5, 6, 7]):
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# 64-QAM
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self.scale = 7
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self.bits_per_sym = 6
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self.cons_points = np.array(
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[complex(self.QAM64_MAPPING[i >> 3],
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self.QAM64_MAPPING[i & 0b111]) for i in range(64)])
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def demodulate(self, carriers):
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bits = []
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for sym in carriers:
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idx = np.argmin(abs(sym*self.scale - self.cons_points))
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bits.extend([int(b) for b in ('{0:0%db}' % (self.bits_per_sym)).format(idx)])
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return bits
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class Signal(object):
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def __init__(self, bits):
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assert len(bits) == 24
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str_bits = ''.join([str(b) for b in bits])
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self.rate_bits = str_bits[:4]
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self.rsvd = str_bits[4]
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self.len_bits = str_bits[5:17]
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self.parity_bits = str_bits[17]
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self.tail_bits = str_bits[18:]
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self.mcs = 0
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self.rate = RATE_BITS.get(self.rate_bits, 0)
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self.length = int(self.len_bits[::-1], 2)
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self.parity_ok = sum(bits[:18]) % 2 == 0
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self.ht = False
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self.mcs = 0
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class HTSignal(object):
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def __init__(self, bits):
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assert len(bits) == 48
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str_bits = ''.join([str(b) for b in bits])
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self.mcs_bits = str_bits[:6]
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self.cbw = str_bits[7]
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|
self.len_bits = str_bits[8:24]
|
|
self.smoothing = str_bits[24]
|
|
self.not_sounding = str_bits[25]
|
|
self.rsvd = str_bits[26]
|
|
self.aggregation = str_bits[27]
|
|
self.stbc = str_bits[28:30]
|
|
self.fec = str_bits[30]
|
|
self.short_gi = str_bits[31]
|
|
self.num_ext_stream = str_bits[32:34]
|
|
self.crc = str_bits[34:42]
|
|
self.tail_bits = str_bits[42:48]
|
|
|
|
self.mcs = int(self.mcs_bits[::-1], 2)
|
|
try:
|
|
self.rate = dot11.mcs_to_rate(self.mcs)
|
|
except:
|
|
self.rate = 0
|
|
self.length = int(self.len_bits[::-1], 2)
|
|
self.expected_crc = ''.join(['%d' % c for c in self.calc_crc(bits[:34])])
|
|
self.crc_ok = self.expected_crc == self.crc
|
|
self.ht = True
|
|
|
|
def calc_crc(self, bits):
|
|
c = [1] * 8
|
|
|
|
for b in bits:
|
|
next_c = [0] * 8
|
|
next_c[0] = b ^ c[7]
|
|
next_c[1] = b ^ c[7] ^ c[0]
|
|
next_c[2] = b ^ c[7] ^ c[1]
|
|
next_c[3] = c[2]
|
|
next_c[4] = c[3]
|
|
next_c[5] = c[4]
|
|
next_c[6] = c[5]
|
|
next_c[7] = c[6]
|
|
c = next_c
|
|
|
|
return [1-b for b in c[::-1]]
|
|
|
|
|
|
class Decoder(object):
|
|
|
|
def __init__(self, path, power_thres=200, skip=0, window=80):
|
|
if path is not None:
|
|
self.fh = open(path, 'rb')
|
|
size = os.path.getsize(path)
|
|
if skip*4 < size:
|
|
self.fh.seek(skip*4)
|
|
else:
|
|
print "[WARN] try to seek beyond end of file %d/%d" % (skip*4, size)
|
|
self.power_thres = 200
|
|
self.window = window
|
|
self.count = skip
|
|
|
|
def decode_next(self, *args, **kwargs):
|
|
trigger = False
|
|
samples = []
|
|
glbl_index = 0
|
|
|
|
while True:
|
|
chunk = array.array('h', self.fh.read(self.window*4))
|
|
chunk = [complex(i, q) for i, q in zip(chunk[::2], chunk[1::2])]
|
|
if not trigger and any([abs(c) > self.power_thres for c in chunk]):
|
|
trigger = True
|
|
samples = []
|
|
print "Power trigger at %d" % (self.count)
|
|
glbl_index = self.count
|
|
|
|
self.count += self.window
|
|
|
|
if trigger:
|
|
samples.extend(chunk)
|
|
|
|
if trigger and all([abs(c) < self.power_thres for c in chunk]):
|
|
start = self.find_pkt(samples)
|
|
if start is None:
|
|
trigger = False
|
|
else:
|
|
print "Decoding packet starting from sample %d" %\
|
|
(glbl_index + start)
|
|
return (glbl_index, ) +\
|
|
self.decode(samples[start:], *args, **kwargs)
|
|
|
|
def find_pkt(self, samples):
|
|
"""
|
|
Returns the index of the first sample of STS
|
|
None if no packet was detected.
|
|
"""
|
|
lts = LONG_PREAMBLE[-64:]
|
|
peaks = np.array([abs(c) for c in np.correlate(
|
|
samples, lts, mode='valid')]).argsort()[-2:]
|
|
if (max(peaks) - min(peaks) == 64) and (min(peaks) - 32 - 160) > 0:
|
|
return min(peaks) - 32 - 160
|
|
else:
|
|
return None
|
|
|
|
def demodulate(self, carriers, signal=None):
|
|
if signal is None:
|
|
demod = Demodulator(rate=6)
|
|
else:
|
|
demod = Demodulator(signal.rate, signal.mcs, signal.ht)
|
|
return demod.demodulate(carriers)
|
|
|
|
def deinterleave(self, in_bits, rate=6, mcs=0, ht=False, verbose=False):
|
|
if not ht:
|
|
n_bpsc, n_cbps, n_dbps = RATE_PARAMETERS[rate]
|
|
n_col = 16
|
|
n_row = 3 * n_bpsc
|
|
else:
|
|
n_bpsc, n_cbps, n_dbps = HT_MCS_PARAMETERS[mcs]
|
|
n_col = 13
|
|
n_row = 4 * n_bpsc
|
|
s = max(n_bpsc/2, 1)
|
|
|
|
first_perm = dict()
|
|
for j in range(0, n_cbps):
|
|
first_perm[j] = (s * (j/s)) + ((j + n_col*j/n_cbps) % s)
|
|
|
|
second_perm = dict()
|
|
for i in range(0, n_cbps):
|
|
second_perm[i] = n_col*i - (n_cbps-1)*(i/n_row)
|
|
|
|
if verbose:
|
|
print "Bit rate: %f Mb/s" % (rate)
|
|
print "Bits per sub carrier: %d" % (n_bpsc)
|
|
print "Coded bits per symbol: %d" % (n_cbps)
|
|
print "Data bits per symbol %d" % (n_dbps)
|
|
print "S = %d" % (s)
|
|
print "====== Overall permutation ========="
|
|
for j in range(0, n_cbps):
|
|
print '%d -> %d -> %d' % (j, first_perm[j], second_perm[first_perm[j]])
|
|
|
|
if in_bits is None:
|
|
idx_map = []
|
|
for k in range(n_cbps):
|
|
idx_map.append((second_perm[first_perm[k]], k))
|
|
return sorted(idx_map)
|
|
|
|
if verbose:
|
|
print '%d bits, %f samples' % (len(in_bits), float(len(in_bits))/n_cbps)
|
|
|
|
out_bits = [0]*len(in_bits)
|
|
for n in range(len(in_bits)/n_cbps):
|
|
for j in range(n_cbps):
|
|
base = n*n_cbps
|
|
out_bits[base+second_perm[first_perm[j]]] = in_bits[base+j]
|
|
return out_bits
|
|
|
|
def viterbi_decode(self, bits, signal=None):
|
|
if signal is None:
|
|
ht = False
|
|
rate = 6
|
|
else:
|
|
ht, rate, mcs = signal.ht, signal.rate, signal.mcs
|
|
|
|
if (not ht and rate in [9, 18, 36, 54]) or (ht and mcs in [2, 4, 6]):
|
|
print '[PUNCTURE] 3/4'
|
|
# 3/4
|
|
new_bits = []
|
|
for i in range(0, len(bits), 12):
|
|
new_bits.extend(bits[i:i+3])
|
|
new_bits.extend([2, 2])
|
|
new_bits.extend(bits[i+3:i+7])
|
|
new_bits.extend([2, 2])
|
|
new_bits.extend(bits[i+7:i+11])
|
|
new_bits.extend([2, 2])
|
|
new_bits.extend(bits[i+11:i+12])
|
|
bits = new_bits
|
|
elif (not ht and rate in [48]) or (ht and mcs in [5]):
|
|
print '[PUNCTURE] 2/3'
|
|
# 2/3
|
|
new_bits = []
|
|
for i in range(0, len(bits), 9):
|
|
new_bits.extend(bits[i:i+3])
|
|
new_bits.append(2)
|
|
new_bits.extend(bits[i+3:i+6])
|
|
new_bits.append(2)
|
|
new_bits.extend(bits[i+6:i+9])
|
|
new_bits.append(2)
|
|
bits = new_bits
|
|
elif ht and mcs in [7]:
|
|
print '[PUNCTURE] 5/6'
|
|
# 5/6
|
|
new_bits = []
|
|
for i in range(0, len(bits), 6):
|
|
new_bits.extend(bits[i:i+3])
|
|
new_bits.extend([2, 2])
|
|
new_bits.extend(bits[i+3:i+5])
|
|
new_bits.extend([2, 2])
|
|
new_bits.append(bits[i+5])
|
|
bits = new_bits
|
|
else:
|
|
print '[NO PUNCTURE]'
|
|
|
|
extended_bits = np.array([0]*2 + bits + [0]*12)
|
|
trellis = cc.Trellis(np.array([7]), np.array([[0133, 0171]]))
|
|
return list(cc.viterbi_decode(extended_bits, trellis, tb_depth=35))[:-7]
|
|
|
|
def descramble(self, bits):
|
|
X = [0]*7
|
|
X[0] = bits[2] ^ bits[6]
|
|
X[1] = bits[1] ^ bits[5]
|
|
X[2] = bits[0] ^ bits[4]
|
|
X[3] = X[0] ^ bits[3]
|
|
X[4] = X[1] ^ bits[2]
|
|
X[5] = X[2] ^ bits[1]
|
|
X[6] = X[3] ^ bits[0]
|
|
|
|
out_bits = []
|
|
for i, b in enumerate(bits):
|
|
feedback = X[6] ^ X[3]
|
|
out_bits.append(feedback ^ b)
|
|
X = [feedback] + X[:-1]
|
|
|
|
return out_bits
|
|
|
|
def check_signal(self, signal):
|
|
if signal.rate_bits not in RATE_BITS:
|
|
print '[SIGNAL] invalid rate: %s' % (signal.rate_bits)
|
|
return False
|
|
|
|
if signal.rsvd != '0':
|
|
print '[SIGNAL] wrong rsvd'
|
|
return False
|
|
|
|
if not signal.parity_ok:
|
|
print '[SIGNAL] wrong parity'
|
|
return False
|
|
|
|
if not all([b == '0' for b in signal.tail_bits]):
|
|
print '[SIGNAL] wrong tail: %s' % (signal.tail_bits)
|
|
return False
|
|
|
|
return True
|
|
|
|
def check_ht_signal(self, signal):
|
|
if signal.mcs > 7:
|
|
print '[HT SIGNAL] mcs not supported: %d' % (signal.mcs)
|
|
return False
|
|
|
|
if signal.cbw != '0':
|
|
print '[HT SIGNAL] CBW not supported'
|
|
return False
|
|
|
|
if signal.rsvd != '1':
|
|
print '[HT SIGNAL] wrong rsvd'
|
|
return False
|
|
|
|
if signal.stbc != '00':
|
|
print '[HT SIGNAL] stbc not supported: %s' % (signal.stbc)
|
|
return False
|
|
|
|
if signal.fec != '0':
|
|
print '[HT SIGNAL] FEC not supported'
|
|
return False
|
|
|
|
if signal.num_ext_stream != '00':
|
|
print '[HT SIGNAL] EXT spatial stream not supported: %s' % (signal.num_ext_stream)
|
|
return False
|
|
|
|
if not all([b == '0' for b in signal.tail_bits]):
|
|
print '[HT SIGNAL] wrong tail: %s' % (signal.tail_bits)
|
|
return False
|
|
|
|
return True
|
|
|
|
def decode(self, samples, *args, **kwargs):
|
|
eq = ChannelEstimator(samples)
|
|
|
|
carriers = eq.next_symbol()
|
|
assert len(carriers) == 48
|
|
carrier_bits = self.demodulate(carriers)
|
|
raw_bits = self.deinterleave(carrier_bits)
|
|
bits = self.viterbi_decode(raw_bits)
|
|
signal = Signal(bits)
|
|
print "[SIGNAL] %s" % (signal.__dict__)
|
|
|
|
if not self.check_signal(signal):
|
|
return
|
|
|
|
cons = []
|
|
|
|
if signal.rate == 6:
|
|
# decode next two OFDM SYMs to detect potential 802.11n packets
|
|
demod_out = []
|
|
for _ in range(2):
|
|
carriers = eq.next_symbol()
|
|
assert len(carriers) == 48
|
|
cons.extend(carriers)
|
|
|
|
# HT-SIG was rotated by 90 degrees, rotate it back
|
|
carriers = [c*complex(0, -1) for c in carriers]
|
|
|
|
carrier_bits = self.demodulate(carriers)
|
|
demod_out.extend(carrier_bits)
|
|
|
|
raw_bits = self.deinterleave(demod_out)
|
|
signal_bits = self.viterbi_decode(raw_bits)
|
|
|
|
ht_signal = HTSignal(signal_bits)
|
|
if ht_signal.crc_ok:
|
|
print "[HT SIGNAL] %s" % (ht_signal.__dict__)
|
|
if not self.check_ht_signal(ht_signal):
|
|
return
|
|
signal = ht_signal
|
|
eq.switch_ht()
|
|
cons = []
|
|
eq.short_gi = ht_signal.short_gi == '1'
|
|
|
|
if signal.ht:
|
|
num_symbol = int(math.ceil(float((16+signal.length*8+6))/
|
|
HT_MCS_PARAMETERS[signal.mcs][2]))
|
|
else:
|
|
num_symbol = int(math.ceil(float((16+signal.length*8.0+6))/
|
|
RATE_PARAMETERS[signal.rate][2]))
|
|
|
|
print "%d DATA OFDM symbols to decode" % (num_symbol)
|
|
|
|
if signal.rate == 6 and not signal.ht:
|
|
num_symbol -= 2
|
|
|
|
for _ in range(num_symbol):
|
|
carriers = eq.next_symbol()
|
|
if signal.ht:
|
|
assert len(carriers) == 52, len(carriers)
|
|
else:
|
|
assert len(carriers) == 48, len(carriers)
|
|
cons.extend(carriers)
|
|
|
|
demod_out = self.demodulate(cons, signal)
|
|
deinter_out = self.deinterleave(demod_out, signal.rate, signal.mcs, signal.ht)
|
|
conv_out = self.viterbi_decode(deinter_out, signal)
|
|
descramble_out = self.descramble(conv_out)
|
|
|
|
if not all([b == 0 for b in descramble_out[:16]]):
|
|
print '[SERVICE] not all bits are 0'
|
|
|
|
# skip the SERVICE bits
|
|
data_bits = descramble_out[16:]
|
|
num_bytes = min(len(data_bits)/8, signal.length)
|
|
|
|
data_bytes = [self.array_to_int(data_bits[i*8:(i+1)*8])
|
|
for i in range(num_bytes)]
|
|
assert len(data_bytes) == num_bytes
|
|
|
|
for i in range(0, num_bytes, 16):
|
|
print '[%3d] %s' %\
|
|
(i, ' '.join([format(data_bytes[j], '02x')
|
|
for j in range(i, min(i+16, num_bytes))]))
|
|
|
|
fh = StringIO(''.join([chr(b) for b in data_bytes]))
|
|
pkt = dot11.Dot11Packet(fh)
|
|
|
|
return signal, cons, demod_out, deinter_out, conv_out, descramble_out, data_bytes, pkt
|
|
|
|
def array_to_int(self, arr):
|
|
assert len(arr) == 8
|
|
return int(''.join(['%d' % (b) for b in arr[::-1]]), 2)
|