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This commit is contained in:
Bastian Bloessl
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/*
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* Copyright (C) 2013 Bastian Bloessl <bloessl@ccs-labs.org>
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <gnuradio/ieee802_11/ofdm_decode_mac.h>
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#include <gnuradio/gr_io_signature.h>
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#include <itpp/itcomm.h>
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#include <iostream>
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#include <iomanip>
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using namespace gr::ieee802_11;
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using namespace itpp;
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enum ENCODING {
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BPSK_1_2,
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BPSK_3_4,
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QPSK_1_2,
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QPSK_3_4,
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QAM16_1_2,
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QAM16_3_4,
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QAM64_2_3,
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QAM64_3_4,
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};
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/**
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* OFDM parameters
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*/
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class GR_IEEE802_11_API ofdm_param {
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public:
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ofdm_param(ENCODING e) {
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encoding = e;
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switch(e) {
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case BPSK_1_2:
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n_bpsc = 1;
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n_cbps = 48;
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n_dbps = 24;
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rate_field = 0x0D; // 0b00001101
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break;
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case BPSK_3_4:
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n_bpsc = 1;
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n_cbps = 48;
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n_dbps = 36;
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rate_field = 0x0F; // 0b00001111
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break;
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case QPSK_1_2:
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n_bpsc = 2;
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n_cbps = 96;
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n_dbps = 48;
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rate_field = 0x05; // 0b00000101
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break;
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case QPSK_3_4:
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n_bpsc = 2;
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n_cbps = 96;
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n_dbps = 72;
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rate_field = 0x07; // 0b00000111
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break;
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case QAM16_1_2:
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n_bpsc = 4;
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n_cbps = 192;
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n_dbps = 96;
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rate_field = 0x09; // 0b00001001
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break;
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case QAM16_3_4:
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n_bpsc = 4;
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n_cbps = 192;
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n_dbps = 144;
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rate_field = 0x0B; // 0b00001011
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break;
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case QAM64_2_3:
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n_bpsc = 6;
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n_cbps = 288;
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n_dbps = 192;
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rate_field = 0x01; // 0b00000001
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break;
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case QAM64_3_4:
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n_bpsc = 6;
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n_cbps = 288;
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n_dbps = 216;
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rate_field = 0x03; // 0b00000011
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break;
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defaut:
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assert(false);
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break;
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}
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}
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void print_out() {
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std::cout << "OFDM Parameters:" << std::endl;
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std::cout << "endcoding :" << encoding << std::endl;
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std::cout << "rate_field :" << (int)rate_field << std::endl;
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std::cout << "n_bpsc :" << n_bpsc << std::endl;
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std::cout << "n_cbps :" << n_cbps << std::endl;
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std::cout << "n_dbps :" << n_dbps << std::endl;
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}
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// data rate
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ENCODING encoding;
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// rate field of the SIGNAL header
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char rate_field;
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// number of coded bits per sub carrier
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int n_bpsc;
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// number of coded bits per OFDM symbol
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int n_cbps;
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// number of data bits per OFDM symbol
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int n_dbps;
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};
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/**
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* packet specific parameters
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*/
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class tx_param {
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public:
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tx_param(ofdm_param &ofdm, int psdu_length) {
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psdu_size = psdu_length;
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// number of symbols (17-11)
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n_sym = (int) ceil((16 + 8 * psdu_size + 6) / (double) ofdm.n_dbps);
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// number of bits of the data field (17-12)
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n_data = n_sym * ofdm.n_dbps;
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// number of padding bits (17-13)
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n_pad = n_data - (16 + 8 * psdu_size + 6);
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n_encoded_bits = n_sym * ofdm.n_cbps;
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}
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// PSDU size in bytes
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int psdu_size;
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// number of OFDM symbols (17-11)
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int n_sym;
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// number of data bits in the DATA field, including service and padding (17-12)
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int n_data;
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// number of padding bits in the DATA field (17-13)
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int n_pad;
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int n_encoded_bits;
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void print_out() {
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std::cout << "TX Parameters:" << std::endl;
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std::cout << "psdu_size: " << psdu_size << std::endl;
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std::cout << "n_sym: " << n_sym << std::endl;
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std::cout << "n_data: " << n_data << std::endl;
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std::cout << "n_pad: " << n_pad << std::endl;
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}
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};
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class ofdm_decode_mac_impl : public ofdm_decode_mac {
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#define dout d_debug && std::cout
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public:
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ofdm_decode_mac_impl(bool debug) : gr_block("ofdm_decode_mac",
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gr_make_io_signature(1, 1, 48 * sizeof(gr_complex)),
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gr_make_io_signature(0, 0, 0)),
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d_debug(debug),
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ofdm(BPSK_1_2),
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tx(ofdm, 0) {
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message_port_register_out(pmt::mp("out"));
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}
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~ofdm_decode_mac_impl(){
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}
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int general_work (int noutput_items, gr_vector_int& ninput_items,
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gr_vector_const_void_star& input_items,
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gr_vector_void_star& output_items) {
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const gr_complex *in = (const gr_complex*)input_items[0];
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int i = 0;
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std::vector<gr_tag_t> tags;
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const uint64_t nread = this->nitems_read(0);
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dout << "Decode MAC: input " << ninput_items[0] << std::endl;
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while(i < ninput_items[0]) {
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get_tags_in_range(tags, 0, nread + i * 48, nread + (i + 1) * 48 - 1,
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pmt::pmt_string_to_symbol("ofdm_start"));
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if(tags.size()) {
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pmt::pmt_t tuple = tags[0].value;
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int len_data = pmt::pmt_to_uint64(pmt::pmt_car(tuple));
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int encoding = pmt::pmt_to_uint64(pmt::pmt_cdr(tuple));
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ofdm = ofdm_param((ENCODING)encoding);
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tx = tx_param(ofdm, len_data);
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if(tx.n_sym > 100) {
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tx.n_sym = 100;
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}
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copied = 0;
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dout << "Decode MAC: frame start -- len " << len_data
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<< " symbols " << tx.n_sym << " encoding "
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<< encoding << std::endl;
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}
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if(copied < tx.n_sym) {
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std::memcpy(sym + (copied * 48), in, 48 * sizeof(gr_complex));
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copied++;
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if(copied == tx.n_sym) {
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dout << "received complete frame - decoding" << std::endl;
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decode();
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break;
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}
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}
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in += 48;
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i++;
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}
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consume(0, i);
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return 0;
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}
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void decode() {
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if(ofdm.encoding > 3) {
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return;
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}
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demodulate();
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deinterleave();
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decode_conv();
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descramble();
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print_output();
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// skip service field
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pmt::pmt_t blob = pmt::pmt_make_blob(out_bytes + 2, tx.psdu_size);
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message_port_pub(pmt::mp("out"), blob);
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}
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void demodulate() {
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gr_complex s;
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for(int i = 0; i < tx.n_sym; i++) {
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for(int n = 0; n < 48; n++) {
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switch(ofdm.encoding) {
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case 0: // BPSK
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case 1:
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bits[i * 48 + n] = -real(sym[i * 48 + n]);
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break;
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case 2: // QPSK
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case 3:
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s = sym[i * 48 + n];
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bits[(i * 48 + n) * 2] = -real(s);
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bits[(i * 48 + n) * 2 + 1] = -imag(s);
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break;
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case 4:
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case 5:
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case 6:
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case 7:
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default:
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assert(false);
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}
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}
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}
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}
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void deinterleave() {
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int n_cbps = ofdm.n_cbps;
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int first[n_cbps];
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int second[n_cbps];
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int s = std::max(ofdm.n_bpsc / 2, 1);
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for(int j = 0; j < n_cbps; j++) {
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first[j] = s * (j / s) + ((j + int(floor(16.0 * j / n_cbps))) % s);
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}
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for(int i = 0; i < n_cbps; i++) {
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second[i] = 16 * i - (n_cbps - 1) * int(floor(16.0 * i / n_cbps));
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}
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for(int i = 0; i < tx.n_sym; i++) {
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for(int k = 0; k < n_cbps; k++) {
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deinter[i * n_cbps + second[first[k]]] = bits[i * n_cbps + k];
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}
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}
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}
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void decode_conv() {
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Punctured_Convolutional_Code code;
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ivec generator(2);
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generator(0)=0133;
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generator(1)=0171;
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code.set_generator_polynomials(generator, 7);
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bmat puncture_matrix;
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switch(ofdm.encoding) {
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case 0:
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case 2:
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puncture_matrix = "1 1; 1 1";
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break;
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case 1:
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case 3:
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puncture_matrix = "1 1 0; 1 0 1;";
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break;
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case 4:
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case 5:
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case 6:
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case 7:
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break;
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default:
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assert(false);
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}
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code.set_puncture_matrix(puncture_matrix);
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code.set_truncation_length(30);
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dout << "coding rate " << code.get_rate() << std::endl;
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dout << tx.n_encoded_bits << std::endl;
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vec rx_signal(deinter, tx.n_encoded_bits);
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code.reset();
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decoded_bits.set_length(tx.n_encoded_bits);
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code.decode_tail(rx_signal, decoded_bits);
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//dout << "length decoded " << decoded_bits.size() << std::endl;
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//std::cout << decoded_bits << std::endl;
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//
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}
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void descramble () {
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int index = 0;
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for(int i = 0; i < 7; i++) {
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if(decoded_bits(i)) {
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index |= 1 << (6 - i);
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}
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}
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int state = scrambler_init[index];
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int feedback;
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for(int i = 0; i < decoded_bits.size(); i++) {
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feedback = ((!!(state & 64))) ^ (!!(state & 8));
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out_bits[i] = feedback ^ decoded_bits(i);
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state = ((state << 1) & 0x7e) | feedback;
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}
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for(int i = 0; i < decoded_bits.size(); i++) {
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int bit = i % 8;
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int byte = i / 8;
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if(bit == 0) {
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out_bytes[byte] = 0;
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}
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if(out_bits[i]) {
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out_bytes[byte] |= (1 << bit);
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}
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}
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}
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void print_output() {
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dout << std::endl;
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for(int i = 0; i < decoded_bits.size() / 8; i++) {
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dout << std::setfill('0') << std::setw(2) << std::hex << ((unsigned int)out_bytes[i] & 0xFF) << std::dec << " ";
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if(i % 16 == 15) {
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dout << std::endl;
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}
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}
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dout << std::endl;
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for(int i = 0; i < decoded_bits.size() / 8; i++) {
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if((out_bytes[i] > 31) && (out_bytes[i] < 127)) {
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dout << ((char) out_bytes[i]);
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} else {
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dout << ".";
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}
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}
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dout << std::endl;
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}
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private:
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gr_complex sym[1000 * 48 * 100];
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double bits[1000 * 48];
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double deinter[1000 * 48];
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char out_bits[40000];
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char out_bytes[40000];
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bvec decoded_bits;
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bool d_debug;
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tx_param tx;
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ofdm_param ofdm;
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int copied;
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static int scrambler_init[128];
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};
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ofdm_decode_mac::sptr
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ofdm_decode_mac::make(bool debug) {
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return gnuradio::get_initial_sptr(new ofdm_decode_mac_impl(debug));
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}
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int ofdm_decode_mac_impl::scrambler_init[128] = {
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0, 73, 18, 91, 36, 109, 54, 127, 72, 1, 90, 19, 108, 37, 126, 55, 89, 16, 75, 2, 125, 52, 111, 38, 17, 88, 3, 74, 53, 124, 39, 110, 50, 123, 32, 105, 22, 95, 4, 77, 122, 51, 104, 33, 94, 23, 76, 5, 107, 34, 121, 48, 79, 6, 93, 20, 35, 106, 49, 120, 7, 78, 21, 92, 100, 45, 118, 63, 64, 9, 82, 27, 44, 101, 62, 119, 8, 65, 26, 83, 61, 116, 47, 102, 25, 80, 11, 66, 117, 60, 103, 46, 81, 24, 67, 10, 86, 31, 68, 13, 114, 59, 96, 41, 30, 87, 12, 69, 58, 115, 40, 97, 15, 70, 29, 84, 43, 98, 57, 112, 71, 14, 85, 28, 99, 42, 113, 56};
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