code changes
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 "utils.h"
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#include <cassert>
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#include <cstring>
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#include <math.h>
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ofdm_param::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
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ofdm_param::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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tx_param::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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void
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tx_param::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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int get_bit(int b, int i) {
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return (b & (1 << i) ? 1 : 0);
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}
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void scramble(const char *in, char *out, tx_param &tx, char initial_state) {
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int state = initial_state;
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int feedback;
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for (int i = 0; i < tx.n_data; i++) {
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feedback = (!!(state & 64)) ^ (!!(state & 8));
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out[i] = feedback ^ in[i];
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state = ((state << 1) & 0x7e) | feedback;
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}
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}
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void reset_tail_bits(char *scrambled_data, tx_param &tx) {
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memset(scrambled_data + tx.n_data - tx.n_pad - 6, 0, 6 * sizeof(char));
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}
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int ones(int n) {
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int sum = 0;
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for(int i = 0; i < 8; i++) {
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if(n & (1 << i)) {
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sum++;
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}
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}
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return sum;
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}
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void convolutional_encoding(const char *in, char *out, tx_param &tx) {
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int state = 0;
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for(int i = 0; i < tx.n_data; i++) {
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assert(in[i] == 0 || in[i] == 1);
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state = ((state << 1) & 0x7e) | in[i];
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out[i * 2] = ones(state & 0155) % 2;
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out[i * 2 + 1] = ones(state & 0117) % 2;
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}
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}
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void puncturing(const char *in, char *out, tx_param &tx, ofdm_param &ofdm) {
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int mod;
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for (int i = 0; i < tx.n_data * 2; i++) {
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switch(ofdm.encoding) {
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case BPSK_1_2:
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case QPSK_1_2:
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case QAM16_1_2:
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*out = in[i];
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out++;
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break;
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case QAM64_2_3:
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if (i % 4 != 3) {
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*out = in[i];
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out++;
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}
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break;
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case BPSK_3_4:
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case QPSK_3_4:
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case QAM16_3_4:
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case QAM64_3_4:
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mod = i % 6;
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if (!(mod == 3 || mod == 4)) {
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*out = in[i];
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out++;
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}
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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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}
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void interleave(const char *in, char *out, tx_param &tx, ofdm_param &ofdm, bool reverse) {
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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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if(reverse) {
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out[i * n_cbps + second[first[k]]] = in[i * n_cbps + k];
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} else {
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out[i * n_cbps + k] = in[i * n_cbps + second[first[k]]];
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}
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}
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}
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}
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void interleave(const double *in, double *out, tx_param &tx, ofdm_param &ofdm, bool reverse) {
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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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if(reverse) {
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out[i * n_cbps + second[first[k]]] = in[i * n_cbps + k];
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} else {
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out[i * n_cbps + k] = in[i * n_cbps + second[first[k]]];
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}
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}
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}
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}
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void split_symbols(const char *in, char *out, tx_param &tx, ofdm_param &ofdm) {
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int symbols = tx.n_sym * 48;
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for (int i = 0; i < symbols; i++) {
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out[i] = 0;
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for(int k = 0; k < ofdm.n_bpsc; k++) {
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assert(*in == 1 || *in == 0);
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out[i] |= (*in << (ofdm.n_bpsc - k - 1));
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in++;
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}
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}
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}
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void generate_signal_field(char *out, tx_param &tx, ofdm_param &ofdm) {
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//data bits of the signal header
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char *signal_header = (char *) malloc(sizeof(char) * 24);
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//signal header after...
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//convolutional encoding
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char *encoded_signal_header = (char *) malloc(sizeof(char) * 48);
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//interleaving
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char *interleaved_signal_header = (char *) malloc(sizeof(char) * 48);
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int length = tx.psdu_size;
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// first 4 bits represent the modulation and coding scheme
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signal_header[ 0] = get_bit(ofdm.rate_field, 3);
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signal_header[ 1] = get_bit(ofdm.rate_field, 2);
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signal_header[ 2] = get_bit(ofdm.rate_field, 1);
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signal_header[ 3] = get_bit(ofdm.rate_field, 0);
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// 5th bit is reserved and must be set to 0
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signal_header[ 4] = 0;
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// then 12 bits represent the length
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signal_header[ 5] = get_bit(length, 0);
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signal_header[ 6] = get_bit(length, 1);
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signal_header[ 7] = get_bit(length, 2);
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signal_header[ 8] = get_bit(length, 3);
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signal_header[ 9] = get_bit(length, 4);
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signal_header[10] = get_bit(length, 5);
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signal_header[11] = get_bit(length, 6);
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signal_header[12] = get_bit(length, 7);
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signal_header[13] = get_bit(length, 8);
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signal_header[14] = get_bit(length, 9);
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signal_header[15] = get_bit(length, 10);
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signal_header[16] = get_bit(length, 11);
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//18-th bit is the parity bit for the first 17 bits
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int sum = 0;
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for(int i = 0; i < 17; i++) {
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if(signal_header[i]) {
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sum++;
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}
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}
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signal_header[17] = sum % 2;
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// last 6 bits must be set to 0
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for (int i = 0; i < 6; i++) {
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signal_header[18 + i] = 0;
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}
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ofdm_param signal_ofdm(BPSK_1_2);
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tx_param signal_tx(signal_ofdm, 3);
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signal_tx.n_data = 24;
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signal_tx.n_sym = 1;
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// convolutional encoding (scrambling is not needed)
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convolutional_encoding(signal_header, encoded_signal_header, signal_tx);
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// interleaving
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//interleave(encoded_signal_header, interleaved_signal_header, signal_tx, signal_ofdm);
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interleave(encoded_signal_header, out, signal_tx, signal_ofdm);
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free(signal_header);
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free(encoded_signal_header);
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free(interleaved_signal_header);
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}
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void generate_bits(const char *psdu, char *data_bits, tx_param &tx) {
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// first 16 bits are zero (SERVICE/DATA field)
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memset(data_bits, 0, 16);
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data_bits += 16;
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for(int i = 0; i < tx.psdu_size; i++) {
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for(int b = 0; b < 8; b++) {
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data_bits[i * 8 + b] = !!(psdu[i] & (1 << b));
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}
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}
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}
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