kopia lustrzana https://github.com/rpp0/gr-lora
Improved sync, automatic CFO correction
rodzic
be8cba4ddb
commit
4a6b45c809
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@ -174,6 +174,17 @@ namespace gr {
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}
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}
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double decoder_impl::cross_correlate(const gr_complex *samples_1, const gr_complex *samples_2, int window) {
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double result = 0.0f;
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for (int i = 0; i < window; i++) {
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result += real(samples_1[i] * conj(samples_2[i]));
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}
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result = result / window;
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return result;
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}
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double decoder_impl::freq_cross_correlate(const gr_complex *samples_1, const gr_complex *samples_2, int window) {
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double result = 0.0f;
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float instantaneous_phase[window];
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@ -207,27 +218,27 @@ namespace gr {
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float fft_mag[d_number_of_bins];
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gr_complex mult_hf[d_samples_per_symbol];
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#ifdef CFO_CORRECT
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/*#ifdef CFO_CORRECT
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determine_cfo(&samples[0]);
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std::cout << "CFO: " << d_cfo_estimation << std::endl;
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correct_cfo(&samples[0], d_samples_per_symbol);
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#endif
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#endif*/
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//samples_to_file("/tmp/data", &samples[0], d_samples_per_symbol, sizeof(gr_complex));
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samples_to_file("/tmp/data", &samples[0], d_samples_per_symbol, sizeof(gr_complex));
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// Multiply with ideal downchirp
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for(uint32_t i = 0; i < d_samples_per_symbol; i++) {
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mult_hf[i] = conj(samples[i] * d_downchirp[i]);
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}
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//samples_to_file("/tmp/mult", &mult_hf[0], d_samples_per_symbol, sizeof(gr_complex));
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samples_to_file("/tmp/mult", &mult_hf[0], d_samples_per_symbol, sizeof(gr_complex));
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// Perform decimation
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for (uint32_t i = 0; i < d_number_of_bins; i++) {
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firdecim_crcf_execute(d_decim, &mult_hf[d_decim_factor*i], &d_mult[i]);
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}
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//samples_to_file("/tmp/resampled", &d_mult[0], d_number_of_bins, sizeof(gr_complex));
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samples_to_file("/tmp/resampled", &d_mult[0], d_number_of_bins, sizeof(gr_complex));
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// Perform FFT
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fft_execute(d_q);
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@ -237,7 +248,7 @@ namespace gr {
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fft_mag[i] = abs(d_fft[i]);
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}
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//samples_to_file("/tmp/fft", &d_fft[0], d_number_of_bins, sizeof(gr_complex));
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samples_to_file("/tmp/fft", &d_fft[0], d_number_of_bins, sizeof(gr_complex));
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// Return argmax here
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return (std::max_element(fft_mag,fft_mag+d_number_of_bins) - fft_mag);
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@ -286,8 +297,8 @@ namespace gr {
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}
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bool decoder_impl::demodulate(gr_complex* samples, bool is_header) {
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//unsigned int bin_idx = max_frequency_gradient_idx(samples);
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unsigned int bin_idx = sync_fft(samples);
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unsigned int bin_idx = max_frequency_gradient_idx(samples);
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//unsigned int bin_idx = sync_fft(samples);
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//unsigned int bin_idx_test = sync_fft(samples);
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unsigned int bin_idx_test = 0;
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@ -467,6 +478,8 @@ namespace gr {
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sum /= d_samples_per_symbol;
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d_cfo_estimation = sum;
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/*d_cfo_estimation = (*std::max_element(instantaneous_freq, instantaneous_freq+d_samples_per_symbol-1) + *std::min_element(instantaneous_freq, instantaneous_freq+d_samples_per_symbol-1)) / 2;*/
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}
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void decoder_impl::correct_cfo(gr_complex* samples, int num_samples) {
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@ -485,9 +498,9 @@ namespace gr {
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}
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}
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int decoder_impl::find_preamble_start_fast(gr_complex* samples) {
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int decoder_impl::find_preamble_start_fast(gr_complex* samples, uint32_t len) {
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int step_size = d_samples_per_symbol / 8;
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for(int i = 0; i < d_samples_per_symbol; i++) {
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for(int i = 0; i < len; i += 8) {
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bool higher = true;
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float last_ifreq = -999999999;
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@ -501,7 +514,7 @@ namespace gr {
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float ifreq = (s[1] - s[0]) / (2.0f * M_PI) * d_samples_per_second;
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d_debug << "F: " << ifreq << std::endl;
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if(ifreq - last_ifreq < (d_bw / 8) - 3000) { // Make sure it rises fast enough
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if(ifreq - last_ifreq < (d_bw / 8) / 1.5) { // Make sure it rises fast enough
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higher = false;
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d_debug << "NOPE" << std::endl;
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break;
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@ -528,23 +541,24 @@ namespace gr {
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switch(d_state) {
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case DETECT: {
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if(calc_energy_threshold(input, noutput_items, 0.002)) {
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//d_debug << "Got something\n";
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// Attempt to synchronize to an upchirp of the preamble
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int chirp_start_pos = -1;
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d_cfo_estimation = 0;
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// Find rough position of preamble
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int i = find_preamble_start_fast(&input[0]);
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int i = find_preamble_start_fast(&input[0], noutput_items);
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// After this step, if i != -1 we know that we are in a rising chirp, starting from i.
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// Calculate the CFO here, and correct for it. Then perform sync_fft until we get a 0
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// The final position where this is the case indicates the start of the preamble.
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if(i != -1) {
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//samples_to_file("/tmp/bcfo", &input[i], noutput_items, sizeof(gr_complex));
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// TODO: Find algorithm to reliably determine CFO
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samples_to_file("/tmp/bcfo", &input[0], noutput_items, sizeof(gr_complex));
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i = find_preamble_start(&input[0]);
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determine_cfo(&input[i]);
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//d_debug << "CFO " << d_cfo_estimation << std::endl;
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d_debug << "CFO " << d_cfo_estimation << std::endl;
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correct_cfo(&input[0], noutput_items);
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//samples_to_file("/tmp/acfo", &input[i], noutput_items, sizeof(gr_complex));
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samples_to_file("/tmp/acfo", &input[0], noutput_items, sizeof(gr_complex));
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// Sync
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i = find_preamble_start(&input[0]);
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@ -565,8 +579,8 @@ namespace gr {
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break;
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}
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case SYNC: {
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double c = freq_cross_correlate(&input[0], &d_downchirp[0], CORRELATION_SEARCH_RANGE);
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//d_debug << "C: " << c << std::endl;
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double c = freq_cross_correlate(&input[0], &d_downchirp[0], d_samples_per_symbol);
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d_debug << "C: " << c << std::endl;
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if(c > 0.045f) {
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d_debug << "SYNC: " << c << std::endl;
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@ -579,7 +593,6 @@ namespace gr {
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d_corr_fails++;
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if(d_corr_fails > 32) {
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d_state = DETECT;
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d_cfo_estimation = 0;
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}
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consume_each(d_samples_per_symbol);
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}
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@ -626,7 +639,6 @@ namespace gr {
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decode(decoded, false);
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d_state = DETECT;
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d_cfo_estimation = 0;
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}
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}
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@ -84,11 +84,12 @@ namespace gr {
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void samples_to_file(const std::string path, const gr_complex* v, int length, int elem_size);
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void samples_debug(const gr_complex* v, int length);
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double freq_cross_correlate(const gr_complex *samples_1, const gr_complex *samples_2, int window);
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double cross_correlate(const gr_complex *samples_1, const gr_complex *samples_2, int window);
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unsigned int sync_fft(gr_complex* samples);
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void determine_cfo(const gr_complex* samples);
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void correct_cfo(gr_complex* samples, int num_samples);
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int find_preamble_start(gr_complex* samples);
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int find_preamble_start_fast(gr_complex* samples);
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int find_preamble_start_fast(gr_complex* samples, uint32_t len);
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unsigned int max_frequency_gradient_idx(gr_complex* samples);
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bool demodulate(gr_complex* samples, bool is_header);
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void deinterleave(int ppm);
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