Fixed iterative frequency refinement; count header errors

impl/src/layer1/freq_est.c

@@ -148,7 +148,7 @@ float freq_est_in_rampup(const float complex *recv, size_t n, float *final_phase
 		float phase = cargf(rotated[i]);
 		if(i > 0) {
 			float phase_delta = phase - prev_phase;
-			if(fabsf(phase_delta) > 3.14159f/4.0f) {
+			if(fabsf(phase_delta) > 3.14159f/2.0f) {
 				// abort because we either have the wrong signal or too much noise.
 				if(final_phase) {
 					*final_phase = 0.0f;

impl/src/layer1/rx.c

@@ -102,21 +102,26 @@ static bool acquire_preamble(layer1_rx_t *rx, const float complex sample)
 
 			float freq_est = freq_est_in_rampup(freq_est_history, FREQ_EST_L, NULL);
 
-			float freq_adjustment = freq_est / RRC_SPS;
+			// freq_est_in_rampup will return exactly 0.0 if (and probably only if)
-			nco_crcf_adjust_frequency(rx->carrier_coarse_nco, freq_adjustment);
+			// the sequency quality is not good enough. We skip the adjustment in
-
+			// this case.
-			float actual_freq = nco_crcf_get_frequency(rx->carrier_coarse_nco);
-			if(actual_freq > MAX_COARSE_FREQ_OFFSET) {
-				//fprintf(stderr, ">");
-				nco_crcf_set_frequency(rx->carrier_coarse_nco, MAX_COARSE_FREQ_OFFSET);
-			} else if(actual_freq < -MAX_COARSE_FREQ_OFFSET) {
-				//fprintf(stderr, "<");
-				nco_crcf_set_frequency(rx->carrier_coarse_nco, -MAX_COARSE_FREQ_OFFSET);
-			}
-
-			//freq_est_history_write_idx = 0;
-
 			if(freq_est != 0.0f) {
+				// apply the frequency adjustment
+				float freq_adjustment = freq_est / RRC_SPS / FREQ_EST_L;
+				nco_crcf_adjust_frequency(rx->carrier_coarse_nco, freq_adjustment);
+
+				// limit the absolute frequency offset value
+				float actual_freq = nco_crcf_get_frequency(rx->carrier_coarse_nco);
+				if(actual_freq > MAX_COARSE_FREQ_OFFSET) {
+					//fprintf(stderr, ">");
+					nco_crcf_set_frequency(rx->carrier_coarse_nco, MAX_COARSE_FREQ_OFFSET);
+				} else if(actual_freq < -MAX_COARSE_FREQ_OFFSET) {
+					//fprintf(stderr, "<");
+					nco_crcf_set_frequency(rx->carrier_coarse_nco, -MAX_COARSE_FREQ_OFFSET);
+				}
+
+				//freq_est_history_write_idx = 0;
+
 				DEBUG_LOG("Freq. est (x%d): %0.6f - Adj (x1): %.6f - carrier frequency (x1): %.6f\n",
 						RRC_SPS, freq_est, freq_adjustment, nco_crcf_get_frequency(rx->carrier_coarse_nco));
 
@@ -227,7 +232,12 @@ result_t layer1_rx_process(layer1_rx_t *rx, const float complex *samples, size_t
 									symbols_int, modem_get_bps(rx->hdr_demod), rx->hdr_len_symbols,
 									header_enc, 8, sizeof(header_enc), &nsyms));
 
-						fec_decode(rx->hdr_fec, sizeof(header), header_enc, header);
+						if(fec_decode(rx->hdr_fec, sizeof(header), header_enc, header) != LIQUID_OK) {
+							DEBUG_LOG("Header decoding failed!\n", rx->modcod);
+							rx->state = RX_STATE_ACQUISITION;
+							rx->callback(RX_EVT_HEADER_ERROR, NULL, 0);
+							break;
+						}
 
 						rx->payload_len_bytes = (((uint16_t)header[0] << 8) | header[1]) & 0x07FF;
 						rx->payload_crc       = ((uint16_t)header[2] << 8) | header[3];
@@ -237,6 +247,7 @@ result_t layer1_rx_process(layer1_rx_t *rx, const float complex *samples, size_t
 						if(!MODCOD_IS_VALID(rx->modcod)) {
 							DEBUG_LOG("Decoded MODCOD %d is invalid!\n", rx->modcod);
 							rx->state = RX_STATE_ACQUISITION;
+							rx->callback(RX_EVT_HEADER_ERROR, NULL, 0);
 							break;
 						}
 
@@ -244,6 +255,7 @@ result_t layer1_rx_process(layer1_rx_t *rx, const float complex *samples, size_t
 						if(rx->payload_len_bytes == 0) {
 							DEBUG_LOG("Packet length %u is not supported.\n", rx->payload_len_bytes);
 							rx->state = RX_STATE_ACQUISITION;
+							rx->callback(RX_EVT_HEADER_ERROR, NULL, 0);
 							break;
 						}
 
@@ -256,6 +268,7 @@ result_t layer1_rx_process(layer1_rx_t *rx, const float complex *samples, size_t
 						if(rx->payload_len_symbols > SYMBOL_BUFFER_SIZE) {
 							DEBUG_LOG("Symbol count %u is too lange for buffer. Ignoring packet.\n", rx->payload_len_symbols);
 							rx->state = RX_STATE_ACQUISITION;
+							rx->callback(RX_EVT_HEADER_ERROR, NULL, 0);
 							break;
 						}
 

impl/src/layer1/rx.h

@@ -18,6 +18,7 @@ typedef enum {
 typedef enum {
 	RX_EVT_PACKET_RECEIVED,
 	RX_EVT_PREAMBLE_FOUND,
+	RX_EVT_HEADER_ERROR,
 	RX_EVT_CHECKSUM_ERROR,
 } rx_evt_t;
 

impl/src/main.c

@@ -38,6 +38,7 @@ static struct {
 	size_t preambles_found;
 	size_t successful_decodes;
 	size_t failed_decodes;
+	size_t header_errors;
 } m_stats;
 
 
@@ -122,6 +123,10 @@ void cb_rx(rx_evt_t evt, uint8_t *packet_data, size_t packet_len)
 			m_stats.failed_decodes++;
 			break;
 
+		case RX_EVT_HEADER_ERROR:
+			m_stats.header_errors++;
+			break;
+
 		case RX_EVT_PACKET_RECEIVED:
 			//fprintf(stderr, "A message of %zu bytes was decoded successfully.\n", packet_len);
 			//fprintf(stderr, "=== DECODED PAYLOAD (%4zu bytes) ===\n", packet_len);
@@ -352,6 +357,8 @@ int main(void)
 				fprintf(stderr, "  Preambles found:    %8zd\n", m_stats.preambles_found);
 				fprintf(stderr, "  Successful decodes: %8zd (%6.2f %%)\n",
 						m_stats.successful_decodes, m_stats.successful_decodes * 100.0f / m_stats.preambles_found);
+				fprintf(stderr, "  Header errors:      %8zd (%6.2f %%)\n",
+						m_stats.header_errors, m_stats.header_errors * 100.0f / m_stats.preambles_found);
 				fprintf(stderr, "  Failed decodes:     %8zd (%6.2f %%)\n",
 						m_stats.failed_decodes, m_stats.failed_decodes * 100.0f / m_stats.preambles_found);
 				next_stats_print_time += 0.5;