hamnet70/impl/src/main.c

#include <stdio.h>
#include <string.h>
#include <assert.h>
#include <math.h>
#include <liquid/liquid.h>

#include "utils.h"
#include "layer1/results.h"
#include "layer1/config.h"
#include "layer1/preamble.h"
#include "layer1/correlator.h"
#include "layer1/freq_est.h"
#include "layer1/whitening.h"
#include "layer1/tx.h"

#define RESULT_CHECK(stmt) { \
	result_t res = stmt; \
	if(res != OK) { \
		printf("Error %d in %s:%d!", res, __FILE__, __LINE__); \
		exit(1); \
	} \
}

typedef enum {
	RX_STATE_ACQUISITION,
	RX_STATE_HEADER,
	RX_STATE_DATA,
} rx_state_t;


void print_complex_array(const char *varname, float complex const *array, size_t len)
{
	printf("%s=np.array([%f%+fj", varname, crealf(array[0]), cimagf(array[0]));
	for(size_t k = 1; k < len; k++) {
		printf(", %f%+fj", crealf(array[k]), cimagf(array[k]));
	}
	printf("])\n");
}


void update_nco_pll(nco_crcf nco, float phase_error)
{
	static const float pll_alpha = 0.05f;                          // phase adjustment factor
	static const float pll_beta  = (pll_alpha * pll_alpha) / 2.0f; // frequency adjustment factor

	nco_crcf_adjust_phase(nco, pll_alpha * phase_error);
	nco_crcf_adjust_frequency(nco, pll_beta * phase_error);
}


int main(void)
{
	uint8_t msg_org[] = "Hello Liquid! This is the message to transmit. Hopefully it can be decoded correctly...";

	layer1_tx_t tx;

	RESULT_CHECK(layer1_tx_init(&tx));
	RESULT_CHECK(layer1_tx_add_packet_to_burst(&tx, msg_org, sizeof(msg_org)));
	RESULT_CHECK(layer1_tx_finalize_burst(&tx));

	size_t burst_len = layer1_tx_get_sample_count(&tx);
	const float complex *whole_burst = layer1_tx_get_sample_data(&tx);

	dump_array_cf(whole_burst, burst_len, 1.0f, "/tmp/tx.cpx");

	// ** RX starts here **

	fec hdr_fec = fec_create(HEADER_CHANNEL_CODE, NULL);
	fec payload_fec = fec_create(PAYLOAD_CHANNEL_CODE, NULL);

	modem hdr_demod = modem_create(HEADER_MODULATION);
	modem payload_demod = modem_create(PAYLOAD_MODULATION);

	channel_cccf channel = channel_cccf_create();

	float snr = 7.0f;
	channel_cccf_add_awgn(channel, -snr, snr);
	channel_cccf_add_carrier_offset(channel, 0.20f, 1.00f);

	// precalculate encoded header length in symbols
	uint8_t header[4];
	unsigned int hdr_len_enc_bytes = fec_get_enc_msg_length(HEADER_CHANNEL_CODE, sizeof(header));
	unsigned int hdr_bps = modem_get_bps(hdr_demod);
	unsigned int hdr_len_symbols = (hdr_len_enc_bytes * 8 + hdr_bps - 1) / hdr_bps;



	// channel
	float complex msg_received[burst_len];

	//memcpy(msg_received, whole_burst, sizeof(whole_burst)); // no noise in channel

	channel_cccf_execute_block(channel, whole_burst, burst_len, msg_received);
	dump_array_cf(msg_received, burst_len, 1.0f, "/tmp/rx.cpx");

	// create NCOs for carrier frequency compensation
	nco_crcf carrier_nco = nco_crcf_create(LIQUID_NCO);
	nco_crcf_set_frequency(carrier_nco, 0.00f);
	nco_crcf_set_phase(carrier_nco, 0.0f);

	nco_crcf carrier_fine_nco = nco_crcf_create(LIQUID_NCO);
	nco_crcf_set_frequency(carrier_fine_nco, 0.00f);
	nco_crcf_set_phase(carrier_fine_nco, 0.0f);

	// create symbol synchronizer
	symsync_crcf symsync = symsync_crcf_create_rnyquist(LIQUID_FIRFILT_RRC, RRC_SPS, RRC_DELAY, RRC_BETA, 32);

	float complex symsync_out[burst_len];
	unsigned int  symsync_out_len = 0;

	float complex symbols_cpx[16384];
	unsigned char symbols_int[16384];
	unsigned int  symbol_counter = 0; // for demodulation

	uint16_t payload_len_symbols;
	uint16_t payload_len_bytes;
	uint16_t payload_crc;
	uint16_t payload_len_enc_bytes;
	uint16_t payload_bps = modem_get_bps(payload_demod);

#define FREQ_EST_L 8
	// General receiver state
	rx_state_t rx_state = RX_STATE_ACQUISITION;

	// Correlator for preamble search
	correlator_ctx_t preamble_correlator;
	correlator_init(&preamble_correlator, preamble_get_symbols(), preamble_get_symbol_count());

	for(unsigned int i = 0; i < burst_len; i++) {
		// Mix the input signal with the carrier NCO, which oscillates at the
		// frequency estimated so far.
		float complex mixed_sample;
		nco_crcf_step(carrier_nco);
		nco_crcf_mix_down(carrier_nco, msg_received[i], &mixed_sample);

		// run the timing synchronizer (works even with shifted frequency)
		unsigned int out_len;
		symsync_crcf_execute(symsync, &mixed_sample, 1, symsync_out + symsync_out_len, &out_len);

		if(out_len != 0) {
			float complex corr_out;
			switch(rx_state) {
				// Try to acquire packets by synchronizing the frequency
				// (symbol-independent search) and correlating the preamble.
				case RX_STATE_ACQUISITION:
					// preamble search
					corr_out = correlator_step(&preamble_correlator, symsync_out[symsync_out_len]);

					if(cabsf(corr_out) > 0.5f * preamble_get_symbol_count()) {
						// Preamble found!
						printf("Preamble found at symbol %u: %.3f > %.3f\n", i/RRC_SPS, cabsf(corr_out), 0.5f * preamble_get_symbol_count());

						float phase_offset;
						float mean_frequency_error = correlator_get_mean_frequency_deviation(&preamble_correlator, FREQ_EST_L, &phase_offset);

						printf("Phase offset:                 %.6f rad\n", phase_offset);
						printf("Preamble frequency deviation: %.6f rad/symbol\n", mean_frequency_error);

						// adjust the frequency and phase of the NCO with the estimations from the preamble
						nco_crcf_set_frequency(carrier_fine_nco, mean_frequency_error / RRC_SPS * 0.5f);
						nco_crcf_set_phase(carrier_fine_nco, phase_offset);

						printf("New estimated carrier frequency: %.6f + %.6f\n", nco_crcf_get_frequency(carrier_nco), nco_crcf_get_frequency(carrier_fine_nco));

						float complex input_history[preamble_get_symbol_count()];
						correlator_get_input_history(&preamble_correlator, input_history);

						printf("import numpy as np\n");
						printf("import matplotlib.pyplot as pp\n");
						print_complex_array("pre", preamble_get_symbols(), preamble_get_symbol_count());
						print_complex_array("recv", input_history, preamble_get_symbol_count());
						printf("pp.plot(np.angle(recv * pre.conj()))\n");
						printf("pp.show()\n");

						// receive and decode the header
						rx_state = RX_STATE_HEADER;
						symbol_counter = 0;
					} else {
						// preamble not found.

						// Run the frequency estimator in blocks of FREQ_EST_L samples.
						// This is an implementation that works with unknown BPSK symbols
						// and therefore can be used during ramp-up and preamble.
						if(((i/RRC_SPS) % FREQ_EST_L) == 0) {
							float freq_est = freq_est_unknown_bpsk(symsync_out + symsync_out_len - FREQ_EST_L, FREQ_EST_L, NULL);

							float freq_adjustment = (freq_est / RRC_SPS) * 0.3f;
							nco_crcf_adjust_frequency(carrier_nco, freq_adjustment);

							printf("Frequency adjustment: %.6f - carrier frequency: %.6f\n", freq_adjustment, nco_crcf_get_frequency(carrier_nco));
						}
					}
					break;

				case RX_STATE_HEADER:
					nco_crcf_mix_down(carrier_fine_nco, symsync_out[symsync_out_len], &mixed_sample);
					if(symbol_counter < hdr_len_symbols) {
						unsigned int sym_demod;
						modem_demodulate(hdr_demod, mixed_sample, &sym_demod);

						float phase_error = modem_get_demodulator_phase_error(hdr_demod);
						printf("Sym: %d; Phase error: %f\n", sym_demod, phase_error);

						update_nco_pll(carrier_fine_nco, phase_error);

						symbols_cpx[symbol_counter] = mixed_sample;
						symbols_int[symbol_counter] = sym_demod;
						symbol_counter++;
					}

					if(symbol_counter == hdr_len_symbols) {
						unsigned int nsyms;
						unsigned char header_enc[4];

						ERR_CHECK_LIQUID(liquid_repack_bytes(
									symbols_int, modem_get_bps(hdr_demod), hdr_len_symbols,
									header_enc, 8, sizeof(header_enc), &nsyms));

						fec_decode(hdr_fec, sizeof(header), header_enc, header);

						payload_len_bytes = ((uint16_t)header[0] << 8) | header[1];
						payload_crc       = ((uint16_t)header[2] << 8) | header[3];

						payload_len_enc_bytes = fec_get_enc_msg_length(PAYLOAD_CHANNEL_CODE, payload_len_bytes);
						payload_len_symbols = (payload_len_enc_bytes * 8 + payload_bps - 1) / payload_bps;

						printf("=== DECODED HEADER ===\n");
						printf("Payload length: %u symbols, %u bytes encoded, %u bytes decoded\n", payload_len_symbols, payload_len_enc_bytes, payload_len_bytes);
						printf("CRC16: 0x%04x\n", payload_crc);
						printf("======================\n");

						dump_array_cf(symbols_cpx, symbol_counter, 1.0f, "/tmp/hdr.cpx");

						rx_state = RX_STATE_DATA;
						symbol_counter = 0;
					}
					break;

				case RX_STATE_DATA:
					nco_crcf_mix_down(carrier_fine_nco, symsync_out[symsync_out_len], &mixed_sample);
					if(symbol_counter < payload_len_symbols) {
						unsigned int sym_demod;
						modem_demodulate(payload_demod, mixed_sample, &sym_demod);

						float phase_error = modem_get_demodulator_phase_error(payload_demod);
						printf("Sym: %d; Phase error: %f\n", sym_demod, phase_error);

						update_nco_pll(carrier_fine_nco, phase_error);

						symbols_cpx[symbol_counter] = mixed_sample;
						symbols_int[symbol_counter] = sym_demod;
						symbol_counter++;
					}

					if(symbol_counter == payload_len_symbols) {
						unsigned int nsyms;
						unsigned char payload_enc[16384];
						unsigned char payload[16384];

						ERR_CHECK_LIQUID(liquid_repack_bytes(
									symbols_int, modem_get_bps(payload_demod), payload_len_symbols,
									payload_enc, 8, sizeof(payload_enc), &nsyms));

						fec_decode(payload_fec, payload_len_bytes, payload_enc, payload);

						// de-whiten the data
						whitening_apply_in_place(payload, payload_len_bytes);

						int valid = crc_validate_message(PAYLOAD_CRC_SCHEME, payload, payload_len_bytes, payload_crc);

						payload[payload_len_bytes] = '\0';

						printf("=== DECODED PAYLOAD (valid: %d) ===\n", valid);
						printf("%s\n", payload);
						printf("==================================\n");

						dump_array_cf(symbols_cpx, symbol_counter, 1.0f, "/tmp/payload.cpx");
						rx_state = RX_STATE_ACQUISITION;
					}
					break;
			}
		}

		symsync_out_len += out_len;
	}

	dump_array_cf(symsync_out, symsync_out_len, 1.0f, "/tmp/synced.cpx");

#if 0
	// demodulate
	unsigned int bps = modem_get_bps(payload_demod);

	unsigned char msg_demod_syms[nsyms];
	unsigned char msg_demod[k+1];

	for(size_t i = 0; i < nsyms; i++) {
		unsigned int symbol;

		modem_demodulate(payload_demod, msg_received[i], &symbol);
		msg_demod_syms[i] = symbol;
	}

	unsigned int received_bytes;
	liquid_repack_bytes(msg_demod_syms, bps, nsyms, msg_demod, 8, sizeof(msg_demod), &received_bytes);

	//assert(received_bytes == k);

	// decode
	uint8_t msg_dec[sizeof(msg_org)];
	//memcpy(msg_dec, msg_enc, sizeof(msg_dec));
	fec_decode(q, sizeof(msg_dec), msg_demod, msg_dec);

	// compare original to decoded message
	for(size_t i = 0; i < sizeof(msg_org); i++)
	{
		printf("%02x  =>  %02x", msg_org[i], msg_dec[i]);
		if(msg_org[i] != msg_dec[i]) {
			printf("  <<< !!!\n");
		} else {
			printf("\n");
		}
	}

	unsigned int bit_errors = count_bit_errors_array(msg_org, msg_dec, sizeof(msg_org));
	printf("%u bit errors detected.\n", bit_errors);
#endif

	nco_crcf_destroy(carrier_nco);

	symsync_crcf_destroy(symsync);

	fec_destroy(hdr_fec);

	modem_destroy(payload_demod);
	modem_destroy(hdr_demod);

	channel_cccf_destroy(channel);

	printf("Done.\n");
}