hamnet70/impl/src/main.c

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

#include "results.h"
#include "utils.h"
#include "packet_mod.h"
#include "config.h"
#include "preamble.h"
#include "transmission.h"
#include "correlator.h"

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");
}


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

	fec q = fec_create(CHANNEL_CODE, NULL);

	modem demod = modem_create(MODULATION);

	channel_cccf channel = channel_cccf_create();

	float snr = 20.0f;
	channel_cccf_add_awgn(channel, -snr, snr);
	channel_cccf_add_carrier_offset(channel, 0.20f, 1.00f);


	packet_mod_ctx_t pmod;
	packet_mod_init(&pmod);

	packet_mod_set_data(&pmod, msg_org, sizeof(msg_org));
	packet_mod_encode(&pmod);
	packet_mod_modulate(&pmod);
	packet_mod_add_header(&pmod);
	packet_mod_add_preamble(&pmod);

	size_t nsyms;
	packet_mod_get_result_cf(&pmod, NULL, &nsyms); // determine number of symbols for allocation

	float complex msg_mod[nsyms];
	packet_mod_get_result_cf(&pmod, msg_mod, &nsyms); // get the data

	size_t burst_len = 0;
	float complex whole_burst[65536];
	size_t len;

	transmission_ctx_t transm;
	transmission_init(&transm);

	len = 65536-burst_len;
	if(transmission_ramp_up(&transm, whole_burst+burst_len, &len) != OK) {
		printf("Ramp-up requires %zd symbols at offset %zd.\n", len, burst_len);
		return 1;
	}
	burst_len += len;

	len = 65536-burst_len;
	if(transmission_filter_packet(&transm, msg_mod, nsyms, whole_burst+burst_len, &len) != OK) {
		printf("Packet requires %zd symbols at offset %zd.\n", len, burst_len);
		return 1;
	}
	burst_len += len;

	len = 65536-burst_len;
	if(transmission_ramp_down(&transm, whole_burst+burst_len, &len) != OK) {
		printf("Ramp-down requires %zd symbols at offset %zd.\n", len, burst_len);
		return 1;
	}
	burst_len += len;

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

	// 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 NCO 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);

	// 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;

#define FREQ_EST_L 8
	float phase_history[FREQ_EST_L];
	memset(phase_history, 0, sizeof(phase_history));

	// 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 mean_phase_error = correlator_get_mean_phase_deviation(&preamble_correlator);
						float mean_frequency_error = correlator_get_mean_frequency_deviation(&preamble_correlator);

						printf("Preamble phase deviation:     %.6f rad\n", mean_phase_error);
						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_adjust_frequency(carrier_nco, -mean_frequency_error / RRC_SPS);
						nco_crcf_adjust_phase(carrier_nco, mean_phase_error);

						printf("New estimated carrier frequency: %.6f\n", nco_crcf_get_frequency(carrier_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(recv * pre.conj())\n");
						printf("pp.show()\n");

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

						// for all the output samples produced, run the frequency
						// estimator. This is an implementation that works with unknown
						// BPSK symbols and therefore can be used during ramp-up and
						// preamble.

						if(out_len < FREQ_EST_L) {
							memmove(phase_history,
									phase_history + out_len,
									(FREQ_EST_L-out_len) * sizeof(phase_history[0]));
						}

						for(unsigned int j = 0; j < out_len; j++) {
							float complex *psymbol = symsync_out + symsync_out_len + j;

							// square the symbol to remove BPSK ambiguity
							float phase = cargf((*psymbol) * (*psymbol));

							phase_history[FREQ_EST_L - out_len + j] = phase;
						}

						// update the frequency estimate
						if(((i/RRC_SPS) % FREQ_EST_L) == 0) {
							float unwrapped_phase_history[FREQ_EST_L];
							memcpy(unwrapped_phase_history, phase_history, sizeof(unwrapped_phase_history));
							liquid_unwrap_phase(unwrapped_phase_history, FREQ_EST_L);

							// calculate slope of LMS-fitted line
							float mean_index = (FREQ_EST_L-1) / 2.0f;
							float mean_phase = 0.0f;
							for(unsigned int j = 0; j < FREQ_EST_L; j++) {
								mean_phase += unwrapped_phase_history[j];
							}
							mean_phase /= FREQ_EST_L;

							float numerator = 0.0f;
							float denominator = 0.0f;
							for(unsigned int j = 0; j < FREQ_EST_L; j++) {
								float delta_index = j - mean_index;
								numerator += delta_index * (unwrapped_phase_history[j] - mean_phase);
								denominator += delta_index*delta_index;
							}

							float lms_phase_change = numerator / denominator;

							float freq_adjustment = (lms_phase_change / RRC_SPS / 2) * 0.5f;
							nco_crcf_adjust_frequency(carrier_nco, freq_adjustment);

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

							if(i/RRC_SPS == 2*FREQ_EST_L) {
								float complex tmp[FREQ_EST_L];
								for(unsigned int j = 0; j < FREQ_EST_L; j++) {
									tmp[j] = unwrapped_phase_history[j];
								}
								dump_array_cf(tmp, FREQ_EST_L, 1.0f, "/tmp/freq_est.cpx");
								printf("MARK\n");
							}
						}
					}
					break;

				case RX_STATE_HEADER:
				case RX_STATE_DATA:
					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(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(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(q);

	modem_destroy(demod);

	channel_cccf_destroy(channel);

	printf("Done.\n");
}