/* CP detection algorithm taken from:
* "SSS Detection Method for Initial Cell Search in 3GPP LTE FDD/TDD Dual Mode Receiver"
* by Jung-In Kim et al.
*/
srslte_cp_t srslte_sync_detect_cp(srslte_sync_t *q, const cf_t *input, uint32_t peak_pos)
{
float R_norm=0, R_ext=0, C_norm=0, C_ext=0;
float M_norm=0, M_ext=0;
uint32_t cp_norm_len = SRSLTE_CP_LEN_NORM(7, q->fft_size);
uint32_t cp_ext_len = SRSLTE_CP_LEN_EXT(q->fft_size);
uint32_t nof_symbols = peak_pos/(q->fft_size+cp_ext_len);
if (nof_symbols > 3) {
nof_symbols = 3;
}
if (nof_symbols > 0) {
const cf_t *input_cp_norm = &input[peak_pos-nof_symbols*(q->fft_size+cp_norm_len)];
const cf_t *input_cp_ext = &input[peak_pos-nof_symbols*(q->fft_size+cp_ext_len)];
for (int i=0;i<nof_symbols;i++) {
R_norm += crealf(srslte_vec_dot_prod_conj_ccc(&input_cp_norm[q->fft_size], input_cp_norm, cp_norm_len));
C_norm += cp_norm_len * srslte_vec_avg_power_cf(input_cp_norm, cp_norm_len);
input_cp_norm += q->fft_size+cp_norm_len;
}
if (C_norm > 0) {
M_norm = R_norm/C_norm;
}
q->M_norm_avg = SRSLTE_VEC_EMA(M_norm/nof_symbols, q->M_norm_avg, CP_EMA_ALPHA);
for (int i=0;i<nof_symbols;i++) {
R_ext += crealf(srslte_vec_dot_prod_conj_ccc(&input_cp_ext[q->fft_size], input_cp_ext, cp_ext_len));
C_ext += cp_ext_len * srslte_vec_avg_power_cf(input_cp_ext, cp_ext_len);
input_cp_ext += q->fft_size+cp_ext_len;
}
if (C_ext > 0) {
M_ext = R_ext/C_ext;
}
q->M_ext_avg = SRSLTE_VEC_EMA(M_ext/nof_symbols, q->M_ext_avg, CP_EMA_ALPHA);
if (q->M_norm_avg > q->M_ext_avg) {
return SRSLTE_CP_NORM;
} else if (q->M_norm_avg < q->M_ext_avg) {
return SRSLTE_CP_EXT;
} else {
if (R_norm > R_ext) {
return SRSLTE_CP_NORM;
} else {
return SRSLTE_CP_EXT;
}
}
} else {
return SRSLTE_CP_NORM;
}
}
int srslte_chest_ul_estimate(srslte_chest_ul_t *q, cf_t *input, cf_t *ce,
uint32_t nof_prb, uint32_t sf_idx, uint32_t cyclic_shift_for_dmrs, uint32_t n_prb[2])
{
if (!q->dmrs_signal_configured) {
fprintf(stderr, "Error must call srslte_chest_ul_set_cfg() before using the UL estimator\n");
return SRSLTE_ERROR;
}
if (!srslte_dft_precoding_valid_prb(nof_prb)) {
fprintf(stderr, "Error invalid nof_prb=%d\n", nof_prb);
return SRSLTE_ERROR_INVALID_INPUTS;
}
int nrefs_sym = nof_prb*SRSLTE_NRE;
int nrefs_sf = nrefs_sym*2;
/* Get references from the input signal */
srslte_refsignal_dmrs_pusch_get(&q->dmrs_signal, input, nof_prb, n_prb, q->pilot_recv_signal);
/* Use the known DMRS signal to compute Least-squares estimates */
srslte_vec_prod_conj_ccc(q->pilot_recv_signal, q->dmrs_pregen.r[cyclic_shift_for_dmrs][sf_idx][nof_prb],
q->pilot_estimates, nrefs_sf);
if (n_prb[0] != n_prb[1]) {
printf("ERROR: intra-subframe frequency hopping not supported in the estimator!!\n");
}
if (ce != NULL) {
if (q->smooth_filter_len > 0) {
average_pilots(q, q->pilot_estimates, ce, nrefs_sym, n_prb);
interpolate_pilots(q, ce, nrefs_sym, n_prb);
/* If averaging, compute noise from difference between received and averaged estimates */
q->noise_estimate = estimate_noise_pilots(q, ce, nrefs_sym, n_prb);
} else {
// Copy estimates to CE vector without averaging
for (int i=0;i<2;i++) {
memcpy(&ce[SRSLTE_REFSIGNAL_UL_L(i, q->cell.cp)*q->cell.nof_prb*SRSLTE_NRE+n_prb[i]*SRSLTE_NRE],
&q->pilot_estimates[i*nrefs_sym],
nrefs_sym*sizeof(cf_t));
}
interpolate_pilots(q, ce, nrefs_sym, n_prb);
q->noise_estimate = 0;
}
}
// Estimate received pilot power
q->pilot_power = srslte_vec_avg_power_cf(q->pilot_recv_signal, nrefs_sf);
return 0;
}
int rf_rssi_scan(srslte_rf_t *rf, float *freqs, float *rssi, int nof_bands, double fs, int nsamp) {
int i, j;
int ret = -1;
cf_t *buffer;
double f;
buffer = calloc(nsamp, sizeof(cf_t));
if (!buffer) {
goto free_and_exit;
}
srslte_rf_set_rx_gain(rf, 20.0);
srslte_rf_set_rx_srate(rf, fs);
for (i=0;i<nof_bands;i++) {
srslte_rf_stop_rx_stream(rf);
f = (double) freqs[i];
srslte_rf_set_rx_freq(rf, f);
srslte_rf_rx_wait_lo_locked(rf);
usleep(10000);
srslte_rf_start_rx_stream(rf, false);
/* discard first samples */
for (j=0;j<2;j++) {
if (srslte_rf_recv(rf, buffer, nsamp, 1) != nsamp) {
goto free_and_exit;
}
}
rssi[i] = srslte_vec_avg_power_cf(buffer, nsamp);
printf("[%3d]: Freq %4.1f Mhz - RSSI: %3.2f dBm\r", i, f/1000000, 10*log10f(rssi[i]) + 30); fflush(stdout);
if (SRSLTE_VERBOSE_ISINFO()) {
printf("\n");
}
}
srslte_rf_stop_rx_stream(rf);
ret = 0;
free_and_exit:
free(buffer);
return ret;
}
int main(int argc, char **argv) {
int ret;
cf_t *sf_buffer;
prog_args_t prog_args;
srslte_cell_t cell;
int64_t sf_cnt;
srslte_ue_sync_t ue_sync;
srslte_ue_mib_t ue_mib;
void *uhd;
srslte_ue_dl_t ue_dl;
srslte_ofdm_t fft;
srslte_chest_dl_t chest;
uint32_t nframes=0;
uint32_t nof_trials = 0;
uint32_t sfn = 0; // system frame number
int n;
uint8_t bch_payload[SRSLTE_BCH_PAYLOAD_LEN];
uint32_t sfn_offset;
float rssi_utra=0,rssi=0, rsrp=0, rsrq=0, snr=0;
cf_t *ce[SRSLTE_MAX_PORTS];
if (parse_args(&prog_args, argc, argv)) {
exit(-1);
}
if (prog_args.uhd_gain > 0) {
printf("Opening UHD device...\n");
if (cuhd_open(prog_args.uhd_args, &uhd)) {
fprintf(stderr, "Error opening uhd\n");
exit(-1);
}
cuhd_set_rx_gain(uhd, prog_args.uhd_gain);
} else {
printf("Opening UHD device with threaded RX Gain control ...\n");
if (cuhd_open_th(prog_args.uhd_args, &uhd, false)) {
fprintf(stderr, "Error opening uhd\n");
exit(-1);
}
cuhd_set_rx_gain(uhd, 50);
}
sigset_t sigset;
sigemptyset(&sigset);
sigaddset(&sigset, SIGINT);
sigprocmask(SIG_UNBLOCK, &sigset, NULL);
signal(SIGINT, sig_int_handler);
cuhd_set_master_clock_rate(uhd, 30.72e6);
/* set receiver frequency */
cuhd_set_rx_freq(uhd, (double) prog_args.uhd_freq);
cuhd_rx_wait_lo_locked(uhd);
printf("Tunning receiver to %.3f MHz\n", (double ) prog_args.uhd_freq/1000000);
uint32_t ntrial=0;
do {
ret = cuhd_search_and_decode_mib(uhd, &cell_detect_config, prog_args.force_N_id_2, &cell);
if (ret < 0) {
fprintf(stderr, "Error searching for cell\n");
exit(-1);
} else if (ret == 0 && !go_exit) {
printf("Cell not found after %d trials. Trying again (Press Ctrl+C to exit)\n", ntrial++);
}
} while (ret == 0 && !go_exit);
if (go_exit) {
exit(0);
}
/* set sampling frequency */
int srate = srslte_sampling_freq_hz(cell.nof_prb);
if (srate != -1) {
if (srate < 10e6) {
cuhd_set_master_clock_rate(uhd, 4*srate);
} else {
cuhd_set_master_clock_rate(uhd, srate);
}
printf("Setting sampling rate %.2f MHz\n", (float) srate/1000000);
float srate_uhd = cuhd_set_rx_srate(uhd, (double) srate);
if (srate_uhd != srate) {
fprintf(stderr, "Could not set sampling rate\n");
exit(-1);
}
} else {
fprintf(stderr, "Invalid number of PRB %d\n", cell.nof_prb);
exit(-1);
}
INFO("Stopping UHD and flushing buffer...\n",0);
cuhd_stop_rx_stream(uhd);
cuhd_flush_buffer(uhd);
if (srslte_ue_sync_init(&ue_sync, cell, cuhd_recv_wrapper, uhd)) {
fprintf(stderr, "Error initiating ue_sync\n");
return -1;
}
if (srslte_ue_dl_init(&ue_dl, cell)) {
fprintf(stderr, "Error initiating UE downlink processing module\n");
return -1;
}
if (srslte_ue_mib_init(&ue_mib, cell)) {
fprintf(stderr, "Error initaiting UE MIB decoder\n");
return -1;
}
/* Configure downlink receiver for the SI-RNTI since will be the only one we'll use */
srslte_ue_dl_set_rnti(&ue_dl, SRSLTE_SIRNTI);
/* Initialize subframe counter */
sf_cnt = 0;
if (srslte_ofdm_rx_init(&fft, cell.cp, cell.nof_prb)) {
fprintf(stderr, "Error initiating FFT\n");
return -1;
}
if (srslte_chest_dl_init(&chest, cell)) {
fprintf(stderr, "Error initiating channel estimator\n");
return -1;
}
int sf_re = SRSLTE_SF_LEN_RE(cell.nof_prb, cell.cp);
cf_t *sf_symbols = srslte_vec_malloc(sf_re * sizeof(cf_t));
for (int i=0;i<SRSLTE_MAX_PORTS;i++) {
ce[i] = srslte_vec_malloc(sizeof(cf_t) * sf_re);
}
cuhd_start_rx_stream(uhd);
float rx_gain_offset = 0;
/* Main loop */
while ((sf_cnt < prog_args.nof_subframes || prog_args.nof_subframes == -1) && !go_exit) {
ret = srslte_ue_sync_get_buffer(&ue_sync, &sf_buffer);
if (ret < 0) {
fprintf(stderr, "Error calling srslte_ue_sync_work()\n");
}
/* srslte_ue_sync_get_buffer returns 1 if successfully read 1 aligned subframe */
if (ret == 1) {
switch (state) {
case DECODE_MIB:
if (srslte_ue_sync_get_sfidx(&ue_sync) == 0) {
srslte_pbch_decode_reset(&ue_mib.pbch);
n = srslte_ue_mib_decode(&ue_mib, sf_buffer, bch_payload, NULL, &sfn_offset);
if (n < 0) {
fprintf(stderr, "Error decoding UE MIB\n");
return -1;
} else if (n == SRSLTE_UE_MIB_FOUND) {
srslte_pbch_mib_unpack(bch_payload, &cell, &sfn);
printf("Decoded MIB. SFN: %d, offset: %d\n", sfn, sfn_offset);
sfn = (sfn + sfn_offset)%1024;
state = DECODE_SIB;
}
}
break;
case DECODE_SIB:
/* We are looking for SI Blocks, search only in appropiate places */
if ((srslte_ue_sync_get_sfidx(&ue_sync) == 5 && (sfn%2)==0)) {
n = srslte_ue_dl_decode_rnti_rv(&ue_dl, sf_buffer, data, srslte_ue_sync_get_sfidx(&ue_sync), SRSLTE_SIRNTI,
((int) ceilf((float)3*(((sfn)/2)%4)/2))%4);
if (n < 0) {
fprintf(stderr, "Error decoding UE DL\n");fflush(stdout);
return -1;
} else if (n == 0) {
printf("CFO: %+6.4f KHz, SFO: %+6.4f Khz, NOI: %.2f, PDCCH-Det: %.3f\r",
srslte_ue_sync_get_cfo(&ue_sync)/1000, srslte_ue_sync_get_sfo(&ue_sync)/1000,
srslte_sch_average_noi(&ue_dl.pdsch.dl_sch),
(float) ue_dl.nof_detected/nof_trials);
nof_trials++;
} else {
printf("Decoded SIB1. Payload: ");
srslte_vec_fprint_byte(stdout, data, n/8);;
state = MEASURE;
}
}
break;
case MEASURE:
if (srslte_ue_sync_get_sfidx(&ue_sync) == 5) {
/* Run FFT for all subframe data */
srslte_ofdm_rx_sf(&fft, sf_buffer, sf_symbols);
srslte_chest_dl_estimate(&chest, sf_symbols, ce, srslte_ue_sync_get_sfidx(&ue_sync));
rssi = SRSLTE_VEC_EMA(srslte_vec_avg_power_cf(sf_buffer,SRSLTE_SF_LEN(srslte_symbol_sz(cell.nof_prb))),rssi,0.05);
rssi_utra = SRSLTE_VEC_EMA(srslte_chest_dl_get_rssi(&chest),rssi_utra,0.05);
rsrq = SRSLTE_VEC_EMA(srslte_chest_dl_get_rsrq(&chest),rsrq,0.05);
rsrp = SRSLTE_VEC_EMA(srslte_chest_dl_get_rsrp(&chest),rsrp,0.05);
snr = SRSLTE_VEC_EMA(srslte_chest_dl_get_snr(&chest),snr,0.05);
nframes++;
}
if ((nframes%100) == 0 || rx_gain_offset == 0) {
if (cuhd_has_rssi(uhd)) {
rx_gain_offset = 10*log10(rssi)-cuhd_get_rssi(uhd);
} else {
rx_gain_offset = cuhd_get_rx_gain(uhd);
}
}
// Plot and Printf
if ((nframes%10) == 0) {
printf("CFO: %+8.4f KHz, SFO: %+8.4f Khz, RSSI: %5.1f dBm, RSSI/ref-symbol: %+5.1f dBm, "
"RSRP: %+5.1f dBm, RSRQ: %5.1f dB, SNR: %5.1f dB\r",
srslte_ue_sync_get_cfo(&ue_sync)/1000, srslte_ue_sync_get_sfo(&ue_sync)/1000,
10*log10(rssi*1000) - rx_gain_offset,
10*log10(rssi_utra*1000)- rx_gain_offset,
10*log10(rsrp*1000) - rx_gain_offset,
10*log10(rsrq), 10*log10(snr));
if (srslte_verbose != SRSLTE_VERBOSE_NONE) {
printf("\n");
}
}
break;
}
if (srslte_ue_sync_get_sfidx(&ue_sync) == 9) {
sfn++;
if (sfn == 1024) {
sfn = 0;
}
}
} else if (ret == 0) {
printf("Finding PSS... Peak: %8.1f, FrameCnt: %d, State: %d\r",
srslte_sync_get_peak_value(&ue_sync.sfind),
ue_sync.frame_total_cnt, ue_sync.state);
}
sf_cnt++;
} // Main loop
srslte_ue_sync_free(&ue_sync);
cuhd_close(uhd);
printf("\nBye\n");
exit(0);
}
