// TODO : test this method
BSYNC() BSYNC(_create_msequence)(unsigned int _g,
unsigned int _k)
{
// validate input
if (_k == 0) {
fprintf(stderr,"bsync_xxxt_create_msequence(), samples/symbol must be greater than zero\n");
exit(1);
}
unsigned int m = liquid_msb_index(_g) - 1;
// create/initialize msequence
msequence ms = msequence_create(m, _g, 1);
BSYNC() fs = (BSYNC()) malloc(sizeof(struct BSYNC(_s)));
unsigned int n = msequence_get_length(ms);
fs->sync_i = bsequence_create(n * _k);
#ifdef TC_COMPLEX
fs->sync_q = bsequence_create(n * _k);
#endif
fs->sym_i = bsequence_create(n * _k);
#ifdef TI_COMPLEX
fs->sym_q = bsequence_create(n * _k);
#endif
msequence_reset(ms);
#if 0
bsequence_init_msequence(fs->sync_i,ms);
#ifdef TC_COMPLEX
msequence_reset(ms);
bsequence_init_msequence(fs->sync_q,ms);
#endif
#else
unsigned int i;
unsigned int j;
for (i=0; i<n; i++) {
unsigned int bit = msequence_advance(ms);
for (j=0; j<_k; j++) {
bsequence_push(fs->sync_i, bit);
#ifdef TC_COMPLEX
bsequence_push(fs->sync_q, bit);
#endif
}
}
#endif
msequence_destroy(ms);
fs->n = _k*n;
return fs;
}
void ofdmframesync_reset(ofdmframesync _q)
{
#if 0
// reset gain parameters
unsigned int i;
for (i=0; i<_q->M; i++)
_q->G[i] = 1.0f;
#endif
// reset synchronizer objects
nco_crcf_reset(_q->nco_rx);
msequence_reset(_q->ms_pilot);
// reset timers
_q->timer = 0;
_q->num_symbols = 0;
_q->s_hat_0 = 0.0f;
_q->s_hat_1 = 0.0f;
_q->phi_prime = 0.0f;
_q->p1_prime = 0.0f;
// set thresholds (increase for small number of subcarriers)
_q->plcp_detect_thresh = (_q->M > 44) ? 0.35f : 0.35f + 0.01f*(44 - _q->M);
_q->plcp_sync_thresh = (_q->M > 44) ? 0.30f : 0.30f + 0.01f*(44 - _q->M);
// reset state
_q->state = OFDMFRAMESYNC_STATE_SEEKPLCP;
}
void ofdmframegen_reset(ofdmframegen _q)
{
msequence_reset(_q->ms_pilot);
// clear internal postfix buffer
unsigned int i;
for (i=0; i<_q->taper_len; i++)
_q->postfix[i] = 0.0f;
}
void bpacketsync_assemble_pnsequence(bpacketsync _q)
{
// reset m-sequence generator
msequence_reset(_q->ms);
unsigned int i;
for (i=0; i<8*_q->pnsequence_len; i++)
bsequence_push(_q->bpn, msequence_advance(_q->ms));
}
// reset frame generator object
void gmskframegen_reset(gmskframegen _q)
{
// reset GMSK modulator
gmskmod_reset(_q->mod);
// reset states
_q->state = STATE_PREAMBLE;
msequence_reset(_q->ms_preamble);
_q->frame_assembled = 0;
_q->frame_complete = 0;
_q->symbol_counter = 0;
}
// generate p/n sequence
void bpacketgen_assemble_pnsequence(bpacketgen _q)
{
// reset m-sequence generator
msequence_reset(_q->ms);
unsigned int i;
unsigned int j;
for (i=0; i<_q->pnsequence_len; i++) {
unsigned char byte = 0;
for (j=0; j<8; j++) {
byte <<= 1;
byte |= msequence_advance(_q->ms);
}
_q->pnsequence[i] = byte;
}
}
void gmskframegen_write_preamble(gmskframegen _q,
float complex * _y)
{
unsigned char bit = msequence_advance(_q->ms_preamble);
gmskmod_modulate(_q->mod, bit, _y);
// apply ramping window to first 'm' symbols
if (_q->symbol_counter < _q->m) {
unsigned int i;
for (i=0; i<_q->k; i++)
_y[i] *= hamming(_q->symbol_counter*_q->k + i, 2*_q->m*_q->k);
}
_q->symbol_counter++;
if (_q->symbol_counter == _q->preamble_len) {
msequence_reset(_q->ms_preamble);
_q->symbol_counter = 0;
_q->state = STATE_HEADER;
}
}
void ofdmoqamframe64sync_reset(ofdmoqamframe64sync _q)
{
// reset pilot sequence generator
msequence_reset(_q->ms_pilot);
// reset auto-correlators
autocorr_cccf_clear(_q->autocorr);
_q->rxx_mag_max = 0.0f;
// reset frequency offset estimation, correction
_q->nu_hat = 0.0f;
nco_crcf_reset(_q->nco_rx);
nco_crcf_reset(_q->nco_pilot);
pll_reset(_q->pll_pilot);
// clear input buffer
windowcf_clear(_q->input_buffer);
// clear analysis filter bank objects
firpfbch_clear(_q->ca0);
firpfbch_clear(_q->ca1);
// reset gain parameters
_q->g = 1.0f; // coarse gain estimate
unsigned int i;
for (i=0; i<_q->num_subcarriers; i++)
_q->G[i] = 1.0f;
for (i=0; i<4; i++)
_q->y_phase[i] = 0.0f;
// reset state
_q->state = OFDMOQAMFRAME64SYNC_STATE_PLCPSHORT;
//_q->state = OFDMOQAMFRAME64SYNC_STATE_PLCPLONG0;
_q->timer = 0;
_q->num_symbols = 0;
_q->num_data_symbols = 0;
_q->num_samples = 0;
_q->sample_phase = 0;
}
int main(int argc, char*argv[]) {
// options
unsigned int m=5; // shift register length, n=2^m - 1
char filename[64] = ""; // output filename
int dopt;
while ((dopt = getopt(argc,argv,"uhm:f:")) != EOF) {
switch (dopt) {
case 'u':
case 'h': usage(); return 0;
case 'm': m = atoi(optarg); break;
case 'f':
// copy output filename string
strncpy(filename,optarg,64);
filename[63] = '\0';
break;
default:
exit(1);
}
}
// ensure output filename is set
if (strcmp(filename,"")==0) {
fprintf(stderr,"error: %s, filename not set\n", argv[0]);
exit(1);
}
// validate m
if (m < 2) {
fprintf(stderr,"error: %s, m is out of range\n", argv[0]);
exit(1);
}
// create and initialize m-sequence
msequence ms = msequence_create_default(m);
msequence_print(ms);
unsigned int n = msequence_get_length(ms);
unsigned int sequence[n]; // sequence
signed int rxx[n]; // auto-correlation
// initialize sequence
unsigned int i;
for (i=0; i<n; i++)
sequence[i] = msequence_advance(ms);
// reset sequence
msequence_reset(ms);
// create and initialize first binary sequence on m-sequence
bsequence bs1 = bsequence_create(n);
bsequence_init_msequence(bs1, ms);
// create and initialize second binary sequence on same m-sequence
bsequence bs2 = bsequence_create(n);
bsequence_init_msequence(bs2, ms);
// when sequences are aligned, autocorrelation is equal to length
unsigned int k=0;
rxx[k++] = 2*bsequence_correlate(bs1, bs2) - n;
// when sequences are misaligned, autocorrelation is equal to -1
for (i=0; i<n-1; i++) {
bsequence_push(bs2, msequence_advance(ms));
rxx[k++] = 2*bsequence_correlate(bs1, bs2)-n;
}
// clean up memory
bsequence_destroy(bs1);
bsequence_destroy(bs2);
msequence_destroy(ms);
//
// generate auto-correlation plot
//
// open output file
FILE * fid = fopen(filename,"w");
if (fid == NULL) {
fprintf(stderr,"error: %s, could not open file \"%s\" for writing.\n", argv[0], filename);
exit(1);
}
// print header
fprintf(fid,"# %s : auto-generated file (do not edit)\n", filename);
fprintf(fid,"# invoked as :");
for (i=0; i<argc; i++)
fprintf(fid," %s",argv[i]);
fprintf(fid,"reset\n");
fprintf(fid,"set terminal postscript eps enhanced color solid rounded\n");
fprintf(fid,"set xrange [-1:%u];\n", n+1);
fprintf(fid,"set size ratio 0.3\n");
fprintf(fid,"set xlabel 'delay (number of samples)'\n");
fprintf(fid,"set nokey # disable legned\n");
//fprintf(fid,"set grid xtics ytics\n");
//fprintf(fid,"set grid linetype 1 linecolor rgb '%s' lw 1\n", LIQUID_DOC_COLOR_GRID);
fprintf(fid,"set multiplot layout 2,1 scale 1.0,1.0\n");
fprintf(fid,"# sequence\n");
fprintf(fid,"set ylabel 'sequence'\n");
fprintf(fid,"set yrange [-0.1:1.1]\n");
fprintf(fid,"plot '-' using 1:2 with steps linetype 1 linewidth 4 linecolor rgb '%s'\n",LIQUID_DOC_COLOR_BLUE);
for (i=0; i<n; i++) {
fprintf(fid," %6u %6u\n", i, sequence[i]);
}
fprintf(fid,"e\n");
fprintf(fid,"# auto-correlation\n");
fprintf(fid,"set ylabel 'auto-correlation'\n");
fprintf(fid,"set yrange [%f:1.1]\n", -5.0f / (float)n);
fprintf(fid,"plot '-' using 1:2 with lines linetype 1 linewidth 4 linecolor rgb '%s'\n",LIQUID_DOC_COLOR_GREEN);
for (i=0; i<n; i++) {
fprintf(fid," %6u %12.4e\n", i, (float)rxx[i] / (float)n);
}
fprintf(fid,"e\n");
fprintf(fid,"unset multiplot\n");
// close output file
fclose(fid);
printf("results written to %s.\n", filename);
return 0;
}