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5G NR: simplify init_timeshift_rotation()

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Only Ncp1 is used, so get rid of the second timeshift_symbol_rotation array.
Also simplify the computation of "t0 * Tc * f".
This commit is contained in:
Thomas Schlichter
2021-04-26 16:09:32 +02:00
parent 942037beb3
commit 5c6865fbc6
3 changed files with 11 additions and 62 deletions
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openair1/PHY/MODULATION/nr_modulation.c
+8 -59
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@@ -747,69 +747,18 @@ void init_symbol_rotation(NR_DL_FRAME_PARMS *fp) {
void init_timeshift_rotation(NR_DL_FRAME_PARMS *fp)
{
const double fd = 15e3*(float)(1<<fp->numerology_index);
const double Tc=(1/480e3/4096);
const double Ncp0=16*64 + (144*64*(1/(float)(1<<fp->numerology_index)));
const double Ncp1=(144*64*(1/(float)(1<<fp->numerology_index)));
double t0;
double poff;
double exp_re;
double exp_im;
double f;
int16_t *timeshift_symbol_rotation;
int i;
for (i = 0; i < fp->ofdm_symbol_size/2; i++) {
timeshift_symbol_rotation = fp->timeshift_symbol_rotation[0];
f = fd * i;
t0 = Ncp0 / fp->ofdm_offset_divisor;
poff = 2 * M_PI * -t0 * Tc * f;
exp_re = cos(poff);
exp_im = sin(-poff);
timeshift_symbol_rotation[i*2] = (int16_t)floor(exp_re * 32767);
timeshift_symbol_rotation[i*2+1] = (int16_t)floor(exp_im * 32767);
timeshift_symbol_rotation = fp->timeshift_symbol_rotation[1];
t0 = Ncp1 / fp->ofdm_offset_divisor;
poff = 2 * M_PI * -t0 * Tc * f;
exp_re = cos(poff);
exp_im = sin(-poff);
timeshift_symbol_rotation[i*2] = (int16_t)floor(exp_re * 32767);
timeshift_symbol_rotation[i*2+1] = (int16_t)floor(exp_im * 32767);
for (int i = 0; i < fp->ofdm_symbol_size; i++) {
double poff = -i * 2.0 * M_PI * 144.0 / 2048.0 / fp->ofdm_offset_divisor;
double exp_re = cos(poff);
double exp_im = sin(-poff);
fp->timeshift_symbol_rotation[i*2] = (int16_t)round(exp_re * 32767);
fp->timeshift_symbol_rotation[i*2+1] = (int16_t)round(exp_im * 32767);
if (i < 10)
LOG_I(PHY,"Timeshift symbol rotation %d => (%d,%d) %f\n",i,
fp->timeshift_symbol_rotation[0][i*2],
fp->timeshift_symbol_rotation[0][i*2+1],
fp->timeshift_symbol_rotation[i*2],
fp->timeshift_symbol_rotation[i*2+1],
poff);
}
i = 1;
for (int j = fp->ofdm_symbol_size-1; j > fp->ofdm_symbol_size/2-1; j--) {
timeshift_symbol_rotation = fp->timeshift_symbol_rotation[0];
f = -fd * i;
t0 = Ncp0 / fp->ofdm_offset_divisor;
poff = 2 * M_PI * -t0 * Tc * f;
exp_re = cos(poff);
exp_im = sin(-poff);
timeshift_symbol_rotation[j*2] = (int16_t)ceil(exp_re * 32767);
timeshift_symbol_rotation[j*2+1] = (int16_t)ceil(exp_im * 32767);
timeshift_symbol_rotation = fp->timeshift_symbol_rotation[1];
t0 = Ncp1 / fp->ofdm_offset_divisor;
poff = 2 * M_PI * -t0 * Tc * f;
exp_re = cos(poff);
exp_im = sin(-poff);
timeshift_symbol_rotation[j*2] = (int16_t)ceil(exp_re * 32767);
timeshift_symbol_rotation[j*2+1] = (int16_t)ceil(exp_im * 32767);
if (j > fp->ofdm_symbol_size-10-1)
LOG_I(PHY,"Timeshift symbol rotation %d => (%d,%d) %f\n",-i,
fp->timeshift_symbol_rotation[0][j*2],
fp->timeshift_symbol_rotation[0][j*2+1],
poff);
i++;
}
}