1）nr_pbch_detection，检测PBCH
1.1）不同序列假设下的 PBCH DMRS相关， PBCH DMRS携带8种序列假设
for (int hf = 0; hf < N_hf; hf++) {
for (int l = 0; l < N_L; l++) {
// computing correlation between received DMRS symbols and transmitted sequence for current i_ssb and n_hf
cd_t cumul = {0};
for (int i = pbch_initial_symbol; i < pbch_initial_symbol + 3; i++) {
c32_t meas = nr_pbch_dmrs_correlation(frame_parms,
proc,
i,
i - pbch_initial_symbol,
Nid_cell,
ssb_start_subcarrier,
nr_gold_pbch(frame_parms->Lmax, Nid_cell, hf, l),
rxdataF);
1.2）=> 调用nr_pbch_dmrs_correlation
一个OFDM符号上的PBCH DMRS相关
生成本地的DMRS为：
nr_pbch_dmrs_rx(dmrss, (uint32_t *)nr_gold_pbch, pilot, false);
第dmrss个符号，PBCH序列为nr_gold_pbch，输出为pilot
逐个RX天线进行相关：
for (int aarx = 0; aarx < fp->nb_antennas_rx; aarx++) {
int re_offset = ssb_offset;
c16_t *pil = pilot;
const c16_t *rxF = &rxdataF[aarx][symbol_offset + k];
本地信号（采样点）为pil，接收信号（采样点）为rxF
symbol_offset=4096
k = Nid_cell % 4
不同的cell ID，DMRS会有不同的偏移，共4种偏移
复数相加并累计起来:
computed_val = c32x16maddShift(*pil, rxF[re_offset], computed_val, 15);
__attribute__((always_inline)) inline c32_t c32x16maddShift(const c16_t a, const c16_t b, const c32_t c, const int Shift) {
return (c32_t) {
.r = ((a.r * b.r - a.i * b.i) >> Shift) + c.r,
.i = ((a.r * b.i + a.i * b.r) >> Shift) + c.i
};
}
computed_val既是输入也是输出
其中：re_offset应该是子载波位置，也是采样点位置，re_offset = ssb_offset，ssb_offset = fp->first_carrier_offset + ssb_start_subcarrier，比如re_offset=1928
具体来说，接收信号逐次加4，即每4个子载波有一个DMRS，re_offset = (re_offset + 4) % fp->ofdm_symbol_size
本地信号逐次加1，pil++
2.3）PBCH DMRS信道估计：nr_pbch_channel_estimation