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fix for computing ssb subcarrier offset

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This commit is contained in:
francescomani
2024-02-02 09:21:40 +01:00
parent 513f060fa7
commit b70eba44a7
5 changed files with 35 additions and 17 deletions
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common/utils/nr/nr_common.c
+26 -12
View File
@@ -755,11 +755,25 @@ void SLIV2SL(int SLIV,int *S,int *L) {
}
}
int get_ssb_subcarrier_offset(uint32_t absoluteFrequencySSB, uint32_t absoluteFrequencyPointA)
int get_ssb_subcarrier_offset(uint32_t absoluteFrequencySSB, uint32_t absoluteFrequencyPointA, int scs)
{
uint32_t absolute_diff = (absoluteFrequencySSB - absoluteFrequencyPointA);
const int scaling_5khz = absoluteFrequencyPointA < 600000 ? 3 : 1;
return ((absolute_diff / scaling_5khz) % 24);
// for FR1 k_SSB expressed in terms of 15kHz SCS
// for FR2 k_SSB expressed in terms of the subcarrier spacing provided by the higher-layer parameter subCarrierSpacingCommon
// absoluteFrequencySSB and absoluteFrequencyPointA are ARFCN
// NR-ARFCN delta frequency is 5kHz if f < 3 GHz, 15kHz for other FR1 freq and 60kHz for FR2
const uint32_t absolute_diff = absoluteFrequencySSB - absoluteFrequencyPointA;
int scaling = 1;
if (absoluteFrequencyPointA < 600000) // correspond to 3GHz
scaling = 3;
if (scs > 2) // FR2
scaling <<= (scs - 2);
int sco_limit = scs == 1 ? 24 : 12;
int subcarrier_offset = (absolute_diff / scaling) % sco_limit;
// 30kHz is the only case where k_SSB is expressed in terms of a different SCS (15kHz)
// the assertion is to avoid having an offset of half a subcarrier
if (scs == 1)
AssertFatal(subcarrier_offset % 2 == 0, "ssb offset %d invalid for scs %d\n", subcarrier_offset, scs);
return subcarrier_offset;
}
uint32_t get_ssb_offset_to_pointA(uint32_t absoluteFrequencySSB,
@@ -767,16 +781,16 @@ uint32_t get_ssb_offset_to_pointA(uint32_t absoluteFrequencySSB,
int ssbSubcarrierSpacing,
int frequency_range)
{
// offset to pointA is expressed in terms of 15kHz SCS for FR1 and 60kHz for FR2
// only difference wrt NR-ARFCN is delta frequency 5kHz if f < 3 GHz for ARFCN
uint32_t absolute_diff = (absoluteFrequencySSB - absoluteFrequencyPointA);
const int scaling_5khz = absoluteFrequencyPointA < 600000 ? 3 : 1;
int sco = get_ssb_subcarrier_offset(absoluteFrequencySSB, absoluteFrequencyPointA);
const int scs_scaling = frequency_range == FR2 ? 1 << (ssbSubcarrierSpacing - 2) : 1 << ssbSubcarrierSpacing;
const int scaled_abs_diff = absolute_diff / scaling_5khz;
const int ssb_offset_point_a =
(scaled_abs_diff - sco) / 12
- 10 * scs_scaling; // absoluteFrequencySSB is the central frequency of SSB which is made by 20RBs in total
AssertFatal(ssb_offset_point_a % scs_scaling == 0, "PRB offset %d can create frequency offset\n", ssb_offset_point_a);
AssertFatal(sco % scs_scaling == 0, "ssb offset %d can create frequency offset\n", sco);
const int scaling = frequency_range == FR2 ? 1 << (ssbSubcarrierSpacing - 2) : 1 << ssbSubcarrierSpacing;
const int scaled_abs_diff = absolute_diff / (scaling_5khz * scaling);
// absoluteFrequencySSB is the central frequency of SSB which is made by 20RBs in total
const int ssb_offset_point_a = ((scaled_abs_diff / 12) - 10) * scaling;
// Offset to point A needs to be divisible by scaling
AssertFatal(ssb_offset_point_a % scaling == 0, "PRB offset %d not valid for scs %d\n", ssb_offset_point_a, ssbSubcarrierSpacing);
return ssb_offset_point_a;
}
common/utils/nr/nr_common.h
+1 -1
View File
@@ -202,7 +202,7 @@ uint32_t get_ssb_offset_to_pointA(uint32_t absoluteFrequencySSB,
uint32_t absoluteFrequencyPointA,
int ssbSubcarrierSpacing,
int frequency_range);
int get_ssb_subcarrier_offset(uint32_t absoluteFrequencySSB, uint32_t absoluteFrequencyPointA);
int get_ssb_subcarrier_offset(uint32_t absoluteFrequencySSB, uint32_t absoluteFrequencyPointA, int scs);
int get_delay_idx(int delay, int max_delay_comp);
void freq2time(uint16_t ofdm_symbol_size,