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Refactor: add common helper functions to construct 5G-S-TMSI

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* 5G-S-TMSI construction is defined in 3GPP TS 23.003 and
  relevant at both gNB and UE side
* Add helper functions to be later used in NG Paging
* Adopt in NAS UE
This commit is contained in:
Guido Casati
2026-02-02 16:25:47 +01:00
parent 9cb79027e4
commit d73a9148de
3 changed files with 40 additions and 1 deletions
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common/utils/nr/nr_common.c
+32
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@@ -1487,3 +1487,35 @@ float get_beta_dmrs(int num_cdm_groups_no_data, bool is_type2)
}
return beta_dmrs_pusch;
}
/** @brief Construct full 5G-S-TMSI from 5G-S-TMSI components
* @param amf_set_id AMF Set ID (10 bits)
* @param amf_pointer AMF Pointer (6 bits)
* @param m_tmsi 5G-TMSI (32 bits)
* @return Full 5G-S-TMSI (48 bits)
* @note The 5G-S-TMSI is constructed as a 48-bit value:
* - Bits 38-47: AMF Set ID (10 bits)
* - Bits 32-37: AMF Pointer (6 bits)
* - Bits 0-31: 5G-TMSI (32 bits)
* @ref 3GPP TS 23.003 */
uint64_t nr_construct_5g_s_tmsi(uint16_t amf_set_id, uint8_t amf_pointer, uint32_t m_tmsi)
{
// Construct full 5G-S-TMSI: <AMF Set ID (10 bits)><AMF Pointer (6 bits)><5G-TMSI (32 bits)>
return ((uint64_t)amf_set_id << 38) | ((uint64_t)amf_pointer << 32) | m_tmsi;
}
/** @brief Construct 5G-S-TMSI-Part1 from 5G-S-TMSI components
* @param amf_set_id AMF Set ID (10 bits)
* @param amf_pointer AMF Pointer (6 bits)
* @param m_tmsi 5G-TMSI (32 bits)
* @return 5G-S-TMSI-Part1 (rightmost 39 bits of the full 5G-S-TMSI)
* @note 5G-S-TMSI-Part1 is the rightmost 39 bits of the full 5G-S-TMSI:
* - Bits 32-37: AMF Pointer (6 bits)
* - Bits 0-31: 5G-TMSI (32 bits)
* @ref 3GPP TS 23.003 */
uint64_t nr_construct_5g_s_tmsi_part1(uint16_t amf_set_id, uint8_t amf_pointer, uint32_t m_tmsi)
{
// Construct full 5G-S-TMSI and extract Part1: rightmost 39 bits
uint64_t full_s_tmsi = nr_construct_5g_s_tmsi(amf_set_id, amf_pointer, m_tmsi);
return full_s_tmsi & ((1ULL << 39) - 1);
}