LTE RNTI vs GUTI-basics of RNTI identifier and GUTI
RNTI stands for Radio Network Temporary Identifiers and GUTI stands for Globally Unique Temporary UE Identity. This page on LTE RNTI vs GUTI describes basics of RNTI identifier and GUTI in LTE system.
LTE RNTI types-P-RNTI,SI-RNTI,RA-RNTI,C-RNTI,TPC-RNTI
Table below covers various LTE RNTI identifiers. It include P-RNTI, SI-RNTI, RA-RNTI, Temporary C-RNTI, C-RNTI, SPS C-RNTI, TPC-PUSCH-RNTI and TPC-PUCCH-RNTI.
| RNTI Identifier type | Function | Range | Logical Channel | Transport Channel |
|---|---|---|---|---|
| P-RNTI | Paging | FFFE | PCCH | PCH |
| SI-RNTI | Broadcast of system Information | FFFF | BCCH | DL-SCH |
| RA-RNTI | Random Access Response | 0001 to 003C | DL-SCH | - |
| Temporary C-RNTI | Contention Resolution when no C-RNTI is available, | 0001 to FFF3(with the exception of values allocated to RA-RNTI) | CCCH | DL-SCH |
| Initial layer-3 message transmission | CCCH, DCCH,DTCH | UL-SCH | ||
| C-RNTI | Dynamically scheduled unicast transmission | DCCH, DTCH | UL-SCH,DL-SCH | |
| Triggering PDCCH ordered random access | - | - | ||
| SPS C-RNTI | Semi persistent schedules unicast transmission (activation, reactivation and retransmission) | UL-SCH,DL-SCH | UL-SCH,DL-SCH | |
| Semi persistent schedules unicast transmission(deactivation) | - | - | ||
| TPC-PUSCH-RNTI | Uplink Power Control | - | - | |
| TPC-PUCCH-RNTI | Uplink power control | - | - |
RNTIs are applicable within the RAN(Radio Access Network). All the RNTI have same length with size 16 bits. P-RNTI is used during paging procedure. UE proceeds to start decoding a paging message after finding a DCI whose CRC bits have been scrambled by P-RNTI.
SI-RNTI (System Information RNTI) is used during the acquisition phase of SIB. UE proceed to decode system information after finding a DCI whose CRC have been scrambled by SI-RNTI.
RA-RNTI (Random Access RNTI) is used during random access procedure . DCI format 1A and 1C will have their CRC bits scrambled by RA-RNTI will allocate PDSCH resources to random access response messages.
Temporary Cell RNTI (C-RNTI) is allocated to LTE UE within random access response message. Temporary C-RNTI is used for contention resolution when C-RNTI is not available. For example while sending RRC connection request on CCCH for initial access.
LTE GUTI
It is used to provide a temporary identity which is globally unique.
LTE GUTI has following three components:
• PLMN Identity: Uniquely identifies network globally
• MME identity(MMEI): Uniquely identifies MME within PLMN
• MME-TMSI(M-TMSI): Uniquely identifies UE within MME
PLMN identity is generated using MCC and MNC. MCC is 3 digits(decimal), MNC is either 2 or 3 digits (decimal).
Each digit is coded using 4 bits BCD.
MMEI is derived from MME Group ID(MMEGI) and MME Code(MMEC).
The MMEGI is unique within PLMN while MMEC is unique within MME Group.
Globally Unique MME Identifier(GUMMEI) is generated from MCC, MNC and also MMEI.
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