5G NR Inactive-RNTI (I-RNTI)

Types of I-RNTI

There are following two types of the I-RNTI depending of the

• Full I-RNTI: A full I-RNTI which has a length of 40 bits which can be included within a 64 bit RRCResumeRequest1 message over Common Control Channel 1
• Short I-RNTI: A short I-RNTI which has a length of 24 bits which can be included within a 48 bit RRCResumeRequest message Common Control Channel

How UE decides which I-RNTI to be used ?

The broadcast information within System Information Block#1 (SIB1) as “useFullResumeID” flag is used to instruct the UE either to use full or short I-RNTI when resuming the RRC connection.

• full I-RNTI and RRCResumeRequest1 if the field is present
• short I-RNTI and RRCResumeRequest if the field is absent

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