Annex F Use and structure of the I-RNTI

The I-RNTI provides an NG-RAN node with a reference to the UE context and a reference to the NG-RAN node that allocated the UE context.

To support an NG-RAN node in resolving the Local NG-RAN ID of the NG-RAN node that allocated the UE context, the I-RNTI structure is as follows:

• the first part (starting from the MSB of the I-RNTI) identifies the I-RNTI profile. It is 2 bits long for a Full I-RNTI or 1 bit long for a short I-RNTI, and it indicates the length of a Local NG-RAN Node Identifier of the NG-RAN Node that allocated the I-RNTI;
• the second part, immediately following the first part, is a Local NG-RAN Node Identifier;
• the third part, immediately following the second part, identifies the UE context stored in the NG-RAN node that allocated the I-RNTI.

In case a NG-RAN node takes an additional Local NG-RAN Node identifier into use or removes a Local NG-RAN Node identifier currently in use it informs its neighbour NG-RAN nodes about this change.

The I-RNTI profiles for Full I-RNTI are described in table F-1.

Table F-1: I-RNTI profiles for Full I-RNTI

The I-RNTI profiles for Short I-RNTI are described in table F-2.

Table F-2: I-RNTI profiles for Short I-RNTI