Cell Radio Network Temporary Identity (C-RNTI) identifies an UE uniquely within one cell and
is assigned by the SRNC (=CRNC). It is used on DTCH and DCCH in uplink, may be used on DCCH in downlink and is used on DTCH in downlink when mapped onto common transport channels except when mapped onto the DSCH transport channel.

UTRAN Radio Network Temporary Identity (U-RNTI) uniquely identifies the UE within the UTRAN,
because the SRNC-Id is included. It consists of S-RNTI and SRNC-Id and is assigned/rleased upon
an RRC connection establishment/release.

The SRNC Radio Network Temporary Identity (S-RNTI) uniquely identifies an UE in the SRNS (e.g. in RNSAP messages) and is assigned by SRNC for a RRC-connection establishment. A S-RNTI is discarded, if the RRC connection is released or when the SRNC changes (e.g. during a SRNC Relocation)

The Drift RNC Radio Network Temporary Identity (D-RNTI) uniquely identifies an UE in RNSAP messages from SRNC to DRNC and is assigned by DRNC.