Question

What are the types of RNTI's? In Which context C-RNTI and U-RNTI used?

Answer 1

Five Types of RNTI exist:

1.Serving RNC RNTI (S-RNTI)
2.Drift RNC RNTI (D-RNTI)
3.Cell RNTI (C-RNTI)
4.UTRAN RNTI (U-RNTI)
5.HS-DSCH RNTI (H-RNTI)

C-RNTI (Cell RNTI) is valid/unique in a cell and is used on DTCH and DCCH in uplink, and may be used on DCCH in downlink (when mapped onto common transport channels like FACH). C-RNTI is given to UE by controlling RNC upon accessing (new) cell.
U-RNTI is used only by network i.e. in downlink direction only. U-RNTI may be used in DCCH mapped over common transport channel (like FACH).

Answer 2

RA-RNTI -- Random access response-- Value: 0001 - 003C
Temporary C-RNTI R8 Random access contention resolution -- Value: 003D - FFF3
C-RNTI--One UL or DL transmission
SPS C-RNTI--Several UL or DL transmissions
TPC-PUCCH-RNTI--Embedded PUCCH TPC command
TPC-PUSCH-RNTI--Embedded PUSCH TPC command
M-RNTI--MBMS change notification -- Value: FFFD
P-RNTI--Paging message -- Value: FFFE
SI-RNTI--System information message -- Value: FFFF