Wireless Oom » c-rnti

UMTS address

wirelessoom — Sun, 26 Jul 2009 16:28:36 +0000

UMTS address can be classified

1. CN address

- IMSI

-TMSI

-P-TMSI

2. UTRAN address

- S-RNTI

- U-RNTI

- C-RNTI

3. UE ID dedicated channels

What is C-RNTI?

wirelessoom — Sun, 26 Jul 2009 16:16:49 +0000

C-RNTI is allocated by the CRNC when a UE access a new cell.

It is only valid within the cell to which the UE is in.

It is 16 bits and used as the main identity while the UE is in a cell and not using DPCHs.

If the UE leaves the clee, then it needs to use a u-RNTI.

UTRAN address

wirelessoom — Sun, 26 Jul 2009 16:12:51 +0000

There are three types of UTRAN addresses:

1. s-RNTI

2. u-RNTI

3. c-RNTI

UE location in Cell_FACH

wirelessoom — Sun, 26 Jul 2009 15:03:09 +0000

In the Cell_FACH, the UE location is known to the cell level.

If the UE detects the change in cell identity, it performs a cell update procedure.

The UE is addressed by the C-RNTI(cell radio network temporary identifier) from the RNC that controls the cell which the UE is in.

What info are in MAC header?

wirelessoom — Wed, 24 Jun 2009 14:06:14 +0000

MAC header includes

1. C/T field: identifies a specific logical channel (when there are multiple logical channels mapped into a single transport channel)

2. UE ID (e.g., C-RNTI): identifies a specific UE when common channels are used (e.g., FACH channel)

Describe the location management in UMTS

wirelessoom — Wed, 24 Jun 2009 06:58:09 +0000

*Idle mode: CN-level

UE is identified with TMSI (temporary mobile subscriber identity)

*RRC connected mode: UTRAN-level

UE is identified with C-RNTI and U-RNTI

Cell_FACH and Cell_PCH: every cell change needs to be reported via cell update

URA_PCH: every URA change needs to be reported via cell update

(less signal overhead from UE perspective, but more paging messages need to be injected into multiple cells)

What is the use for RNTI?

wirelessoom — Thu, 18 Jun 2009 05:03:21 +0000

RNTI (radio network temporary identifier) is used to address the UE (user equipment) on common transport channels.

If dedicated channels are used, then no need for RNTI.

Two types:

1. C-RNTI (cell)

2. U-RNTI(URA)

C-RNTI identifies a UE within a cell, so it can only be used when the UE’s location is known.

Otherwise, U-RNTI is used.

C-RNTI will be allocated to a UE every time it moves to a new cell and conducts a cell-update procedure.

FACH channel also use C-RNTI to whether the data is for me or not.