Wireless Oom » umts

What is ISUP?

wirelessoom — Sat, 29 May 2010 08:27:29 +0000

ISDN user part
Part of SS7 protocol for telephone call setup.
In UMTS, part of this is being used for CS call.

IAM: Initial Address Message
ACM: Address Complete Message
ANM: Answer Message
REL: Release message
RLC: Release complete Message

MO call setup

wirelessoom — Fri, 28 May 2010 14:40:48 +0000

Why do we have a cellular network?
To make a call or do data connection. (something useful)

Here, I post brief step for Mobile Originated call setup.
Detailed call flow can be found at here

What is AN’s role?

wirelessoom — Thu, 27 May 2010 18:15:46 +0000

What is AN (Access Network, UTRAN)’s role ?

Provide simple connectivity to the core network (CN) – whether it is a CS or PS.

Remember that UE wishes to make a call or data connection to do some useful and helpful thing.

AN just helps it in the middle between UE and CN.

What is direct tunnel ?

wirelessoom — Thu, 27 May 2010 07:51:31 +0000

In connected mode, the GTP-U can be established between GGSN and AN (without SGSN), which is more efficient.

No more confusion re. RB, SRB and RAB

wirelessoom — Wed, 26 May 2010 19:30:00 +0000

I drew some figure to clarify the definition of RB, SRB and RAB.

Cell reselection

wirelessoom — Mon, 15 Mar 2010 20:56:38 +0000

Here, for example, Squal <= Sintersearch in SIB3/4

Then, the UE starts to measure the signal strengths of neighboring cells.

Rs = Qmeas,s + Qhysts
Rn = Qmeas,n – Qoffset,n

Rs is for the serving cell and Rn is for neighbor cell.
Qhysts is for reduce ping-pong effects between serving and neighbor cells.
Qoffset,n is an offset parameter between the serving and the neighbor cells.

Pick the best cell with the largest R value.

What is suitable cell to camp? (signal level cell selection criteria)

wirelessoom — Mon, 15 Mar 2010 20:45:10 +0000

Among many, in this post, we focus on signal level perspective.

Suitable cell is defined:

Srxlev > 0
Squal > 0

Then, questions arise: what is Srxlev and Squal?

Srxlev = Qrxlev_meas – Qrxlevmin – Pcompensation

Qrxlevmin is the minimum received signal level defined for the cell (broadcast information). Qrxlevmin ranges from -115dBm to -25dBm.
Here, we use RSCP (power measured by a receiver on a particular physical communication channel. It is used as an indication of signal strength, as a handover criterion, in downlink power control, and to calculate path loss).

Pcompensation = Max (UE_TXPWR_MAX_RACH – P_MAX, 0)

UE_TXPWR_MAX_RACH is the broadcast value of the maximum RACH power and P_MAX is the UE maximum TX power.

Qrxlev_meas is the measured RSCP value at the device.
———————–

Squal = Qqual_meas – Qqualmin

Qqualmin is the minimum received signal quality defined for the cell. (broadcast value).
Here we use CPICH Ec/Io( measurement defined as the ration of the received energy per chip and the total receiver interference plus noise power spectral density.)

Qqual_meas is the received CPICH Ec/Io at the receiver.

Cell_PCH data call flow

wirelessoom — Mon, 15 Mar 2010 20:00:27 +0000

Pre release 7

Release 7

What is “B” party type?

wirelessoom — Mon, 15 Mar 2010 19:55:21 +0000

“B” party number means called number.

It could be landline, mobile, and same or other PLMN.

Paging Figure

wirelessoom — Mon, 15 Mar 2010 19:45:58 +0000

The device periodically wakes up and check if there is page for me or not.
The below diagram shows when the device wakes up to check its page. (Only at a particular PI location, otherwise in sleeping.)