New home

My blog found a new home at

Leave a Comment

What is PI?

PI (Paging indication)


a short indicator that is transmitted on the PICH to tell the UE that there is a paging message on an associated paging channel carried by the SCCPCH.

The number of PIs per radio frame (Np) can be 18, 36, 72 or 144.

Once the UE knows paging occasion (SFN), then the UE needs to know which PI to look for in the SFN.

The equation is

PI = DRX index mod Np


DRX index = IMSI div 8192

If the PI bits are set in the paging occasion (SFN), the UE reads the paging message on the PCH transmitted on the associated SCCPCH.

Leave a Comment

What are main methods for measurement control?

Two types:

1. direct method using measurement control

2. method using broadcast

Leave a Comment

What is the distinct difference between Cell_DCH and other states' measurements?

In Cell_DCH, the UE makes measurements and reports them to the UTRAN for action by the UTRAN.

However, in other states, the measurements are not reported to the UTRAN and the UE takes action based on the measurements. (though Cell_FACH measurement has some common things with Cell_DCH)

Leave a Comment

What is RRC connection?

RRC connection


when a UE went through the connection establishment procedure and has been allocated resources in the UTRAN and a U-RNTI.

With RRC connection, some SRBs are allocated.

Leave a Comment

What is PDP contexts?

PDP context


for PS service.

It consists of

1. RAB

2. CN bearer (bearer between SGSN and GGSN)

The PDP context is created with a defined QoS that is requested by the UE and granted by the network.

Leave a Comment

What is RAB?

RAB (Radio Access Bearer)


created to provide user plane data transfer.

RAB comprises

1. RB and

2. connection from the SRNC to the SGSN (Iu bearer).

The RAB is created on reequest from the SGSN with a specific QoS request.

For a given UE, there can be multiple RABs per NAS service (speech or PS data service).

Leave a Comment

What is RB?

RB (Radio Bearer)

is a layer 2 connection between the UE and the RNC.

It is used for both control signaling and user data.

RB used for signaling is called an SRB.

Leave a Comment

What is RL?

RL (Radio Link)


the physical connection between the UE and Node B.

Each RL is defined by its RF frequency, channelization code and scrambling code.

Leave a Comment

Various radio and data connections

various types of connections that the UE will have with the network:

1. RL

2. RB

3. RAB

4. SRB

5. PDP

6. RRC connection

RL (UE-Node B)

RB (UE-Node B-RNC)


PDP context (UE-Node B-RNC-SGSN-GGSN)

Leave a Comment

Older Posts »