Posts Tagged pch

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

List UMTS transport channels

Transport channels care about how and which characteristics the data from MAC layer are transmitted through the radio interface.

It is not about what information which logical channels take care.

Thus, two main categoires: (1) dedicated and (2) common

1. Dedicated

DCH (Dedicated Channel):  DCH includes either user or control information.

In the case of single service, a usual situation is that two DCHs are allocated;

one for the traffic logical channel (DTCH) and another for the signaling (DCCH).

Four DCCHs (SRBs) can be multiplexed into a single transport channel (DCH).

Also note that there will be uplink DCH and downlink DCH.


2. Common

a. BCH (Broadcast Channel):

only in the downlink

transport BCCH logical channel which includes system information.

a fixed low bit rate and relatively high power level in order for all UEs in the cell to decode its information

b. PCH (Paging Channel):

only in the downlink.

transport the PCCH logical channel, which contains pagings and notifications from the network to specific UEs.

c. RACH (Random Access Channel):

only in the uplink.

very low quality requirements (transmission of short packets without delay constraints) or for signal info during the initial access to the system.

different transmission bit rates may be used.

d. FACH (Forward Access Channel):

only in the downlink.

differnt bit rates.

e. HS-DSCH (High Speed Downlink Shared Channel):

to support HSDPA


Different transport channels may be multiplexed together over the same physical resources forming a Coded Composite Transport Channel (CCTrCH).

CPCH (Common Packet Channel) and DSCH (Downlink Shared Channel) are obsolete.

Leave a Comment