The purpose of the paging procedure is as follows:
-The core network (CN) originates the paging procedure to inform selected UEs of service requests and to trigger reading of updated UTRAN system information.
-The UTRAN originates the paging procedure to trigger state transitions from URA_PCH to CELL_FACH or idle mode for selected UEs.
1-Paging Types
Paging UE in Idle, CELL_PCH, URA_PCH State (Type 1)
+When an UE is in idle, CELL_PCH, or URA_PCH state, UTRAN sends a paging message to the UE through the PCCH.
Paging type 1 procedure is used to transmit paging information to the selected UEs in idle mode, CELL_PCH or URA_PCH state using the PCCH. With this feature, upper layers in the network can:
-Trigger UE establishing an RRC signaling connection.
-Trigger CELL UPDATE procedure of UE in CELL_PCH or URA_PCH state.
-Trigger reading of updated system broadcast of UE in idle mode, CELL_PCH or URA_PCH state.
-Trigger releasing signaling connection of UE in CELL_PCH or URA_PCH state.
+When the CN sends data to UEs in CELL_PCH or URA_PCH state, the UTRAN shall repeat the paging process five times in case of a paging failure towards a UE for some reasons (For example, the UE has moved out of the UTRAN and transferred to an inter-RAT network.). If the UTRAN still fails to page the UE, the UTRAN considers that the paging towards the UE fails and releases the RRC connection with the UE.
Paging UE in CELL_FACH, CELL_DCH State (Type 2)
The network can control the UE in CELL_FACH or CELL_DCH state which has DCCH with paging type 2 procedures. In paging type 2, UTRAN sends a paging message to the UE in CELL_FACH or CELL_DCH state through the DCCH or FACH.
Reception Technology
+To reduce power consumption, the UE can read the information from the PICH only at a particular time. This is known as the Discontinuous Reception (DRX) technology. The interval between two consecutive receiving occasion is called DRX cycle.
+For Frequency Division Duplex (FDD), the DRX cycle length shall be 2k frames, where k is an integer and is determined by the following three parameters:
-CN domain specific DRX cycle length for CS
-CN domain specific DRX cycle length for PS
-UTRAN DRX cycle length coefficient
The description of the parameters is as follows:
-CN domain specific DRX cycle lengths
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-The UE may be attached to different CN domains with different CN domain specific DRX cycle lengths. The UE shall store these lengths for all CN domains where the UE is attached and shall use the shortest one.
-UTRAN DRX cycle length
+For a UE in idle mode, the DRX cycle length equals the shortest value of the stored DRX cycle length for the CN domains where the UE is attached, with no signaling connection established.
+For a UE in CELL_PCH state or URA_PCH state, the DRX cycle length equals the shortest value of the following lengths:
-UTRAN DRX cycle length
-Any of the stored DRX cycle length for the CN domains where the UE is attached, with no signaling connection established
If you set a great DRX cycle length coefficient, the period for UE detect paging information will be long; therefore, the UE can reduce the power consumption, but the delay for responding to a paging will be long.