13 L2 and L3 Downlink enhancements for UMTS

25.3003GPPGeneral descriptionRelease 17Stage 2TSUniversal Terrestrial Radio Access Network (UTRAN)

13.1 Retrievable configurations

The retrievable configurations feature allows the UE to store configurations together with an identity. When the network invokes a retrievable configuration, it needs to signal only its identity. A retrievable configuration can be signalled to a UE in any state except for idle. Retrievable configurations are cleared when entering idle mode and at SRNS relocation.

There are two ways of signalling the retrievable configurations: one way is that as a result of an RRC signalling procedure, the UE stores the received configuration as a retrievable configuration, and the other way is that the network preconfigures the UE with at least one retrievable configuration. The network can signal a delta to a stored configuration for either of the two ways. The UE validates a retrievable configuration when it invokes it.

13.2 URA_PCH with seamless transition

The feature URA_PCH with seamless transition to CELL_FACH is described in 3GPP TS 25.319 [3].

13.3 Optimization from IDLE to CONNECTED state

If the UE supports "NodeB triggered HS-DPCCH transmission", the RNC can issue the indication to trigger acquisition of the common E-DCH resource or to release the allocated common E-DCH resource for the particular UE.

13.4 Blind HARQ retransmissions for HSDPA

The feature blind HARQ retransmissions for HSDPA is described in 3GPP TS 25.308 [2].

13.5 Enhanced state transition

This feature allows the UE to move to a more power efficient state without explicit RRC reconfiguration. The UE sends the RRC indication to the RNC and moves to the target state upon reception of the RLC ACK from the RNC. The state transition is applicable to the following cases: from CELL_DCH to CELL_FACH, from CELL_FACH to CELL_PCH/URA_PCH, and from CELL_DCH to CELL_PCH/URA_PCH.

While configuring a UE with enhanced state transition, the RNC can provide RRC configuration that will be applied once the UE enters the target state.

13.6 Improved synchronized RRC procedures

In improved synchronized RRC procedures, firstly the UE receives an RRC reconfiguration message for a synchronized RRC procedure indicating that the activation time shall be dynamically determined. Then, when the UE is ready to switch to the new configuration indicated in the RRC message, it sends a MAC Control Information to the Node B. On reception of the HARQ ACK to the MAC Control Information, the UE calculates the activation time by adding an offset to the current CFN. The UE reconfigures at the calculated activation time and sends an RRC configuration complete message upon successful completion of the procedure.

The network can also indicate a legacy activation time, at which the switch to the new configuration latest shall occur. The UE will choose the smallest value of the legacy activation time and the calculated activation time as the final activation time.