25 Enhanced TTI switching (FDD only)

25.3193GPPEnhanced uplinkOverall descriptionStage 2TS

For FDD, certain categories of UEs may be configured to perform enhanced TTI switching. This feature allows for performing filtered UPH measurements and a fast and robust 2ms to 10ms (and 10ms to 2ms) TTI switching procedure.

The filtered UPH measurements are controlled by filtering and reporting criteria parameters, which can be configured in a UE by the network via the RRC protocol. When the triggering criteria for the filtered UPH measurement are met, the UE sends the filtered UPH report to the network.

The network may also preconfigure the UE with information for the TTI length. To switch to a different TTI length, the network can indicate this to the UE using a HS-SCCH order. The UE and the Node B(s) will perform the switch of TTI after a configured offset of the CFN.

When enhanced TTI switching for Dual Cell E-DCH operation enhancements is configured, this feature can be used to switch TTI either on Primary or Secondary Uplink Frequency or both, and the UE can send a filtered UPH report in MAC Control Information to the network on the uplink frequency where the report is triggered.