High speed uplink packet access (HSUPA) is a technology introduced in the 3rd Generation Partnership Project (3GPP) Release 6 (R6). This technology is optimization and evolution directing to packet services in the uplink direction (direction from a mobile terminal to a radio access network). Using self-adaptation encoding, physical-layer hybrid retransmission, Node B-based fast scheduling, and 2-ms transmission time interval (TTI)-based short-frame transmission, HSUPA enhances the highest data transmission rate and cell throughput, and reduces the delay.
HSUPA further reduces the transmission delay by using the 2-ms TTI transmission mode. However, 2-ms TTI-based short-frame transmission mode is not applicable to the user equipment (UE) that works at the edge of a cell. Therefore, the coverage of the UE is narrowed down. Especially in the case of a period of time after the UE's total transmit power reaches the maximum transmit power, the 2-ms TTI needs to be switched to 10-ms TTI to enhance the uplink coverage. The detailed process is as follows:
(1) The network configures 6d event for the UE by a measuring control message.
(2) When the UE transmit power reaches the maximum allowable transmit power and stays for a period of time, the UE reports a measurement report to the network.
(3) Upon receiving the measurement report, a radio network controller (RNC) judges whether the UE uplink transmit power is limited, and sends a reconfiguration message (may include a radio bearer reconfiguration message, transmission channel reconfiguration message) to the UE to reconfigure the TTI length.
(4) Upon receiving the reconfiguration message, the UE performs the reconfiguration according to the reconfiguration message at a time specified by the network to implement switching from 2-ms TTI to 10-ms TTI.
As described above, in the prior art, the UE reports 6d event and the RNC judges, according to 6d event, whether the UE transmit power is limited, and initiates the reconfiguration message to configure the UE for TTI switching. Therefore, the delay is long when the UE switches to 10-ms TTI transmission mode.