1. Field of the Invention
The invention generally relates to the handling of Secondary Cell (SCell) reactivation, and more particularly, to apparatuses and methods for handling reactivation of an activated SCell with configured uplink, so as to avoid unnecessary triggering of the Power Headroom Reporting (PHR) procedure and to avoid resetting associated timers.
2. Description of the Related Art
In order to meet user demand for higher data rates in wireless communications, support for wider transmission bandwidths is required. A so-called Carrier Aggregation (CA) technique has been proposed to allow expansion of effective bandwidths delivered to a User Equipment (UE) through concurrent utilization of radio resources across multiple carriers. The CA technique is most useful when it is difficult to derive a contiguous and extra wide bandwidth. With the CA technique, more than 2 frequency bands may be aggregated to form a larger transmission/receive bandwidth. Each of the aggregated frequency channels is generally referred to as a Component Carrier (CC), which may be taken as a component of the aggregated bandwidth.
Taking the Long Term Evolution (LTE) technology in compliance with release 10 of the 3rd Generation Partnership Project (3GPP) technical specifications as an example, a UE may have one Primary CC (also referred to as PCell) and up to 4 Secondary CCs (also referred to as SCells), and each of the SCells needs to be configured and activated before it may be used for data transmission or reception. An LIE system may first transmit a Radio Resource Control (RRC) message to configure the SCell(s) for the UE, and then activate the SCell(s) by dedicated signaling, such as an Activation/Deactivation Medium Access Control (MAC) Control Element (CE). Later, if a smaller transmission bandwidth is required instead, the LIE system may transmit another Activation/Deactivation MAC CE to the UE to deactivate one of the activated SCell(s). In addition, a deactivation timer may be maintained both in the network side and the UE to count a predetermined time period when the corresponding activated SCell may stay activated. When the deactivation timer expires, the LTE system and the UE may deactivate the corresponding SCell to save power consumed for monitoring the physical downlink shared channel (PDSCH) and physical downlink control channel (PDCCH) corresponding to the deactivated SCell.
Meanwhile, in a mobile communication system supporting the CA technique, how to efficiently distribute/allocate uplink transmission resources between multiple UEs is always a critical issue from the viewpoint of the network side. For better radio resource management, the Power Headroom Reporting (PHR) procedure has been introduced for enabling the UEs to provide specific power status information to the network side. Specifically, the report includes information about the difference between the nominal UE maximum transmit power and the estimated power for UpLink-Shared Channel (UL-SCH) transmission per activated SCell and also information about the difference between the nominal UE maximum power and the estimated power for UL-SCH and PUCCH transmission on the PCell. The reported information is especially important for the network side when allocating the transmission format (bandwidth and modulation and coding scheme) to different UEs. The network entity (eNB) can use the reported information to determine how much more uplink bandwidth per subframe a UE is capable of using, so as to avoid allocating uplink transmission resources to UEs which are unable to use them. Thus, the Signal to Interference-plus-Noise Ratio (SINR) may be decreased and the system capacity may be improved.