1. Field of the Invention
The present invention relates generally to enhanced physical downlink control channel (ePDCCH) transmission, and more particularly, to a method and an apparatus for providing advanced notification of ePDCCH transmission for a user equipment (UE).
2. Description of the Related Art
In the 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) standard, a physical downlink shared channel (PDSCH) carries all user data signaling messages and a physical downlink control channel (PDCCH) carries layer one downlink control information (DCI). PDCCH is transmitted in a downlink control region and is allocated within a number of orthogonal frequency division multiplexing (OFDM) symbols at the beginning of each subframe. This allocation allows a UE to decode the PDCCH first and determine its potential assignments early, without having to read and buffer the entire subframe. Therefore, the UE can ignore the remaining portions of the subframe when the UE determines that no downlink assignment exists for that UE in the PDSCH region of the subframe. This mechanism has the potential to save power and extend battery life of the UE.
In order to increase the capacity of control channels to accommodate more complicated features, the concept of ePDCCH has been introduced. FIG. 1 is a diagram illustrating the incorporation of ePDCCH into a subframe. Specifically, ePDCCH regions 102 are disposed between PDSCH regions 104 in frequency, and after a PDCCH region 106 in time, within the subframe. As illustrated in FIG. 1, the ePDCCH regions 102 have a time range that begins after the PDCCH region 106 and lasts until the end of the subframe. Thus, if an ePDCCH transmission to the UE is allowed on the subframe, the UE is required to buffer the entire subframe, and then attempt to decode an ePDCCH transmission targeted to the UE. If the UE successfully decodes DCI in the PDCCH that corresponds to a downlink assignment for the UE, the UE also attempts to the decode the corresponding PDSCH transmission.
The battery life of the UE is negatively affected when the receiver of the UE remains active for an entire subframe and when the UE reads and buffers the entire subframe for all subframes on which an ePDCCH transmission for the UE is allowed.