Section: 6.8A.1 EPDCCH formats
Content: The enhanced physical downlink control channel (EPDCCH) carries scheduling assignments. An enhanced physical downlink control channel is transmitted using an aggregation of one or several consecutive enhanced control channel elements (ECCEs) where each ECCE consists of multiple enhanced resource element groups (EREGs), defined in clause 6.2.4A. The number of ECCEs used for one EPDCCH depends on the EPDCCH format as given by Table 6.8A.1-2 and the number of EREGs per ECCE is given by Table 6.8A.1-1. Both localized and distributed transmission is supported. An EPDCCH can use either localized or distributed transmission, differing in the mapping of ECCEs to EREGs and PRB pairs. A UE shall monitor multiple EPDCCHs as defined in TS 36.213[ Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures ]  [4]. One or two sets of physical resource-block pairs which a UE shall monitor for EPDCCH transmissions can be configured. All EPDCCH candidates in EPDCCH set use either only localized or only distributed transmission as configured by higher layers. Within EPDCCH set in subframe , the ECCEs available for transmission of EPDCCHs are numbered from 0 to and ECCE number corresponds to - EREGs numbered in PRB index for localized mapping, and - EREGs numbered in PRB indices for distributed mapping, where , is the number of EREGs per ECCE, and is the number of ECCEs per resource-block pair. The physical resource-block pairs constituting EPDCCH set are in this paragraph assumed to be numbered in ascending order from 0 to . Table 6.8A.1-1: Number of EREGs per ECCE, Table 6.8A.1-2: Supported EPDCCH formats Case A in Table 6.8A.1-2 is used when the conditions corresponding to case 1 in clause 9.1.4 of TS 36.213[ Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures ]  [4] are satisfied, otherwise case B is used. The quantity for a particular UE and referenced in TS 36.213[ Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures ]  [4] is defined as the number of downlink resource elements available for EPDCCH transmission in a physical resource-block pair configured for possible EPDCCH transmission of EPDCCH set and fulfilling all of the following criteria: - they are part of any one of the 16 EREGs in the physical resource-block pair, and - they are assumed by the UE not to be used for cell-specific reference signals, where the positions of the cell-specific reference signals are given by clause 6.10.1.2 with the number of antenna ports for and the frequency shift of cell-specific reference signals derived as described in clause 6.10.1.2 unless other values for these parameters are provided by clause 9.1.4.3 in TS 36.213[ Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures ]  [4], and- - they are assumed by the UE not to be used for transmission of CSI reference signals, where the positions of the CSI reference signals are given by clause 6.10.5.2 with the configuration for zero power CSI reference signals obtained as described in clause 6.10.5.2 unless other values are provided by clause 9.1.4.3 in TS 36.213[ Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures ]  [4], and with the configuration for non-zero power CSI reference signals obtained as described in clause 6.10.5.2, and - for frame structure type 1 and 2, the index in the first slot in a subframe fulfils where is given by clause 9.1.4.1 of TS 36.213[ Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures ]  [4], and - for frame structure type 3, - if the higher layer parameter subframeStartPosition indicates 's07' and if the downlink transmission starts in the second slot of a subframe - the index in the second slot in the subframe fulfils where is given by clause 9.1.4.1 of TS 36.213[ Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures ]  [4], - otherwise - the index in the first slot in the subframe fulfils where is given by clause 9.1.4.1 of TS 36.213[ Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures ]  [4].