Section: 6.8C.1 SPDCCH formats
Content: The short physical downlink control channel (SPDCCH) carries scheduling assignments and other control information for subslot PDSCH, slot-PDSCH, subslot-PUSCH, and slot-PUSCH. A SPDCCH is transmitted using an aggregation of one or several consecutive short control channel elements (SCCEs) where each SCCE consists of multiple short resource element groups (SREGs), defined in clause 6.2.4B. The number of resource elements used for one SPDCCH depends on the SPDCCH format as given by Table 6.8C.1-2 and the number of SREGs per SCCE is given by Table 6.8C.1-1. Table 6.8C.1-1: Number of SREGs per SCCE, Table 6.8C.1-2: Supported SPDCCH formats A UE shall monitor multiple SPDCCHs as defined in TS 36.213[ Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures ]  [4]. One or two resource sets which a UE shall monitor for SPDCCH transmissions in a slot/subslot can be configured. The SPDCCH can use either localized or distributed transmission. All SPDCCH candidates in SPDCCH set use either only localized or only distributed transmission as configured by higher layers (see transmissionType in TS 36.331[ Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification ]  [9]). Similarly, all SPDCCH candidates in SPDCCH set use either only CRS-based demodulation or only DMRS-based demodulation as configured by higher layers (see spdcch-SetReferenceSig in TS 36.331[ Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification ]  [9]). For a resource set with CRS-based SPDCCH, the distributed transmission is implemented at the SREG level, i.e. in the SCCE-to-SREG mapping. For a resource set with DMRS-based SPDCCH, the distributed transmission is implemented at the SCCE level, i.e. in the SPDCCH candidate-to-SCCE mapping. The number of OFDM symbols spanned by a SPDCCH resource set configured with CRS based demodulation can be configured to be one or two. For slot based transmission, the number of OFDM symbols spanned by each SPDCCH candidate of a resource set configured with DMRS-based demodulation is fixed to 2. For subslot based transmission, the number of OFDM symbols spanned by each SPDCCH candidate of a resource set configured with DMRS-based demodulation is equal to the number of OFDM symbols used for the subslot based PDSCH transmission (which depends on the starting symbol index, as specified in Table 6.4.2-1). The physical resource blocks in frequency domain constituting SPDCCH set are in this paragraph assumed to be numbered in ascending order from 0 to . For a CRS-based SPDCCH, SREGs within an SPDCCH set are numbered in a frequency-first time-second manner from 0 to, where is the number of configured OFDM symbols (OS). The frequency-first, time-second mapping of the SREGs within a SPDCCH set is performed from the lowest resource block in frequency domain to the highest resource blocks in frequency domain for the first symbol, and from the highest resource block in frequency domain to the lowest resource block in frequency domain for the second symbol. For a DMRS-based SPDCCH, SREGs within an SPDCCH set are numbered in a time-first frequency-second manner from 0 to. Within CRS-based SPDCCH set , the SCCEs available for transmission of SPDCCHs are numbered from 0 to where for localized mapping and for distributed mapping. Within DMRS-based SPDCCH set , the SCCEs available for transmission of SPDCCHs are numbered from 0 to where . The SCCE number corresponds - SREGs numbered for localized SPDCCH mapping with CRS and DMRS based demodulation and for distributed SPDCCH mapping with DMRS-based demodulation - SREGs numbered for distributed SPDCCH mapping with CRS-based demodulation. where and is the number of SREGs per SCCE. NOTE:represents the number of SREGs per each configured OFDM symbol in the SPDCCH resource set and is the total number of SREGs in SPDCCH resource set .