6.7 Physical control format indicator channel

36.2113GPPEvolved Universal Terrestrial Radio Access (E-UTRA)Physical channels and modulationRelease 17TS

The physical control format indicator channel carries information about the number of OFDM symbols used for transmission of PDCCHs in a subframe. The set of OFDM symbols possible to use for PDCCH in a subframe is given by Table 6.7-1.

Table 6.7-1: Number of OFDM symbols used for PDCCH

Subframe	Number of OFDM symbols for PDCCH when	Number of OFDM symbols for PDCCH when
Subframe 1 and 6 for frame structure type 2 or a subframe for frame structure type 3 with the same duration as the DwPTS duration of a special subframe configuration	1, 2	2
MBSFN subframes with and configured with 1 or 2 cell-specific antenna ports	1, 2	2
MBSFN subframes with and configured with 4 cell-specific antenna ports	2	2
MBSFN subframes with kHz or MBSFN slots with kHz	0	0
Non-MBSFN subframes (except subframe 6 for frame structure type 2) configured with positioning reference signals	1, 2, 3	2, 3
All other cases	1, 2, 3	2, 3, 4

The UE may assume the PCFICH is transmitted when the number of OFDM symbols for PDCCH is greater than zero unless stated otherwise in [4, clause 12].

6.7.1 Scrambling

The block of bits transmitted in one subframe shall be scrambled with a cell-specific sequence prior to modulation, resulting in a block of scrambled bitsaccording to

where the scrambling sequence is given by clause 7.2. The scrambling sequence generator shall be initialised with at the start of each subframe.

6.7.2 Modulation

The block of scrambled bits shall be modulated as described in clause 7.1, resulting in a block of complex-valued modulation symbols. Table 6.7.2-1 specifies the modulation mappings applicable for the physical control format indicator channel.

Table 6.7.2-1: PCFICH modulation schemes

Physical channel	Modulation schemes
PCFICH	QPSK

6.7.3 Layer mapping and precoding

The block of modulation symbols shall be mapped to layers according to one of clauses 6.3.3.1 or 6.3.3.3 with and precoded according to one of clauses 6.3.4.1 or 6.3.4.3, resulting in a block of vectors , , where represents the signal for antenna port and where and the number of antenna ports for cell-specific reference signals . The PCFICH shall be transmitted on the same set of antenna ports as the PBCH.

6.7.4 Mapping to resource elements

The mapping to resource elements is defined in terms of quadruplets of complex-valued symbols. Let denote symbol quadruplet for antenna port. For each of the antenna ports, symbol quadruplets shall be mapped in increasing order of to the four resource-element groups in the first OFDM symbol in a downlink subframe or DwPTS with the representative resource-element as defined in clause 6.2.4 given by

where the additions are modulo ,

and is the physical-layer cell identity as given by clause 6.11.