6.6 Physical broadcast channel
36.2113GPPEvolved Universal Terrestrial Radio Access (E-UTRA)Physical channels and modulationRelease 17TS
The PBCH is not transmitted for frame structure type 3.
6.6.1 Scrambling
The block of bits
, where 
, the number of bits transmitted on the physical broadcast channel, equals 1920 for normal cyclic prefix and 1728 for extended cyclic prefix, shall be scrambled with a cell-specific sequence prior to modulation, resulting in a block of scrambled bits 
according to
where the scrambling sequence 
is given by clause 7.2. The scrambling sequence shall be initialised with 
in each radio frame fulfilling 
. For an MBMS-dedicated cell, the scrambling sequence shall be initialised with 
in each radio frame fulfilling 
.
6.6.2 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 6.6.2-1 specifies the modulation mappings applicable for the physical broadcast channel.
Table 6.6.2-1: PBCH modulation schemes.
|
Physical channel |
Modulation schemes |
|
PBCH |
QPSK |
6.6.3 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 
.
6.6.4 Mapping to resource elements
The block of complex-valued symbols
for each antenna port shall
– for an MBMS-dedicated cell, be transmitted during 4 consecutive radio frames fulfilling 
, starting in each radio frame fulfilling 
, and
– otherwise, be transmitted during 4 consecutive radio frames, starting in each radio frame fulfilling 
.
The block of complex-valued symbols shall be mapped in sequence starting with 
to resource elements 
constituting the core set of PBCH resource elements. The mapping to resource elements 
not reserved for transmission of reference signals shall be in increasing order of first the index
, then the index 
in slot 1 in subframe 0 and finally the radio frame number. The resource-element indices are given by
where resource elements reserved for reference signals shall be excluded. The mapping operation shall assume cell-specific reference signals for antenna ports 0-3 being present irrespective of the actual configuration. The UE shall assume that the resource elements assumed to be reserved for reference signals in the mapping operation above but not used for transmission of reference signal are not available for PDSCH or MPDCCH transmission. The UE shall not make any other assumptions about these resource elements.
For an MBMS-dedicated cell configured with repetition, the physical broadcast channel shall be repeated as described in clause 6.6.4.1.
If a cell is configured with repetition of the physical broadcast channel
– symbols mapped to core resource element 
in slot 1 in subframe 0 within a radio frame 
according to the mapping operation above, and
– cell-specific reference signals in OFDM symbols 
in slot 1 in subframe 0 within a radio frame 
with 
according to the mapping operation above
shall additionally be mapped to resource elements 
in slot number 
within radio frame 
unless resource element 
is used by CSI reference signals.
For frame structure type 1, 
, 
, and 
are given by Table 6.6.4-1.
For frame structure type 2,
– if 
, 
and 
are given by Table 6.6.4-2 and 
;
– if 
, 
and 
are given by Table 6.6.4-2 and 
, except that repetitions with 
and 
are not applied.
For both frame structure type 1 and frame structure type 2, repetition of the physical broadcast channel is not applicable if 
.
Resource elements already reserved or used for transmission of cell-specific reference signals in absence of repetition shall not be used for additional mapping of cell-specific reference signals.
Table 6.6.4-1: Frame offset, slot and symbol number triplets for repetition of PBCH for frame structure type 1.
|
|
Frame offset, slot and symbol number triplets |
|
|
Normal cyclic prefix |
Extended cyclic prefix |
|
|
0 |
(1,18,3), (1,19,0), (1,19,4), (0,0,4) |
(1,18,3), (1,19,0), (1,19,5) |
|
1 |
(1,18,4), (1,19,1). (1,19,5), (0,1,4) |
(1,18,4), (1,19,1). (0,0,3) |
|
2 |
(1,18,5), (1,19,2), (1,19,6), (0,1,5) |
(1,18,5), (1,19,2), (0,1,4) |
|
3 |
(1,18,6), (1,19,3), (0,0,3), (0,1,6) |
(1,19,3), (1,19,4), (0,1,5) |
Table 6.6.4-2: Slot and symbol number pairs for repetition of PBCH for frame structure type 2.
|
|
Slot and symbol number pairs |
|
|
Normal cyclic prefix |
Extended cyclic prefix |
|
|
0 |
(0,3), (1,4), (10,3), (11,0), (11,4) |
(0,3), (10,3), (11,0) |
|
1 |
(0,4), (1,5), (10,4), (11,1), (11,5) |
(0,4), (10,4), (11,1) |
|
2 |
(0,5), (10,5), (11.2) |
(0,5), (10,5), (11.2) |
|
3 |
(0,6), (10,6), (11.3) |
(1,4), (11,3), (11.4) |
6.6.4.1 PBCH repetition in the cell acquisition subframe
For a MBMS-dedicated cell with ,
– symbols mapped to core resource element in slot 1 in subframe 0 within a radio frame according to the mapping operation in clause 6.6.4, and
– cell-specific reference signals in OFDM symbols in slot 1 in subframe 0 within a radio frame with according to the mapping operation in clause 6.6.4
shall additionally be multiplied by and mapped to resource elements in slot number within radio frame where and are given by Table 6.6.4.1-1 in frames fulfilling
– for ;
– for
Resource elements already reserved or used for transmission of cell-specific reference signals in absence of repetition shall not be used for additional mapping of cell-specific reference signals.
The quantity is given by
where the relationship between and is defined in clause 6.6.4, and the pseudo-random sequence is given by clause 7.2 and initialized for each OFDM symbol with
Table 6.6.4.1-1: Slot and symbol number pair for repetition of PBCH.
|
Slot and symbol number pair |
||
|
Normal cyclic prefix |
Extended cyclic prefix |
|
|
0 |
(0, 4) |
– |
|
1 |
(1, 4) |
(0, 3) |
|
2 |
(1, 5) |
(1, 4) |
|
3 |
(0, 3), (1, 6) |
(1, 5) |