6.10.5 CSI reference signals
36.2113GPPEvolved Universal Terrestrial Radio Access (E-UTRA)Physical channels and modulationRelease 17TS
CSI reference signals are transmitted on 1, 2, 4, 8, 12, 16, 20, 24, 28, or 32 antenna ports using 
, 
, 
, 
, 
, 
,
, 
, 
and
, respectively.
For CSI reference signals using more than eight antenna ports, 
CSI-RS configurations in the same subframe, numbered from 0 to 
, where value 0 corresponds to the configured resourceConfig-r11 or resourceConfig-r10 and value k (k>0) corresponds to the configured k-th entry of NZP-ResourceConfig-r13 from an aggregated list consisting of nzp-resourceConfigList-r13 followed by nzp-resourceConfigListExt-r14 (if configured), are aggregated to obtain 
antenna ports in total. Each CSI-RS configuration in such an aggregation corresponds to 
antenna ports and one of the configurations in the range 0-19 in Table 6.10.5.2-1 for normal cyclic prefix, and one of the configurations in the range 0-15 in Table 6.10.5.2-2 for extended cyclic prefix. The supported configurations of aggregated CSI-RS configurations are shown in Table 6.10.5-1. If the higher layer parameter NZP-TransmissionComb is not configured, 
unique CSI-RS configurations from Table 6.10.5.2-1 for normal cyclic prefix and from Table 6.10.5.2-2 for extended cyclic prefix are aggregated to form 12, 16, 20, 24, 28, or 32 antenna ports.
For CSI reference signals using more than sixteen antenna ports, when higher layer parameter NZP-TransmissionComb is configured, the number of unique CSI-RS configurations from Table 6.10.5.2-1 for normal cyclic prefix and from Table 6.10.5.2-2 for extended cyclic prefix that are aggregated to form 20, 24, 28, or 32 antenna ports can be less than or equal to . The number of antenna ports within each such unique CSI-RS resource configuration is an integer multiple of 
.
CSI reference signals are defined for 
only.
Table 6.10.5-1: Aggregation of CSI-RS configurations.
|
Total number of |
Number of antenna ports per CSI-RS configuration |
Number of CSI-RS configurations |
|
12 |
4 |
3 |
|
16 |
8 |
2 |
|
20 |
4 |
5 |
|
24 |
8 |
3 |
|
28 |
4 |
7 |
|
32 |
8 |
4 |
6.10.5.1 Sequence generation
The reference-signal sequence 
is defined by
where 
is the slot number within a radio frame and 
is the OFDM symbol number within the slot. The pseudo-random sequence 
is defined in clause 7.2. The pseudo-random sequence generator shall be initialised with 
at the start of each OFDM symbol where
The quantity 
equals 
unless configured by higher layers.
6.10.5.2 Mapping to resource elements
In subframes configured for CSI reference signal transmission, the reference signal sequence 
shall be mapped to complex-valued modulation symbols 
used as reference symbols on antenna port 
. The mapping depends on the higher-layer parameter CDMType.
For the case of CDMType is not configured or is configured to CDM2:
where
For the case of CDMType equal to CDM4:
where
and where 
is given by Table 6.10.5.2-0.
Table 6.10.5.2-0: The sequence 
for CDM4.
|
|
|
|
|
|
|
|
|
15 |
15,17 |
|
|
16 |
16,18 |
|
|
17 |
19,21 |
|
|
18 |
20,22 |
|
If neither of the higher-layer parameters NZP-FrequencyDensity and NZP-TransmissionComb are configured, 
.
If the UE is configured with one or more of the parameters NZP-FrequencyDensity and NZP-TransmissionComb,
– if either NZP-FrequencyDensity equals 1, 
– if NZP-FrequencyDensity equals 1/2 and NZP-TransmissionComb equals 0, 
– if NZP-FrequencyDensity equals 1/2 and NZP-TransmissionComb equals 1, 
– if NZP-FrequencyDensity equals 1/3 and NZP-TransmissionComb equals 0, 
– if NZP-FrequencyDensity equals 1/3 and NZP-TransmissionComb equals 1, 
– if NZP-FrequencyDensity equals 1/3 and NZP-TransmissionComb equals 2, 
The quantity 
and the necessary conditions on 
are given by Tables 6.10.5.2-1 and 6.10.5.2-2 for normal and extended cyclic prefix, respectively.
The relation between the antenna port number 
and the quantity 
depends on the number of CSI-RS antenna ports:
– for CSI reference signals using up to eight antenna ports, 
– for CSI reference signals using more than eight antenna ports when the higher-layer parameter CDMType equals CDM2
where 
is the CSI-RS resource number.
– for CSI reference signals using more than eight antenna ports when the higher-layer parameter CDMType equals CDM4, antenna port number 
where 
for CSI-RS resource number 
.
For the case of CDMType equal to CDM8 and the number of CSI-RS antenna ports equal to 32:
where
The resource elements for the 
CDM8 pattern, where 
, are determined by aggregating pairs of resource elements 
satisfying 
from the 
aggregated CSI-RS configurations, where at most one pair of resource elements is drawn from each of the 
aggregated CSI-RS configurations. For the case of CDMType equal to CDM8 and the number of CSI-RS antenna ports equal to 32, the aggregated CSI-RS configurations from Table 6.10.5.2-1 for normal cyclic prefix and from Table 6.10.5.2-2 for extended cyclic prefix are restricted to one of 
, 
, or 
. Antenna port number 
where 
for CSI-RS resource number 
. The sequence
is given by Table 6.10.5.2-0A, where 
.
Table 6.10.5.2-0A: The sequence 
for CDM8 with 32 CSI-RS antenna ports.
|
|
|
|
15, 17, 19, 21 |
|
|
16, 18, 20, 22 |
|
|
23, 25, 27, 29 |
|
|
24, 26, 28, 30 |
|
|
31, 33, 35, 37 |
|
|
32, 34, 36, 38 |
|
|
39, 41, 43, 45 |
|
|
40, 42, 44, 46 |
|
For the case of CDMType equal to CDM8 and the number of CSI-RS antenna ports equal to 24:
where
For the case of CDMType equal to CDM8 and the number of CSI-RS antenna ports equal to 24, the aggregated CSI-RS configurations from Table 6.10.5.2-1 for normal cyclic prefix are restricted to 
in that order. Resource elements for CDM8 patterns are determined as follows:
– Aggregating resource element quadruplet 
satisfying 
from CSI-RS configuration 1 with resource element quadruplet 
satisfying 
from CSI-RS configuration 2
– Aggregating resource element quadruplet 
satisfying 
from CSI-RS configuration 3 with resource element quadruplet 
satisfying 
from CSI-RS configuration 1
– Aggregating resource element quadruplet 
satisfying 
from CSI-RS configuration 2 with resource element quadruplet 
satisfying 
from CSI-RS configuration 3
Antenna port number 
where 
for CSI-RS resource number 
. The sequence
is given by Table 6.10.5.2-0B. The sequence index 
is determined as follows:
– For resource element quadruplet 
satisfying 
from CSI-RS configuration 1, resource element quadruplet 
satisfying 
from CSI-RS configuration 2, or resource element quadruplet 
satisfying 
from CSI-RS configuration 3, 
.
– For resource element quadruplet 
satisfying 
from CSI-RS configuration 1, resource element quadruplet 
satisfying 
from CSI-RS configuration 2, or resource element quadruplet 
satisfying 
from CSI-RS configuration 3, 
.
Table 6.10.5.2-0B: The sequence 
for CDM8 with 24 CSI-RS antenna ports.
|
|
|
|
15, 25, 31 |
|
|
16, 26, 32 |
|
|
19, 29, 35 |
|
|
20, 30, 36 |
|
|
17, 23, 33 |
|
|
18, 24, 34 |
|
|
21, 27, 37 |
|
|
22, 28, 38 |
|
Multiple CSI reference signal configurations can be used in a given cell. A UE can be configured with multiple sets of CSI reference signals,
– one or more configurations for CSI reporting for which the UE shall assume non-zero transmission power for the CSI-RS, and
– zero or more configurations for which the UE shall assume zero transmission power, and
– zero or more configurations valid across the system downlink bandwidth as part of the discovery signals for which the UE shall assume non-zero transmission power for the CSI-RS.
The CSI-RS configurations for which the UE shall assume non-zero transmission power are provided by higher layers.
The CSI-RS configurations for which the UE shall assume zero transmission power in a subframe are given by a bitmap derived according to clause 7.2.7 in TS 36.213 [4]. For each bit set to one in the 16-bit bitmap, the UE shall assume zero transmission power for the resource elements corresponding to the four CSI reference signal column in Tables 6.10.5.2-1 and 6.10.5.2-2 for normal and extended cyclic prefix, respectively, except for resource elements that overlap with those for which the UE shall assume non-zero transmission power CSI-RS as configured by higher layers. The most significant bit corresponds to the lowest CSI reference signal configuration index and subsequent bits in the bitmap correspond to configurations with indices in increasing order.
CSI reference signals not corresponding to higher layer configured parameters csi-RS-ConfigNZP-ApList or csi-RS-ConfigZP-ApList can only occur in
– downlink slots where 
fulfils the condition in Tables 6.10.5.2-1 and 6.10.5.2-2 for normal and extended cyclic prefix, respectively, and
– where the subframe number fulfils the conditions in clause 6.10.5.3.
CSI reference signals corresponding to either higher layer configured parameter csi-RS-ConfigNZP-ApList or csi-RS-ConfigZP-ApList can only occur in
– downlink slots where 
fulfils the condition in Tables 6.10.5.2-1 and 6.10.5.2-2 for normal and extended cyclic prefix, respectively.
The UE shall assume that CSI reference signals are not transmitted
– in the DwPTS for special subframe configuration 0, 5, 9 and 10 for normal cyclic prefix and special subframe configuration 0, 4 and 7 for extended cyclic prefix, in case of frame structure type 2,
– in the DwPTS for normal CP for the case of CDMType equal to CDM8 and the number of CSI-RS antenna ports equal to 24,
– in subframes where PDSCH/EPDCCH transmission starts in the second slot of a subframe for frame structure type 3,
– in subframes where PDSCH/EPDCCH transmission ends prior to the end of a subframe for frame structure type 3,
– in an empty subframe where there is no PDSCH or discovery signal transmission for frame structure type 3,
– in subframes where transmission of a CSI-RS would collide with SystemInformationBlockType1 messages,
– in the primary cell in subframes configured for transmission of paging messages in the primary cell for any UE with the cell-specific paging configuration.
For special subframe configuration {1, 2, 6, or 7}, a UE does not expect to be configured with one of CSI-RS configurations {1, 2, 3, 4, 6, 7, 8, 9, 12, 13, 14, 15, 16, 17} in DwPTS for normal CP.
The UE shall assume that none of the CSI reference signals corresponding to a CSI reference signal configuration are transmitted in subframes where transmission of any of those CSI reference signals would collide with transmission of synchronization signals or the core part of PBCH.
Resource elements 
used for transmission of CSI reference signals on any of the antenna ports in the set 
, where 
, 
, 
, 
, 
, 
, 
, 
, 
, 
, 
, 
, 
, 
, 
, 
or 
shall not be used for transmission of PDSCH on any antenna port in the same slot if higher layer parameter CDMType is not configured, or is configured to CDM2.
Resource elements 
used for transmission of CSI reference signals on any of the antenna ports in the set 
, where
– 
, 
or 
for CSI reference signals on 12 ports, or
– 
, 
, 
or 
for CSI reference signals on 16 ports, or
– 
, 
, 
, 
or
for CSI reference signals on 20 ports, or
– 
, 
, 
, 
, 
or 
for CSI reference signals on 24 ports, or
– 
, 
, 
, 
,
, 
or 
for CSI reference signals on 28 ports, or
– 
, 
, 
, 
, 
, 
, 
or 
for CSI reference signals on 32 ports
shall not be used for transmission of PDSCH on any antenna port in the same slot if higher layer parameter CDMType is configured to CDM4.
Resource elements 
used for transmission of CSI reference signals on any of the antenna ports in the set 
, where
– 
, 
or 
for CSI reference signals on 24 ports, or
– 
, 
, 
or 
for CSI reference signals on 32 ports
shall not be used for transmission of PDSCH on any antenna port in the same slot if higher layer parameter CDMType is configured to CDM8.
The mapping for CSI reference signal configuration 0 is illustrated in Figures 6.10.5.2-1 and 6.10.5.2-2.
Table 6.10.5.2-1: Mapping from CSI reference signal configuration to 
for normal cyclic prefix
|
CSI-RS |
Number of CSI reference signals configured |
|||||||||||
|
1 or 2 |
4 |
8 |
||||||||||
|
Normal subframe |
Special subframe |
Normal subframe |
Special subframe |
Normal subframe |
Special subframe |
|||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
0 |
(9,5) |
0 |
(9,5) |
0 |
(9,5) |
0 |
(9,5) |
0 |
(9,5) |
0 |
(9,5) |
0 |
|
1 |
(11,2) |
1 |
(11,5) |
0 |
(11,2) |
1 |
(11,5) |
0 |
(11,2) |
1 |
(11,5) |
0 |
|
2 |
(9,2) |
1 |
(9,2) |
1 |
(9,2) |
1 |
(9,2) |
1 |
(9,2) |
1 |
(9,2) |
1 |
|
3 |
(7,2) |
1 |
(7,5) |
0 |
(7,2) |
1 |
(7,5) |
0 |
(7,2) |
1 |
(7,5) |
0 |
|
4 |
(9,5) |
1 |
(9,5) |
1 |
(9,5) |
1 |
||||||
|
5 |
(8,5) |
0 |
(8,5) |
0 |
(8,5) |
0 |
(8,5) |
0 |
||||
|
6 |
(10,2) |
1 |
(10,5) |
0 |
(10,2) |
1 |
(10,5) |
0 |
||||
|
7 |
(8,2) |
1 |
(8,2) |
1 |
(8,2) |
1 |
(8,2) |
1 |
||||
|
8 |
(6,2) |
1 |
(6,5) |
0 |
(6,2) |
1 |
(6,5) |
0 |
||||
|
9 |
(8,5) |
1 |
(8,5) |
1 |
||||||||
|
10 |
(3,5) |
0 |
(3,5) |
0 |
||||||||
|
11 |
(2,5) |
0 |
(2,5) |
0 |
||||||||
|
12 |
(5,2) |
1 |
(5,5) |
0 |
||||||||
|
13 |
(4,2) |
1 |
(4,5) |
0 |
||||||||
|
14 |
(3,2) |
1 |
(3,2) |
1 |
||||||||
|
15 |
(2,2) |
1 |
(2,2) |
1 |
||||||||
|
16 |
(1,2) |
1 |
(1,5) |
0 |
||||||||
|
17 |
(0,2) |
1 |
(0,5) |
0 |
||||||||
|
18 |
(3,5) |
1 |
||||||||||
|
19 |
(2,5) |
1 |
||||||||||
|
20 |
(11,1) |
1 |
(11,1) |
1 |
(11,1) |
1 |
||||||
|
21 |
(9,1) |
1 |
(9,1) |
1 |
(9,1) |
1 |
||||||
|
22 |
(7,1) |
1 |
(7,1) |
1 |
(7,1) |
1 |
||||||
|
23 |
(10,1) |
1 |
(10,1) |
1 |
||||||||
|
24 |
(8,1) |
1 |
(8,1) |
1 |
||||||||
|
25 |
(6,1) |
1 |
(6,1) |
1 |
||||||||
|
26 |
(5,1) |
1 |
||||||||||
|
27 |
(4,1) |
1 |
||||||||||
|
28 |
(3,1) |
1 |
||||||||||
|
29 |
(2,1) |
1 |
||||||||||
|
30 |
(1,1) |
1 |
||||||||||
|
31 |
(0,1) |
1 |
||||||||||
Note: 
. Configurations 0 – 19 for normal subframes are available for frame structure types 1, 2 and 3. Configurations 20 – 31 and configurations for special subframes are available for frame structure type 2 only.
Table 6.10.5.2-2: Mapping from CSI reference signal configuration to 
for extended cyclic prefix.
|
CSI-RS |
Number of CSI reference signals configured |
|||||||||||
|
1 or 2 |
4 |
8 |
||||||||||
|
Normal subframe |
Special subframe |
Normal subframe |
Special subframe |
Normal Subframe |
Special subframe |
|||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
0 |
(11,4) |
0 |
(11,4) |
0 |
(11,4) |
0 |
(11,4) |
0 |
(11,4) |
0 |
(11,4) |
0 |
|
1 |
(9,4) |
0 |
(9,4) |
0 |
(9,4) |
0 |
(9,4) |
0 |
(9,4) |
0 |
(9,4) |
0 |
|
2 |
(10,4) |
1 |
(10,4) |
1 |
(10,4) |
1 |
||||||
|
3 |
(9,4) |
1 |
(9,4) |
1 |
(9,4) |
1 |
||||||
|
4 |
(5,4) |
0 |
(5,4) |
0 |
(5,4) |
0 |
(5,4) |
0 |
||||
|
5 |
(3,4) |
0 |
(3,4) |
0 |
(3,4) |
0 |
(3,4) |
0 |
||||
|
6 |
(4,4) |
1 |
(4,4) |
1 |
||||||||
|
7 |
(3,4) |
1 |
(3,4) |
1 |
||||||||
|
8 |
(8,4) |
0 |
(8,4) |
0 |
||||||||
|
9 |
(6,4) |
0 |
(6,4) |
0 |
||||||||
|
10 |
(2,4) |
0 |
(2,4) |
0 |
||||||||
|
11 |
(0,4) |
0 |
(0,4) |
0 |
||||||||
|
12 |
(7,4) |
1 |
||||||||||
|
13 |
(6,4) |
1 |
||||||||||
|
14 |
(1,4) |
1 |
||||||||||
|
15 |
(0,4) |
1 |
||||||||||
|
16 |
(11,1) |
1 |
(11,1) |
1 |
(11,1) |
1 |
(11,1) |
1 |
(11,1) |
1 |
(11,1) |
1 |
|
17 |
(10,1) |
1 |
(10,1) |
1 |
(10,1) |
1 |
(10,1) |
1 |
(10,1) |
1 |
(10,1) |
1 |
|
18 |
(9,1) |
1 |
(9,1) |
1 |
(9,1) |
1 |
(9,1) |
1 |
(9,1) |
1 |
(9,1) |
1 |
|
19 |
(5,1) |
1 |
(5,1) |
1 |
(5,1) |
1 |
(5,1) |
1 |
||||
|
20 |
(4,1) |
1 |
(4,1) |
1 |
(4,1) |
1 |
(4,1) |
1 |
||||
|
21 |
(3,1) |
1 |
(3,1) |
1 |
(3,1) |
1 |
(3,1) |
1 |
||||
|
22 |
(8,1) |
1 |
(8,1) |
1 |
||||||||
|
23 |
(7,1) |
1 |
(7,1) |
1 |
||||||||
|
24 |
(6,1) |
1 |
(6,1) |
1 |
||||||||
|
25 |
(2,1) |
1 |
(2,1) |
1 |
||||||||
|
26 |
(1,1) |
1 |
(1,1) |
1 |
||||||||
|
27 |
(0,1) |
1 |
(0,1) |
1 |
||||||||
Note: 
. Configurations 0 – 15 for normal subframes are available for both frame structure type 1 and type 2. Configurations 16 – 27 and configurations for special subframes are available for frame structure type 2 only.
Figure 6.10.5.2-1: Mapping of CSI reference signals (CSI configuration 0, normal cyclic prefix)
Figure 6.10.5.2-2: Mapping of CSI reference signals (CSI configuration 0, extended cyclic prefix)
6.10.5.3 CSI reference signal subframe configuration
The subframe configuration period 
and the subframe offset 
for the occurence of CSI reference signals are listed in Table 6.10.5.3-1. The parameter 
can be configured separately for CSI reference signals for which the UE shall assume non-zero and zero transmission power. Subframes containing CSI reference signals that do not correspond to either higher layer configured parameter csi-RS-ConfigNZP-ApList or csi-RS-ConfigZP-ApList shall satisfy 
.
Table 6.10.5.3-1: CSI reference signal subframe configuration
|
CSI-RS-SubframeConfig |
CSI-RS periodicity (subframes) |
CSI-RS subframe offset (subframes) |
|
0 – 4 |
5 |
|
|
5 – 14 |
10 |
|
|
15 – 34 |
20 |
|
|
35 – 74 |
40 |
|
|
75 – 154 |
80 |
|
