Optimized signaling of demodulation reference signal patterns
Orthogonality in cyclic shift (CS) and orthogonal cover code (OCC) selection for DMRS in MIMO is improved by new n DMRS to n DMRS (2) mapping patterns. Values in the mapping tables are arranged in sets, with minimum CS separation between the values in each set. Additionally, the semi-static n DMRS is independently configurable for each UL component carrier (CC) in the case of cross-CC scheduling in carrier aggregation, and the PHICH allocation formula that defines the allocation of the PHICH process relative to the k th codeword (CW) on the c th UL CC is a function of both the CS index n DMRS,k,c (2) that is dynamically assigned to a certain layer of the considered CW and the semi-static CS offset n DMRS,c (1) for the c th CC.
1. A method of determining cyclic shift (CS) and orthogonal cover code (OCC) values associated with DeModulation Reference Signals (DMRS), for a plurality of transmission layers, by a device in a wireless communication system employing Multiple Input Multiple Output (MIMO) operation, comprising:
receiving a semi-static cyclic shift (CS) value n DMRS (1) ;
receiving a dynamic CS index value n DMRS ;
indexing a predetermined table with n DMRS to obtain a first CS value n DMRS (2) and an orthogonal cover code (OCC) value n DMRS OCC associated with DMRS for layer 0;
deriving a first CS value associated with DeModulation Reference Signals (DMRS) for each other layer by adding a different integer multiple of a predetermined minimum offset to n DMRS (2) ; and
calculating a second CS value for each layer by adding n DMRS (1) to the first CS value;
wherein within the predetermined table, the CS values n DMRS (2) are arranged in two or more sets of CS values n DMRS (2) , the CS values n DMRS (2) within each set being separated by the predetermined minimum offset.
2. The method of claim 1 wherein the dynamic CS value n DMRS comprises three bits.
3. The method of claim 1 further comprising deriving an OCC value associated with DMRS for other layers by adding a predetermined OCC offset to the OCC value n DMRS OCC associated with DMRS for layer 0.
4. The method of claim 3 further comprising encoding DMRS for all layers using the second CS value for each layer and the final OCC value for each layer.
5. The method of claim 1 wherein the predetermined minimum offset is three.
6. The method of claim 1 wherein receiving a dynamic CS value n DMRS comprises receiving n DMRS in a Downlink Control Information (DCI) format.
7. The method of claim 1 wherein receiving from a transmitter a semi-static CS value n DMRS (1) comprises receiving n DMRS (1) via higher layer signaling.
8. The method of claim 1 wherein the predetermined table comprises:
n DMRS
n DMRS (2)
n DMRS OCC
000
0
[+1 +1]
001
6
[+1 +1]
010
3
[+1 −1]
011
4
[+1 +1]
100
1
[+1 +1]
101
7
[+1 −1]
110
10
[+1 −1]
111
9
[+1 −1].
9. The method of claim 1 wherein the predetermined table comprises:
n DMRS
n DMRS (2)
n DMRS OCC
000
0
[+1 +1]
001
6
[+1 +1]
010
3
[+1 −1]
011
5
[+1 +1]
100
2
[+1 +1]
101
8
[+1 −1]
110
11
[+1 −1]
111
9
[+1 −1].
10. The method of claim 1 wherein the predetermined table comprises:
n DMRS
n DMRS (2)
n DMRS OCC
000
1
[+1 +1]
001
7
[+1 +1]
010
4
[+1 −1]
011
5
[+1 +1]
100
2
[+1 +1]
101
8
[+1 −1]
110
11
[+1 −1]
111
10
[+1 −1].
11. The method of claim 1 wherein the predetermined table comprises twelve mapping entries.
12. The method of claim 11 wherein the predetermined table the CS values n DMRS (2) are arranged in two sets.
13. An apparatus for determining cyclic shift (CS) and orthogonal cover code (OCC) values associated with DeModulation Reference Signals (DMRS) for multiple transmission layers in a wireless communication system employing Multiple Input Multiple Output (MIMO) operation, comprising:
a receiver operable to receive a semi-static cyclic shift (CS) value n DMRS (1) and a dynamic CS index value n DMRS ; and
a controller operable to:
index a predetermined table with n DMRS to obtain a first CS value n DMRS (2) and an orthogonal cover code (OCC) value n DMRS OCC associated with DeModulaton Reference Signals (DMRS) for layer 0;
derive a first CS value associated with DMRS for each other layer by adding a different integer multiple of a predetermined minimum offset to n DMRS (2) ; and
calculate a second CS value for each layer by adding n DMRS (1) to the first CS value;
wherein within the predetermined table, the CS values n DMRS (2) are arranged in two or more sets of CS values n DMRS (2) , the CS values n DMRS (2) within each set being separated by the predetermined minimum offset.