Method and apparatus to enable CSI reporting in wireless communication systems
A method for operating a user equipment (UE) comprises, in response to a condition being satisfied, selecting, from a full basis set, a basis subset comprising M l bases for each layer l of a plurality of v layers; in response to the condition not being satisfied, selecting, from the full basis set, an intermediate basis set comprising N′ bases that are common among the plurality of v layers, and selecting, from the selected intermediate basis set, the basis subset comprising M l bases for each layer l of the plurality of v layers; transmitting, to a base station (BS), for each layer l of the plurality of v layers, an indicator i 1,6,l indicating indices of the M l bases included in the selected basis subset; and based on the condition not being satisfied, transmitting, to the BS, an indicator i 1,5 indicating indices of the N′ bases included in the selected intermediate basis set.
1. A user equipment (UE), the UE comprising:
a processor configured to:
in response to a condition being satisfied, select, from a full basis set, a basis subset comprising M l bases for each layer l of a plurality of v layers; and
in response to the condition not being satisfied, select, from the full basis set, an intermediate basis set (IntS) comprising N′ bases that are common among the plurality of v layers, and select, from the selected intermediate basis set, the basis subset comprising M l bases for each layer l of the plurality of v layers; and
a transceiver operably connected to the processor, the transceiver configured to:
transmit, to a base station (BS), for each layer l of the plurality of v layers, an indicator i 1,6,l indicating indices of the M l bases included in the selected basis subset; and
based on the condition not being satisfied, transmit, to the BS, an indicator i 1,5 indicating indices of the N′ bases included in the selected intermediate basis set (IntS);
wherein the full basis set comprises N 3 bases, and
wherein N 3 , N′, and M l are positive integers; M l <N 3 when the condition is satisfied and M l <N′<N 3 when the condition is not satisfied; l∈{1, . . . , v}; and v≥1 is a rank value.
2. The UE of claim 1 , wherein the processor is configured to determine that:
when a value of N 3 is less than or equal to nineteen (N 3 ≤19), the condition is satisfied; and
when the value of N 3 is greater than nineteen (N 3 >19), the condition is not satisfied.
3. The UE of claim 2 , wherein one of the indices of the M l bases included in the selected basis subset is fixed to zero for each layer l of the plurality of v layers.
4. The UE of claim 3 , wherein the indicator i 1,6,l indicates the indices of the remaining M l −1 bases included in the selected basis subset for each layer l of the plurality of v layers, wherein a payload of the indicator i 1,6,l is
⌈
log
2
(
N
3
-
1
M
l
-
1
)
⌉
bits
when the condition is satisfied and
⌈
log
2
(
N
′
-
1
M
l
-
1
)
⌉
bits
when the condition is not satisfied, and ┌ ┐ is a ceiling function.
5. The UE of claim 3 , wherein when the condition is not satisfied, the indicator i 1,5 indicates an initial basis index (M initial ) of the intermediate basis set (IntS), which is determined as
IntS={( M initial +i )mod N 3 , i= 0,1, . . . , N′− 1},
where mod is a modulo function.
6. The UE of claim 1 , wherein:
the processor is further configured to determine a channel state information (CSI) report; and
the transceiver is further configured to transmit the CSI report to the BS,
wherein the CSI report includes a pre-coding matrix indicator (PMI), the PMI including the indicator i 1,6,l for each layer l of the plurality of v layers, and based on the condition not being satisfied, the indicator i 1,5 .
7. The UE of claim 1 , wherein the full basis set comprises a set of discrete Fourier transform (DFT) vectors:
w
n
=
[
1
e
j
2
π
n
N
3
e
2
j
2
π
n
N
3
…
e
(
N
3
-
1
)
j
2
π
n
N
3
]
,
where n=0, 1, . . . , N 3 −1.
8. The UE of claim 1 , wherein the processor is configured to determine a value of N′ such that N′=2M l .
9. A base station (BS), the BS comprising:
a transceiver configured to receive, from a user equipment (UE), (i) for each layer l of a plurality of v layers, an indicator i 1,6,l indicating indices of M l bases included in a basis subset and (ii) based on a condition not being satisfied, an indicator i 1,5 indicating indices of N′ bases included in an intermediate basis set (IntS); and
a processor operably connected to the transceiver, the processor configured to:
when the condition is satisfied, use the indicator i 1,6,l to determine, from a full basis set, M l bases included in the basis subset for each layer l of the plurality of v layers; and
when the condition is not satisfied, use the indicator i 1,5 to determine, from the full basis set, N′ bases included in the intermediate basis set (IntS) that are common among the plurality of v layers, and use the received indicator i 1,6,l to determine, from the intermediate basis set, M l bases included in the basis subset for each layer l of the plurality of v layers,
wherein the full basis set comprises N 3 bases, and
wherein N 3 , N′, and M l are positive integers; M l ≤N 3 when the condition is satisfied and M l <N′<N 3 when the condition is not satisfied; l∈{1, . . . , v}; and v≥1 is a rank value.
10. The BS of claim 9 , wherein:
when a value of N 3 is less than or equal to nineteen (N 3 ≤19), the condition is satisfied; and
when the value of N 3 is greater than nineteen (N 3 >19), the condition is not satisfied.
11. The BS of claim 10 , wherein one of the indices of the M l bases included in the basis subset is fixed to zero for each layer l of the plurality of v layers.
12. The BS of claim 11 , wherein the indicator i 1,6,l indicates the indices of the remaining M l −1 bases included in the basis subset for each layer l of the plurality of v layers, wherein a payload of the indicator i 1,6,l is
⌈
log
2
(
N
3
-
1
M
l
-
1
)
⌉
bits
when the condition is satisfied and
⌈
log
2
(
N
′
-
1
M
l
-
1
)
⌉
bits
when the condition is not satisfied, and ┌ ┐ is a ceiling function.
13. The BS of claim 11 , wherein when the condition is not satisfied, the indicator i 1,5 indicates an initial basis index (M initial ) of the intermediate basis set (IntS), which is determined as
IntS={( M initial +i )mod N 3 ,i= 0,1, . . . , N′− 1},
where mod is a modulo function.
14. The BS of claim 9 , wherein:
the transceiver is further configured to receive a channel state information (CSI) report from the UE; and
the CSI report includes a pre-coding matrix indicator (PMI), the PMI including the indicator i 1,6,l for each layer l of the plurality of v layers, and based on the condition not being satisfied, the indicator i 1,5 .
15. The BS of claim 9 , wherein the full basis set comprises a set of discrete Fourier transform (DFT) vectors:
w
n
=
[
1
e
j
2
π
n
N
3
e
2
j
2
π
n
N
3
…
e
(
N
3
-
1
)
j
2
π
n
N
3
]
,
where n=0, 1, . . . , N 3 −1.
16. The BS of claim 9 , wherein a value of N′ is such that N′=2M l .
17. A method for operating a user equipment (UE), the method comprising:
in response to a condition being satisfied, selecting, from a full basis set, a basis subset comprising M l bases for each layer l of a plurality of v layers;
in response to the condition not being satisfied, selecting, from the full basis set, an intermediate basis set (IntS) comprising N′ bases that are common among the plurality of v layers, and selecting, from the selected intermediate basis set, the basis subset comprising M l bases for each layer l of the plurality of v layers;
transmitting, to a base station (BS), for each layer l of the plurality of v layers, an indicator i 1,6,l indicating indices of the M l bases included in the selected basis subset; and
based on the condition not being satisfied, transmitting, to the BS, an indicator i 1,5 indicating indices of the N′ bases included in the selected intermediate basis set (IntS);
wherein the full basis set comprises N 3 bases, and
wherein N 3 , N′, and M l are positive integers; M l <N 3 when the condition is satisfied and M l <N′<N 3 when the condition is not satisfied; l∈{1, . . . , v}; and v≥1 is a rank value.
18. The method of claim 17 , wherein:
when a value of N 3 is less than or equal to nineteen (N 3 ≤19), the condition is satisfied; and
when the value of N 3 is greater than nineteen (N 3 >19), the condition is not satisfied.
19. The method of claim 18 , wherein:
one of the indices of the M l bases included in the selected basis subset is fixed to zero for each layer l of the plurality of v layers;
the indicator i 1,6,l indicates the indices of the remaining M l −1 bases included in the selected basis subset for each layer l of the plurality of v layers, wherein a payload of the indicator i 1,6,l is
⌈
log
2
(
N
3
-
1
M
l
-
1
)
⌉
bits
when the condition is satisfied and
⌈
log
2
(
N
′
-
1
M
l
-
1
)
⌉
bits
when the condition is not satisfied, and ┌ ┐ is a ceiling function; and
when the condition is not satisfied, the indicator i 1,5 indicates an initial basis index (M initial ) of the intermediate basis set (IntS), which is determined as
IntS={( M initial +i )mod N 3 ,i= 0,1, . . . , N′− 1},
where mod is a modulo function.
20. The method of claim 17 , wherein:
the full basis set is a set of discrete Fourier transform (DFT) vectors:
w
n
=
[
1
e
j
2
π
n
N
3
e
2
j
2
π
n
N
3
…
e
(
N
3
-
1
)
j
2
π
n
N
3
]
,
where n=0, 1, . . . , N 3 −1; and
a value of N′ is such that N′=2M l .