Scheduling information of overlapping co-scheduled users in an OFDMA-MU-MIMO system
View Patent ↗A user equipment (UE) used in a multi-user (MU)-multiple input multiple output (MIMO) orthogonal frequency division multiple access (OFDMA) system is disclosed. The UE includes a receiving unit to receive from a base station an indication of an estimate of or an upper-bound on the total number of MU-MIMO user equipments (|S|) that are scheduled on a sub-band by the base station, wherein the sub-band includes one or more resource units, a calculation unit to calculate channel quality based on the indication of the estimate of or the upper-bound on the total number of MU-MIMO user equipments, and a transmission unit to transmit to the base station an indication of the channel quality. Other methods and apparatuses also are disclosed.
1. A user equipment (UE) used in a multi-user (MU)-multiple input multiple output (MIMO) orthogonal frequency division multiple access (OFDMA) system, the UE comprising:
a receiving unit to receive from a base station an indication of an estimate of or an upper-bound on the total number of MU-MIMO user equipments (|S|) that will be scheduled together on a sub-band by the base station and whose resource block (RB) assignment has a non-zero overlap or intersection in at-least one RB in the sub-band, wherein the sub-band includes one or more resource units;
a calculation unit to calculate channel quality based on the indication of the estimate of or the upper-bound on the total number of MU-MIMO user equipments after receiving the indication of the estimate of or the upper-bound on the total number of MU-MIMO user equipments; and
a transmission unit to transmit to the base station an indication of the channel quality,
wherein the estimate of or the upper-bound on the total number of MU-MIMO user equipments is capable of conveying a different value from the number of transmit antennas at the base station.
2. The UE as in claim 1 ,
wherein the indication of the channel quality comprises a channel quality index (CQI).
3. The UE as in claim 1 ,
wherein the calculation of the channel quality assumes that there are |S| user equipments that will be scheduled together on the subband by the base station.
4. The UE as in claim 1 , further comprising:
a determining unit to determine a signal-to-interference-plus-noise ratio (SINR) based on the estimate of or the upper-bound on the total number of MU-MIMO user equipments that will be scheduled together on the subband,
wherein the calculation of the channel quality is made according to the SINR.
5. The UE as in claim 1 ,
wherein one indication of the channel quality is transmitted per sub-band.
6. The UE as in claim 1 ,
wherein the estimate of or the upper-bound on the total number of MU-MIMO user equipments that will be scheduled together on the subband is equal to the number of transmit antennas at the base station.
7. The UE as in claim 2 , further comprising:
a second determining unit to determine a precoder matrix index (PMI) by calculating ĉ; and
a second transmission unit to transmit the PMI to the base station,
wherein
c
^
is
arg
max
c
∈
C
{
c
†
H
†
(
I
+
ρ
^
HH
†
)
-
1
Hc
}
,
where
ρ
^
is
ρ
(
S
-
1
)
S
(
M
-
1
)
,
ρ is a constant that is proportional to the maximum bound of a sum power constraint, M is the number of transmit antennas at the base station, c is an arbitrary beam forming vector from a codebook (C) of unit-norm vectors, and H is a representative channel matrix for the sub-band.
8. The UE as in claim 4 ,
wherein the SINR is determined by calculating
ρ
~
c
^
†
H
†
(
I
+
ρ
^
HH
†
)
-
1
H
c
^
1
-
ρ
^
c
^
†
H
†
(
I
+
ρ
^
HH
†
)
-
1
H
c
^
,
where
ρ
~
is
ρ
S
and I is the identity matrix.
9. The UE as in claim 4 ,
wherein the indication of the channel quality comprises the SINR.
10. The UE as in claim 4 ,
wherein the calculation of the channel quality employs a lookup table with the SINR.
11. The UE as in claim 8 ,
wherein one PMI for all available sub-bands is transmitted to the base station.
12. The UE as in claim 7 ,
wherein one PMI is transmitted per sub-band.
13. The UE as in claim 11 , wherein the transmission of the PMI comprises:
a second calculation unit to calculate a CQI for each sub-band;
a selection unit to select a beam forming vector from C having a highest CQI of the CQIs calculated for each sub-band;
a re-computing unit to re-compute a CQI for each sub-band other than the sub-band having the highest CQI based on the selected beam forming vector; and
a third transmission unit to transmit the re-computed CQIs and the highest CQI to the base station.
14. A base station used in a multi-user (MU)-multiple input multiple output (MIMO) orthogonal frequency division multiple access (OFDMA) system, the base station comprising:
a transmission unit to transmit to a user equipment (UE) an indication of an estimate of or an upper-bound on the total number of MU-MIMO user equipments (|S|) that will be scheduled together on a sub-band by the base station and whose resource block (RB) assignment has a non-zero overlap or intersection in at-least one RB in the sub-band, wherein the sub-band includes one or more resource units, in order to enable the UE to calculate channel quality based on the indication of the estimate of or the upper-bound on the total number of MU-MIMO user equipments after receiving the indication of the estimate of or the upper-bound on the total number of MU-MIMO user equipments; and
a receiving unit to receive from the UE an indication of channel quality,
wherein the estimate of or the upper-bound on the total number of MU-MIMO user equipments is capable of conveying a different value from the number of transmit antennas at the base station.
15. The base station as in claim 14 ,
wherein the indication of the channel quality comprises a channel quality index (CQI).
16. The base station as in claim 14 ,
wherein the calculation of the channel quality assumes that there are |S| user equipments that will be scheduled together on the subband by the base station.
17. The base station as in claim 14 ,
wherein one indication of the channel quality is transmitted per sub-band.
18. The base station as in claim 14 ,
wherein the estimate of or the upper-bound on the total number of MU-MIMO user equipments that will be scheduled together on the subband is equal to the number of transmit antennas at the base station.
19. A multi-user (MU)-multiple input multiple output (MIMO) orthogonal frequency division multiple access (OFDMA) system comprising:
a user equipment (UE); and
a base station to transmit to the UE an indication of an estimate of or an upper-bound on the total number of MU-MIMO user equipments (|S|) that will be scheduled together on a sub-band by the base station and whose resource block (RB) assignment has a non-zero overlap or intersection in at-least one RB in the sub-band, wherein the sub-band includes one or more resource units,
wherein the UE calculates channel quality based on the indication of the estimate of or the upper-bound on the total number of MU-MIMO user equipments after receiving the indication of the estimate of or the upper-bound on the total number of MU-MIMO user equipments,
wherein the UE transmits to the base station an indication of the channel quality, and
wherein the estimate of or the upper-bound on the total number of MU-MIMO user equipments is capable of conveying a different value from the number of transmit antennas at the base station.
20. The MU-MIMO OFDMA system as in claim 19 ,
wherein the indication of the channel quality comprises a channel quality index (CQI).
21. The MU-MIMO OFDMA system as in claim 19 ,
wherein the calculation of the channel quality assumes that there are |S| user equipments that will be scheduled together on the subband by the MU-MIMO OFDMA system.
22. The MU-MIMO OFDMA system as in claim 19 ,
wherein one indication of the channel quality is transmitted per sub-band.
23. The MU-MIMO OFDMA system as in claim 19 ,
wherein the estimate of or the upper-bound on the total number of MU-MIMO user equipments that will be scheduled together on the subband is equal to the number of transmit antennas at the MU-MIMO OFDMA system.