Enhancement of download multi-user multiple-input multiple-output wireless communications

• US 8,761,129 B2
• Filed: 04/26/2012
• Issued: 06/24/2014
• Est. Priority Date: 04/29/2011
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Laboratories America Inc (NEC Corporation)
• Inventors: Prasad, Narayan, Yue, Guosen, Jiang, Meilong, Khojastepour, Mohammad A., Rangarajan, Sampath
• Primary Examiner(s): Duong, Frank
• Application Number:
  US13/456,845
• Publication Number:
  US 20120275313A1
• Time in Patent Office: 789 Days
• Field of Search: 370208-210, 370328-339, 370/365
• US Class Current: 370/335
• CPC Class Codes: H04B 7/0417 Feedback systems
• CPC Class Codes: H04B 7/0452 Multi-user MIMO systems
• CPC Class Codes: H04B 7/0469 taking special antenna structures, e.g. cross polarized antennas into account
• CPC Class Codes: H04B 7/0486 taking channel rank into account
• CPC Class Codes: H04B 7/0626 Channel coefficients, e.g. channel state information [CSI]
• CPC Class Codes: H04B 7/063 Parameters other than those covered in groups H04B7/0623 - H04B7/0634, e.g. channel matrix rank or transmit mode selection
• CPC Class Codes: H04B 7/065 Variable contents, e.g. long-term or short-short
• CPC Class Codes: H04W 24/10 Scheduling measurement reports ; Arrangements for measurement reports

Abstract

A method implemented in a user equipment configured to be used in a multi-user (MU) multiple-input multiple-output (MIMO) wireless communications system is disclosed. In an aspect, the user equipment transmits to a base station a first channel state information (CSI) report determined according to a single-user (SU) MIMO rule and a second CSI report based on a residual error.

Claims

1. A method implemented in a user equipment configured to be used in a multi-user (MU) multiple-input multiple-output (MIMO) wireless communications system, the method comprising:

transmitting to a base station a first channel state information (CSI) report determined according to a single-user (SU) MIMO rule; and

transmitting to the base station a second CSI report based on a residual error,

wherein the second CSI report includes an indication or a quantized value of a dominant diagonal value of R₁ along with a corresponding column in Q₁ where Q₁ is a semi-unitary matrix whose columns lie in the orthogonal complement of {circumflex over (V)}₁, {circumflex over (V)}₁ being a semi-unitary matrix whose columns represent preferred channel directions, and R₁ is a matrix which satisfies the Frobenius-norm constraint ∥

R₁∥

_F²≦

ε

₁², ε

₁ being the residual error norm.

2. The method of claim 1, wherein the first CSI report is transmitted in a first interval configured for SU CSI reporting and the second CSI report is transmitted in a second interval configured for the second CSI report.

3. The method of claim 1, wherein the first CSI report and the second CSI report are transmitted in a common interval configured for CSI reporting.

4. The method of claim 1, wherein the first CSI report is transmitted in a first interval configured for SU CSI reporting and the first CSI report and the second CSI report are transmitted in a second interval configured for combined CSI reporting.

5. The method of claim 1, further comprising:

receiving at least one of sequence configuration information and sub-sequence configuration information from the base station,

wherein the sequence configuration information comprises at least one of first periodicity and first offset for the first CSI report, and

wherein the sub-sequence configuration information comprises at least one of second periodicity and second offset for the second CSI report.

6. The method of claim 1, wherein the first CSI report includes at least one of a preferred rank, a precoder of the preferred rank, and a corresponding quantized SINR (signal to interference plus noise ratio).

7. The method of claim 1, further comprising:

assuming a post scheduling model.

8. The method of claim 7, wherein the post scheduling model can be expressed as

y₁={circumflex over (D)}₁^1/2{circumflex over (V)}₁^†

U₁s₁+{circumflex over (D)}₁^1/2({circumflex over (V)}₁^†

+R₁^†

Q₁^†

)U₁s₁+η

₁

where y₁ represents an N×

1 received signal vector on a representative resource element in a resource block (RB), N being the number of receive antennas at the user equipment, {circumflex over (D)}₁^1/2 is a diagonal matrix of effective channel gains, {circumflex over (V)}₁ denotes a semi-unitary matrix whose columns represent preferred channel directions and {circumflex over (V)}₁^†

represents Hermitian of {circumflex over (V)}₁, U₁ and U₁represent precoding matrices used by the base station to transmit data to the user equipment and a co-scheduled user equipment, respectively, s₁ and s₁represent transmit symbol vectors intended for the user equipment and the co-scheduled user equipment, respectively, Q₁ is a semi-unitary matrix whose columns lie in the orthogonal complement of {circumflex over (V)}₁, and R₁ is a matrix which satisfies the Frobenius-norm constraint ∥

R₁∥

_F²≦

ε

₁², ε

₁ being the residual error, and η

₁ represents an additive noise vector.

9. The method of claim 8, wherein Q₁^†

{circumflex over (V)}₁=0.

10. The method of claim 1, further comprising:

receiving residual error form configuration information from the base station.

11. The method of claim 1, wherein the second CSI report comprises an enhancement to the first CSI report.

12. The method of claim 1, wherein the second CSI report includes an indication of residual error norm.

13. The method of claim 12, wherein the residual error norm can be expressed as

ε

₁=√

{square root over (tr(F₁H₁^†

P₁H₁F₁^†

{tilde over (D)}₁<sup>−

1</sup>))}

where tr(.) denotes a trace operation, F₁H₁^†

denotes a filtered user channel, and P₁=(I−

{circumflex over (V)}₁{circumflex over (V)}₁^†

) is a projection matrix, {circumflex over (V)}₁ being a precoding matrix of rank r₁, and {tilde over (D)}₁=diag{SI{circumflex over (N)}R₁¹, . . . , SI{circumflex over (N)}R₁^r1}, {SI{circumflex over (N)}R₁ⁱ}_i=1^r1 being r₁ quantized signal to interference plus noise ratios (SINRs).

14. The method of claim 1, wherein the second CSI report includes an indication or an approximation of at least one of a residual error matrix and a residual error correlation matrix.

15. The method of claim 1, wherein the second CSI report includes an indication or a quantized value of at least one of a diagonal value of C₁ and a trace of C₁, where

C₁=F₁H₁^†

P₁H₁F₁^†

{tilde over (D)}₁<sup>−

1</sup>,

F₁H₁^†

denotes a filtered user channel, and P₁=(I−

{circumflex over (V)}₁{circumflex over (V)}₁^†

) is a projection matrix, {circumflex over (V)}₁ being a precoding matrix of rank r₁, and {tilde over (D)}₁=diag{SI{circumflex over (N)}R₁¹, . . . , SI{circumflex over (N)}R₁^r1}, {SI{circumflex over (N)}R₁ⁱ}_i=1^r1 being r₁ quantized signal to interference plus noise ratios (SINRs).

16. A multi-user (MU) multiple-input multiple-output (MIMO) wireless communications system, comprising:

a base station; and

a user equipment,

wherein the user equipment transmits to the base station a first channel state information (CSI) report determined according to a single-user (SU) MIMO rule, and a second CSI report based on a residual error,

wherein the second CSI report includes an indication or a quantized value of a dominant diagonal value of R₁ along with a corresponding column in Q₁ where Q₁ is a semi-unitary matrix whose columns lie in the orthogonal complement of {circumflex over (V)}₁, {circumflex over (V)}₁ being a semi-unitary matrix whose columns represent preferred channel directions, and R₁ is a matrix which satisfies the Frobenius-norm constraint ∥

R₁∥

_F²≦

ε

₁², ε

₁ being the residual error norm.

17. A method implemented in a base station configured to be used in a multi-user (MU) multiple-input multiple-output (MIMO) wireless communications system, the method comprising:

receiving from a user equipment a first channel state information (CSI) report determined according to a single-user (SU) MIMO rule; and

receiving from the user equipment a second CSI report based on a residual error,

wherein the second CSI report includes an indication or a quantized value of a dominant diagonal value of R₁ along with a corresponding column in Q₁ where Q₁ is a semi-unitary matrix whose columns lie in the orthogonal complement of {circumflex over (V)}₁, {circumflex over (V)}₁ being a semi-unitary matrix whose columns represent preferred channel directions, and R₁ is a matrix which satisfies the Frobenius-norm constraint ∥

R₁∥

_F²≦

ε

₁², ε

₁ being the residual error norm.