Two-dimensional UE pairing in MIMO systems

Patent metadata

Field	Value
Publication number	US-9392607-B2
Application number	US-201013884998-A
Country	US
Kind code	B2
Filing date	Nov 15, 2010
Priority date	Nov 15, 2010
Publication date	Jul 12, 2016
Grant date	Jul 12, 2016

Abstract

A method and a radio base station are provided for selecting a first User Equipment (UE) and at least a second UE from a plurality of UEs, for sharing a transmission resource in the time-frequency dimension in a multiple input multiple output (MIMO) transmission. A first and second imperfection of Channel State Information (CSI) made available for the first UE and second UE, respectively is estimated ( 410, 420 ). Spatial correlation between the first UE and the at least second UE is estimated ( 450 ), and the first and at least second UE are selected ( 470 ) to share a transmission resource in the time-frequency dimension, if both of the first and second imperfections are determined above ( 430, 440 ) a first threshold and the spatial correlation is determined below ( 460 ) a second threshold.

First claim

The invention claimed is:

1. A method in a radio base station (RBS) for selecting a first Use Equipment (UE) and at least one second UE from a plurality of UEs for sharing a transmission resource in a time-frequency dimension in a Multiple-Input, Multiple-Output (MIMO) transmission, the RBS comprising transceiver and antenna elements configured for MIMO transmission on one or more channels, the method comprising:
estimating a first imperfection of Channel State Information (CSI) made available for the first UE by:
calculating a first correlation (R 1 ′) between an estimation of a first transmission channel for the first UE and an estimation of a second transmission channel for the first UE; and
estimating the first imperfection of the CSI using the first correlation (R 1 ′);

estimating a second imperfection of CSI made available for the at least one second UE by:
calculating a second correlation (R 1 ″) between an estimation of a third transmission channel for the second UE and an estimation of a fourth transmission channel for the second UE; and
estimating the second imperfection of the CSI using the second correlation (R 1 ″);

estimating a spatial correlation between the first UE and the at least one second UE; and
selecting the first UE and the at least one second UE to use the same transmission resource in the time-frequency dimension if both the first correlation (R 1 ′) and the second correlation (R 1 ″) are above a first threshold and the spatial correlation is below a second threshold scheduling the first UE and the at least one second UE to share the transmission resource in the time and frequency dimensions.

2. The method of claim 1 , further comprising:
assigning the first UE and the at least one second UE different antenna ports of the antenna elements of the RBS.

3. The method of claim 1 :
wherein the first transmission channel for the first UE comprises a first true transmission channel and the second transmission channel for the first UE comprises a first estimated transmission channel; and
wherein the third transmission channel for the at least one second UE comprises a second true transmission channel and the fourth transmission channel for the at least one second UE comprises a second estimated transmission channel.

4. The method of claim 1 , further comprising:
determining a first Doppler frequency and a first scheduling delay for the first UE;
determining a second Doppler frequency and a second scheduling delay for the at least one second UE; and
estimating R 1 ′ and R 1 ″ according to R 1 =J 0 (2πf d t Δ ), where J 0 (•) represents a zeroth order Bessel function of the first kind, f d represents a Doppler frequency for the corresponding UE, and t Δ represents a scheduling delay for the corresponding UE.

5. The method of claim 1 , wherein estimating the first and second imperfections of the CSI comprises estimating the first and second imperfections of the CSI using a ratio of NACK messages to ACK messages received from the first UE and the at least one second UE during a respective scheduling delay established for each of the first UE and the at least one second UE.

6. The method of claim 5 :
wherein the first and third transmission channels comprise a true transmission channel for respective ones of the first UE and the at least one second UE;
wherein the second and fourth transmission channels comprise an estimated transmission channel for respective ones of the first UE and the at least one second UE; and
wherein the ratio of received NACK messages to received ACK messages from each of the first UE and the at least one second UE is established and used to estimate the imperfection of CSI between the estimated transmission channel and the true transmission channel during the respective scheduling delay of each UE.

7. The method of claim 1 , wherein estimating the spatial correlation between the first UE and the at least one second UE comprises estimating a correlation (R 2 ) between a channel matrix (H 1 ) for a first transmission channel for the first UE and a channel matrix (H 2 ) for a second transmission channel for the at least one second UE.

8. The method of claim 7 , wherein estimating R 2 comprises calculating R 2 =|u 1 H u 2 |, where weight vectors u 1 and u 2 represent first column vectors of U 1 and U 2 respectively, where U 1 and U 2 represent unitary matrices obtained by decomposing H 1 and H 2 using singular value decomposition (SVD), and where H i =U i Λ i V i H for i=1, 2.

9. The method of claim 1 , wherein estimating the spatial correlation between the first UE and the at least one second UE comprises:
receiving a first Precoder Matrix Information (PMI) feedback (W 1 ) from the first UE;
receiving a second PMI feedback (W 2 ) from the at least one second UE;
wherein estimating the spatial correlation comprises estimating the spatial correlation according to

R
2

=

trace
⁢

{



W
1
H

*

W
2



}

N

,

where H represents a conjugate transpose operation and N represents a number of supported layers.

10. The method of claim 1 , wherein the channels comprise uplink or downlink channels in a Frequency Division Duplex system or a Time Division Duplex system.

11. The method of claim 1 , wherein the CSI is made available as at least one of measurements and calculations performed in the RBS for the first UE and the at least one second UE.

12. The method of claim 1 , wherein the CSI is made available as at least one of measurement and calculations received in a transmission from the first UE and the at least one second UE.

13. The method of claim 1 , wherein the CSI comprises at least one of Channel Quality Indication (CQI) information, Precoder Matrix Information (PMI), and ACK/NACK information.

14. A Radio Base Station (RBS) configured for Multiple-Input, Multiple-Output (MIMO) transmission on one or more channels comprising:
a transceiver and two or more antenna elements;
processing circuitry configured to select a first User Equipment (UE) and at least one second UE from a plurality of UEs for sharing a transmission resource in a time-frequency dimension in the MIMO transmission, wherein the processing circuitry is further configured to:
estimate a first imperfection of Channel State Information (CSI) made available for the first UE by:
calculating a first correlation (R 1 ′) between an estimation of a first transmission channel for the first UE and an estimation of a second transmission channel for the first UE; and
estimating the first imperfection of the CSI using the first correlation (R 1 ′);

estimate a second imperfection of the CSI made available for the at least one second UE by:
calculating a second correlation (R 1 ″) between an estimation of a third transmission

Assignees

• Huang Weilan
• Hu Yang
• Ericsson Telefon Ab L M

Inventors

• Huang Weilan
• Hu Yang

Classifications

• H04W72/54 Primary

  based on quality criteria · CPC title

• H04L5/0023

  Time-frequency-space · CPC title

• H04W72/08 Primary

  Electricity · mapped topic

• H04B7/0452 Primary

  Multi-user MIMO systems · CPC title

• H04B7/024

  Co-operative use of antennas of several sites, e.g. in co-ordinated multipoint or co-operative multiple-input multiple-output [MIMO] systems · CPC title