Efficient large-scale multiple input multiple output communications

Patent metadata

Field	Value
Publication number	US-9537587-B2
Application number	US-201514738268-A
Country	US
Kind code	B2
Filing date	Jun 12, 2015
Priority date	Jun 12, 2014
Publication date	Jan 3, 2017
Grant date	Jan 3, 2017

Abstract

Methods and systems for beam forming, implemented in a base station used in a communication system, include measuring channel state information (CSI) for a number of active phased-array antennas less than a full number of phased-array antennas. Analog beam forming weights are determined using the measured CSI. An optimal digital precoder is determined from the analog beam forming weights. The analog beam forming weights and optimal digital precoder are applied to one phased-array antenna.

First claim

The invention claimed is:

1. A method for beam forming, implemented in equipment used in a communication system, the method comprising:
measuring channel state information (CSI) for communication links for a number of active phased-array antennas less than all available phased-array antennas, CSI being channel properties of a communication link related to how a signal propagates from a transmitter and receiver;
determining analog beam forming weights using the measured CSI;
determining an optimal digital precoder from the analog beam forming weights; and
applying the analog beam forming weights and optimal digital precoder to one phased-array antenna;

wherein determining the analog beam forming weights comprises solving:

B
^

=

arg
⁢

⁢

max
B

⁢

∑

1
≤
s
≤
S

⁢

log
2

⁢

det
⁡

(

I
+

H
s

⁢

BB
T

⁢

H
s
T

)

where B is a set of beam forming weights, s is a subcarrier among S subcarriers, H s is the CSI on the s th subcarrier and I is a basband in-phase.

2. The method of claim 1 , further comprising updating CSI for inactive antennas by interpolating the CSIs of nearby active antennas.

3. The method of claim 1 , wherein CSI is measured by comparing a received training frame from each of the active antennas to a known value.

4. The method of claim 1 , wherein measuring the CSI selects the active antennas randomly.

5. The method of claim 1 , wherein the equipment is in a multi-cell network.

6. The method of claim 5 , wherein determining the analog beam forming weights comprises solving:

B
^

=

arg
⁢

⁢

max
B

⁢

∑

1
≤
s
≤
S

⁢

log
2

⁢

det
⁡

(

I
+

H
s

⁢

BB
T

⁢

H
s
T

)

∑
i

⁢

∑

1
≤
s
≤
S

⁢

log
2

⁢

det
⁡

(

I
+

H
s

(
i
)

⁢

BB
T

⁢

H
s

(
i
)

⁢
T

)

where B is a set of beam forming weights, s is a subcarrier among S subcarriers, H s is the CSI on the s th subcarrier, H s (i) is the CSI from users in adjacent cells and I is a basband in-phase.

Assignees

• Nec Lab America Inc
• Nec Corp

Inventors

• Chai Eugene
• Xie Xiufeng
• Khojastepour Mohammad
• Sundaresan Karthikeyan
• Rangarajan Sampath

Classifications

• H04B7/0626 Primary

  Channel coefficients, e.g. channel state information [CSI] · CPC title

• H04B17/104 Primary

  of other parameters, e.g. DC offset, delay or propagation times · CPC title

• H04B17/309 Primary

  Measuring or estimating channel quality parameters · CPC title

• H04B7/0617

  for beam forming · CPC title

• H04B7/0452

  Multi-user MIMO systems · CPC title