Beamforming method for an SDM/MIMO system

• US 20050254477A1
• Filed: 05/17/2005
• Published: 11/17/2005
• Est. Priority Date: 05/17/2004
• Status: Abandoned Application

• Current Assignee: Korea Advanced Institute of Science and Technology, Samsung Electronics Co. Ltd.
• Original Assignee: Korea Advanced Institute of Science and Technology, Samsung Electronics Co. Ltd.
• Inventors: Nam, Seung-Hoon, Chung, Jae-Hak, Chun, Joo-Hwan, Lee, Kyung-Chun
• Application Number:
  US11/130,942
• Publication Number:
  US 20050254477A1
• Time in Patent Office: Days
• US Class Current: 370/342
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0626 Channel coefficients, e.g. channel state information [CSI]

Abstract

A beamforming method in a communication system having a transmitter for transmitting signals to users on a plurality of transmit antennas, and spatially identifying the users and a plurality of receivers for receiving the signals discriminately. A beamforming weight is determined based on channel information received from each of the receivers, based on whether the each receiver uses a single antenna or a plurality of antennas. A transmission signal is multiplied by the beamforming weight and transmitted.

Claims

1. A beamforming method for use in a communication system having a transmitter for transmitting signals to users on a plurality of transmit antennas, and spatially identifying the users, and a plurality of receivers for selectively receiving the signals, comprising the steps of:

determining a beamforming weight based on channel information received from each of the plurality of receivers, based on whether the each of the plurality of receivers uses a single antenna or a plurality of antennas;

multiplying a transmission signal by the beamforming weight; and

transmitting the multiplied transmission signal.

2. The beamforming method of claim 1, wherein the step of determining the beamforming weight is performed to minimize a power of the transmission signal.

3. The beamforming method of claim 1, wherein the step of determining the beamforming weight comprises the step of computing a beamforming weight for a k^th receiver by

{tilde over (W)}_k,1=(I−

NN^†

)Ŵ

_k

where I is an identity matrix with an appropriate size and N is an orthogonal basis for the zero space of an estimation matrix including channel estimates of K receivers, Ĥ

=[Ĥ

₁;

Ĥ

₂;

. . . ;

Ĥ

_K;

]

4. The beamforming method of claim 1, wherein the beamforming weight is designed such that an average power of an interference signal caused by channel estimation errors is minimized.

5. The beamforming method of claim 1, wherein the beamforming weight is computed by

${\tilde{W}}_{k,2}=\{I-{(\frac{1}{N_{r,\mathrm{all}}}}^{}$

σ

2 ⁢

H ^ H ⁢

H ^ + I ) - 1 } ⁢

W ^ k

where I is an identity matrix with an appropriate size, N_r,all is the number of antennas in the each receiver, σ

² is a standard deviation of channel estimation errors, and H is a matrix made up of channel matrices of all receivers.

6. A beamforming method in a communication system utilizing space division multiplexing (SDM) and multiple-input and multiple-output (MIMO), the method comprising the steps of:

determining a beamforming weight for a terminal based on a number of antennas of the terminal and channel information received from the terminal;

generating a transmission signal for the terminal using the beamforming weight; and

transmitting the transmission signal.

7. The beamforming method of claim 6, wherein the beamforming weight is designed such that the power of the transmission signal is minimized.

8. The beamforming method of claim 7, wherein the beamforming weight is computed by

{tilde over (W)}_k,1=(I−

NN^†

)Ŵ

_k

where I is an identity matrix with an appropriate size and N is an orthogonal basis for the zero space of an estimation matrix including channel estimates of K receivers, Ĥ

=[Ĥ

₁;

Ĥ

₂;

. . . ;

Ĥ

_K;

].

9. The beamforming method of claim 8, wherein the beamforming weight is designed such that an average power of an interference signal caused by channel estimation errors is minimized.

10. The beamforming method of claim 9, wherein the beamforming weight is computed by

${\tilde{W}}_{k,2}=\{I-{(\frac{1}{N_{r,\mathrm{all}}}}^{}$

σ

2 ⁢

H ^ H ⁢

H ^ + I ) - 1 } ⁢

W ^ k

where I is an identity matrix with an appropriate size, N_r,all is the number of antennas in the receiver, σ

² is a standard deviation of channel estimation errors, and H is a matrix made up of channel matrices of all receivers.