METHOD AND APPARATUS FOR DETERMINING DOWNLINK BEAMFORMING VECTORS IN HIERARCHICAL CELL COMMUNICATION SYSTEM

• US 20120077485A1
• Filed: 09/19/2011
• Published: 03/29/2012
• Est. Priority Date: 09/29/2010
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Shin, Won Jae, Lee, Nam Yoon, Noh, Won Jong, Hong, Young Jun, Choi, Hyun Ho, Shin, Chang Yong, Jang, Kyung Hun
• Granted Patent: US 8,532,647 B2
• Time in Patent Office: Days
• US Class Current: 455/422.1
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0619 using feedback from receiving side feedback signaling for adaptive modulation/coding H04L1/0001
• CPC Class Codes: H04B 7/0639 Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection
• CPC Class Codes: H04B 7/0658 Feedback reduction
• CPC Class Codes: H04W 28/04 Error control
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 84/045 using private Base Stations, e.g. femto Base Stations, home Node B
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

Provided is a method and apparatus for determining a downlink beamforming vector in a hierarchical cell communication system. Small base stations may determine transmit beamforming vectors of the small base stations so that interference from the small base stations may be reduced in a macro terminal. A macro terminal and small terminals may determine receive beamforming vectors based on the transmit beamforming vectors of the small base stations. A macro base station may determine a transmit beamforming vector based on effective channels to terminals using the receive beamforming vectors of the terminals.

Claims

1. A communication method of a macro base station, the communication method comprising:

obtaining information associated with a first small effective channel formed between a first small terminal corresponding to a first small base station and a macro base station;

obtaining information associated with a second small effective channel formed between a second small terminal corresponding to a second small base station and the macro base station; and

determining a transmit beamforming vector of the macro base station based on information associated with the first small effective channel and information associated with the second small effective channel,

wherein a receive beamforming vector of each of the at least one macro terminal is determined based on the transmit beamforming vector of the first small base station and the transmit beamforming vector of the second small base station.

2. The communication method of claim 1, wherein the determining comprises determining the transmit beamforming vector of the macro base station based on information associated with the first small effective channel and information associated with the second small effective channel, such that interference from the macro base station is nulled in each of the first small terminal and the second small terminal.

3. The communication method of claim 2, further comprising:

receiving information associated with a first macro effective channel formed between a first macro terminal and the macro base station, and information associated with a second macro effective channel formed between a second macro terminal and the macro base station,

wherein the first macro effective channel is associated with a receive beamforming vector of the first macro terminal and the second macro effective channel is associated with a receive beamforming vector of the second macro terminal, and the determining comprises determining the transmit beamforming vector of the macro base station based on information associated with the first macro effective channel and information associated with the second macro effective channel, such that interference from the macro base station caused by a signal for the second macro terminal is nulled in the first macro terminal and such that interference from the macro base station caused by a signal for the first macro terminal is nulled in the second macro terminal.

4. The communication method of claim 2, further comprising:

obtaining information associated with an effective channel that is formed between a neighboring macro terminal corresponding to a neighboring macro base station and the macro base station,

wherein the effective channel is associated with a receive beamforming vector of the neighboring macro terminal, and the determining comprises determining the transmit beamforming vector of the macro base station based on information associated with the effective channel formed between the macro base station and the neighboring macro terminal, such that interference from the macro base station to the neighboring macro terminal is nulled in the neighboring macro terminal.

5. The communication method of claim 1, wherein the receive beamforming vector of each of the at least one macro terminal is determined based on the transmit beamforming vector of the first small base station and the transmit beamforming vector of the second small base station, such that interference from the first small base station and the second small base station is nulled in each of the at least one macro terminal.

6. The communication method of claim 1, further comprising:

receiving information associated with channels formed between each of the first small base station and the second small base station and each of the at least one macro terminal; and

transferring, to the first small base station and the second small base station, information associated with the channels formed between each of the first small base station and the second small base station and each of the at least one macro terminal.

7. A communication method of a macro terminal corresponding to a macro base station, the communication method comprising:

feeding back information associated with a first interference channel formed between a first small base station and the macro terminal, and a second interference channel formed between a second small base station and the macro terminal;

determining a receive beamforming vector of the macro terminal based on a transmit beamforming vector of the first small base station and a transmit beamforming vector of the second small base station;

calculating an effective channel formed between the macro base station and the macro terminal based on the receive beamforming vector of the macro terminal; and

feeding back, to the macro base station, information associated with the effective channel formed between the macro base station and the macro terminal.

8. The communication method of claim 7, wherein the feeding back comprises feeding back information in which information associated with the first interference channel and information associated with the second interference channel are combined.

9. The communication method of claim 7, wherein the feeding back comprises feeding back, to the macro base station, information associated with the first interference channel and the second interference channel such that information associated with the first interference channel and the second interference channel are transferred to the first small base station and the second small base station.

10. The communication method of claim 7, further comprising:

receiving information associated with the transmit beamforming vector of the first small base station and information associated with the transmit beamforming vector of the second small base station,

wherein the transmit beamforming vector of the first small base station and the transmit beamforming vector of the second small base station are determined such that interference from the first small base station and interference from the second small base station are aligned in the macro terminal.

11. The communication method of claim 7, wherein the determining comprises determining the receive beamforming vector of the macro terminal such that interference from the first small base station is cancelled in the macro terminal based on the transmit beamforming vector of the first small base station and the first interference channel, and such that interference from the second small base station is cancelled in the macro terminal based on the transmit beamforming vector of the second small base station and the second interference channel.

12. The communication method of claim 11, wherein the determining comprises determining the receive beamforming vector of the macro terminal to be orthogonal with respect to a direction of the interference from the first small base station and a direction of the interference from the second small base station.

13. A macro base station, comprising:

a receiver to obtain information associated with a first small effective channel formed between a first small terminal corresponding to a first small base station and a macro base station, and to obtain information associated with a second small effective channel formed between a second small terminal corresponding to a second small base station and the macro base station; and

a transmit beamforming vector determining unit to determine a transmit beamforming vector of the macro base station based on information associated with the first small effective channel and information associated with the second small effective channel,

wherein a receive beamforming vector of each of the at least one macro terminal is determined based on the transmit beamforming vector of the first small base station and the transmit beamforming vector of the second small base station.

14. The macro base station of claim 13, wherein the transmit beamforming vector determining unit is configured to determine the transmit beamforming vector of the macro base station based on information associated with the first small effective channel and information associated with the second small effective channel, such that interference from the macro base station is nulled in each of the first small terminal and the second small terminal.

15. The macro base station of claim 14, wherein:

if the at least one macro terminal comprises a first macro terminal and a second macro terminal, the receiver is configured to receive information associated with a first macro effective channel formed between the first macro terminal and the macro base station, and information associated with a second macro effective channel formed between the second macro terminal and the macro base station, the first macro effective channel is associated with a receive beamforming vector of the first macro terminal and the second macro effective channel is associated with a receive beamforming vector of the second macro terminal, and

the transmit beamforming vector determining unit is configured to determine the transmit beamforming vector of the macro base station based on information associated with the first macro effective channel and information associated with the second macro effective channel, such that interference from the macro base station occurring due to a signal for the second macro terminal is nulled in the first macro terminal and such that interference from the macro base station occurring due to a signal for the first macro terminal is nulled in the second macro terminal.

16. The macro base station of claim 14, wherein:

the receiver is configured to obtain information associated with an effective channel formed between a neighboring macro terminal corresponding to a neighboring macro base station and the macro base station, and the effective channel is associated with a receive beamforming vector of the neighboring macro terminal, and

the transmit beamforming vector determining unit is configured to determine the transmit beamforming vector of the macro base station based on information associated with the effective channel formed between the macro base station and the neighboring macro terminal, such that interference from the macro base station to the neighboring macro terminal is nulled in the neighboring macro terminal.

17. The macro base station of claim 15, wherein the receive beamforming vector of each of the at least one macro terminal is determined based on the transmit beamforming vector of the first small base station and the transmit beamforming vector of the second small base station, such that interference from the first small base station and the second small base station is nulled in each of the at least one macro terminal.

18. The macro base station of claim 13, wherein:

the receiver is configured to receive information associated with channels formed between each of the first small base station and the second small base station and each of the at least one macro terminal, and

the macro base station further comprises;

a transfer unit to transfer, to the first small base station and the second small base station, information associated with the channels formed between each of the first small base station and the second small base station and each of the at least one macro terminal.

19. A communication method of a targeted small terminal corresponding to a targeted small base station, the communication method comprising:

obtaining information associated with an effective channel from a macro base station to the targeted small terminal based on a transmit beamforming vector of the macro base station, and information associated with a channel from a neighboring small base station to the targeted small terminal;

determining a transmit beamforming vector of the neighboring small base station such that interference from the macro base station and interference from the neighboring small base station are aligned in the targeted small terminal; and

determining a receive beamforming vector of the targeted small terminal such that interference from the macro base station is nulled in the targeted small terminal.

20. The communication method of claim 19, wherein:

the determining of the transmit beamforming vector of the neighboring small base station comprises determining the transmit beamforming vector of the neighboring small base station based on the same codebook as a codebook used to generate the transmit beamforming vector of the macro base station, and

the determining of the receive beamforming vector of the targeted small base station comprises determining the receive beamforming vector of the targeted small terminal based on the same codebook as the codebook used to generate the transmit beamforming vector of the macro base station.