User selection method in a zero-forcing beamforming algorithm

• US 20070058590A1
• Filed: 06/26/2006
• Published: 03/15/2007
• Est. Priority Date: 06/24/2005
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd., Tsinghua University
• Original Assignee: Samsung Electronics Co. Ltd., Tsinghua University
• Inventors: Zhou, Yong-Xing, Kim, Sung-Jin, Li, Jianjun, Wang, Jing, Zheng, Haibo
• Granted Patent: US 7,729,333 B2
• Time in Patent Office: Days
• US Class Current: 370/334
• CPC Class Codes: H04B 7/0452 Multi-user MIMO systems
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0632 Channel quality parameters, e.g. channel quality indicator [CQI]

Abstract

In a method for selecting a transmission target terminal in a zero-forcing beamforming algorithm, information about a channel capacity of each terminal is received from all K terminals. A terminal with a largest channel capacity is selected as an initial transmission target terminal. A determination is made as to whether the number of currently selected terminals, i, is equal to the predefined number N. If the number of currently selected terminals, i, is different from the predefined number N, information about channel capacities of remaining terminals except previously selected transmission target terminals is received until i is equal to N and a terminal with a largest channel capacity is selected as a transmission target terminal.

Claims

1. A method for selecting a transmission target terminal in a zero-forcing beamforming algorithm in which a base station with multiple transmit antennas selects predefined number N of downlink transmission target terminals using channel information received from a plurality of terminals with at least two receive antennas, comprising the steps of:

receiving information about a channel capacity of each terminal from all K terminals;

selecting a terminal with a largest channel capacity as an initial transmission target terminal;

determining whether the number of currently selected terminals, i, is equal to the predefined number N; and

receiving information about channel capacities of remaining terminals except previously selected transmission target terminals until i is equal to N if the number of currently selected terminals, i, is different from the predefined number N, and selecting a terminal with a largest channel capacity as a transmission target terminal.

2. The method of claim 1, further comprising:

outputting an index set of the selected terminals if the number of selected terminals, i, is equal to the predefined number N.

3. The method of claim 1, wherein the step of receiving the information about the channel capacities from all the terminals comprises:

broadcasting a pilot beam to all K terminals; and

receiving the information about the channel capacities of the terminals in response to the pilot beam.

4. The method of claim 3, wherein the pilot beam is a form of an identity matrix.

5. The method of claim 1, wherein the step of selecting the transmission target terminal comprises:

receiving a channel matrix of an associated terminal from the initial transmission target terminal;

computing a null space of the received channel matrix;

broadcasting a null space beam based on the null space; and

receiving the information about the channel capacities from the remaining terminals except the selected transmission target terminal in response to the null space beam.

6. The method of claim 1, wherein the channel capacity is a sum of capacities of all receive antennas of an associated terminal.

7. A method for selecting a transmission target terminal in a zero-forcing beamforming algorithm in which a base station with multiple transmit antennas selects a predefined number N of downlink transmission target terminals using channel information received from a plurality of terminals with at least two receive antennas, comprising the steps of:

broadcasting a pilot beam to all K terminals;

receiving information about a channel capacity of each terminal from the terminals in response to the pilot beam;

selecting a terminal with a largest channel capacity as an initial transmission target terminal;

determining whether the number of currently selected terminals, i, is equal to the predefined number N;

receiving a channel matrix of an associated terminal from the initial transmission target terminal if the number of currently selected terminals, i, is different from the predefined number N;

computing a null space of the received channel matrix;

broadcasting a null space beam based on the null space; and

receiving information about channel capacities from remaining terminals except the selected transmission target terminal in response to the null space beam, and selecting a terminal with a largest channel capacity as a transmission target terminal.

8. The method of claim 7, wherein the pilot beam is a form of an identity matrix.

9. The method of claim 7, further comprising:

outputting an index set of the selected terminals if the number of selected terminals, i, is equal to the predefined number N.