BEAM SELECTING METHOD, BASE STATION, AND USER EQUIPMENT

1 . A beam selection method in a mobile communication system that includes a base station with multiple antennas and user equipment conducting radio communication with the base station, comprising the steps of:

at the base station, detecting a direction in which the user equipment is located;

transmitting precoded reference signals toward the detected direction by spatial multiplexing using same frequency and time resources; and

determining a beam for the user equipment based upon feedback information from the user equipment.

2 . The beam selection method as claimed in claim 1 , wherein the base station transmits information about signal sequences, multiplexing positions on time and frequency axes, and a part or all of orthogonal codes of the reference signals by signaling.

3 . The beam selection method as claimed in claim 1 , wherein when receiving a first beam selection result indicating selection of a beam that carries a first reference signal among the reference signals from a first user equipment and receiving a second beam selection result indicating selection of a beam that carries a second reference signal from a second user equipment, the base station determines the first user equipment and the second user equipment as a user pair to which multi-user special multiplexing is applied.

4 . A base station that conducts radio communication with user equipment using multiple antennas; comprising:

a detector configured to detect a direction in which the user equipment is positioned;

a precoding controller configured to determine precoding vectors to be applied to a reference signal such that multiple beams are formed in the detected direction;

a reference signal generator configured to generate precoded reference signals with directivity by multiplexing the precoding vectors with the reference signal;

a transmitter configured to transmit the precoded reference signals using the multiple antennas;

a receiver configured to receive feedback information from the user equipment; and

a feedback information processor configured to process the feedback information to acquire a beam selection result contained in the feedback information,

wherein the precoding controller determines a beam for the user equipment based upon the selection result.

5 . The base station as claimed in claim 4 , further comprising:

a reporting block configured to supply information about signal sequences, multiplexing positions on time and frequency axes, and a part or all of orthogonal codes of the precoded reference signals by signaling.

6 . The base station as claimed in claim 4 , wherein:

the reference signal generator generates mutually orthogonal reference signals; and

when the receiver receives a first beam selection result indicating selection of a beam that carries a first reference signal among the mutually orthogonal reference signals from a first user equipment and a second beam selection result indicating selection of a beam that carries a second reference signal from a second user equipment, the precoding controller determines the first user equipment and the second user equipment as a user pair to which multi-user special multiplexing is applied.

7 . The base station as claimed in claim 4 , wherein:

the transmitter transmits a plurality of first precoded reference signals simultaneously using a plurality of first beams toward the detected direction,

then, after receiving the feedback information as to the first precoded reference signals, the transmitter transmits second precoded reference signals using a plurality of second beams with a beam width narrower than the first beams toward a direction selected from the first beams and indicated by the feedback information, and

the receiver receives additional feedback information as to the second precoded reference signals, and p 1 wherein the precoding controller determines a beam for the user equipment based upon the additional feedback information.

8 . The base station as claimed in claim 7 ,

wherein the receiver receives the feedback information as to the first precoded reference signals at a first period, and receives the additional feedback information as to the second precoded reference signals at a second period shorter than the first period.

9 . The base station as claimed in claim 4 , wherein the precoding controller determines a rank index based upon a number of selected beams contained in the feedback information.

10 . A user equipment communicating with a base station using multiple antennas, comprising:

a receiver configured to receive reference signals transmitted simultaneously from the base station using multiple directional beams and signaling information about the reference signals, the signaling information including signal sequences, multiplexing positions on time and frequency axes, and a part or all of orthogonal codes of the reference signals;

a measurement unit configured to measure a quality of each of the reference signals;

a controller configured to select one or more beams from among the multiple directional beams based upon a measurement result acquired the measurement unit;

a feedback information generator configured to generate feedback information based upon a selection result selected by the controller; and

a transmitter configured to transmit the feedback information to the base station.