Method and apparatus for determining downlink beamforming vectors in hierarchical cell communication system
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.
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;
wherein 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.
2. The communication method of claim 1 , 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.
3. The communication method of claim 1 , 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.
4. 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.
5. 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.
6. 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;
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.
7. The macro base station of claim 6 , 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 10 second macro terminal.
8. The macro base station of claim 6 , 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.
9. The macro base station of claim 7 , 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.
10. The macro base station of claim 6 , 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.