Method, apparatus and system for forming time division duplex multi-input multi-output downlink beams

A base station, comprising:

• a first downlink channel vector calculating unit corresponding to transmitting antenna of a mobile terminal, the first downlink channel vector calculating unit configured to measure an uplink channel vector of a transmitting antenna, and regard the uplink channel vector as a downlink channel vector corresponding to the transmitting antenna of the mobile terminal according to uplink-downlink channel symmetry of a Time Division Duplex (TDD) system;
• a second downlink channel vector calculating unit corresponding to non-transmitting antenna of the mobile terminal, the second downlink channel vector calculating unit configured to receive an index of a codebook element, wherein the codebook element refers to a codebook element whose correlation value has a greatest modulus value among correlation values that are calculated by the mobile terminal and are about correlation between the codebook element and a downlink channel corresponding to a non-transmitting antenna of the mobile terminal;
• and calculate a downlink channel vector corresponding to the non-transmitting antenna of the mobile terminal according to the index of the codebook element;
• and
• a unit for determining a best transmitting precoding matrix, configured to perform Singular Value Decomposition (SVD) by using downlink channel vectors of antennas of the mobile terminal to determine a best transmitting precoding matrix, wherein the downlink channel vectors of the antennas of the mobile terminal are composed of the downlink channel vector corresponding to the non-transmitting antenna of the mobile terminal and the downlink channel vector corresponding to the transmitting antenna of the mobile terminal.

A communication system, comprising:

• a base station;
• and
• a receiver configured to receive beams transmitted by the base station;
• wherein the base station is configured to:
• receive an index of a codebook element, wherein the codebook element refers to a codebook element whose correlation value has a greatest modulus value among correlation values that are calculated by the receiver and are about correlation between the codebook element and a downlink channel corresponding to a non-transmitting antenna of the receiver;
• calculate a downlink channel vector corresponding to the non-transmitting antenna of the receiver according to the index of the codebook element;
• obtain a downlink channel vector corresponding to a transmitting antenna of the receiver according to the uplink-downlink channel symmetry of a Time Division Duplex (TDD) system, make up channel vectors of antennas of the receiver by using the downlink channel vector corresponding to the transmitting antenna of the receiver and the calculated downlink channel vector corresponding to the non-transmitting antenna of the receiver;
• and
• perform Singular Value Decomposition (SVD) for the channel vectors of the antennas of the receiver to determine a best transmitting precoding matrix.