Transmission control apparatus and program

1. A transmission control apparatus comprising:

a first antenna;

a second antenna that is orthogonal to the first antenna;

a third antenna arranged parallel to the first antenna;

a fourth antenna that is orthogonal to the third antenna; and

a processor configured to

determine a beam direction of a beam formed by the transmission control apparatus and a polarization characteristic of the beam formed by the transmission control apparatus based on a feedback signal received from a mobile terminal capable of wireless communication with the transmission control apparatus;

determine a first phase difference, for a phase difference between an electric wave output by the first antenna and an electric wave output by the second antenna and for a phase difference between an electric wave output by the third antenna and an electric wave output by the fourth antenna, based on the determined polarization characteristic;

determine a second phase difference, for a phase difference between the electric wave output by the first antenna and the electric wave output by the third antenna and for a phase difference between the electric wave output by the second antenna and the electric wave output by the fourth antenna, based on the determined beam direction; and

control phases of the electric waves output by the first antenna, the second antenna, the third antenna, and the fourth antenna according to the first phase difference and the second phase difference, wherein

a path between the first antenna and the mobile terminal is the same as a path between the second antenna and the mobile terminal, and

a path between the third antenna and the mobile terminal is the same as a path between the fourth antenna and the mobile terminal.

2. The transmission control apparatus according to claim 1 , wherein the processor is further configured to

determine the first phase difference in a first layer among a plurality of layers in which are respectively transmitted a plurality of beams that differ from each other with respect to at least one of the beam direction and the polarization characteristic,

determine the second phase difference in the first layer,

determine a third phase difference, which forms a polarization plane orthogonal to a polarization plane formed by the first phase difference, for the phase difference between the electric wave output by the first antenna and the electric wave output by the second antenna and for the phase difference between the electric wave output by the third antenna and the electric wave output by the fourth antenna in a second layer among the plurality of layers;

determine a fourth phase difference, which is the same as the second phase difference, for the phase difference between the electric wave output by the first antenna and the electric wave output by the third antenna and for the phase difference between the electric wave output by the second antenna and the electric wave output by the fourth antenna in the second layer, and

control the phases of the electric waves output by the first antenna, the second antenna, the third antenna, and the fourth antenna based on the first phase difference, the second phase difference, the third phase difference, and the fourth phase difference.

3. The transmission control apparatus according to claim 2 , wherein in a case where the processor determines that the beam direction is θ 0 , the polarization plane of the first layer has vertical polarization, and the polarization plane of the second layer has horizontal polarization, the processor is further configured to:

determine a value of 0 for the phase difference between the electric wave output by the first antenna and the electric wave output by the second antenna and for the phase difference between the electric wave output by the third antenna and the electric wave output by the fourth antenna,

determine a value δ according to Expression 1 for the phase difference between the electric wave output by the first antenna and the electric wave output by the third antenna and for the phase difference between the electric wave output by the second antenna and the electric wave output by the fourth antenna,

determine a value of 180 degrees for the phase difference between the electric wave output by the first antenna and the electric wave output by the second antenna and for the phase difference between the electric wave output by the third antenna and the electric wave output by the fourth antenna, and

determine the value δ according to Expression 1 for the phase difference between the electric wave output by the first antenna and the electric wave output by the third antenna and for the phase difference between the electric wave output by the second antenna and the electric wave output by the fourth antenna, and

d ·sin θ 0 =δλ/2π.  Expression 1 is defined as:

4. The transmission control apparatus according to claim 2 , wherein in a case where the processor determines that the beam direction is θ 0 , the polarization plane of the first layer has left-handed circular polarization, and the polarization plane of the second layer has right-handed circular polarization, the processor is further configured to:

set the phase of the first antenna to be −1, sets the phase of the second antenna to be j, and determines a value of 90 degrees for the phase difference between the electric wave output by the first antenna and the electric wave output by the second antenna and for the phase difference between the electric wave output by the third antenna and the electric wave output by the fourth antenna,

determine a value δ according to Expression 1 for the phase difference between the electric wave output by the first antenna and the electric wave output by the third antenna and for the phase difference between the electric wave output by the second antenna and the electric wave output by the fourth antenna,

set the phase of the first antenna to j, sets the phase of the second antenna to −1, and determines a value of 90 degrees for the phase difference between the electric wave output by the first antenna and the electric wave output by the second antenna and for the phase difference between the electric wave output by the third antenna and the electric wave output by the fourth antenna, and

determine the value δ according to Expression 1 for the phase difference between the electric wave output by the first antenna and the electric wave output by the third antenna and for the phase difference between the electric wave output by the second antenna and the electric wave output by the fourth antenna, and

δ=2π d ·sin θ 0 /λ.  Expression 1 is defined as:

5. The transmission control apparatus according to claim 2 , wherein the processor is further configured to:

acquire a codebook for precoding in Transmission Mode 4, which is an LTE (Long Term Evolution) transmission mode defined according to 3GPP (3rd Generation Partnership Project);

edit the acquired codebook based on the first phase difference, the second phase difference, the third phase difference, and the fourth phase difference, and

control the phases of the electric waves output by the first antenna, the second antenna, the third antenna, and the fourth antenna using the edited codebook.

6. The transmission control apparatus according to claim 1 , wherein

the first antenna and the second antenna form a cross dipole antenna, and

the third antenna and the fourth antenna form a cross dipole antenna.

7. The transmission control apparatus according to claim 1 , wherein

the transmission control apparatus conforms to Transmission Mode 8, which is an LTE (Long Term Evolution) transmission mode defined according to 3GPP (3rd Generation Partnership Project).

8. A non-transitory computer readable medium storing thereon a program that causes a computer to perform operations comprising:

determining a beam direction of a beam formed by a transmission control apparatus and a polarization characteristic of the beam formed by the transmission control apparatus based on a feedback signal received from a mobile terminal capable of wireless communication with the transmission control apparatus;

determining a first phase difference, for a phase difference between an electric wave output by a first antenna of the transmission control apparatus and an electric wave output by a second antenna of the transmission control apparatus and for a phase difference between an electric wave output by a third antenna of the transmission control apparatus and an electric wave output by a fourth antenna of the transmission control apparatus, based on the determined polarization characteristic, the second antenna being orthogonal to the first antenna, the third antenna being arranged parallel to the first antenna, the fourth antenna being orthogonal to the third antenna, a path between the second antenna and the mobile terminal being the same as a path between the first antenna and the mobile terminal, and a path between the fourth antenna and the mobile terminal being the same as a path between the third antenna and the mobile terminal;

determining a second phase difference, for a phase difference between the electric wave output by the first antenna and the electric wave output by the third antenna and for a phase difference between the electric wave output by the second antenna and the electric wave output by the fourth antenna, based on the determined beam direction; and

controlling phases of the electric waves output by the first antenna, the second antenna, the third antenna, and the fourth antenna according to the first phase difference and the second phase difference.

9. The non-transitory computer readable medium according to claim 8 , wherein the operations further comprise:

determining the first phase difference in a first layer among a plurality of layers in which are respectively transmitted a plurality of beams that differ from each other with respect to at least one of the beam direction and the polarization characteristic,

determining the second phase difference in the first layer,

determining a third phase difference, which forms a polarization plane orthogonal to a polarization plane formed by the first phase difference, for the phase difference between the electric wave output by the first antenna and the electric wave output by the second antenna and for the phase difference between the electric wave output by the third antenna and the electric wave output by the fourth antenna in a second layer among the plurality of layers;

determining a fourth phase difference, which is the same as the second phase difference, for the phase difference between the electric wave output by the first antenna and the electric wave output by the third antenna and for the phase difference between the electric wave output by the second antenna and the electric wave output by the fourth antenna in the second layer, and

controlling the phases of the electric waves output by the first antenna, the second antenna, the third antenna, and the fourth antenna based on the first phase difference, the second phase difference, the third phase difference, and the fourth phase difference.

10. The non-transitory computer readable medium according to claim 9 , wherein in a case where it is determined that the beam direction is θ 0 , the polarization plane of the first layer has vertical polarization, and the polarization plane of the second layer has horizontal polarization, the operations further comprise:

determining a value of 0 for the phase difference between the electric wave output by the first antenna and the electric wave output by the second antenna and for the phase difference between the electric wave output by the third antenna and the electric wave output by the fourth antenna,

determining a value δ according to Expression 1 for the phase difference between the electric wave output by the first antenna and the electric wave output by the third antenna and for the phase difference between the electric wave output by the second antenna and the electric wave output by the fourth antenna,

determining a value of 180 degrees for the phase difference between the electric wave output by the first antenna and the electric wave output by the second antenna and for the phase difference between the electric wave output by the third antenna and the electric wave output by the fourth antenna, and

determining the value δ according to Expression 1 for the phase difference between the electric wave output by the first antenna and the electric wave output by the third antenna and for the phase difference between the electric wave output by the second antenna and the electric wave output by the fourth antenna, and

d ·sin θ 0 =δλ/2π.  Expression 1 is defined as:

11. The non-transitory computer readable medium according to claim 9 , wherein in a case where it is determined that the beam direction is θ 0 , the polarization plane of the first layer has left-handed circular polarization, and the polarization plane of the second layer has right-handed circular polarization, the operations further comprise:

setting the phase of the first antenna to be −1, sets the phase of the second antenna to be j, and determines a value of 90 degrees for the phase difference between the electric wave output by the first antenna and the electric wave output by the second antenna and for the phase difference between the electric wave output by the third antenna and the electric wave output by the fourth antenna,

determining a value δ according to Expression 1 for the phase difference between the electric wave output by the first antenna and the electric wave output by the third antenna and for the phase difference between the electric wave output by the second antenna and the electric wave output by the fourth antenna,

setting the phase of the first antenna to j, sets the phase of the second antenna to −1, and determines a value of 90 degrees for the phase difference between the electric wave output by the first antenna and the electric wave output by the second antenna and for the phase difference between the electric wave output by the third antenna and the electric wave output by the fourth antenna, and

determining the value δ according to Expression 1 for the phase difference between the electric wave output by the first antenna and the electric wave output by the third antenna and for the phase difference between the electric wave output by the second antenna and the electric wave output by the fourth antenna, and

δ=2π d ·sin θ 0 /λ.  Expression 1 is defined as:

12. The non-transitory computer readable medium according to claim 9 , wherein the operations further comprise:

acquiring a codebook for precoding in Transmission Mode 4, which is an LTE (Long Term Evolution) transmission mode defined according to 3GPP (3rd Generation Partnership Project);

editing the acquired codebook based on the first phase difference, the second phase difference, the third phase difference, and the fourth phase difference, and

controlling the phases of the electric waves output by the first antenna, the second antenna, the third antenna, and the fourth antenna using the edited codebook.

13. The non-transitory computer readable medium according to claim 8 , wherein

the first antenna and the second antenna form a cross dipole antenna, and

the third antenna and the fourth antenna form a cross dipole antenna.

14. The non-transitory computer readable medium according to claim 8 , wherein

the computer conforms to Transmission Mode 8, which is an LTE (Long Term Evolution) transmission mode defined according to 3GPP (3rd Generation Partnership Project).