MIMO communication system for propagation environment including deterministic communication channel, and antennas for MIMO communication system

• US 9,608,705 B2
• Filed: 05/29/2014
• Issued: 03/28/2017
• Est. Priority Date: 05/30/2013
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Maru, Tsuguo
• Primary Examiner(s): HA, DAC V
• Application Number:
  US14/894,013
• Publication Number:
  US 20160134345A1
• Time in Patent Office: 1,034 Days
• US Class Current: 1/1
• CPC Class Codes: H04B 7/0456 Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver

Abstract

In a MIMO communication system that includes a transmitter and a receiver and forms line-of-sight orthogonal channels between the transmitter-side transmitting antenna and the receiver-side receiving antenna, the MIMO communication system is provided between the transmitting antenna and the receiving antenna with an optimum antenna-to-antenna spacing shortening unit to shorten an optimum antenna-to-antenna spacing by changing the phase rotation of a carrier wave used for directly opposed waves between opposed antennas, and the phase rotation of a carrier wave used for intersecting waves between oblique antennas in such a manner that the amount by which one of the phase rotations changes is different from that by which the other phase rotation changes.

Claims

1. A MIMO communication system which includes a transmitter and a receiver and forms line-of-sight orthogonal channels between a transmitter-side transmitting antenna and a receiver-side receiving antenna under propagation environment including a deterministic communication channel, in which an optimum antenna-to-antenna spacing shortening unit is provided between the transmitting antenna and the receiving antenna to shorten an optimum antenna-to-antenna spacing by changing a phase rotation of a carrier wave used for directly opposed waves between opposed antennas and a phase rotation of a carrier wave used for intersecting waves between oblique antennas in such a manner that an amount by which one of the phase rotations changes is different from that by which the other phase rotation changes.

2. The MIMO communication system according to claim 1, wherein the optimum antenna-to-antenna spacing shortening unit comprises anisotropic metamaterial dielectrics and dielectric elements of the anisotropic metamaterial dielectrics are arranged such that they are inclined with respect to a direction of the opposed antennas.

3. The MIMO communication system according to claim 2, wherein the optimum antenna-to-antenna spacing shortening unit is provided with an inclination angle modification unit to modify an angle of the inclination of the dielectric elements by liquid crystals such that the present antenna-to-antenna spacing is rendered into an optimum antenna-to-antenna spacing.

4. The MIMO communication system according to claim 1, wherein the optimum antenna-to-antenna spacing shortening unit is a metallic plate guide comprising a collective body of parallel metallic plates and a guiding direction of the metallic plate guide is arranged such that it is inclined with respect to the direction of the opposed antennas.

5. The MIMO communication system according to claim 4, wherein the optimum antenna-to-antenna spacing shortening unit is provided with an inclination angle modification unit to modify an angle of the inclination of the metallic plate guide by MEMS (Micro Electro Mechanical System) such that the present antenna-to-antenna spacing is rendered into the optimum antenna-to-antenna spacing.

6. The MIMO communication system according to claim 1, wherein the optimum antenna-to-antenna spacing shortening unit is provided in front of one of the transmitting antenna, the receiving antenna and both of the transmitting and receiving antennas.

7. The MIMO communication system according to claim 1, wherein a matrix operation processing unit to execute a matrix operation processing based on a matrix for forming orthogonal channels that is a matrix representing the matrix operation processing for forming the orthogonal channels is provided on one of a transmitting side, a receiving side and both of the transmitting and receiving sides and the orthogonal channels are formed at the matrix operation processing unit.

8. The MIMO communication system according to claim 1, wherein to render an eigenvalue of a communication channel matrix into a geometric multiplicity (double eigenvalue or multiple eigenvalue), a geometric parameter according to the antenna-to-antenna spacing of the communication channel is set and the orthogonal channels are formed by performing the matrix operation on one of the transmitting side and the receiving side by a unitary matrix arranged based on one of a singular vector obtained based on the eigenvalue and a singular vector obtained by a linear sum of the vectors.

9. The MIMO communication system according to claim 1, wherein the matrix for forming the orthogonal channels are renewed at the matrix operation processing unit by one of a positional fluctuation of the transmitting antenna, a positional fluctuation of the receiving antenna, positional fluctuations of the transmitting and receiving antennas and a fluctuation of the channels.

10. The MIMO communication system according to claim 1, wherein to render the eigenvalue of the communication channel matrix into a geometric multiplicity (double eigenvalue or multiple eigenvalue), a geometric parameter of the communication channel is set and virtual orthogonal channels are formed by performing a unitary matrix operation arranged based on one of an eigenvector obtained based on the eigenvalue and an eigenvector obtained by a linear sum of the vectors only on one of the transmitting and receiving sides.

11. The MIMO communication system according to claim 1, wherein the MIMO communication system is a fixed microwaves communication system with a plurality of antennas in use and independent local oscillators are adopted for each antenna on one of the transmitting side, the receiving side and the transmitting and receiving sides.

12. A MIMO communication method in a MIMO communication system forming line-of-sight orthogonal channels between a transmitter-side transmitting antenna and a receiver-side receiving antenna under propagation environment including a deterministic communication channel, wherein the method comprises an optimum antenna-to-antenna spacing shortening step of shortening an optimum antenna-to-antenna spacing by changing between the transmitting antenna and the receiving antenna a phase rotation of a carrier wave used for directly opposed waves between opposed antennas and a phase rotation of a carrier wave used for intersecting waves between oblique antennas in such a manner that an amount by which one of the phase rotations changes is different from that by which the other phase rotation changes.

13. The MIMO communication method according to claim 12, wherein at the optimum antenna-to-antenna spacing shortening step materials comprising anisotropic metamaterial dielectrics are arranged such that dielectric elements of the anisotropic metamaterial dielectrics are inclined with respect to a direction of the opposed antennas.

14. The MIMO communication method according to claim 13, wherein the optimum antenna-to-antenna spacing shortening step includes an inclination angle modification step of modifying an angle of the inclination of the dielectric elements by liquid crystals such that the present antenna-to-antenna spacing is rendered into the optimum antenna-to-antenna spacing.

15. The MIMO communication method according to claim 13, wherein at the optimum antenna-to-antenna shortening step the materials are provided in front of one of the transmitting antenna, the receiving antennas and both of the transmitting and receiving antennas.

16. The MIMO communication method according to claim 12, wherein at the optimum antenna-to-antenna shortening step a metallic plate guide comprising a collective body of parallel metallic plates is arranged such that a guiding direction of the metallic plate guide is inclined with respect to the direction of the opposed antennas.

17. The MIMO communication method according to claim 16, wherein the optimum antenna-to-antenna shortening step includes an inclination angle modification step of modifying an angle of the inclination of the metallic plate guide by MEMS (Micro Electro Mechanical System) such that the present antenna-to-antenna spacing is rendered into the optimum antenna-to-antenna spacing.

18. The MIMO communication method according to claim 16, wherein at the optimum antenna-to-antenna shortening step the metallic plate guide is provided in front of one of the transmitting antenna, the receiving antenna and both of the transmitting and receiving antennas.

19. The MIMO communication method according to claim 12 comprising a matrix operation processing step of executing a matrix operation processing based on a matrix for forming orthogonal channels that is a matrix representing the matrix operation processing for forming the orthogonal channels on one of a transmitting side, a receiving side and both of the transmitting and receiving sides, wherein the orthogonal channels are formed at the matrix operation processing unit.

20. A non-transitory computer-readable medium on which a program is recorded, said program, when executed, causing a computer to optimize an antenna-to-antenna spacing in one of a transmitter and a receiver of a MIMO communication system in which line-of-sight orthogonal channels are formed between a transmitter-side transmitting antenna and a receiver-side receiving antenna under propagation environment including a deterministic communication channel;

an optimum antenna-to-antenna spacing shortening unit is provided between a transmitting antenna and a receiving antenna to shorten an optimum antenna-to-antenna spacing by changing a phase rotation of a carrier wave used for directly opposed waves between opposed antennas, and a phase rotation of a carrier wave used for intersecting waves between oblique antennas in such a manner that an amount by which one of the phase rotations changes is different from that by the other phase rotation changes; and

the optimum antenna-to-antenna shortening unit is made from anisotropic metamaterial dielectrics and dielectric elements of the anisotropic metamaterial dielectrics are disposed such that their inclination angle with regard to a direction of the opposed antennas is freely changeable, wherein the program makes a computer to function as a control unit to change the inclination angle such that the present antenna-to-antenna spacing is rendered into an optimum antenna-to-antenna spacing.