REDUCING LOCATION-DEPENDENT INTERFERENCE IN DISTRIBUTED ANTENNA SYSTEMS OPERATING IN MULTIPLE-INPUT, MULTIPLE-OUTPUT (MIMO) CONFIGURATION, AND RELATED COMPONENTS, SYSTEMS, AND METHODS

• US 20160134348A1
• Filed: 01/18/2016
• Published: 05/12/2016
• Est. Priority Date: 03/30/2012
• Status: Active Grant

• Current Assignee: Corning Optical Communications LLC (Corning Incorporated)
• Original Assignee: Corning Optical Communications LLC (Corning Incorporated)
• Inventors: George, Jacob, Ng'Oma, Anthony, Yang, Hejie
• Granted Patent: US 9,813,127 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H04B 10/25753 Distribution optical network, e.g. between a base station and a plurality of remote units
• CPC Class Codes: H04B 7/024 Co-operative use of antennas of several sites, e.g. in co-ordinated multipoint or co-operative multiple-input multiple-output [MIMO] systems
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04B 7/0469 taking special antenna structures, e.g. cross polarized antennas into account
• CPC Class Codes: H04B 7/06 at the transmitting station
• CPC Class Codes: H04B 7/10 Polarisation diversity; Directional diversity

Abstract

Components, systems, and methods for reducing location-based interference in distributed antenna systems operating in multiple-input, multiple-output (MIMO) configuration are disclosed. Interference is defined as issues with received MIMO communications signals that can cause a MIMO algorithm to not be able to solve a channel matrix for MIMO communications signals received by MIMO receivers in client devices. These issues may be caused by lack of spatial (i.e., phase) separation in the received MIMO communications signals. Thus, to provide phase separation of received MIMO communication signals, multiple MIMO transmitters are each configured to employ multiple transmitter antennas, which are each configured to transmit in different polarization states. In certain embodiments, one of the MIMO communications signals is phase shifted in one of the polarization states to provide phase separation between received MIMO communication signals. In other embodiments, multiple transmitter antennas in a MIMO transmitter can be offset to provide phase separation.

Claims

1. A multiple-input multiple-output (MIMO) remote unit configured to wirelessly distribute MIMO communications signals to wireless client devices, comprising:

a first MIMO transmitter comprising a first MIMO transmitter antenna configured to transmit MIMO communications signals in a first polarization and a second MIMO transmitter antenna configured to transmit MIMO communications signals in a second polarization different from the first polarization; and

a second MIMO transmitter comprising a third MIMO transmitter antenna configured to transmit MIMO communications signals in the first polarization and a fourth MIMO transmitter antenna configured to transmit MIMO communications signals in the second polarization;

the first MIMO transmitter configured to;

receive a first optical downlink MIMO communications signal in a first phase over a first downlink communications medium, and transmit the first optical downlink MIMO communications signal wirelessly as a first downlink MIMO communications signal over the first MIMO transmitter antenna in the first polarization; and

receive a second optical downlink MIMO communications signal in the first phase over a second downlink communications medium, and transmit the second optical downlink MIMO communications signal wirelessly as a second downlink MIMO communications signal over the second MIMO transmitter antenna in the second polarization;

the second MIMO transmitter configured to;

receive a third optical downlink MIMO communications signal in the first phase over a third downlink communications medium, and transmit the third optical downlink MIMO communications signal wirelessly as a third downlink MIMO communications signal over the third MIMO transmitter antenna in the first polarization; and

receive a fourth optical downlink MIMO communications signal over a fourth downlink communications medium, and transmit the fourth optical downlink communications signal in a second phase shifted from the first phase, wirelessly as a fourth downlink MIMO communications signal over the fourth MIMO transmitter antenna in the second polarization.

2. The MIMO remote unit of claim 1, wherein:

the first MIMO transmitter further comprises a first optical-to-electrical (0/E) converter configured to convert the first optical downlink MIMO communications signal to the first downlink MIMO communications signal and a second 0/E converter configured to convert the second optical downlink MIMO communications signal to the second MIMO downlink communications signal; and

the second MIMO transmitter further comprises a third 0/E converter configured to convert the third optical downlink MIMO communications signal to the third downlink MIMO communications signal and a fourth 0/E converter configured to convert the fourth optical downlink MIMO communications signal to the second downlink MIMO communications signal.

3. The MIMO remote unit of claim 2, wherein:

the first MIMO transmitter is further configured to transmit the first and second downlink MIMO communications signals wirelessly to a line-of-sight (LOS) wireless client; and

the second MIMO transmitter is configured to transmit the third and fourth downlink MIMO communications signals wirelessly to the line-of-sight (LOS) wireless client.

4. The MIMO remote unit of claim 2, further comprising at least one phase shifter configured to phase shift the fourth optical downlink MIMO communications signal to the second phase.

5. The MIMO remote unit of claim 2, wherein the second MIMO transmitter is configured to receive the fourth optical downlink MIMO communications signal in the second phase as a result of a phase shift of the fourth optical downlink MIMO communications signal in a central unit.

6. The MIMO remote unit of claim 2, wherein the second MIMO transmitter is configured to receive the fourth optical downlink MIMO communications signal in the second phase as a result of a phase shift of the fourth optical downlink MIMO communications signal in the fourth downlink communications medium.

7. The MIMO remote unit of claim 6, wherein the fourth downlink communications medium is positioned between a central unit of a wireless communications system and the second MIMO transmitter.

8. The MIMO remote unit of claim 2, wherein the third MIMO transmitter antenna is phase offset from the fourth MIMO transmitter antenna by the third MIMO transmitter antenna being positioned in distance from the fourth MIMO transmitter antenna.

9. The MIMO remote unit of claim 2, wherein the first MIMO transmitter antenna is position offset from the second MIMO transmitter antenna by positioning the first MIMO transmitter antenna in distance from the second MIMO transmitter antenna.

10. A method of transmitting multiple-input multiple-output (MIMO) communications signals to wireless client devices, comprising:

receiving a first optical downlink MIMO communications signal in a first phase over a first downlink communications medium;

transmitting the first optical downlink MIMO communications signal wirelessly as a first downlink MIMO communications signal over a first MIMO transmitter antenna in a first polarization; and

receiving a second optical downlink MIMO communications signal in the first phase over a second downlink communications medium;

transmitting the second optical downlink MIMO communications signal wirelessly as a second downlink MIMO communications signal over a second MIMO transmitter antenna in a second polarization;

receiving a third optical downlink MIMO communications signal in the first phase over a third downlink communications medium;

transmitting the third optical downlink MIMO communications signal wirelessly as a third downlink MIMO communications signal over a third MIMO transmitter antenna in the first polarization;

receiving a fourth optical downlink MIMO communications signal over a fourth downlink communications medium; and

transmitting the fourth optical downlink MIMO communications signal in a second phase shifted from the first phase, wirelessly as a fourth downlink MIMO communications signal over a fourth MIMO transmitter antenna in the second polarization.

11. The method of claim 10, further comprising transmitting the first downlink MIMO communications signal wirelessly to a line-of-sight (LOS) wireless client.

12. The method of claim 11, further comprising phase shifting the fourth optical downlink MIMO communications signal to the second phase.

13. The method of claim 11, further comprising receiving the fourth optical downlink MIMO communications signal in the second phase from a central unit that phase shifts the fourth optical downlink MIMO communications signal from the first phase to the second phase.

14. The method of claim 11, further comprising receiving the fourth optical downlink MIMO communications signal in the second phase via the fourth downlink communications medium configured to phase shift the fourth optical downlink MIMO communications signal from the first phase to the second phase.

15. The method of claim 10, further comprising phase offsetting the third MIMO transmitter antenna from the fourth MIMO transmitter antenna by positioning the third MIMO transmitter antenna in distance from the fourth MIMO transmitter to phase shift the fourth optical downlink MIMO communications signal to the second phase.

16. The method of claim 10, further comprising position offsetting the first MIMO transmitter antenna from the second MIMO transmitter antenna by positioning the first MIMO transmitter antenna in distance from the second MIMO transmitter antenna.

17. A distributed antenna system for distributing multiple-input multiple-output (MIMO) communications signals to wireless client devices, comprising:

a central unit comprising a central unit transmitter configured to transmit a first optical downlink MIMO communications signal over a first downlink communications medium, a second optical downlink MIMO communications signal over a second downlink communications medium, a third optical downlink MIMO communications signal over a third downlink communications medium, and a fourth optical downlink MIMO communications signal over a fourth downlink communications medium; and

a plurality of remote units in communications with the central unit, a first of the remote units comprising;

a first MIMO transmitter comprising a first MIMO transmitter antenna configured to transmit MIMO communications signals in a first polarization and a second MIMO transmitter antenna configured to transmit MIMO communications signals in a second polarization different from the first polarization;

a second MIMO transmitter comprising a third MIMO transmitter antenna configured to transmit MIMO communications signals in the first polarization and a fourth MIMO transmitter antenna configured to transmit MIMO communications signals in the second polarization;

the first MIMO transmitter configured to;

receive the first optical downlink MIMO communications signal in a first phase over the first downlink communications medium, and transmit the first optical downlink MIMO communications signal wirelessly as a first downlink MIMO communications signal over the first MIMO transmitter antenna in the first polarization; and

receive the second optical downlink MIMO communications signal in the first phase over the second downlink communications medium, and transmit the second optical downlink MIMO communications signal wirelessly as a second downlink MIMO communications signal over the second MIMO transmitter antenna in the second polarization;

the second MIMO transmitter configured to;

receive the third optical downlink MIMO communications signal in the first phase over the third downlink communications medium, and transmit the third optical downlink MIMO communications signal wirelessly as a third downlink MIMO communications signal over the third MIMO transmitter antenna in the first polarization; and

receive the fourth optical downlink MIMO communications signal over the fourth downlink communications medium, and transmit the fourth downlink MIMO communications signal in a second phase shifted from the first phase, wirelessly as a fourth downlink MIMO communications signal over the fourth MIMO transmitter antenna in the second polarization; and

at least one phase shifter configured to phase shift the fourth optical downlink MIMO communications signal to the second phase.

18. The distributed antenna system of claim 17, wherein:

the first MIMO transmitter is further configured to transmit the first and second downlink MIMO communications signals wirelessly to a line-of-sight (LOS) wireless client; and

the second MIMO transmitter is configured to transmit the third and fourth downlink MIMO communications signals wirelessly to the LOS wireless client.

19. The distributed antenna system of claim 17, wherein the first downlink communications medium comprises at least one optical fiber.