Reducing location-dependent interference in distributed antenna systems operating in multiple-input, multiple-output (MIMO) configuration, and related components, systems, and methods

• US 9,258,052 B2
• Filed: 09/16/2014
• Issued: 02/09/2016
• 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
• Primary Examiner(s): DEPPE, BETSY LEE
• Application Number:
  US14/487,232
• Publication Number:
  US 20150003565A1
• Time in Patent Office: 511 Days
• Field of Search: 375/267, 375/299, 455/101, 398/140, 398/152
• 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 in a distributed antenna system, 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 downlink MIMO communications signal in a first phase over a first downlink communications medium, and transmit the first downlink MIMO communications signal wirelessly as a first electrical downlink MIMO communications signal over the first MIMO transmitter antenna in the first polarization; and

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

the second MIMO transmitter configured to;

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

receive a fourth downlink MIMO communications signal over a 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 electrical 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 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.

3. The MIMO remote unit of claim 1, further comprising at least one phase shifter configured to phase shift the fourth downlink MIMO communications signal to the second phase.

4. The MIMO remote unit of claim 1, wherein the second MIMO transmitter is configured to receive the fourth downlink MIMO communications signal in the second phase as a result of a phase shift of the fourth downlink MIMO communications signal in a central unit.

5. The MIMO remote unit of claim 1, wherein the second MIMO transmitter is configured to receive the fourth downlink MIMO communications signal in the second phase as a result of a phase shift of the fourth downlink MIMO communications signal in the fourth downlink communications medium.

6. The MIMO remote unit of claim 1, wherein the third MIMO transmitter antenna is phase offset from the fourth MIMO transmitter antenna by positioning the third MIMO transmitter antenna in distance from the fourth MIMO transmitter antenna.

7. The MIMO remote unit of claim 5, 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.

8. The MIMO remote unit of claim 1, 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.

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

the first downlink MIMO communications signal further comprises a first optical downlink MIMO communications signal;

the second downlink MIMO communications signal further comprises a second optical downlink MIMO communications signal;

the third downlink MIMO communications signal further comprises a third optical downlink MIMO communications signal; and

the fourth downlink MIMO communications signal further comprises a fourth optical downlink MIMO communications signal.

10. The MIMO remote unit of claim 9, wherein:

the first MIMO transmitter further comprises;

a first optical-to-electrical (O/E) converter configured to convert the first optical downlink MIMO communications signal to the first electrical downlink MIMO communications signal; and

a second O/E converter configured to convert the second optical downlink MIMO communications signal to the second electrical downlink MIMO communications signal; and

the second MIMO transmitter further comprises;

a third O/E converter configured to convert the third optical downlink MIMO communications signal to the third electrical downlink MIMO communications signal; and

a fourth O/E converter configured to convert the fourth optical downlink MIMO communications signal to the fourth electrical downlink MIMO communications signal.

11. The MIMO remote unit of claim 1, wherein at least one of the first electrical downlink MIMO communications signal, the second electrical downlink MIMO communications signal, the third electrical downlink MIMO communications signal, and the fourth electrical downlink MIMO communications signal include a carrier frequency having an extremely high frequency (EHF) between 30 GHz and 300 GHz.

12. A method of transmitting multiple-input multiple-output (MIMO) communications signals to wireless client devices in a distributed antenna system, comprising:

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

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

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

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

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

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

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

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

13. The method of claim 12, further comprising:

transmitting the first downlink MIMO communications signal wirelessly to a line-of-sight (LOS) wireless client;

transmitting the second downlink MIMO communications signal wirelessly to the LOS wireless client;

transmitting the third downlink MIMO communications signal wirelessly to the LOS wireless client; and

transmitting the fourth downlink MIMO communications signal wirelessly to the LOS wireless client.

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

15. The method of claim 14, further comprising receiving the fourth downlink MIMO communications signal in the second phase from a central unit that phase shifts the fourth downlink MIMO communications signal from the first phase to the second phase.

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

17. The method of claim 14, comprising phase shifting the fourth downlink MIMO communications signal to the second phase for transmission over the fourth MIMO transmitter antenna.

18. The method of claim 12, 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 antenna to phase shift the fourth downlink MIMO communications signal to the second phase.

19. The method of claim 12, 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.

20. 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 receive a downlink communications signal, and transmit the received downlink communications signal as a first downlink MIMO communications signal over a first downlink communications medium, a second downlink MIMO communications signal over a second downlink communications medium, a third downlink MIMO communications signal over a third downlink communications medium, and a fourth downlink MIMO communications signal over a fourth downlink communications medium; and

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

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

the second MIMO transmitter configured to;

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

receive the fourth 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 electrical 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 downlink MIMO communications signal to the second phase.

21. The distributed antenna system of claim 20, 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.

22. The distributed antenna system of claim 20, wherein:

the central unit further comprises one or more electrical-to-optical (E/O) converters configured to;

convert the first downlink MIMO communications signal into a first optical downlink MIMO communications signal, and provide the first optical downlink MIMO communications signal to the remote unit over an optical fiber communications medium;

convert the second downlink MIMO communications signal into a second optical downlink MIMO communications signal, and provide the second optical downlink MIMO communications signal to the remote unit over the optical fiber communications medium;

convert the third downlink MIMO communications signal into a third optical downlink MIMO communications signal, and provide the third optical downlink MIMO communications signal to the remote unit over the optical fiber communications medium; and

convert the fourth downlink MIMO communications signal into a fourth optical downlink MIMO communications signal, and provide the fourth optical downlink MIMO communications signal to the remote unit over the optical fiber communications medium; and

the remote unit further comprises one or more optical-to-electrical (O/E) converters configured to;

receive the first optical downlink MIMO communications signal over the optical fiber communications medium, and convert the first optical downlink MIMO communications signal into the first downlink MIMO communications signal;

receive the second optical downlink MIMO communications signal over the optical fiber communications medium, and convert the second optical downlink MIMO communications signal into the second downlink MIMO communications signal;

receive the third optical downlink MIMO communications signal over the optical fiber communications medium, and convert the third optical downlink MIMO communications signal into the third downlink MIMO communications signal; and

receive the fourth optical downlink MIMO communications signal over the optical fiber communications medium, and convert the fourth optical downlink MIMO communications signal into the fourth downlink MIMO communications signal.

23. The distributed antenna system of claim 20, wherein the second MIMO transmitter is configured to receive the fourth downlink MIMO communications signal in the second phase as a result of a phase shift of the fourth downlink MIMO communications signal in a central unit.

24. The distributed antenna system of claim 20, wherein the second MIMO transmitter is configured to receive the fourth downlink MIMO communications signal in the second phase as a result of a phase shift of the fourth downlink MIMO communications signal in the fourth downlink communications medium.

25. The distributed antenna system of claim 20, wherein the third MIMO transmitter antenna is phase offset from the fourth MIMO transmitter antenna by positioning the third MIMO transmitter antenna in distance from the fourth MIMO transmitter antenna.

26. The distributed antenna system of claim 20, 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.

27. The distributed antenna system of claim 20, wherein at least one of the first electrical downlink MIMO communications signal, the second electrical downlink MIMO communications signal, the third electrical downlink MIMO communications signal, and the fourth electrical downlink MIMO communications signal include a carrier frequency having an extremely high frequency (EHF) between 30 GHz and 300 GHz.