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

• US 9,929,786 B2
• Filed: 12/08/2016
• Issued: 03/27/2018
• Est. Priority Date: 07/30/2014
• Status: Active Grant

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: George, Jacob, Ng'Oma, Anthony, Yang, Hejie
• Primary Examiner(s): Curs, Nathan
• Application Number:
  US15/372,490
• Publication Number:
  US 20170093472A1
• Time in Patent Office: 474 Days
• CPC Class Codes: H04B 10/2575 Radio-over-fibre, e.g. radio frequency signal modulated onto an optical carrier
• 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 10/25891 Transmission components H04B10/40 takes precedence
• CPC Class Codes: H04B 7/022 Site diversity; Macro-diversity using two or more spaced independent antennas H04B7/04
• 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 7/10 Polarisation diversity; Directional diversity
• CPC Class Codes: H04W 72/51 based on terminal or device properties
• CPC Class Codes: H04W 72/541 using the level of interference
• CPC Class Codes: H04W 88/10 adapted for operation in multiple networks, e.g. multi-mode access points

Abstract

Components, systems, and methods for reducing location-dependent destructive 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 separation (i.e., phase, amplitude) in the received MIMO communications signals. Thus, to provide amplitude separation of received MIMO communications 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 amplitude adjusted in one of the polarization states to provide amplitude separation between received MIMO communications signals. In other embodiments, multiple transmitter antennas in a MIMO transmitter can be offset to provide amplitude separation.

Claims

1. A distributed communication system, comprising:

a central unit;

a plurality of optical fibers; and

a plurality of multiple-input, multiple-output (MIMO) remote units coupled to the central unit by the plurality of optical fibers, at least one of the MIMO remote units being configured to wirelessly distribute MIMO communications signals to wireless client devices located in a coverage area, the at least one MIMO 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; 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, wherein

the first MIMO transmitter is configured to;

receive a first optical downlink MIMO communications signal at a first amplitude over a first one of the optical fibers and, to transmit the first downlink MIMO communications signal as a first electrical downlink MIMO communications signal wirelessly over the first MIMO transmitter antenna in the first polarization; and

receive a second optical downlink MIMO communications signal at the first amplitude and, to transmit the second downlink MIMO communications signal as a second electrical downlink MIMO communications signal wirelessly over the second MIMO transmitter antenna in the second polarization, and wherein

the second MIMO transmitter is configured to;

receive a third optical downlink MIMO communications signal at the first amplitude and, to transmit the third downlink MIMO communications signal as a third electrical downlink MIMO communications signal wirelessly over the third MIMO transmitter antenna in the first polarization; and

receive a fourth optical downlink MIMO communications signal and, to transmit the fourth downlink MIMO communications signal at a second amplitude modified from the first amplitude, as a fourth electrical downlink MIMO communications signal wirelessly over the fourth MIMO transmitter antenna in the second polarization.

2. The distributed communication system of claim 1, wherein the at least one MIMO remote unit comprises at least one optical-to-electrical (O/E) converter configured to convert the first optical downlink MIMO communications signal before transmission of the first electrical downlink MIMO communications signal.

3. The distributed communication system of claim 2, further comprising at least one amplitude adjustment circuit configured to amplitude adjust the fourth optical downlink MIMO communications signal at the second amplitude.

4. The distributed communication system of claim 3, wherein the at least one amplitude adjustment circuit is further configured to be electronically tunable to adjust the fourth optical downlink MIMO communications signal at the second amplitude.

5. The distributed communication system of claim 3, wherein the amplitude adjustment circuit is configured to attenuate the fourth optical downlink MIMO communications signal at the second amplitude.

6. The distributed communication system of claim 3, wherein the amplitude adjustment circuit is configured to amplify the fourth optical downlink MIMO communications signal at the second amplitude.

7. The distributed communication system of claim 3, wherein the amplitude adjustment circuit is configured to adjust a bias signal of an optical modulator to amplitude adjust the fourth optical downlink MIMO communications signal at the second amplitude.

8. The distributed communication system of claim 3, wherein the second MIMO transmitter is configured to receive the fourth optical downlink MIMO communications signal in the second amplitude as a result of an amplitude adjustment of the fourth optical downlink MIMO communications signal.

9. The distributed communication system of claim 3, 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 approximately 30 GHz and approximately 300 GHz.

10. The distributed communication system of claim 3, wherein:

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

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

11. The distributed communication system of claim 2, wherein the second MIMO transmitter is configured to receive the fourth optical downlink MIMO communications signal at the second amplitude as a result of an amplitude adjustment of the fourth optical downlink MIMO communications signal in the central unit.

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

receiving a first optical downlink MIMO communications signal at a first amplitude over a first downlink communications medium;

converting the first optical downlink MIMO communications signal to a first electrical downlink MIMO communications signal;

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

receiving a second optical downlink MIMO communications signal at the first amplitude;

converting the second optical downlink MIMO communications signal to a second electrical downlink MIMO communications signal;

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

receiving a third optical downlink MIMO communications signal at the first amplitude;

converting the third optical downlink MIMO communications signal to a third electrical downlink MIMO communications signal;

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

receiving a fourth optical downlink MIMO communications signal;

converting the fourth optical downlink MIMO communications signal to a fourth electrical downlink MIMO communications signal; and

transmitting the fourth electrical downlink MIMO communications signal at a second amplitude modified from the first amplitude, over a fourth MIMO transmitter antenna in the second polarization.

13. The method of claim 12, wherein:

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

transmitting the second electrical downlink MIMO communications signal comprises transmitting to a LOS wireless client;

transmitting the third electrical downlink MIMO communications signal comprises transmitting to a LOS wireless client; and

transmitting the fourth electrical downlink MIMO communications signal comprises transmitting to a LOS wireless client.

14. The method of claim 12, further comprising amplitude adjusting the fourth optical downlink MIMO communications signal at the second amplitude.

15. The method of claim 14, further comprising receiving the fourth optical downlink MIMO communications signal at the second amplitude modified from the first amplitude in a central unit.

16. The method of claim 14, further comprising receiving the fourth optical downlink MIMO communications signal at the second amplitude modified from the first amplitude in the fourth downlink communications medium.

17. The method of claim 13, further comprising amplitude adjusting the fourth optical downlink MIMO communications signal at the second amplitude.