TIME-DIVISION DUPLEXING (TDD) IN DISTRIBUTED COMMUNICATIONS SYSTEMS, INCLUDING DISTRIBUTED ANTENNA SYSTEMS (DASS)

• US 20160088623A1
• Filed: 12/08/2015
• Published: 03/24/2016
• Est. Priority Date: 06/12/2013
• Status: Active Grant

• Current Assignee: Corning Optical Communications LLC (Corning Incorporated)
• Original Assignee: Corning Optical Communications Wireless Ltd. (Corning Incorporated)
• Inventors: Shapira, Isaac, Ben-Shlomo, Dror
• Granted Patent: US 9,974,074 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H04B 1/48 in circuits for connecting transmitter and receiver to a common transmission path, e.g. by energy of transmitter H04B1/46 takes precedence
• CPC Class Codes: H04B 17/318 Received signal strength
• CPC Class Codes: H04L 5/14 Two-way operation using the same type of signal, i.e. duplex
• CPC Class Codes: H04W 72/0446 Resources in time domain, e.g. slots or frames
• CPC Class Codes: H04W 72/20 Control channels or signalling for resource management

Abstract

Time-division duplexing (TDD) in distributed communications systems, including distributed antenna systems (DASs) is disclosed. In one embodiment, a control circuit is provided and configured to control the TDD transmit mode of a DAS to control the allocation of time slots for uplink and downlink communications signal distribution in respective uplink path(s) and downlink path(s). The control circuit includes separate power detectors configured to detect either a transmit power level in a downlink path or a receive power level in an uplink path. If the transmit power detected in the downlink path is greater than receive power detected in the uplink path, the control circuit switches the TDD transmit mode to the downlink direction. In this manner, the control circuit does not have to control the TDD transmit mode based solely on detected power in the downlink path, where a directional coupler may leak uplink power in the downlink path.

Claims

1. A control circuit for controlling switching between a time-division duplexing (TDD) transmit mode and a TDD receive mode in a system supporting TDD, the control circuit comprising:

a first power detector configured to determine a first power level from a radio source in the downlink direction on a downlink path;

a second power detector configured to determine a second power level in the uplink direction on an uplink path;

a receive/transmit comparator coupled to the first power detector and to the second power detector, wherein the receive/transmit comparator compares the first power level to the second power level to provide first indication that the system should be switched to a TDD transmit mode when the first power level exceeds the second power level; and

a logic circuit coupled to the receive/transmit comparator for receiving the first indication, and for further receiving at least one additional indication.

2. The control circuit of claim 1, further comprising means for generating a transmit power reference, and a second power comparator configured to determine a second indication whether the first power level exceeds a value of the transmit power reference, the logic circuit coupled to the second power comparator for receiving the second indication.

3. The control circuit of claim 2, further comprising means for generating a saturation level reference, and a saturation comparator configured to provide a third indication of saturation of the first power detector by comparing the first power level with the saturation level reference, the logic circuit coupled to the saturation comparator for receiving the indication.

4. The control circuit of claim 2, wherein the receive/transmit comparator and the second power comparator have as an input the output of the first power detector.

5. The control circuit of claim 2, wherein the logic circuit has a first state in which the second power level exceeds the first power level to indicate TDD receive mode.

6. The control circuit of claim 2, wherein the logic circuit has a second state in which the first power level exceeds the second power level and the first power level does not exceed the value of the transmit power reference to indicate TDD receive mode.

7. The control circuit of claim 2, wherein the logic circuit has a third state in which the first power level exceeds the second power level and the value of the transmit power reference to indicate TDD transmit mode.

8. The control circuit of claim 2, further comprising a TDD switching circuit configured to effect the TDD transmit mode and a TDD receive mode for the system.

9. The control circuit of claim 8, wherein the TDD switching circuit comprises an input switch and an antenna switch located upstream and downstream the downlink path, respectively.

10. The control circuit of claim 9, wherein the TDD switching circuit comprises a transmit amplifier and a receive amplifier located between the input switch and the antenna switch.

11. The control circuit of claim 10, wherein the input switch and the antenna switch are configured to operate in coordination to effect the TDD transmit mode and the TDD receive mode.

12. The control circuit of claim 8, further comprising a directional coupler configured to receive and transmit communications between the TDD switching circuit and the radio source.

13. The control circuit of claim 11, wherein the logic circuit schedules toggling of the input switch and the antenna switch to effect the TDD transmit mode and the TDD receive mode.

14. The control circuit of claim 3, wherein the receive/transmit comparator and the saturation comparator have as an input the output of the first power detector.

15. A distributed communication system capable of supporting time-division duplexing (TDD), the distributed communication system comprising:

a central unit configured to receive a plurality of downlink signals from at least one radio source;

a plurality of remote units each configured to receive downlink signals from the central unit, and to return uplink signals to the central unit; and

a control circuit for controlling TDD switching in the distributed communication system, the control circuit comprising;

a first power detector configured to determine a first power level from the at least one radio source;

a second power detector configured to determine a second power level from an uplink path; and

a receive/transmit comparator coupled to the first power detector and to the second power detector, wherein the receive/transmit comparator compares the first power level to the second power level to provide an indication that the distributed communication system should be switched to a TDD transmit mode when the first power level exceeds the second power level.

16. The distributed communication system of claim 15, further comprising a transmit power comparator configured to determine whether the first power level exceeds a reference value.

17. The distributed communication system of claim 16, further comprising a saturation comparator configured to compare the first power level with a saturation level reference.

18. The distributed communication system of claim 16, wherein the transmit power comparator and the receive/transmit comparator have outputs coupled to a logic circuit.

19. The distributed communication system of claim 15, further comprising a TDD switching circuit configured to effect the TDD transmit mode and a TDD receive mode for the distributed communication system.

20. The distributed communication system of claim 19, wherein the TDD switching circuit comprises:

an input switch and an antenna switch located between the input switch and the distributed communication system; and

a transmit amplifier and a receive amplifier located between the input switch and the antenna switch.

21. The distributed communication system of claim 20, wherein the input switch and the antenna switch are configured to operate in coordination to effect the TDD transmit mode and the TDD receive mode.

22. The distributed communication system of claim 19, further comprising a directional coupler configured to receive and transmit communications between the TDD switching circuit, the at least one radio source, the first power detector, and the second power detector.

23. The distributed communication system of claim 15, wherein the first power detector comprises a diode, the second power detector comprises a diode, and wherein the receive/transmit comparator, the transmit power comparator, and the saturation comparator have as an input the output of the first power detector.

24. The distributed communication system of claim 15, wherein the central unit further comprises at least one electrical-to-optical converter configured to convert downlink electrical signals from the at least one radio source to downlink optical signals.

25. The distributed communication system of claim 24, wherein the plurality of remote units are each configured to transmit wireless communications into a coverage area and receive wireless communications from client devices in a coverage area.