Hybrid wireless optical and radio frequency communication link

• US 6,763,195 B1
• Filed: 01/13/2000
• Issued: 07/13/2004
• Est. Priority Date: 01/13/2000
• Status: Expired due to Term

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: LightPointe Communications, Inc.
• Inventors: Achour, Maha, Willebrand, Heinz
• Primary Examiner(s): Pascal, Leslie
• Assistant Examiner(s): Phan, Hanh
• Application Number:
  US09/482,782
• Time in Patent Office: 1,643 Days
• Field of Search: 398/115, 398/116, 398/118, 398/120, 398/135, 398/17, 398/19, 398/23, 398/24, 455/103, 455/74
• US Class Current: 398/115
• CPC Class Codes: H04B 10/1123 Bidirectional transmission
• CPC Class Codes: H04B 10/114 Indoor or close-range type systems

Abstract

A hybrid wireless optical and radio frequency (RF) communication link utilizes parallel free-space optical and RF paths for transmitting data and control and status information. The optical link provides the primary path for the data, and the RF link provides a concurrent or backup path for the network data, as well as a reliable and primary path for the control and status information. When atmospheric conditions degrade the optical link to the point at which optical data transmission fails, the hybrid communication link switches to the RF link to maintain availability of data communications. The switch may occur automatically, based on an assessment of the quality of the optical signal communicated through the optical path.

Claims

1. A method of communicating data in a communication link extending across a terrestrial free-space region between two stations at ends of the link, comprising the steps of:

communicating the data in an optical signal transmitted through an outdoor free-space optical path between the two stations;

communicating control and status information in a radio frequency (RF) signal transmitted through an outdoor free-space RF path between the two stations concurrently with the transmission of the optical signal that includes the data; and

communicating the data and control and status information in an RF signal transmitted in the free-space RF path between the two stations when the data is not transmitted in the optical signal through the optical path.

2. A method as defined in claim 1 further comprising the step of:

communicating the RF signal containing the control and status information between the stations continuously.

3. A method as defined in claim 1 further comprising the steps of:

selecting one of either the optical path or the RF path for communicating the data based on the control and status information; and

communicating the data in the selected path.

4. A method as defined in claim 1 further comprising the steps of:

sensing a characteristic of the optical signal received from the optical path;

selecting one of either the optical path or the RF path for communicating the data based upon the sensed characteristic of the optical signal; and

communicating the data in the selected path.

5. A method as defined in claim 4 further comprising the steps of:

sensing a failure to receive the optical signal communicated in the optical path as the characteristic for selecting the path; and

communicating the data in the RF path upon sensing a failure to receive the optical signal.

6. A method as defined in claim 4 further comprising the steps of:

sensing a power level of the optical signal communicated in the optical path as the characteristic for selecting the path; and

communicating the data in the RF path upon the power level of the optical signal communicated in the optical path falling below a predetermined threshold level.

7. A method as defined in claim 6 wherein:

the step of sensing the power level senses a received power level and a transmitted power level of the optical signal communicated in the optical path as a combined characteristic for selecting the path; and

the data is communicated in the RF path upon the received power level of the optical signal falling below the predetermined threshold level and the transmitted power level of the optical signal being at about a maximum threshold level.

8. A method as defined in claim 4 further comprising the steps of:

sensing a transmissive capability the optical signal communicated in the optical path as the characteristic for selecting the path; and

communicating the data in the RF path upon the transmissive capability of the optical signal communicated in the optical path falling below a transmissive capability of the RF signal communicated in the RF path.

9. A method as defined in claim 4 further comprising the step of:

transmitting a synchronization optical signal through the optical path while the data is communicated in the RF path.

10. A method as defined in claim 9 further comprising the steps of:

including information of a characteristic of the received synchronization signal in the control and status information; and

switching the communication of data from the RF path to the optical path based on the information describing the characteristic of the received synchronization signal included in the control and status information.

11. A method as defined in claim 4 further comprising the steps of:

including information of the sensed characteristic in the control and status information; and

switching the communication of the data from one path to the other path based on the sensed characteristic information included in the control and status information.

12. A method as defined in claim 1 further comprising the step of:

adjusting an optical power level at which the optical signal is transmitted through the optical path by both stations to maintain a received optical power level within a receiver operational window between a predetermined maximum level and a predetermined minimum level.

13. A method as defined in claim 1 further comprising the step of:

adjusting an optical power level at which the optical signal is transmitted through the optical path by both stations to approximately the same level.

14. A method as defined in claim 13 further comprising the steps of:

transmitting optical power level synchronization information in the control and status information transmitted between the two stations; and

establishing the same optical power level for the optical signal transmitted from each of the two stations based on the optical power level synchronization information.

15. A method as defined in claim 14 further comprising the steps of:

generating the control and status information at the one station transmitting-the optical signal to the other station; and

including adjustment information in the control and status information which indicates an amount by which the other station is to adjust the optical power level at which the other station transmits the optical signal to the one station.

16. A method as defined in claim 15 further comprising the step of:

adjusting the optical power level at which the other station transmits the optical signal to the one station according to the adjustment information included in the control and status information.

17. A method as defined in claim 15 further comprising the step of:

adjusting the optical power level at which the one station transmits the optical signal by the same amount indicated by the adjustment information which was generated by the one station.

18. A method as defined in claim 1 further comprising the steps of:

selecting one of either the optical path or the RF path for communicating the data based on an external control factor supplied to the stations; and

communicating the data in the selected path.

19. A hybrid wireless optical and radio frequency (RF) communication link for communicating data between first and second stations, the first and second stations receiving and delivering the data through respective first and second input/output (I/O) signal paths, comprising:

a free-space optical link portion comprising a first optical transceiver at the first station and a second optical transceiver at the second station for transmitting and receiving an optical signal through an outdoor free-space optical path therebetween; and

a free-space RF link portion in parallel with the optical link portion and comprising a first RF transceiver at the first station and a second RF transceiver at the second station for transmitting and receiving an RF signal through an outdoor free-space RF path therebetween;

wherein the RF signal communicates control and status information for controlling the operation of the optical and RF transceivers and is transmitted concurrently with the optical signal when the optical signal communicates the data, and wherein the RF signal communicates the data and control and status information when the optical signal does not communicate the data.

20. A hybrid wireless optical and radio frequency (RF) communication link for communicating data between first and second stations, the first and second stations receiving and delivering the data through respective first and second input/output (I/O) signal paths, comprising:

a free-space optical link portion comprising a first optical transceiver at the first station and a second optical transceiver at the second station for transmitting and receiving an optical signal therebetween containing the data;

a free-space RF link portion in parallel with the optical link portion and comprising a first RF transceiver at the first station and a second RF transceiver at the second station for transmitting and receiving an RF signal therebetween containing the data and control and status information for controlling the operation of the optical and RF transceivers;

a first switch at the first station connected to the optical link portion, the RF link portion and the first I/O signal path, the first switch routing the data between the first optical transceiver and the first I/O signal path in an active mode and routing the data between the first RF transceiver and the first I/O signal path in a standby mode; and

a second switch at the second station connected to the optical link portion, the RF link portion and the second I/O signal path, the second switch routing the data between the second optical transceiver and the second I/O signal path in an active mode and routing the data between the second RF transceiver and the second I/O signal path in a standby mode; and

the first switch responds to the control and status information to switch between the active and standby modes.

21. A communication link as defined in claim 20 wherein:

one of the first or second optical transceivers of the optical link portion generates a transmission status signal indicative of whether the optical link portion can effectively communicate the data.

22. A communication link as defined in claim 21 wherein:

the transmission status signal is included in the control and status information; and

the first switch responds to the transmission status signal to switch between the active and standby modes.

23. A communication link as defined in claim 20 wherein:

one of the first or second switches switches from the active mode to the standby mode in response to the absence of data transmitted through the optical link portion.

24. A communication link as defined in claim 20 wherein:

the first and second switches operate in the active mode when the optical link portion transmits data; and

the first and second switches operate in the standby mode when the optical link portion fails to transmit the data.

25. A hybrid wireless optical and radio frequency (RF) communication link for communicating data between first and second stations, the first and second stations receiving and delivering the data through respective first and second input/output (I/O) signal paths, comprising:

a free-space optical link portion comprising a first optical transceiver at the first station and a second optical transceiver at the second station for transmitting and receiving an optical signal therebetween containing the data;

a free-space RF link portion in parallel with the optical link portion and comprising a first RF transceiver at the first station and a second RF transceiver at the second station for transmitting and receiving an RF signal therebetween containing the data and control and status information for controlling the operation of the optical and RF transceivers;

a first switch at the first station connected to the optical link portion, the RF link portion and the first I/O signal path, the first switch routing the data between the first optical transceiver and the first I/O signal path in an active mode and routing the data between the first RF transceiver and the first I/O signal path in a standby mode; and

a second switch at the second station connected to the optical link portion, the RF link portion and the second I/O signal path, the second switch routing the data between the second optical transceiver and the second I/O signal path in an active mode and routing the data between the second RF transceiver and the second I/O signal path in a standby mode; and

the first switch responds to the control and status information to switch between the active and standby modes;

wherein,

the control and status information includes a control token packet which is transmitted back and forth between the first and second stations through the RF link portion and which contains power adjustment information;

the power adjustment information generated by a sending one of the first or second optical transceivers;

the power adjustment information indicating an amount by which the other receiving one of the first or second optical transceivers is to change an optical transmission power level at which the receiving optical transceiver should transmit the optical signal to the sending optical transceiver.

26. A communication link as defined in claim 25 wherein:

the receiving optical transceiver responds to receipt of the power adjustment information contained in the control token packet by changing the optical transmission power level at which the receiving optical transceiver transmits the optical signal.

27. A communication link as defined in claim 25 wherein:

the sending optical transceiver changes the optical transmission power level at which the sending optical transceiver transmits the optical signal by the same amount indicated by the power adjustment information which the sending optical transceiver generated.

28. A method for use in free-space communications, comprising the steps of:

transmitting data in an optical signal through an outdoor free-space optical path of a communication link;

transmitting control and status information in a radio frequency (RF) signal through an outdoor free-space RF path of the communication link concurrently with the transmission of the optical signal that includes the data; and

transmitting the data and control and status information in the RF signal through the free-space RF path of the communication link when the data is not transmitted in the optical signal through the optical path.

29. A method in accordance with claim 28, wherein the data is switched from being transmitted in the optical signal to being transmitted in the RF signal based on the control and status information.

30. A method in accordance with claim 28, further comprising the step of:

continuing to transmit the optical signal through the free-space optical path when the data and control and status information is being transmitted in the RF signal through the free-space RF path.

31. An apparatus for use in free-space communications, comprising:

means for transmitting data in an optical signal through an outdoor free-space optical path of a communication link;

means for transmitting control and status information in a radio frequency (RF) signal through an outdoor free-space RF path of the communication link concurrently with the transmission of the optical signal that includes the data; and

means for transmitting the data and control and status information in the RF signal through the free-space RF path of the communication link when the data is not transmitted in the optical signal through the optical path.

32. An apparatus in accordance with claim 31, further comprising:

means for switching the data from being transmitted in the optical signal to being transmitted in the RF signal based on the control and status information.

33. An apparatus in accordance with claim 31, further comprising:

means for continuing to transmit the optical signal through the free-space optical path when the data and control and status information is being transmitted in the RF signal through the free-space RF path.

34. An apparatus for use in free-space communications, comprising:

an optical transceiver configured to transmit data in an optical signal through an outdoor free-space optical path of a communication link during an active mode of operation; and

a radio frequency (RF) transceiver configured to transmit control and status information in an RF signal through an outdoor free-space RF path of the communication link concurrently with the transmission of the optical signal that includes the data during the active mode of operation;

wherein the RF transceiver is further configured to transmit the data and control and status information in the RF signal through the free-space RF path of the communication link during a standby mode of operation.

35. An apparatus in accordance with claim 34, wherein the optical transceiver is further configured to transmit the optical signal through the free-space optical path during the standby mode of operation.

36. An apparatus for use in free-space communications, comprising:

an optical transceiver configured to transmit optical signals through an outdoor free-space optical path of a communication link;

a radio frequency (RF) transceiver configured to transmit RF signals through an outdoor free-space RF path of the communication link; and

interface circuitry coupled to the optical transceiver and the RF transceiver and configured to,

send data to the optical transceiver for transmission through the free-space optical path during an active mode of operation,

send control and status information to the RF transceiver for transmission through the free-space RF path concurrently with the transmission of data through the free-space optical path during the active mode of operation, and

send data and control and status information to the RF transceiver for transmission through the free-space RF path during a standby mode of operation.

37. An apparatus in accordance with claim 36, wherein the interface circuitry is further configured to switch from the active mode to the standby mode based on the control and status information.

38. An apparatus in accordance with claim 36, wherein the interface circuitry is further configured to cause the optical transceiver to transmit during the standby mode of operation.