Wireless communications systems employing free-space optical communications links

• US 5,844,705 A
• Filed: 02/13/1997
• Issued: 12/01/1998
• Est. Priority Date: 02/13/1997
• Status: Expired due to Term

• Current Assignee: AT&T Corporation (AT&T, Inc.)
• Original Assignee: AT&T Corporation (AT&T, Inc.)
• Inventors: Rutledge, Christopher L.
• Primary Examiner(s): NEGASH, KINFE MICHAEL
• Application Number:
  US08/799,885
• Time in Patent Office: 656 Days
• Field of Search: 359/145, 359/152, 359/167, 359/172, 359/130, 370/310, 455/14, 455/561-562
• US Class Current: 398/66
• CPC Class Codes: H04B 10/0773 Network aspects, e.g. central monitoring of transmission parameters
• CPC Class Codes: H04B 10/1125 using a single common optical path
• CPC Class Codes: H04B 10/25752 Optical arrangements for wireless networks
• CPC Class Codes: H04B 2210/078 using a separate wavelength

Abstract

The cells of a wireless communications system can be subdivided into smaller subcells, in each of which the available radio frequencies can be re-used to allow denser use of the system. To avoid having to run hard-wired communications links to broadcast antennas of the subcells, substantially unguided, free-space, optical communication is used between the antenna that formerly served the cell and the subcell antennas. The existing hard-wired connection from the central antenna to the remainder of the wireless communications system infrastructure continues to be used for communication to and from the cell.

Claims

1. A wireless communication method comprising:

a) communicating information between a communication network and a central location;

b) communicating at least some of said information between said central location and each of a plurality of remote locations via substantially unguided light passing between said central location and each of said remote locations; and

;

c) communicating at least some of said information between each of said remote locations and wireless communication devices in the vicinity of said remote location via radio signals broadcast between said remote location and said wireless communication devices;

wherein said communicating of information between said communication network and said central location is via optical communication; and

wherein said information includes message information and control information.

2. The method defined in claim 1 wherein said optical communication is guided via optical fiber between said communication network and said central location.

3. The method defined in claim 1 wherein said communicating between said communication network and said central location is bi-directional.

4. The method defined in claim 3 wherein light of different wavelengths is used for communicating in each direction.

5. The method defined in claim 1 wherein said communicating between s aid central location and each of said remote locations is bi-directional.

6. The method defined in claim 5 wherein light of a different wavelength is used for communicating from each of said remote locations to said central location.

7. The method defined in claim 1 wherein said communicating between said remote locations and said wireless communication devices is bi-directional.

8. The method defined in claim 1 wherein said communicating between said communication network and said central location is bi-directional, and wherein light of different wavelengths is used for communicating in each direction.

9. A wireless communications system comprising:

a plurality of central optical transceivers associated with a cell;

a plurality of remote optical transceivers, each of which is associated with a respective one of a plurality of subcells within said cell, each of said remote optical transceivers being adapted to communicate with a respective one of said central optical transceivers via substantially unguided light passing between said remote optical transceiver and the associated central optical transceiver; and

electronic circuitry associated with each of said remote optical transceivers for converting between radio frequency signals in the associated subcell and light communicated by said remote optical transceiver;

wireless communications control circuitry remote from said central and remote optical transceivers; and

a communications link between said wireless communications control circuitry and said central optical transceivers.

10. A wireless communications system comprising:

a plurality of central optical transceivers associated with a cell;

a plurality of remote optical transceivers, each of which is associated with a respective one of a plurality of subcells within said cell, each of said remote optical transceivers being adapted to communicate with a respective one of said central optical transceivers via substantially unguided light passing between said remote optical transceiver and the associated central optical transceiver; and

electronic circuitry associated with each of said remote optical transceivers for converting between radio frequency signals in the associated subcell and light communicated by said remote optical transceiver;

wireless communications control circuitry remote from said central and remote optical transceivers;

a communications link between said wireless communications control circuitry and said central optical transceivers; and

wherein said communication link comprises optical fiber between said wireless communications control circuitry and said central optical transceivers.

11. The apparatus defined in claim 10 wherein light having a unique wavelength is used for communicating information associated with each of said subcells.

12. The apparatus defined in claim 10 wherein light having a first unique wavelength is used for communicating information to each subcell and wherein light having a second unique wavelength is used for communicating information from each subcell.

13. The apparatus defined in claim 12 wherein each of said central optical transceivers transmits to the associated remote optical transceiver light which includes said wavelengths used for communication to all of said subcells.

14. The apparatus defined in claim 13 wherein each of said remote optical transceivers includes optical filter apparatus for selecting from the wavelengths received by said transceiver the wavelength used for communication to the associated subcell.

15. The apparatus defined in claim 14 wherein said optical filter apparatus comprises Bragg grating apparatus.

16. The apparatus defined in claim 12 wherein light having a further unique wavelength is used for communicating control information to all of said subcells.

17. A wireless communications system comprising:

a plurality of central optical transceivers associated with a cell;

a plurality of remote optical transceivers, each of which is associated with a respective one of a plurality of subcells within said cell, each of said remote optical transceivers being adapted to communicate with a respective one of said central optical transceivers via substantially unguided light passing between said remote optical transceiver and the associated central optical transceiver; and

electronic circuitry associated with each of said remote optical transceivers for converting between radio frequency signals in the associated subcell and light communicated by said remote optical transceiver;

wherein light having a first unique wavelength is used for communicating information to each subcell and wherein light having a second unique wavelength is used for communicating information from each subcell; and

wherein light having a further unique wavelength is used for communicating control information to all of said subcells.

18. The apparatus defined in claim 17 wherein each of said central optical transceivers transmits to the associated remote optical transceiver light which includes said wavelengths used for communicating said information and said control information to all of said subcells.

19. The apparatus defined in claim 18 wherein each of said remote optical transceivers includes optical filter apparatus for selecting from the wavelengths received by said transceiver the wavelength used for communicating said information to the associated subcell and the wavelength used for communicating said control information to all of said subcells.

20. The apparatus defined in claim 19 wherein said filter apparatus comprises Bragg grating apparatus.

21. A wireless communications system comprising:

a plurality of central optical transceivers associated with a cell;

a plurality of remote optical transceivers, each of which is associated with a respective one of a plurality of subcells within said cell, each of said remote optical transceivers being adapted to communicate with a respective one of said central optical transceivers via substantially unguided light passing between said remote optical transceiver and the associated central optical transceiver; and

electronic circuitry associated with each of said remote optical transceivers for converting between radio frequency signals in the associated subcell and light communicated by said remote optical transceiver;

wireless communications control circuitry remote from said central and remote optical transceivers; and

a communications link between said wireless communications control circuitry and said central optical transceivers;

wherein said communication link comprises optical fiber between said wireless communications control circuitry and said central optical transceivers; and

wherein said optical fiber transmits light from said wireless communications control circuitry to said central optical transceivers, each of which passes a portion of said light on to the associated remote optical transceiver.

22. The apparatus defined in claim 21 wherein said optical fiber includes erbium doped fiber amplifier apparatus for optically amplifying light being transmitted via said optical fiber.

23. A wireless communications system comprising:

a plurality of central optical transceivers associated with a cell;

a plurality of remote optical transceivers, each of which is associated with a respective one of a plurality of subcells within said cell, each of said remote optical transceivers being adapted to communicate with a respective one of said central optical transceivers via substantially unguided light passing between said remote optical transceiver and the associated central optical transceiver; and

electronic circuitry associated with each of said remote optical transceivers for converting between radio frequency signals in the associated subcell and light communicated by said remote optical transceiver;

wireless communications control circuitry remote from said central and remote optical transceivers;

a communications link between said wireless communications control circuitry and said central optical transceivers;

wherein said communication link comprises optical fiber between said wireless communications control circuitry and said central optical transceivers; and

wherein said optical fiber transmits to said wireless communications control circuitry light received by each of said central optical transceivers from the associated remote optical transceiver.

24. The apparatus defined in claim 23 wherein each of said remote optical transceivers transmits light of a unique wavelength to the associated central optical transceiver, and wherein said apparatus further comprises optical coupler apparatus for combining, for application to said optical fiber, the light received by all of said central optical transceivers from said remote optical transceivers.

25. The apparatus defined in claim 23 wherein said optical fiber includes erbium doped fiber amplifier apparatus for optically amplifying light being transmitted via said optical fiber from said central optical transducers to said wireless communications control circuitry.

26. A wireless communication method comprising:

a) communicating information between a communication network and a central location;

b) communicating at least some of said information between said central location and each of a plurality of remote locations via substantially unguided light passing between said central location and each of said remote locations; and

;

c) communicating at least some of said information between each of said remote locations and wireless communication devices in the vicinity of said remote location via radio signals broadcast between said remote location and said wireless communication devices;

wherein said information includes message information and control information; and

wherein said control information includes radio frequency assignment information for controlling selection of radio frequencies to be used for said communicating between said remote locations and said wireless communication devices.

27. A wireless communication method comprising:

a) communicating information between a communication network and a central location;

b) communicating at least some of said information between said central location and each of a plurality of remote locations via substantially unguided light passing between said central location and each of said remote locations; and

;

c) communicating at least some of said information between each of said remote locations and wireless communication devices in the vicinity of said remote location via radio signals broadcast between said remote location and said wireless communication devices;

wherein said communicating between said communication network and said central location is via optical communication;

wherein said communicating between said communication network and said central location is bi-directional, and wherein light of different wavelengths is used for communicating in each direction; and

wherein said information includes message information and control information, and wherein light of different wavelengths is used for communicating said message information and said control information from said communication network to said central location.

28. The method defined in claim 27 wherein said message information includes a plurality of message portions, each of which is for use at a respective one of said remote locations, and wherein light of a different wavelength is used for communicating each of said message portions from said communication network to said central location.

29. A wireless communication method comprising:

a) communicating information between a communication network and a central location;

b) communicating at least some of said information between said central location and each of a plurality of remote locations via substantially unguided light passing between said central location and each of said remote locations; and

;

c) communicating at least some of said information between each of said remote locations and wireless communication devices in the vicinity of said remote location via radio signals broadcast between said remote location and said wireless communication devices;

wherein said communicating between said communication network and said central location is bi-directional;

wherein light of different wavelengths is used for communicating in each direction; and

wherein said information includes message information and control information, and wherein light of different wavelengths is used for communicating said message information and said control information from said central location to said remote locations.

30. The method defined in claim 29 wherein said message information includes a plurality of message portions, each of which is for use at a respective one of said remote locations, and wherein light of a different wavelength is used for communicating each of said message portions from said central location to said remote locations.

31. The method defined in claim 30 wherein said central location communicates all of said message portions to all of said remote locations.

32. The method defined in claim 31 further comprising:

filtering at each of said remote locations to select the wavelength used for the message portion for use at that remote location and to reject the wavelengths used for the message portions for use at others of said remote locations.