MIMO-adapted distributed antenna system

• US 7,822,148 B2
• Filed: 01/25/2009
• Issued: 10/26/2010
• Est. Priority Date: 02/12/2007
• Status: Active Grant

• Current Assignee: Corning Optical Communications Wireless Ltd. (Corning Incorporated)
• Original Assignee: Mobileaccess Networks Limited (Corning Incorporated)
• Inventors: Holtzman, Yehuda, Saban, Ofer, Harel, Dror, Shapira, Isaac
• Primary Examiner(s): Bayard; Emmanuel
• Application Number:
  US12/359,321
• Publication Number:
  US 20090154621A1
• Time in Patent Office: 639 Days
• Field of Search: 375/346, 375/144, 375/147, 375/148, 375/347, 375/349, 375/299
• US Class Current: 375/299
• CPC Class Codes: G01S 3/023 Monitoring or calibrating
• CPC Class Codes: G01S 5/04 Position of source determined by a plurality of spaced direction-finders
• CPC Class Codes: H04B 7/02 Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas RAKE receivers H04B1/7115
• 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 7/10 Polarisation diversity; Directional diversity
• CPC Class Codes: H04L 27/00 Modulated-carrier systems
• CPC Class Codes: H04L 27/125 using a controlled oscillator in an open loop
• CPC Class Codes: H04L 5/0035 Resource allocation in a cooperative multipoint environment
• CPC Class Codes: H04L 5/1469 using time-sharing

Abstract

Methods and systems for carrying different signals required for MIMO communication using a single coaxial cable between two endpoints of a distributed antenna system (DAS) network. Original MIMO signals having the same frequency are frequency-separated at a first endpoint of the network. The frequency-separated signals are propagated together over the single coaxial cable and then reconstructed to their original frequency at a second endpoint of the network.

Claims

1. A system for carrying signals of two different services between two endpoints of a distributed antenna system (DAS) network comprising:

a) a master unit associated with one endpoint of the DAS network and used to serve simultaneously the two different services, wherein at least one service uses MIMO signals;

b) a remote unit associated with another endpoint of the DAS network; and

c) a single coaxial cable used to transfer bi-directionally reverse path and forward path signals of the two services between the master and remote units;

wherein the remote unit is operatively coupled to two antennas, transmits respective MIMO forward path signals via the two antennas and receives respective MIMO reverse path signals via the two antennas.

2. The system of claim 1, wherein the master unit includes a master unit frequency shifter which is used for frequency shifting a MIMO reverse path signal and a MIMO forward path signal using time domain division (TDD), the frequency shifting resulting in a forward path frequency shifted signal and a reverse path signal shifted back to an original frequency.

3. The system of claim 2, wherein the remote unit includes a remote unit frequency shifter which is used for frequency shifting a MIMO forward path signal and a MIMO reverse path signal using time domain division (TDD), the frequency shifting resulting in a reverse path frequency shifted signal and a forward path signal shifted back to an original frequency.

4. The system of claim 1, wherein one of the at least one service that uses MIMO signals is a MIMO frequency domain division (FDD) service wherein the master unit includes two master unit frequency shifters, one master unit frequency shifter used for frequency shifting a MIMO reverse path signal and another master unit frequency shifter used for frequency shifting a MIMO forward path signal of the FDD service, the frequency shifting resulting in a forward path frequency shifted signal and a reverse path signal shifted back to an original frequency.

5. The system of claim 4, wherein the remote unit includes two remote unit frequency shifters, one remote unit frequency shifter used for frequency shifting a MIMO reverse path signal and another remote unit frequency shifter used for frequency shifting a MIMO forward path signal of the FDD service, the frequency shifting resulting in a reverse path frequency shifted signal and a forward path signal shifted back to an original frequency.

6. The system of claim 5, wherein the master unit includes an additional master unit frequency shifter which is used for frequency shifting the reverse path signal and the forward path signal using time domain division (TDD).

7. The system of claim 6, wherein the remote unit includes an additional remote unit frequency shifter which is used for frequency shifting the forward path signal and reverse path signal using time domain division (TDD).

8. The system of claim 2, wherein the master unit includes a plurality of band pass filters for selecting an reverse path signal received through the coaxial cable before it is passed to the master unit frequency shifter.

9. The system of claim 4, wherein the master unit includes a plurality of band pass filters for selecting an reverse path signal received through the coaxial cable before it is passed to the master unit frequency shifter.

10. The system of claim 3, wherein the remote unit includes a plurality of band pass filters for selecting a forward path signal received through the coaxial cable before it is passed to the remote unit frequency shifter.

11. The system of claim 5, wherein the remote unit includes a plurality of band pass filters for selecting a forward path signal received through the coaxial cable before it is passed to the remote unit frequency shifter.

12. The system of claim 2, wherein another MIMO reverse path signal and another MIMO forward path signal that use TDD bypass the master unit frequency shifter, so that the other MIMO reverse path signal is transmitted to the service that uses MIMO signals without being shifted in frequency and so that the other MIMO forward path signal is transmitted to the remote unit without being shifted in frequency.

13. The system of claim 3, wherein another MIMO forward path signal and another MIMO reverse path signal that use TDD bypass the remote unit frequency shifter, so that the other MIMO forward path signal is transmitted via its respective one of the two antennas without being shifted in frequency and so that the other MIMO reverse path signal is transmitted to the master unit without being shifted in frequency.

14. The system of claim 4, wherein another MIMO reverse path signal and another MIMO forward path signal of the FDD service bypass the master unit frequency shifter, so that the other MIMO reverse path signal is transmitted to the one service without being shifted in frequency and so that the other MIMO forward path signal is transmitted to the remote unit without being shifted in frequency.

15. The system of claim 5, wherein another MIMO forward path signal and another MIMO reverse path signal of the FDD service bypass the remote unit frequency shifter, so that the other MIMO forward path signal is transmitted via its respective one of the two antennas without being shifted in frequency and so that the other MIMO reverse path signal is transmitted to the master unit without being shifted in frequency.

16. The system of claim 1, wherein the master unit includes two master unit frequency shifters which are used for frequency shifting respective MIMO reverse path signals and respective MIMO forward path signals using time domain division (TDD), the frequency shifting resulting in two different forward path frequency shifted signals at two different respective forward path frequencies and two reverse path signals shifted back to respective original frequencies.

17. The system of claim 16, wherein the remote unit includes two remote frequency shifters which are used for frequency shifting respective MIMO forward path signals and respective MIMO reverse path signals using TDD, the frequency shifting resulting in two different reverse path frequency shifted signals at two different respective reverse path frequencies and two forward path signals shifted back to respective original frequencies.

18. The system of claim 1, wherein each of the at least one service that uses MIMO signals is a MIMO frequency domain division (FDD) service, wherein the master unit includes two master unit frequency shifters used for frequency shifting respective MIMO reverse path signals of each FDD service and two other master unit frequency shifters used for frequency shifting respective MIMO forward path signals of each FDD service, the frequency shifting resulting in two forward path frequency shifted signals at two different respective forward path frequencies and two reverse path signals shifted back to respective original frequencies.

19. The system of claim 18, wherein the remote unit includes two remote unit frequency shifters used for frequency shifting respective MIMO reverse path signals and two other remote unit frequency shifters used for frequency shifting respective MIMO forward path signals of each FDD service, the frequency shifting resulting in two reverse path frequency shifted signals at two different respective reverse path frequencies and two forward path signals shifted back to respective original frequencies.

20. The system of claim 1, further comprising:

d) a transmission medium, other than a coaxial cable, that is operatively coupled in series with the single coaxial cable and that cooperates with the single coaxial cable to transfer bi-directionally the reverse path and forward path signals of the two services between the master and remote units.

21. The system of claim 20, wherein the transmission medium is a fiber optic cable.

22. A method for carrying signals of two different services between two endpoints of a distributed antenna system (DAS) network comprising the steps of:

a) providing a master unit associated with one endpoint of the DAS network and used to serve simultaneously the two different services, wherein at least one service uses MIMO signals;

b) providing a remote unit associated with another endpoint of the DAS network and operatively coupled to two antennas;

c) transferring bi-directionally reverse path and forward path signals of the two services between the master and remote units through a single coaxial cable;

d) transmitting respective MIMO forward path signals via the two antennas; and

e) receiving respective MIMO reverse path signals via the two antennas.

23. The method of claim 22, wherein one of the at least one service that uses MIMO signals is a MIMO time domain division (TDD) service, wherein the step of transferring includes, at the master unit, frequency shifting a MIMO reverse path signal of the one service and a MIMO forward path signal of the one service using time domain division, the frequency shifting resulting in a forward path frequency shifted signal and a reverse path signal shifted back to an original frequency, the two signals being transferred bi-directionally through the single coaxial cable.

24. The method of claim 23, wherein the step of transferring further includes, at the remote unit, frequency shifting a MIMO forward path signal of the one service and a MIMO reverse path signal of the one service using time domain division, the frequency shifting resulting in a reverse path frequency shifted signal and a forward path signal shifted back to an original frequency, the two signals being transferred bi-directionally through the single co-axial cable.

25. The method of claim 22, wherein one of the at least one service that uses MIMO signals is a MIMO frequency domain division (FDD) service, wherein the master unit includes two master unit frequency shifters, and wherein the step of transferring includes, at the master unit, frequency shifting a MIMO reverse path signal of the FDD service using one master unit frequency shifter and frequency shifting a MIMO forward path signal of the FDD service using the other master unit frequency shifter, the frequency shifting resulting in a forward path frequency shifted signal and a reverse path signal shifted back to an original frequency, the two signals being transferred bi-directionally through the single coaxial cable.

26. The method of claim 25, wherein the remote unit includes two remote unit frequency shifters, and wherein the step of transferring further includes, at the remote unit, frequency shifting a MIMO forward path signal of the FDD service using one remote unit frequency shifter and frequency shifting a MIMO reverse path signal of the FDD service using the other remote unit frequency shifter, the frequency shifting resulting in a reverse path frequency shifted signal and a forward path signal shifted back to an original frequency, the two signals being transferred bi-directionally through the single co-axial cable.

27. The method of claim 26, wherein the master unit includes an additional master unit frequency shifter and wherein the frequency shifting at the master unit further includes frequency shifting the reverse path and forward path signals using time domain division (TDD).

28. The method of claim 27, wherein the remote unit includes an additional remote unit frequency shifter and wherein the frequency shifting at the remote unit further includes frequency shifting the reverse path and forward path signals using time domain division (TDD).

29. The method of claim 23, wherein the step of transferring includes, at the master unit, transferring another MIMO reverse path signal of the one service from the single coaxial cable to the one service without frequency shifting the other MIMO reverse path signal of the one service and transferring another MIMO forward path signal of the one service from the one service to the single coaxial cable without frequency shifting the other MIMO forward path signal of the one service.

30. The method of claim 24, wherein the step of transferring includes, at the remote unit, transferring another MIMO forward path signal of the one service to its respective one of the two antennas from the single coaxial cable without frequency shifting the other MIMO forward path signal of the one service and transferring another MIMO reverse path signal of the one service from its respective one of the two antennas to the single coaxial cable without frequency shifting the other MIMO reverse path signal of the one service.

31. The method of claim 25, wherein the step of transferring further includes, at the master unit, transferring another MIMO reverse path signal of the FDD service from the single coaxial cable to the FDD service without frequency shifting the other MIMO reverse path signal of the FDD service and transferring another MIMO forward path signal of the FDD service from the FDD service to the single coaxial cable without frequency shifting the other MIMO forward path signal of the FDD service.

32. The method of claim 26, wherein the step of transferring includes, at the remote unit, transferring another MIMO forward path signal of the FDD service to its respective one of the two antennas from the single coaxial cable without frequency shifting the other MIMO forward path signal of the FDD service and transferring another MIMO reverse path signal of the FDD service from its respective one of the two antennas to the single coaxial cable without frequency shifting the other MIMO reverse path signal of the FDD service.

33. The method of claim 22, wherein each of the at least one service that uses MIMO signals is a MIMO time domain division (TDD) service, wherein the step of transferring includes, at the master unit, shifting respective MIMO reverse path signals of each service and respective MIMO forward path signals of each service using time domain division, the frequency shifting resulting in two respective forward path frequency shifted signals at two different respective forward path frequencies and two respective reverse path signals shifted back to respective original frequencies, the four signals being transferred bi-directionally through the single coaxial cable.

34. The method of claim 33, wherein the step of transferring further includes, at the remote unit, frequency shifting respective MIMO forward path signals of each service and respective MIMO reverse path signals of each service using time domain division, the frequency shifting resulting in two respective reverse path frequency shifted signals at two different respective reverse path frequencies and two respective forward path signals shifted back to respective original frequencies, the four signals being transferred bi-directionally through the single coaxial cable.

35. The method of claim 22, wherein each of the at least one service that uses MIMO signals is a MIMO frequency domain division (FDD) service, wherein the master unit includes four master unit frequency shifters, and wherein the step of transferring includes, at the master unit, frequency shifting two respective MIMO reverse path signals of each FDD service using two respective master unit frequency shifters and frequency shifting two respective MIMO forward path signals of each FDD service using two other respective master unit frequency shifters, the frequency shifting resulting in two respective forward path frequency shifted signals at two different respective forward path frequencies and two respective reverse path signals shifted back to respective original frequencies, the four signals being transferred bi-directionally through the single coaxial cable.

36. The method of claim 35, wherein the remote unit includes four remote unit frequency shifters, and wherein the step of transferring further includes, at the remote unit, frequency shifting two respective MIMO forward path signals of each FDD service using two respective remote unit frequency shifters and frequency shifting two respective MIMO reverse path signals of each FDD service using two other respective remote unit frequency shifters, the frequency shifting resulting in two respective reverse path frequency shifted signals at two different respective reverse path frequencies and two respective forward path signals shifted back to respective original frequencies, the four signals being transferred bi-directionally through the single coaxial cable.

37. The method of claim 22, wherein the reverse path and forward path signals of the two services are transferred bi-directionally between the master and remote units through both the single coaxial cable and another transmission medium, other than a coaxial cable, that is operatively coupled in series with the single coaxial cable.

38. The method of claim 22, wherein the transmission medium is a fiber optic cable.

39. A remote unit, for a distributed antenna system, comprising:

a) a coaxial cable port for receiving a plurality of signals of at least one MIMO service, in different respective frequency bands, from a single coaxial cable;

b) a corresponding plurality of frequency shifters for, for each at least one MIMO service, shifting respective signals from said respective frequency bands to a frequency band of the each MIMO service;

c) a service combiner for directing each signal to its respective frequency shifter; and

d) for each frequency shifter, a respective antenna port for transmitting the respective shifted signal of the each frequency shifter to a respective MIMO antenna.

40. The remote unit of claim 39, wherein the coaxial cable port is also for receiving a reference signal, and wherein the remote unit further comprises:

e) an oscillator that is synchronized with the reference signal.

41. The remote unit of claim 39, wherein the at least one MIMO service is a WiFi service.

42. The remote unit of claim 39, wherein the coaxial cable port is for receiving a respective plurality of the signals from each of a plurality of MIMO services, each antenna port having associated therewith one frequency shifter for each MIMO service;

and wherein the remote unit further comprises;

e) for each antenna port, a respective multiplexer for combining the respective shifted signals of the frequency shifters that are associated therewith for transmission via the respective MIMO antenna of the each antenna port.

43. A remote unit, for a distributed antenna system, comprising:

a) a plurality of antenna ports for receiving respective signals of at least one MIMO service;

b) for each antenna port and for each MIMO service, a respective frequency shifter for shifting the respective signal of the each antenna port and the each MIMO service to a different respective shifted frequency band;

c) a service combiner for combining all the shifted signals; and

d) a coaxial cable port for transmitting the combined shifted signals via a single coaxial cable.

44. The remote unit of claim 43, wherein the coaxial cable port is also for receiving a reference signal, and wherein the remote unit further comprises:

e) an oscillator that is synchronized with the reference signal.

45. The remote unit of claim 43, wherein the at least one MIMO service is a WiFi service.

46. The remote unit of claim 43, wherein the plurality of antenna ports is for receiving respective signals of each of a plurality of MIMO services;

and wherein the remote unit further comprises;

e) for each antenna port, a respective multiplexer for directing the respective signal, of each MIMO service, that is received at the each antenna port, to the respective frequency shifter of the each signal of the each MIMO service.