Demodulation Reference Signals in a Communication System

• US 20120106473A1
• Filed: 04/27/2009
• Published: 05/03/2012
• Est. Priority Date: 04/27/2009
• Status: Active Grant

• Current Assignee: Beijing Xiaomi Mobile Software Co., Ltd. (Xiaomi Corp.)
• Original Assignee: Nokia Solutions and Networks US LLC (Nokia Corporation)
• Inventors: Tiirola, Esa Tapani, Hooli, Kari Juhani, Pajukoski, Kari Pekka
• Granted Patent: US 8,644,238 B2
• Time in Patent Office: Days
• US Class Current: 370/329
• CPC Class Codes: H04L 27/2613 Structure of the reference signals
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04L 5/0073 Allocation arrangements that take into account other cell interferences for intercell interference mitigation or co-ordination in orthogonal multiplex systems H04J11/005
• CPC Class Codes: H04L 5/0091 Signaling for the administration of the divided path

Abstract

At least two modes of communicating demodulation reference signals in a system providing a multiple of communication points for communication devices are provided. In a first mode demodulation reference signals are communicated based on an sequence group and separation of sequences provided by adjustment of transmitted demodulation reference signals. In a second mode demodulation reference signals are communicated based on one or more sequence groups and non-adjusted transmission of demodulation reference signals.

Claims

1. A method, comprising

providing at least two modes of communicating demodulation reference signals in a system providing a multiple of communication points for communication devices, wherein

in a first mode demodulation reference signals are communicated based on an sequence group and separation of sequences provided by adjustment of transmitted demodulation reference signals;

and

in a second mode demodulation reference signals are communicated based on one or more sequence groups and non-adjusted transmission of demodulation reference signals.

2. A method as claimed in claim 1, wherein the separation in the first mode comprises orthogonalisation of the reference signals.

3. A method as claimed in claim 1, wherein the separation in the first mode comprises cyclic shifting of the demodulation reference signals.

4. A method as claimed in claim 1, comprising coordinating use of the different modes by a bandwidth tree.

5. A method as claimed in claim 4, wherein the bandwidth tree resembles a sounding reference signal bandwidth tree.

6. A method as claimed in claim 4, wherein the bandwidth tree is arranged to have wider bandwidths that are multiples of a narrower bandwidth or the bandwidth tree is arranged to provide different bandwidth options.

7. A method as claimed in claim 4, comprising providing an indication for a communication device of a bandwidth tree to be used.

8. A method as claimed in claim 1, wherein the separation in the first mode comprises adjusting bandwidth and/or applying an interleaved frequency division multiple access (IFDMA) comb to the demodulation reference signals.

9. A method as claimed in claim 1, wherein the first mode comprises adjusting cyclic shifting of the demodulation reference signal.

10. A method as claimed in claim 5, comprising adjusting the bandwidth to be the same within a set of communication devices with substantially similar bandwidth allocations.

11. A method as claimed in claim 1, comprising use of block spreading to separate demodulation reference signals.

12. A method as claimed in claim 1, comprising providing acceptable cross-correlation properties in a system comprising a plurality of base stations by ensuring that acceptable orthogonality is maintained between the base stations when needed.

13. A method as claimed in claim 1, comprising selecting the first mode when substantially orthogonal demodulation reference signal sequences are considered necessary and selecting the second mode where demodulation when demodulation reference signal orthogonality is not considered necessary.

14. A method as claimed in claim 1, wherein the separation in the first mode comprises adjusting demodulation reference signals to provide substantially orthogonal demodulation references signals in a plurality of cells.

15. A method as claimed in claim 1, comprising selecting at a communication device one of the available modes.

16. A method as claimed in claim 15, comprising selecting the mode based on dedicated signalling.

17. A method as claimed in claim 15, comprising selecting the mode based on radio resource control signalling and/or uplink grant signalling.

18. A method as claimed in claim 15, comprising selecting the mode based on a scheduling rank and a threshold.

19. A method as claimed in claim 15, comprising selecting the mode based on information regarding frequency location of a physical resource block allocation.

20. A method as claimed in claim 1, comprising switching from a mode to another mode in response to detection of a predefined event.

21. A method as claimed in claim 20, comprising using the second mode as a default mode and switching to the first mode in response to determination of a need for improved orthogonality.

22. A method as claimed in claim 1, wherein the sequence group of the first mode is one of sequence groups available for the second mode.

23. A method as claimed in claim 1, wherein the sequence group of the first mode is different from the one or more sequence groups of the second mode.

24. A method as claimed in claim 1, comprising assigning the first mode and second mode to different frequency regions.

25. A method as claimed in claim 1, wherein the multiple communication points comprise stations of a cellular system, the method comprising use of the at least two modes for uplink coordinated multi-point communications.

26. A method as claimed in claim 1, wherein the multiple communication points are provided by elements of an multiple input multiple output apparatus, the method comprising use of the at least two modes for uplink communication with the multiple input multiple output apparatus.

53. A computer program comprising program code means adapted to perform the steps of claim 1 when the program is run on a data processing apparatus.

27. A control apparatus configured to control use of at least two modes of demodulation reference signals communications in a system providing a multiple of communication points for communication devices, wherein in a first mode demodulation reference signals are communicated based on an adjusted sequence group and separation of sequences provided by adjustment of transmitted demodulation reference signals and in a second mode demodulation reference signals are communicated based on one or more sequence groups and non-adjusted transmission of demodulation reference.

28. A control apparatus as claimed in claim 27, configured to provide the separation of the reference signals in the first mode by means of orthogonalisation of the reference signals.

29. A control apparatus as claimed in claim 27, configured to provide the separation of the reference signals in the first mode by means of cyclic shifting of the demodulation reference signals.

30. A control apparatus as claimed in claim 27, configured to coordinate use of the different modes by means of a bandwidth tree.

31. A control apparatus as claimed in claim 30, wherein the bandwidth tree resembles a sounding reference signal bandwidth tree.

32. A control apparatus as claimed in claim 30, wherein the bandwidth tree is arranged to have wider bandwidths that are multiples of a narrower bandwidth or the bandwidth tree is arranged to provide different bandwidth options.

33. A control apparatus as claimed in claim 30, configured to provide an indication for a communication device of a bandwidth tree to be used.

34. A control apparatus as claimed in claim 27, configured to provide the separation in the first mode by adjusting bandwidth and/or applying an interleaved frequency division multiple access (IFDMA) comb to the demodulation reference signals.

35. A control apparatus as claimed in claim 27, configured to adjust cyclic shifting of the demodulation reference signal in the first mode.

36. A control apparatus as claimed in claim 35, configured to adjust the bandwidth to be the same within a set of communication devices with substantially similar bandwidth allocations.

37. A control apparatus as claimed in claim 27, configured to use block spreading to separate demodulation reference signals.

38. A control apparatus as claimed in claim 27, configured to provide acceptable cross-correlation properties in a system comprising a plurality of base stations by ensuring that acceptable orthogonality is maintained between the base stations when needed.

39. A control apparatus as claimed in claim 27, configured to select the first mode when substantially orthogonal demodulation reference signal sequences are considered necessary and to select the second mode where demodulation when demodulation reference signal orthogonality is not considered necessary.

40. A control apparatus as claimed in claim 27, configured to provide the separation in the first mode by means of adjusting demodulation reference signals to provide substantially orthogonal demodulation references signals in a plurality of cells.

41. A control apparatus as claimed in claim 27, configured to provide switching from a mode to another mode in response to detection of a predefined event.

42. A control apparatus as claimed in claim 41, configured to use the second mode as a default mode and to switch to the first mode in response to determination of a need for improved orthogonality.

43. A control apparatus as claimed in claim 27, configured to assign the first mode and second mode to different frequency regions.

44. A control apparatus as claimed in claim 27, wherein the multiple communication points of the system comprise stations of a cellular system, the control apparatus being configured to use the at least two modes for uplink coordinated multi-point communications.

45. A control apparatus as claimed in claim 27, wherein the multiple communication points are provided by elements of an multiple input multiple output apparatus, the control apparatus being configured to use of the at least two modes for uplink communication with the multiple input multiple output apparatus.

46. A control apparatus as claimed in claim 27, wherein the control apparatus is configured to select the mode based on radio resource control signalling and/or uplink grant signalling.

47. A control apparatus as claimed in claim 27, wherein the mode is selected based on a scheduling rank and a threshold.

48. A control apparatus method as claimed in claim 27, comprising selecting the mode based on information regarding frequency location of a physical resource block allocation.

49. A communication device comprising a control apparatus in accordance with claim 27.

50. A communication device as claimed in claim 49, wherein the control apparatus is configured to select one of the available modes based on signals from a base station.

51. A base station apparatus comprising a comprising a control apparatus in accordance with claim 27.

52. A base station apparatus as claimed in claim 51, wherein the control apparatus is configured to communicate information regarding mode selection to a communication based on dedicated signalling and/or broadcasting.

54. A communication system comprising a control apparatus, a communication device and/or base station in accordance with claim 27.