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1. (WO2011018121) IMPROVEMENTS FOR COORDINATED MULTIPOINT TRANSMISSION
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CLAIMS

1. A method comprising

controlling a coordinated transmission between network control elements and terminals on resource elements,

detecting whether a resource element comprises a specific element, and

selecting a resource element for the coordinated

transmission, when it is detected that the resource element does not comprise a specific element.

2. The method according to claim 1, wherein the specific element is a reference signal.

3. The method according to claim 2, further comprising

canceling interference caused by a transmission of a reference signal in a resource element not selected for coordinated transmission.

4. The method according to claim 3, wherein the canceling is carried out in a terminal by subtracting known interference.

5. The method according to one of the claims 2 to 4, wherein the method is carried out by a central network control element by applying precompensation .

6. A method comprising

receiving a coordinated transmission from network control elements on resource elements, and

canceling interference caused by a transmission of a reference signal in a resource element not selected for the coordinated transmission, by subtracting known interference.

7. The method according to one of the claims 2 to 6, wherein the reference signal is a common reference signal.

8. The method according to claim 1, wherein the specific element is a control channel symbol used for a control

channel .

9. The method according to claim 8, wherein the detecting is performed by detecting the number of control channel symbols assigned to a particular subframe in a cell.

10. The method according to claim 9, wherein the number is detected by referring to a control format indicator.

11. The method according to one of the claims 8 to 10, wherein a predetermined number of transmission points on resource elements are scheduled for the coordinated transmission, the method further comprising

applying, in case the number of transmission points which are used for the coordinated transmission is less than the predetermined number, a precompensation for the transmission, and/or interleaving of the transmission and/or applying a different modulation and coding scheme per symbol in the transmission .

12. The method according to one of the claims 8 to 11, wherein the resource elements used in a subframe which do not contain a control channel symbol are used for a shared channel for transmitting data.

13. The method according to one of the claims 8 to 12, wherein all the resource elements constitute OFDM symbols, the control channel is a physical downlink control channel and the shared channel is a physical downlink shared channel.

14. An apparatus comprising

a transmission controller configured to control a

coordinated transmission between network control elements and terminals on resource elements,

a detector configured to detect whether a resource element comprises a specific element, and

a selector configured to select a resource element for the coordinated transmission, when it is detected that the

resource element does not comprise a specific element.

15. The apparatus according to claim 14, wherein the specific element is a reference signal.

16. The apparatus according to claim 15, further comprising a cancelling unit configured to cancel interference caused by a transmission of a reference signal in a resource element not selected for the coordinated transmission.

17. The apparatus according to claim 16, wherein the apparatus is configured to perform the cancellation by applying

precompensation .

18. An apparatus comprising

a receiver configured to receive a coordinated

transmission from network control elements on resource

elements, and

a controller configured to cancel interference caused by a transmission of a common reference signal in a resource

element not selected for the coordinated transmission, by subtracting known interference.

19. The apparatus according to one of the claims 15 to 18, wherein the reference signal is a common reference signal.

20. The apparatus according to claim 14, wherein the specific element is a control channel symbol used for a control

channel .

21. The apparatus according to claim 20, wherein the detector is configured to detect the number of control channel symbols assigned to a particular subframe in a cell.

22. The apparatus according to claim 21, wherein the detector is configured to detect the number by referring to a control format indicator.

23. The apparatus according to one of the claims 20 to 22, wherein a predetermined number of transmission points on resource elements are scheduled for the coordinated

transmission,

wherein the controller is configured to apply, in case the number of transmission points which are used for the

coordinated transmission is less than the predetermined number, a precompensation for the transmission points, and/or interleaving of the transmission points and/or applying a different modulation and coding scheme per symbol in the transmission points.

24. The apparatus according to one of the claims 20 to 23, wherein the resource elements used in a subframe which do not contain a control channel symbol are used for a shared channel for transmitting data.

25. The apparatus according to one of the claims 20 to 24, wherein all the resource elements constitute OFDM symbols, the control channel is a physical downlink control channel and the shared channel is a physical downlink shared channel.

26. A method comprising

controlling transmitting of reference signals in resource elements of a resource block in a coordinated transmission between network control elements and terminals,

using, for a sequence of reference signals, a single reference signal for all terminals, and

spatially precoding the single reference signal for each terminal .

27. The method according to claim 26, wherein the reference signal is a precoded dedicated reference signal.

28. The method according to claim 26 or 27, further comprising using, for first reference signals in a first resource block of the sequence of the reference signals, orthogonal reference signals.

29. The method according to claim 28, wherein, during the transmission, in predetermined resource elements and/or predetermined resource blocks orthogonal reference signals are used.

30. The method according to claim 28 or 29, wherein the orthogonal reference signal is an orthogonal precoded

dedicated reference signal.

31. The method according to one of the claims 26 to 30, wherein a zero force like precoding is used in the coordinated transmission .

32. The method according to one of the claims 26 to 31, wherein the spatially precoding is performed by beamforming.

33. The method according to one of the claims 26 to 32, wherein the method is carried out by one of the network control elements or by a central unit.

34. An apparatus comprising

a controller configured to control transmitting of reference signals in resource elements of a resource block in a coordinated transmission between network control elements and terminals, and to use, for a sequence of reference

signals, a single reference signal for all terminals, and

a precoding unit configured to spatially precode the single reference signal for each terminal.

35. The apparatus according to claim 34, wherein the reference signal is a precoded dedicated reference signal.

36. The apparatus according to claim 34 or 35, wherein

the controller is configured to use, for first reference signals in a first resource block of the sequence of the reference signals, orthogonal reference signals.

37. The apparatus according to claim 36, wherein

the controller is configured to use, during the

transmission, in predetermined resource elements and/or in predetermined resource blocks orthogonal reference signals.

38. The apparatus according to claim 36 or 37, wherein the orthogonal reference signal is an orthogonal precoded

dedicated reference signal.

39. The apparatus according to one of the claims 34 to 38, wherein the precoding unit is configured to use a zero force like precoding in the coordinated transmission.

40. The apparatus according to one of the claims 34 to 39, wherein the precoding unit is configured to perform the spatially precoding by beamforming.

41. The apparatus according to one of the claims 34 to 40, wherein the apparatus is one of the network control elements or is part of one of the network control elements, or is a central unit or is part of a central unit.

42. A method comprising

sending an orthogonal precoded dedicated reference signal to a terminal,

receiving a channel estimation result, which is estimated by the terminal using the precoded dedicated reference signal, and

determining channel information based on the received channel estimation result.

43. The method according to claim 42, wherein

the orthogonal precoded dedicated reference signal is sent to a plurality of terminals, a plurality of channel estimation results is received, and the channel information is determined based on the plurality of channel estimation results.

44. The method according to claim 42 or 43, further comprising receiving, from the terminal, interference information with respect to interference from other terminals estimated based on the orthogonal precoded dedicated reference signal, wherein the channel information is determined based on the received channel estimation result and the received

interference information.

45. The method according to one of the claims 42 to 44, wherein in the determination of the channel information, a precoding correction matrix is calculated, and the precoding correction matrix is used for further transmissions.

46. The method according to one of the claims 42 to 45, wherein for estimating a channel state, first channel state information reference signals are used, and the estimated channel state is corrected by performing repeatedly the sending of the orthogonal precoded dedicated reference signal, receiving an channel estimation result, and determining the channel information.

47. The method according to one of the claims 42 to 46, wherein a plurality of orthogonal precoded dedicated reference signals are sent to a plurality of terminals, wherein the orthogonal precoded dedicated reference signals are allocated on at least one subframe based on frequency division multiplex and/or code division multiplex and/or time division multiplex.

48. The method according to claim 47, further comprising allocating the orthogonal precoded dedicated reference signal for each terminal on the at least one subframe by using code division multiplex, frequency division multiplex or time division multiplex precoded by weights to be used of other terminals with an overlapping resource block allocation, or precoded by weights to be used for the same terminal in a next scheduling event.

49. The method according to one of the claims 42 to 46, wherein precoded dedicated reference signals are sent on resource elements currently not scheduled in order to allow for sounding radio channels corresponding to the resource elements for future scheduling decisions.

50. A method comprising

receiving an orthogonal precoded dedicated reference signal,

performing channel estimation using the precoded dedicated reference signal, and

sending a channel estimation result to a network control element .

51. The method according to claim 50, further comprising

estimating interference from other terminal based on the precoded dedicated reference signal, and

sending the interference information to the network control element.

52. An apparatus comprising

a sender configured to send an orthogonal precoded dedicated reference signal to a terminal,

a receiver configured to receive a channel estimation result, which is estimated by the terminal using the

orthogonal precoded dedicated reference signal, and

a controller configured to determine channel information based on the received channel estimation result.

53. The apparatus according to claim 52, wherein

the sender is configured to send orthogonal precoded dedicated reference signals to a plurality of terminals, the receiver is configured to receive a plurality of channel estimation results, and the controller is configured to determine the channel information based on the plurality of channel estimation results.

54. The apparatus according to claim 52 or 53, wherein

the receiver is configured to receive, from the terminal, interference information with respect to interference from other terminals estimated based on the orthogonal precoded dedicated reference signal, and

the controller is configured to determine the channel information based on the received channel estimation result and the received interference information.

55. The apparatus according to one of the claims 52 to 54, wherein the controller is configured to calculate a precoding correction matrix, wherein the precoding correction matrix is used for further transmissions.

56. The apparatus according to one of the claims 52 to 55, wherein the controller is configured to use, for estimating a channel state, first channel state information reference signals and to correct the estimated channel state by

performing repeatedly the sending of the orthogonal precoded dedicated reference signal, receiving an channel estimation result, and determining the channel information.

57. The apparatus according to one of the claims 52 to 56, wherein the sender is configured to send a plurality of orthogonal precoded dedicated reference signals to a plurality of terminals, and wherein

the controller is configured to allocate the orthogonal precoded dedicated reference signals on at least one subframe based on frequency division multiplex and/or code division multiplex .

58. The apparatus according to claim 57, wherein the

controller is configured to allocate the orthogonal precoded dedicated reference signal for each terminal on the at least one subframe by using code division multiplex, frequency division multiplex or time division multiplex precoded by weights to be used of other terminals with an overlapping resource block allocation, or precoded by weights to be used for the same terminal in a next scheduling event.

59. The apparatus according to one of the claims 52 to 58, wherein the controller is configured to send precoded

dedicated reference signals on resource elements currently not scheduled in order to allow for sounding radio channels corresponding to the resource elements for future scheduling decisions .

60. An apparatus comprising

a receiver configured to receive an orthogonal precoded dedicated reference signal,

a controller configured to perform a channel estimation using the orthogonal precoded dedicated reference signal, and a sender configured to send a channel estimation result to a network control element.

61. The apparatus according to claim 60, wherein

the controller is configured to estimate interference from at least one other terminal based the orthogonal precoded dedicated reference signal, and

the sender is configured to send the interference

information to the network control element.

62. The method according one of claims 1 to 13, 26 to 33 or 42 to 51, wherein the coordinated transmission is a multipoint coordinated (CoMP) transmission or a multi-user multiple input multiple output (MU-MIMO) transmission.

63. The apparatus according one of claims 14 to 25, 34 to 41 or 52 to 61, wherein the coordinated transmission is a

multipoint coordinated (CoMP) transmission or a multi-user multiple input multiple output (MU-MIMO) transmission.

64. A computer program product including a program for a processing device, comprising software code portions for performing the steps of any one of claims 1 to 13, 26 to 33 or 42 to 51 when the program is run on the processing device.

65. The computer program product according to claim 64, wherein the computer program product comprises a computer-readable medium on which the software code portions are stored.

66. The computer program product according to claim 64, wherein the program is directly loadable into an internal memory of the processing device.