Method and apparatus for transmitting/receiving downlink data for UE in soft handover region in an OFDM system

• US 20060293056A1
• Filed: 06/27/2006
• Published: 12/28/2006
• Est. Priority Date: 06/27/2005
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kim, Young-Bum, Kim, Dong-Hee, Lee, Ju-Ho, Kwon, Hwan-Joon
• Granted Patent: US 7,978,662 B2
• Time in Patent Office: Days
• US Class Current: 455/442
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection

Abstract

A method and apparatus for transmitting and receiving downlink data for signal combining at a UE in an OFDM cellular system are provided. A Node B sends combining information to the UE, and combinable cells use the same radio resources and the same scrambling sequence in data transmission to the UE. Therefore, the UE can receive naturally combined data without an additional operation. Also, the UE combines channel estimates calculated using pilot signals received form the cells and compensates the combined data signal using the combined channel estimate.

Claims

1. A method of transmitting downlink data to a user equipment (UE) located in a soft handover region in an orthogonal frequency division multiplexing (OFDM) system, the method comprising:

allocating first radio resources and a first scrambling sequence to the UE for use in a serving cell;

notifying at least one non-serving cell associated with the soft handover region of the allocated first radio resources and first scrambling sequence;

sending a first data signal using the first radio resources and the first scrambling sequence to the UE and sending a first pilot signal for identification of the serving cell using second radio resources and the first scrambling sequence to the UE by the serving cell;

sending a second data signal identical to the first data signal using the first radio resources and the first scrambling sequence to the UE and sending a second pilot signal for identification of the at least one non-serving cell using the second radio resources and a second scrambling sequence to the UE by the at least one non-serving cell; and

sending a combining indication to the UE by the serving cell, the combining indication indicating the at least one non-serving cell that sends the second data signal combinable with the first data signal.

2. The method of claim 1, further comprising:

sending control information about the first and second data signals using radio resources and the first scrambling sequence to the UE by the serving cell.

3. The method of claim 2, wherein the control information comprises at least one of a modulation scheme, a data block size, a channel encoding scheme, and radio resources used for the first and second data signals.

4. The method of claim 1, wherein sending a combining indication to the UE comprises sending the combining indication to the UE by at least one of physical layer signaling and higher-layer signaling by the serving cell.

5. The method of claim 1, wherein the first and second pilot signals are used for channel compensation of the first and second data signals, respectively.

6. The method of claim 1, further comprising:

sending to the UE dedicated pilot signals for channel compensation of the first and second data signals using radio resources and the first scrambling sequence by the serving cell and the at least one non-serving cell.

7. The method of claim 6, wherein the combining indication information further comprises an indicator indicating that the serving cell and the at least one non-serving cell send the dedicated pilot signals.

8. The method of claim 5, further comprising:

sending to the UE a third data signal identical to the first data signal using third radio resources and a third scrambling sequence and a third pilot signal for channel compensation of the third data signal using the second radio resources and the third scrambling sequence by a non-serving cell to which the first radio resources are not available.

9. The method of claim 8, wherein the combining indication separately indicates the at least one non-serving cell that sends the second data signal using the first radio resources and the non-serving cell that sends the third data signal using the third radio resources.

10. The method of claim 1, wherein the allocation and notification steps are performed by at least one of a scheduler in the serving cell and a scheduler in a Node B for managing the serving cell and the at least one non-serving cell.

11. A cell transmitting apparatus for transmitting downlink data to a user equipment (UE) located in a soft handover region in an orthogonal frequency division multiplexing (OFDM) system, comprising:

a scheduler for allocating first radio resources and a first scrambling sequence to the UE for use in a serving cell, and notifying at least one non-serving cell associated with the soft handover region of the allocated first radio resources and first scrambling sequence;

a serving cell transmitter in the serving cell, for sending to the UE a first data signal using the first radio resources and the first scrambling sequence and sending to the UE a first pilot signal for identification of the serving cell using second radio resources and the first scrambling sequence; and

at least one non-serving cell transmitter in the at least one non-serving cell, for sending to the UE a second data signal identical to the first data signal using the first radio resources and the first scrambling sequence and sending to the UE a second pilot signal for identification of the at least one non-serving cell using the second radio resources and a second scrambling sequence,

wherein the serving cell transmitter sends a combining indication to the UE, the combining indication indicating the at least one non-serving cell that sends the second data signal combinable with the first data signal.

12. The cell transmitting apparatus of claim 11, wherein the serving cell transmitter sends to the UE control information about the first and second data signals using radio resources and the first scrambling sequence.

13. The cell transmitting apparatus of claim 12, wherein the control information comprises at least one of a modulation scheme, a data block size, a channel encoding scheme, and radio resources used for the first and second data signals.

14. The cell transmitting apparatus of claim 11, wherein the serving cell transmitter sends the combining indication to the UE by at least one of physical layer signaling and higher-layer signaling.

15. The cell transmitting apparatus of claim 11, wherein the first and second pilot signals are used for channel compensation of the first and second data signals, respectively.

16. The cell transmitting apparatus of claim 11, wherein the serving cell transmitter and the at least one non-serving cell transmitter send to the UE dedicated pilot signals for channel compensation of the first and second data signals using radio resources and the first scrambling sequence.

17. The cell transmitting apparatus of claim 16, wherein the combining indication information further comprises an indicator indicating that the serving cell and the at least one non-serving cell sends the dedicated pilot signals.

18. The cell transmitting apparatus of claim 15, wherein a non-serving cell transmitter in a non-serving cell to which the first radio resources are not available sends to the UE a third data signal identical to the first data signal using third radio resources and a third scrambling sequence and a third pilot signal for channel compensation of the third data signal using the second radio resources and the third scrambling sequence.

19. The cell transmitting apparatus of claim 18, wherein the combining indication separately indicates the at least one non-serving cell that sends the second data signal using the first radio resources and the non-serving cell that sends the third data signal using the third radio resources.

20. The cell transmitting apparatus of claim 11, wherein the scheduler is provided in at least one of the serving cell or in a Node B for managing the serving cell and the at least one non-serving cell.

21. A method of receiving downlink data in a user equipment (UE) located in a soft handover region in an orthogonal frequency division multiplexing (OFDM) system, the method comprising:

receiving from a serving cell associated with the soft handover region a combining indication indicating at least one non-serving cell that sends a second data signal combinable with a first data signal sent from the serving cell;

receiving a combined data signal including the first data signal and the second data signal sent from the serving cell and the at least one non-serving cell, the first and second data signals using first radio resources and a first scrambling sequence allocated for the serving cell; and

channel-compensating the combined data signal using a first pilot signal received from the serving cell and a second pilot signal from the at least one non-serving cell.

22. The method of claim 21, further comprising:

receiving from the serving cell control information about the first and second data signals using radio resources and the first scrambling sequence.

23. The method of claim 22, wherein the control information comprises at least one of a modulation scheme, a data block size, a channel encoding scheme, and radio resources used for the first and second data signals.

24. The method of claim 21, wherein receiving from a serving cell associated with the soft handover region a combining indication comprises receiving the combining indication from the serving cell by at least one of physical layer signaling or higher-layer signaling.

25. The method of claim 21, further comprising:

sending the first pilot signal using second radio resources and the first scrambling code by the serving cell;

sending the second pilot signal using the second radio resources and a second scrambling code by the at least one non-serving cell; and

wherein channel compensating the combined data signal comprises;

calculating a first channel estimate using the first pilot signal;

calculating a second channel estimate using the second pilot signal;

combining the first and second channel estimates; and

channel-compensating the combined data signal using the combined channel estimate.

26. The method of claim 21, further comprising:

sending the first and second pilot signals using radio resources and the first scrambling code, for channel compensation of the first and second data signals by the serving cell and the at least one non-serving cell; and

wherein channel compensating the combined data signal comprises;

receiving a combined pilot signal including the first and second pilot signals;

calculating a channel estimate using the combined pilot signal; and

channel-compensating the combined data signal using the channel estimate.

27. The method of claim 26, wherein the combining indication information further comprises an indicator indicating that the serving cell and the at least one non-serving cell send the first and second pilot signals using the radio resources and the first scrambling sequence.

28. The method of claim 25, further comprising:

receiving from a non-serving cell to which the first radio resources are not available a third data signal identical to the first data signal using fourth radio resources and a third scrambling sequence;

receiving from the non-serving cell a third pilot signal using the second radio resources and the third scrambling sequence, for channel compensation of the third data signal;

calculating a third channel estimate using the third pilot signal;

channel-compensating the third data signal using the third channel estimate; and

combining the channel-compensated signal including the first and second data signals with the channel-compensated third data signal.

29. The method of claim 28, wherein the combining indication separately indicates the at least one non-serving cell that sends the second data signal using the first radio resources and the non-serving cell that sends the third data signal using the third radio resources.

30. The method of claim 21, wherein at least one of a scheduler in the serving cell and a scheduler in a Node B for managing the serving cell and the at least one non-serving cell allocates the first radio resources and the first scrambling sequence to the serving cell and the scheduler notifies the at least one non-serving cell of the first radio resources and the first scrambling sequence.

31. An apparatus for receiving downlink data in a user equipment (UE) located in a soft handover region in an orthogonal frequency division multiplexing (OFDM) system, comprising:

a combining indication receiver for receiving from a serving cell associated with the soft handover region a combining indication indicating at least one non-serving cell that sends a second data signal combinable with a first data signal sent from the serving cell; and

a reception path for receiving a combined data signal including the first data signal and the second data signal sent from the serving cell and the at least one non-serving cell, the first and second data signals using first radio resources and a first scrambling sequence allocated for the serving cell, and channel-compensating the combined data signal using a first pilot signal received from the serving cell and a second pilot signal from the at least one non-serving cell.

32. The apparatus of claim 31, wherein the reception path receives from the serving cell control information about the first and second data signals using radio resources and the first scrambling sequence.

33. The apparatus of claim 32, wherein the control information comprises at least one of a modulation scheme, a data block size, a channel encoding scheme, and radio resources used for the first and second data signals.

34. The apparatus of claim 31 wherein the combining indication receiver receives the combining indication from the serving cell by at least one of physical layer signaling and higher-layer signaling.

35. The apparatus of claim 31, wherein the first pilot signal is sent using second radio resources and the first scrambling code by the serving cell and the second pilot signal is sent using the second radio resources and a second scrambling code by the at least one non-serving cell, and wherein the reception path comprises:

a channel estimator for calculating a first channel estimate using the first pilot signal, calculating a second channel estimate using the second pilot signal, and calculating a final channel estimate by combining the first and second channel estimates; and

a channel compensator for channel-compensating the combined data signal using the final channel estimate.

36. The apparatus of claim 31, wherein the first and second pilot signals are sent using radio resources and the first scrambling code, for channel compensation of the first and second data signals by the serving cell and the at least one non-serving cell, and wherein the reception path comprises:

a channel estimator for receiving a combined pilot signal including the first and second pilot signals, and calculating a final channel estimate using the combined pilot signal; and

a channel compensator for channel-compensating the combined data signal using the channel estimate.

37. The apparatus of claim 36, wherein the combining indication information further comprises an indicator indicating that the serving cell and the at least one non-serving cell send the first and second pilot signals using the radio resources and the first scrambling sequence.

38. The apparatus of claim 35, further comprising:

an additional reception path for receiving from a non-serving cell to which the first radio resources are not available a third data signal identical to the first data signal using fourth radio resources and a third scrambling sequence, receiving from the non-serving cell a third pilot signal for channel compensation of the third data signal using the second radio resources and the third scrambling sequence, and channel-compensating the third data signal using the third pilot signal; and

a combiner for combining the channel-compensated data signal including the first and second data signals with the channel-compensated third data signal.

39. The apparatus of claim 38, wherein the combining indication separately indicates the at least one non-serving cell that sends the second data signal using the first radio resources and the non-serving cell that sends the third data signal using the third radio resources.

40. The apparatus of claim 31, wherein a scheduler in the serving cell or a scheduler in a Node B for managing the serving cell and the at least one non-serving cell allocates the first radio resources and the first scrambling sequence to the serving cell and the scheduler notifies the at least one non-serving cell of the first radio resources and the first scrambling sequence.