PILOT DESIGN FOR IMPROVED CHANNEL AND INTERFERENCE ESTIMATION

• US 20080165891A1
• Filed: 03/26/2007
• Published: 07/10/2008
• Est. Priority Date: 01/05/2007
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Gorokhov, Alexei, Gore, Dhananjay A., Budianu, Petru Cristian
• Granted Patent: US 8,130,867 B2
• Time in Patent Office: Days
• US Class Current: 375/299
• CPC Class Codes: H04L 25/0202 Channel estimation
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver

Abstract

Techniques for transmitting pilot and for processing received pilot to obtain channel and interference estimates are described. A terminal may generate pilot symbols for a first cluster in a time frequency block based on a first sequence and may generate pilot symbols for a second cluster in the time frequency block based on a second sequence. The first and second sequences may include common elements arranged in different orders and may be considered as different versions of a single sequence. The terminal may transmit the pilot symbols in their respective clusters. A base station may obtain received pilot symbols from multiple clusters in the time frequency block. The base station may form each of multiple basis vectors with multiple versions of the sequence assigned to the terminal and may process the received pilot symbols with the multiple basis vectors to obtain a channel estimate for the terminal.

Claims

1. An apparatus comprising:

a processor configured to generate pilot symbols for a first cluster in a time frequency block based on a first sequence, and to generate pilot symbols for a second cluster in the time frequency block based on a second sequence; and

a memory coupled to the processor.

2. The apparatus of claim 1, wherein the first and second sequences include common elements arranged in different orders.

3. The apparatus of claim 2, wherein the elements in the second sequence are in a reverse order with respect to the elements in the first sequence.

4. The apparatus of claim 1, wherein the pilot symbols in the second cluster are symmetric with respect to the pilot symbols in the first cluster about a center of the time frequency block.

5. The apparatus of claim 1, wherein the processor is configured to generate pilot symbols for a third cluster in the time frequency block based on the first sequence, and to generate pilot symbols for a fourth cluster in the time frequency block based on the second sequence.

6. The apparatus of claim 1, wherein the processor is configured to generate pilot symbols for a third cluster in the time frequency block based on a third sequence, and to generate pilot symbols for a fourth cluster in the time frequency block based on a fourth sequence.

7. The apparatus of claim 6, wherein the first, second, third and fourth sequences include common elements arranged in different orders.

8. The apparatus of claim 1, wherein the processor is configured to generate M pilot symbols for the first cluster based on M elements in the first sequence, and to generate M pilot symbols for the second cluster based on M elements in the second sequence, where M is an integer greater than one.

9. The apparatus of claim 1, wherein the first sequence is assigned to a terminal and is orthogonal to at least one other sequence assigned to at least one other terminal for the first cluster.

10. The apparatus of claim 1, wherein the first and second sequences are assigned to a terminal, wherein the first sequence is orthogonal to a first set of at least one other sequence assigned to at least one other terminal for the first cluster, and wherein the second sequence is orthogonal to a second set of at least one other sequence assigned to the at least one other terminal for the second cluster.

11. The apparatus of claim 1, wherein the first sequence includes elements in a column of a Fourier matrix.

12. The apparatus of claim 1, wherein the first and second sequences each include three elements used to generate three pilot symbols for one cluster.

13. The apparatus of claim 1, wherein the first and second sequences each include four elements used to generate four pilot symbols for one cluster.

14. A method comprising:

generating pilot symbols for a first cluster in a time frequency block based on a first sequence; and

generating pilot symbols for a second cluster in the time frequency block based on a second sequence.

15. The method of claim 14, wherein the first and second sequences include common elements arranged in different orders.

16. The method of claim 14, further comprising:

generating pilot symbols for a third cluster in the time frequency block based on the first sequence; and

generating pilot symbols for a fourth cluster in the time frequency block based on the second sequence.

17. The method of claim 14, further comprising:

generating pilot symbols for a third cluster in the time frequency block based on a third sequence; and

generating pilot symbols for a fourth cluster in the time frequency block based on a fourth sequence.

18. The method of claim 14, wherein the first and second sequences are assigned to a terminal, wherein the first sequence is orthogonal to a first set of at least one other sequence assigned to at least one other terminal for the first cluster, and wherein the second sequence is orthogonal to a second set of at least one other sequence assigned to the at least one other terminal for the second cluster.

19. An apparatus comprising:

means for generating pilot symbols for a first cluster in a time frequency block based on a first sequence; and

means for generating pilot symbols for a second cluster in the time frequency block based on a second sequence.

20. The apparatus of claim 19, further comprising:

means for generating pilot symbols for a third cluster in the time frequency block based on the first sequence; and

means for generating pilot symbols for a fourth cluster in the time frequency block based on the second sequence.

21. The apparatus of claim 19, further comprising:

means for generating pilot symbols for a third cluster in the time frequency block based on a third sequence; and

means for generating pilot symbols for a fourth cluster in the time frequency block based on a fourth sequence.

22. A processor-readable medium including instructions stored thereon, comprising:

a first instruction set for generating pilot symbols for a first cluster in a time frequency block based on a first sequence; and

a second instruction set for generating pilot symbols for a second cluster in the time frequency block based on a second sequence.

23. An apparatus comprising:

a processor configured to obtain received pilot symbols from multiple clusters in a time frequency block, to form each of multiple basis vectors with multiple versions of a sequence assigned to a transmitter, and to process the received pilot symbols with the multiple basis vectors; and

a memory coupled to the processor.

24. The apparatus of claim 23, wherein the multiple versions of the sequence correspond to different orderings of elements in the sequence.

25. The apparatus of claim 23, wherein the processor is configured to form each basis vector based on an original version and a flipped version of the sequence.

26. The apparatus of claim 23, wherein the processor is configured to form each basis vector based on four versions of the sequence used to generate pilot symbols for the multiple clusters, the pilot symbols being symmetric about a center of the time frequency block.

27. The apparatus of claim 23, wherein the processor is configured to form the multiple basis vectors further based on a channel model with linearly varying time component and linearly varying frequency component.

28. The apparatus of claim 23, wherein the processor is configured to obtain multiple complex values based on dot products of the received pilot symbols with the multiple basis vectors, and to derive a channel estimate for the transmitter based on the multiple complex values.

29. The apparatus of claim 28, wherein the multiple complex values comprise a first complex value indicative of an average channel gain for the time frequency block.

30. The apparatus of claim 29, wherein the multiple complex values comprise a second complex value indicative of channel variation across frequency and a third complex value indicative of channel variation across time.

31. The apparatus of claim 23, wherein the processor is configured to obtain at least one complex value based on dot product of the received pilot symbols with at least one other basis vector, and to derive a noise and interference estimate based on the at least one complex value.

32. A method comprising:

obtaining received pilot symbols from multiple clusters in a time frequency block;

forming each of multiple basis vectors with multiple versions of a sequence assigned to a transmitter; and

processing the received pilot symbols with the multiple basis vectors.

33. The method of claim 32, wherein the multiple versions of the sequence correspond to different orderings of elements in the sequence.

34. The method of claim 32, wherein the processing the received pilot symbols with the multiple basis vectors comprises

obtaining multiple complex values based on dot products of the received pilot symbols with the multiple basis vectors, and

deriving a channel estimate for the transmitter based on the multiple complex values.

35. The method of claim 34, wherein the multiple complex values comprise a first complex value indicative of an average channel gain for the time frequency block, a second complex value indicative of channel variation across frequency, and a third complex value indicative of channel variation across time.

36. The method of claim 32, further comprising:

obtaining at least one complex value based on dot product of the received pilot symbols with at least one other basis vector; and

deriving a noise and interference estimate based on the at least one complex value.

37. An apparatus comprising:

means for obtaining received pilot symbols from multiple clusters in a time frequency block;

means for forming each of multiple basis vectors with multiple versions of a sequence assigned to a transmitter; and

means for processing the received pilot symbols with the multiple basis vectors.

38. The apparatus of claim 37, wherein the means for processing the received pilot symbols with the multiple basis vectors comprises

means for obtaining multiple complex values based on dot products of the received pilot symbols with the multiple basis vectors, and

means for deriving a channel estimate for the transmitter based on the multiple complex values.

39. The apparatus of claim 37, further comprising:

means for obtaining at least one complex value based on dot product of the received pilot symbols with at least one other basis vector; and

means for deriving a noise and interference estimate based on the at least one complex value.

40. A processor-readable medium including instructions stored thereon, comprising:

a first instruction set for obtaining received pilot symbols from multiple clusters in a time frequency block;

a second instruction set for forming each of multiple basis vectors with multiple versions of a sequence assigned to a transmitter; and

a third instruction set for processing the received pilot symbols with the multiple basis vectors.