Segment sensitive scheduling

• US 20070060178A1
• Filed: 10/27/2005
• Published: 03/15/2007
• Est. Priority Date: 08/22/2005
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Gorokhov, Alexei, Ji, Tingfang
• Granted Patent: US 9,209,956 B2
• Time in Patent Office: Days
• US Class Current: 455/506
• CPC Class Codes: H04L 1/0002 by adapting the transmission rate
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/1812 Hybrid protocols; Hybrid automatic repeat request [HARQ]
• CPC Class Codes: H04L 25/0398 Restoration of channel reciprocity
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0044 allocation of payload
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04L 5/0057 Physical resource allocation for CQI
• CPC Class Codes: H04L 5/006 Quality of the received signal, e.g. BER, SNR, water filling
• CPC Class Codes: H04L 5/0064 Rate requirement of the data, e.g. scalable bandwidth, data priority
• CPC Class Codes: H04L 5/1438 Negotiation of transmission parameters prior to communication modified according to link quality H04L1/0001

Abstract

Systems and methods of scheduling sub-carriers in an OFDMA system in which a scheduler takes into account channel conditions experienced by the communication devices to optimize channel conditions. The scheduler can partition a set of sub-carriers spanning an operating bandwidth into a plurality of segments. The segments can include a plurality of global segments that each includes a distinct non-contiguous subset of the sub-carriers spanning substantially the entire operating bandwidth. One or more of the global segments can be further partitioned into a plurality of local segments that each has a bandwidth that is less than a channel coherence bandwidth. The scheduler determines channel characteristics experienced by each communication device via reporting or channel estimation, and allocates one or more segments to communication links for each device according to the channel characteristics.

Claims

1. A method of scheduling in a communication system including a plurality of sub-carriers spanning an operating frequency band partitioned into a plurality of segments, the method comprising:

determining a segment preference indicative of a preferred segment based upon channel characteristics experienced by a receiver; and

assigning a subset of sub-carriers within the preferred segment to a particular communication link associated with the segment preference.

2. The method of claim 1, wherein the plurality of segments comprises at least one global segment having a non-contiguous subset of the plurality of sub-carriers that span a substantial fraction of the operating bandwidth.

3. The method of claim 2, wherein the plurality of segments further comprises a plurality of local segments, each local segment having a subset of the plurality of sub-carriers distinct from any other local segment or global segment, and each local segment having a bandwidth less than a total bandwidth.

4. The method of claim 1, wherein the plurality of segments comprises a plurality of local segments, each local segment having a distinct subset of the plurality of sub-carriers, and each local segment having a bandwidth less than a total bandwidth.

5. The method of claim 4, wherein the plurality of local segments have substantially equal bandwidths.

6. The method of claim 4, wherein each of the plurality of local segments comprises a multiple of 16 sub-carriers.

7. The method of claim 1, wherein determining the segment preference comprises analyzing a pilot signal to determine channel characteristics corresponding to each of the plurality of segments, and selecting a preferred segment based on a comparison of the segment channel characteristics.

8. The method of claim 1, wherein determining the segment preference comprises:

receiving a reverse link pilot signal generated transmitted from a transmitter co-located with the receiver;

determining channel characteristics corresponding to at least two of the plurality of segments; and

selecting a segment base in part on the channel characteristics.

9. The method of claim 1, wherein determining the channel preference comprises receiving a reporting message from the receiver indicative of the segment preference.

10. The method of claim 1, wherein determining the segment preference comprises determining the segment preference based on a reverse link pilot signal;

and

wherein assigning the subset of sub-carriers comprises assigning the subset of carriers to a reverse link communication.

11. The method of claim 1, wherein determining the segment preference comprises determining the segment preference based on a reverse link pilot signal;

and

wherein assigning the subset of sub-carriers comprises assigning the subset of carriers to a forward link communication.

12. The method of claim 1, wherein assigning the subset of sub-carriers comprises mapping a data stream to the subset of sub-carriers in a forward link transmission.

13. The method of claim 1, wherein assigning the subset of sub-carriers comprises transmitting an assignment message to the receiver identifying at least one of the subset of sub-carriers.

14. The method of claim 1, further comprising enforcing a frequency hopping scheme within the preferred segment.

15. A method of scheduling in a communication system including a plurality of sub-carriers spanning an operating frequency band partitioned into a plurality of segments, the method comprising:

determining user data constraints;

assigning sub-carriers from a global segment having a non-contiguous subset of sub-carriers spanning a substantial fraction of the operating band if the user data constraints include a data bandwidth requirement greater than a total bandwidth;

determining, if the data bandwidth requirement is not greater than the total bandwidth, a segment preference indicative of a preferred local segment based upon channel characteristics experienced by a receiver, the preferred local segment selected from a plurality of local segments, each of the plurality of local segments having a bandwidth less than the total bandwidth; and

assigning a subset of sub-carriers within the preferred local segment to a communication link associated with the segment preference.

16. The method of claim 15, wherein the global segment includes sub-carriers that span at least one half the operating bandwidth.

17. The method of claim 15, wherein determining the segment preference comprises:

analyzing a received pilot signal to determine channel characteristics corresponding to each of the plurality of segments;

comparing the channel characteristics corresponding to each of the plurality of segments; and

selecting a segment corresponding to a greatest signal to noise ratio (SNR) value.

18. The method of claim 15, wherein determining the segment preference comprises receiving a reporting message indicating the segment preference.

19. An apparatus for c scheduling in a communication system including a plurality of sub-carriers spanning an operating frequency band, the apparatus comprising:

a channel estimator configured to determine a channel estimate corresponding to each of a plurality of segments spanning the operating frequency band based on the pilot signal, each of the segments having a bandwidth less than a total bandwidth;

a signal mapper configured to map data symbols to a subset of the plurality of sub-carriers in the communication system; and

a scheduler coupled to the channel estimator and configured to determine a first preferred segment based on the channel estimates, select the subset of the plurality of sub-carriers from within the first preferred segment, and further configured to control the signal mapper to map the data symbols to the subset of the plurality of sub-carriers.

20. The apparatus of claim 19, further comprising a receiver module configured to receive reverse link pilot signals and wherein the scheduler is configured to select the subset of the plurality of sub-carriers for a forward link transmission based on the reverse link pilot signals.

21. The apparatus of claim 19, wherein the pilot signals comprise reverse link pilot signals and the scheduler is configured to generate a reverse link resource assignment message for transmission to a user terminal based on the channel estimates.

22. The apparatus of claim 19, wherein the scheduler is configured to select the first preferred segment as a segment having a largest signal to noise ratio determined from the pilot signals.

23. The apparatus of claim 19, further comprising:

a Channel Quality Indicator (CQI) receiver coupled to the receiver module and configured to process channel characteristic reporting messages received by the receiver to determine a second preferred segment and further configured to generate a resource assignment message based on the channel characteristic reporting messages.

24. The apparatus of claim 19, further comprising a frequency hopper module configured to enforce a frequency hopping scheme within the first preferred segment.

25. An apparatus for channel sensitive scheduling in a communication system including a plurality of sub-carriers spanning an operating frequency band, the apparatus comprising:

a receiver module configured to receive a reverse link pilot signal and at least one channel characteristic reporting message; and

a scheduler coupled to the receiver module and configured to determine, based on the reverse link pilot signal, a channel characteristic corresponding to each of a plurality of segments spanning the operating frequency band, each of the segments having a bandwidth less than a total bandwidth, the scheduler configured to determine a reverse link resource assignment based on the channel characteristics and further configured to determine a forward link resource assignment based on the at least one channel characteristic reporting message.

26. The apparatus of claim 25, wherein the channel characteristic comprises a signal to noise ratio (SNR) value.

27. The apparatus of claim 25, wherein the channel characteristic comprises an interference value.

28. The apparatus of claim 25, further comprising a signal mapper coupled to the scheduler and configured to map data symbols to forward link sub-carriers in accordance with the forward link resource assignment.

29. The apparatus of claim 25, wherein the scheduler is configured to assign sub-carriers corresponding to a global segment comprising a non-contiguous subset of the plurality of sub-carriers that span a substantial fraction of the operating frequency band for channels requiring a bandwidth greater than the coherent channel bandwidth.

30. An apparatus for channel sensitive scheduling in a communication system including a plurality of sub-carriers spanning an operating frequency band, the apparatus comprising:

means for determining a channel preference indicative of a preferred segment from a plurality of segments substantially spanning at least a portion of the operating band based upon channel characteristics experienced by a receiver; and

means for assigning a subset of sub-carriers within the preferred segment to a particular communication link associated with the channel preference.

31. The apparatus of claim 30, wherein the means for determining the channel preference comprises:

means for receiving a pilot signal;

means for determining a channel characteristic corresponding to each of the plurality of segments; and

means for selecting the channel preference based on the channel characteristics.

32. The apparatus of claim 30, wherein the means for determining the channel preference comprises means for receiving a channel reporting message indicative of the channel preference.

33. A method of reporting channel characteristics in a communication system including a plurality of sub-carriers spanning an operating frequency band, the method comprising:

receiving a pilot signal;

determining a channel characteristic corresponding to each of a plurality of segments spanning the operating band, each segment having a bandwidth less than a coherent channel bandwidth;

determining a preferred segment from the plurality of segments;

comparing the channel characteristic corresponding to the preferred segment to a reporting threshold; and

generating a reporting message based on the preferred segment if the channel characteristic corresponding to the preferred segment exceeds the reporting threshold.

34. The method of claim 33, further comprising transmitting the reporting message to a scheduler.

35. The method of claim 33, wherein the pilot signal comprises a forward link pilot signal.

36. The method of claim 33, wherein the channel characteristic comprises a signal to noise ratio (SNR).

37. The method of claim 33, wherein the channel characteristic comprises an interference value.

38. The method of claim 33, wherein the channel characteristic comprises a pilot signal strength.

39. The method of claim 33, wherein determining the preferred segment comprises selecting a segment corresponding to a largest signal to noise ratio.

40. The method of claim 33, wherein determining the preferred segment comprises selecting a segment corresponding to a least interference value.

41. The method of claim 33, wherein comparing the channel characteristic corresponding to the preferred segment to the reporting threshold comprises determining whether a signal to noise ratio corresponding to the preferred segment exceeds an average SNR ratio by a predetermined amount.

42. The method of claim 33, wherein comparing the channel characteristic corresponding to the preferred segment to the reporting threshold comprises:

receiving a differential value from a scheduler; and

determining whether a signal to noise ratio corresponding to the preferred segment exceeds an average SNR ratio by the differential value.