OFDMA reverse link scheduling

• US 8,654,712 B2
• Filed: 06/13/2006
• Issued: 02/18/2014
• Est. Priority Date: 06/16/2005
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Julian, David Jonathan, Sutivong, Arak
• Primary Examiner(s): Magloire, Vladimir
• Assistant Examiner(s): PLATA, EDD RIANNE L
• Application Number:
  US11/452,722
• Publication Number:
  US 20060293076A1
• Time in Patent Office: 2,807 Days
• Field of Search: 370/329, 455/450, 455/451, 455/452.1, 455/452.2, 455/453, 455/454
• US Class Current: 370/329
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0053 Allocation of signaling, i.e. of overhead other than pilot signals
• CPC Class Codes: H04L 5/023 Multiplexing of multicarrier modulation signals multicarrier modulation H04L27/2601
• CPC Class Codes: H04W 52/146 Uplink power control
• CPC Class Codes: H04W 52/16 Deriving transmission power values from another channel
• CPC Class Codes: H04W 52/223 predicting future states of the transmission
• CPC Class Codes: H04W 52/241 taking into account channel quality metrics, e.g. SIR, SNR, CIR, Eb/lo
• CPC Class Codes: H04W 52/247 where the output power of a terminal is based on a path parameter sent by another terminal
• CPC Class Codes: H04W 72/0473 the resource being transmission power
• CPC Class Codes: H04W 72/12 Wireless traffic scheduling
• CPC Class Codes: H04W 72/1268 of uplink data flows
• CPC Class Codes: H04W 72/542 using measured or perceived quality

Abstract

Systems and methodologies are described that facilitate scheduling via a power control algorithm that dynamically update a scheduling metric (e.g., adjusting transmission power for sub-carriers) based on a prediction function and/or inference model of expected power requirements. In one aspect, the power prediction component can include two further components, namely: the data channel component and the control channel component—wherein a carrier to interference ratio (C/I) information is being transmitted on such control channel and the power is adjusted to obtain performance requirements. Accordingly, an efficient scheduling of users on a reverse link in an orthogonal manner can be provided, to optimally use system resources, while simultaneously: maintaining a predetermined and/or arbitrary fairness metrics, maintaining quality of service and maximizing throughput.

Claims

1. A method of scheduling users in a wireless communication network comprising:

receiving signals from access terminals, wherein the received signals indicate power spectral density per subcarrier reported by an access terminal as an offset from a control channel transmit power level;

predicting expected power requirements for subsequent transmissions by the access terminals on subcarriers of a frequency division multiplexed reverse link based on the received signals; and

assigning frequency sets of the subcarriers to the access terminals based on the predicted expected power requirements, wherein predicting the expected power requirements comprises;

determining a second offset from the control channel transmit power level; and

determining a power spectral density that is supportable by at least one of the access terminals for data channel transmissions based on the second offset.

2. The method of claim 1 wherein the assignment of the frequency sets comprises defining a sticky assignment by preassigning a subcarrier to one of the access terminals, wherein the preassigned subcarrier remains assigned to the one of the access terminals during subsequent subcarrier assignments until another one of the access terminals is swapped into the preassigned subcarrier.

3. The method of claim 1 wherein the assignment of the frequency sets comprises employing a fairness criteria for the wireless communication network, wherein start times for scheduling the access terminals are weighted such that service for the access terminals is proportional to channel conditions for the access terminals.

4. The method of claim 1, wherein the assignment of the frequency sets comprises determining a quantity of the subcarriers that are supportable for the data channel transmissions based on the determined supportable power spectral density.

5. The method of claim 1 wherein the assignment of the frequency sets comprises changing assignments of the subcarriers to the access terminals as a result of a change in the predicted expected power requirements for the subcarriers.

6. The method of claim 1 wherein the assignment of the frequency sets comprises:

computing data spectral density in bits per subcarrier based on the received signals, wherein the received signals indicate transmit power spectral density per subcarrier reported by the access terminals; and

determining a quantity of subcarriers for sending data based on buffer levels reported by the access terminals and the computed data spectral density in bits per subcarrier.

7. The method of claim 1 further comprising adjusting transmit powers of the subcarriers based on the predicted expected power requirements.

8. The method of claim 1, wherein the prediction of the expected power requirements further comprises:

determining at least one factor, associated with estimation of the offset, of the group consisting of ate termination, packet error, and efficiency of allocation of system resource; and

predicting transmit power based on the determination.

9. The method of claim 1 further comprising:

determining traffic behavior at a base station that receives transmissions from one of the access terminals over at least one of the subcarriers; and

adjusting transmit power for the at least one of the subcarriers based on the determined traffic behavior.

10. The method of claim 9 wherein the traffic behavior relates to late termination, packet error, or inefficient allocation of system resources.

11. The method of claim 1 further comprising:

determining signal fading associated with at least one of the subcarriers; and

adjusting the assignment of the frequency sets of the subcarriers based on the determined fade condition.

12. The method of claim 1 further comprising adjusting a start time for transmissions by at least one of the access terminals on at least one of the subcarriers based on at least one channel condition associated with the at least one user.

13. The method of claim 12 wherein the at least one channel condition is indicated by mean data spectral efficiency for the at least one access terminal.

14. An apparatus for scheduling access terminals in a wireless communication network comprising:

means for receiving signals from the access terminals, wherein the received signals indicate power spectral density per subcarrier reported by an access terminal as an offset from a control channel transmit power level;

means for predicting expected power requirements for subsequent transmissions by the access terminals on subcarriers of a frequency division multiplexed reverse link based on the received signals; and

means for assigning frequency sets of the subcarriers to the access terminals based on the predicted expected power requirements, wherein predicting the expected power requirements comprises;

determining a second offset from the control channel transmit power level; and

determining a power spectral density one of the access terminals for data channel transmissions based on the second offset.

15. The apparatus of claim 14 further comprising means for defining a sticky assignment by preassigning a subcarrier to one of the access terminals, wherein the preassigned subcarrier remains assigned to the one of the access terminals during subsequent subcarrier assignments until another one of the access terminals is swapped into the preassigned subcarrier.

16. The apparatus of claim 14 further comprising means for maintaining a fairness metric wherein start times for scheduling the access terminals are weighted such that service for the access terminals is proportional to channel conditions for the access terminals.

17. The apparatus of claim 14 further comprising means for predicting a data rate for at least one of the subsequent transmissions by determining a received pilot carrier to interference ratio (C/I) associated with a pilot received from one of the access terminals, applying an offset based on predicted power spectral density traffic to the pilot, predicting a data received carrier to interference ratio based on the offset, and selecting the data rate based on the predicted data received carrier to interference ratio.

18. The apparatus of claim 14 further comprising means for allocating a top-down resource allocation by selecting one of the access terminals with a smallest head of line start time and supplying the selected access terminal with a largest available resource assignment.

19. The apparatus of claim 14 further comprising means for allocating a middle-out resource allocation by selecting one of the access terminals with a smallest head of line start time and supplying the selected access terminal with a smallest available resource assignment that is greater than or equal to a resource granularity size.

20. The apparatus of claim 14 further comprising means for allocating a bottom up resource allocation by selecting one of the access terminals with a smallest head of line start time and supplying the selected access terminal with a smallest available resource assignment that is larger than a current resource assignment for the selected user.

21. The apparatus of claim 14 wherein the means for assigning frequency sets changes assignments of the subcarriers to the access terminals as a result of a change in the predicted expected power requirements for the subcarriers.

22. The apparatus of claim 14 further comprising means for adjusting transmit powers of the subcarriers based on the predicted expected power requirements.

23. A processor configured to execute the following instructions:

receiving signals from access terminals, wherein the received signals indicate power spectral density per subcarrier reported by an access terminal as an offset from a control channel transmit power level;

predicting expected power requirements for subsequent transmissions by the access terminals on subcarriers of a frequency division multiplexed reverse link based on the received signals; and

assigning frequency sets of the subcarriers to the access terminals based on the predicted expected power requirements, wherein predicting the expected power requirements comprises;

determining a second offset from the control channel transmit power level; and

determining a power spectral density one of the access terminals for data channel transmissions based on the second offset.

24. The processor of claim 23 further configured to execute the assigning of the frequency sets based on reported buffer levels, reported maximum number of subcarriers supportable by a access terminal based on maximum power constraints, and power control data transmit power spectral density in power per subcarrier.

25. The processor of claim 23 further configured to execute allocating resources via a top-down resource allocation by selecting one of the access terminals with a smallest head of line start time and supplying the selected access terminal with a largest available resource assignment.

26. The processor of claim 23 further configured to execute allocating resources via a middle-out resource allocation by selecting one of the access terminals with a smallest head of line start time and supplying the selected access terminal with a smallest available resource assignment that is greater than or equal to a resource granularity size.

27. The processor of claim 23 further configured to execute allocating resources via a bottom-up resource allocation by selecting one of the access terminals with a smallest head of line start time and supplying the selected access terminal with a smallest available resource assignment that is larger than a current resource assignment for the selected user.

28. The processor of claim 23 further configured to execute predicting a data rate for at least one of the subsequent transmissions by determining a received pilot carrier to interference ratio (C/I) associated with a pilot received from one of the access terminals, applying an offset based on predicted power spectral density traffic to the pilot, predicting a data received carrier to interference ratio based on the offset, and selecting the data rate based on the predicted data received carrier to interference ratio.

29. The processor of claim 23 further configured to execute maintaining a fairness metric wherein start times for scheduling the access terminals are weighted such that service for the access terminals is proportional to channel conditions for the access terminals.

30. A non-transitory machine-readable medium having stored thereon machine-executable instructions for:

receiving signals from access terminals, wherein the received signals indicate power spectral density per subcarrier reported by an access terminal as an offset from a control channel transmit power level;

predicting expected power requirements for subsequent transmissions by the access terminals on subcarriers of a frequency division multiplexed reverse link based on the received signals; and

assigning frequency sets of the subcarriers to the access terminals based on the predicted expected power requirements, wherein predicting the expected power requirements comprises;

determining a second offset from the control channel transmit power level; and

determining a power spectral density one of the access terminals for data channel transmissions based on the second offset.

31. The machine-readable medium of claim 30 further comprising machine-executable instructions for defining a sticky assignment by preassigning a subcarrier to one of the access terminals, wherein the preassigned subcarrier remains assigned to the one of the access terminals during subsequent subcarrier assignments until another one of the access terminals is swapped into the preassigned subcarrier.

32. The machine-readable medium of claim 30 wherein the received signals comprise power spectral density per subcarrier reported by an access terminal.

33. The machine-readable medium of claim 30 further comprising machine-executable instructions for allocating resources based on a top-down approach comprising selecting one of the access terminals with a smallest head of line start time and supplying the selected access terminal with a largest available resource assignment.

34. The machine-readable medium of claim 30 further comprising machine-executable instructions for changing assignments of the subcarriers to access terminals as a result of a change in the predicted expected power requirements for the subcarriers.

35. The machine-readable medium of claim 30 further comprising machine-executable instructions for adjusting transmit powers of the subcarriers based on the predicted expected power requirements.

36. A wireless communications apparatus, comprising:

a memory that retains data related to signals received from access terminals, wherein the received signals indicate power spectral density per subcarrier reported by an access terminal as an offset from a control channel transmit power level; and

a processor that predicts expected power requirements for subsequent transmissions by the access terminals on subcarriers of a frequency division multiplexed reverse link based on the data, and that enables assigning frequency sets of the subcarriers to access terminals based on the predicted expected power requirements,

wherein predicting the expected power requirements comprises;

determining a second offset from the control channel transmit power level; and

determining a power spectral density one of the access terminals for data channel transmissions based on the second offset.

37. The wireless communications apparatus of claim 36, wherein the processor further defines a sticky assignment by preassigning a subcarrier to one of the access terminals, wherein the preassigned subcarrier remains assigned to the one of the access terminals during subsequent subcarrier assignments until another one of the access terminals is swapped into the preassigned subcarrier.

38. The wireless communications apparatus of claim 36, wherein the processor further allocates access terminals based on a bottom-up approach by selecting one of the access terminals with a smallest head of line start time and supplying the selected access terminal with a smallest available resource assignment that is larger than a current resource assignment for the selected user.

39. The wireless communication apparatus of claim 36, wherein the received signals indicate power spectral density per subcarrier reported by an access terminal.

40. The wireless communication apparatus of claim 36 wherein the assignment of the frequency sets comprises changing assignments of the subcarriers to the access terminals as a result of a change in the predicted expected power requirements for the subcarriers.

41. The wireless communication apparatus of claim 36 wherein the assigning the frequency sets comprises:

computing data spectral density in bits per subcarrier based on the received signals, wherein the received signals transmit power spectral density per subcarrier reported by the access terminals; and

determining a quantity of subcarriers for sending data based on buffer levels reported by the access terminals and the computed data spectral density in bits per subcarrier.

42. The wireless communication apparatus of claim 36 wherein the processor adjusts transmit powers of the subcarriers based on the predicted expected power requirements.

43. A method of scheduling users in a wireless communication network comprising:

receiving signals from access terminals;

predicting expected power requirements for subsequent transmissions by the access terminals on subcarriers of a frequency division multiplexed reverse link based on the received signals; and

assigning frequency sets of the subcarriers to the access terminals based on the predicted expected power requirements, wherein;

the received signals indicate power spectral density information received from one of the access terminals;

the received power spectral density information is reported as a first offset from a control channel transmit power level;

transmit power for a data channel for the one of the access terminals is set as a second offset from the control channel transmit power level;

the prediction of the expected power requirements comprises determining the second offset, and determining data spectral density supportable by the one of the access terminals based on the received power spectral density information and the second offset; and

the assignment of the frequency sets of the subcarriers comprises determining a quantity of the subcarriers that are supportable for transmissions on the data channel based on the determined data spectral density supportable by the one user.

44. The method of claim 43 further comprising:

determining traffic behavior at a base station that receives the transmissions on the data channel; and

adjusting the second offset based on the determined traffic behavior.

45. The method of claim 44 wherein the traffic behavior relates to late termination, packet error, or inefficient allocation of system resources.

46. The method of claim 43 further comprising adjusting transmit power for at least one of the subcarriers based on the received power spectral density information.

47. A method of scheduling users in a wireless communication network comprising:

receiving signals from access terminals;

predicting expected power requirements for subsequent transmissions by the access terminals on subcarriers of a frequency division multiplexed reverse link, wherein predicting the expected power requirements comprises inferring, upon sending by a scheduler component a conflicting resource assignment message to a first access terminal, whether to reassign a resource previously assigned to a second access terminal; and

assigning frequency sets of the subcarriers to the access terminals based on the predicted expected power requirements.

48. The method of claim 47, wherein the received signals indicate power spectral density per subcarrier reported by an access terminal as an offset from a closed loop power controlled pilot.

49. The method of claim 48, wherein predicting the expected power requirements further comprises:

determining a second offset from the closed loop power controlled pilot; and

determining a power spectral density that is supportable by the access terminal for data channel transmissions based on the second offset.

50. The method of claim 47, wherein the assignment of the frequency sets comprises determining a quantity of the subcarriers that are supportable for the data channel transmissions based on the determined supportable power spectral density.

51. The method of claim 47, further comprising adjusting transmit power of at least one subcarrier based on the predicted expected power requirements.