Channel-Dependent Frequency-Domain Scheduling in an Orthogonal Frequency Division Multiplexing Communications System

• US 20090110087A1
• Filed: 10/30/2007
• Published: 04/30/2009
• Est. Priority Date: 10/30/2007
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Wan, Lei, Liu, Yin
• Granted Patent: US 7,933,350 B2
• Time in Patent Office: Days
• US Class Current: 375/260
• CPC Class Codes: H04L 1/0021 in which the algorithm uses adaptive thresholds
• CPC Class Codes: H04L 25/0224 using sounding signals
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0039 Frequency-contiguous, i.e. with no allocation of frequencies for one user or terminal between the frequencies allocated to another
• CPC Class Codes: H04L 5/0044 allocation of payload
• CPC Class Codes: H04L 5/006 Quality of the received signal, e.g. BER, SNR, water filling
• CPC Class Codes: H04L 5/0075 Allocation using proportional fairness
• CPC Class Codes: H04L 5/0094 Indication of how sub-channels of the path are allocated
• CPC Class Codes: H04W 72/54 based on quality criteria

Abstract

Methods and apparatus are disclosed for scheduling sub-carriers in an Orthogonal Frequency Division Multiplexing (OFDM) communication system. In an exemplary method, channel quality metric values for each of a plurality of sub-channels are determined, in view of a selected mobile terminal. For each of two or more threshold levels for the channel quality metric, sub-carrier groups composed of sub-carriers corresponding to sub-channels having channel quality metric values superior to the threshold level are identified, and an estimated data throughput is calculated for each of the identified sub-carrier groups. One or more of the identified sub-carrier groups is allocated to the selected mobile terminal according to the estimated data throughputs.

Claims

1. A method of scheduling sub-carriers in an Orthogonal Frequency Division Multiplexing (OFDM) communication system, the method comprising:

for each of two or more threshold interference levels, identifying one or more sub-carrier groups composed of contiguous sub-carriers corresponding to sub-channels having interference levels below the threshold interference level;

calculating an estimated data throughput for each of the identified sub-carrier groups in view of a selected mobile terminal; and

allocating at least one of the identified sub-carrier groups to the selected mobile terminal according to the estimated data throughputs.

2. The method of claim 1, further comprising determining the two or more threshold interference levels based on a plurality of measured sub-channel interference levels.

3. The method of claim 1, further comprising generating a signaling message for the selected mobile terminal, the signaling message comprising a first parameter identifying a sub-carrier in a first one of the at least one allocated sub-carrier groups and a second parameter indicating the number of sub-carriers in the first one of the at least one allocated sub-carrier groups.

4. The method of claim 1, wherein the sub-carriers are organized into resource blocks comprising two or more contiguous sub-carriers, and wherein identifying one or more sub-carrier groups composed of contiguous sub-carriers corresponding to sub-channels having interference levels below the threshold interference level comprises identifying one or more sub-carrier groups composed of contiguous resource blocks, wherein each of the contiguous resource blocks is composed of sub-carriers corresponding to sub-channels having interference levels below the threshold interference level.

5. The method of claim 4, further comprising generating a signaling message for the selected mobile terminal, the signaling message comprising a first parameter identifying a resource block in a first one of the at least one allocated sub-carrier groups and a second parameter indicating the number of resource blocks in the first one of the at least one allocated sub-carrier groups.

6. The method of claim 1, wherein calculating an estimated data throughput comprises selecting one or more modulation formats and coding schemes based on the interference levels for the identified sub-carrier group and calculating the estimated data throughput as a function of the selected modulation formats and coding schemes.

7. The method of claim 1, wherein allocating at least one of the identified sub-carrier groups to the selected mobile terminal according to the estimated data throughputs comprises allocating an identified sub-carrier group having the highest estimated data throughput to the selected mobile terminal.

8. The method of claim 1, wherein allocating at least one of the identified sub-carrier groups to the selected mobile terminal according to the estimated data throughputs comprises selecting two or more of the identified sub-carrier groups having an aggregate estimated data throughput equal to or exceeding a data throughput target for the selected mobile terminal.

9. The method of claim 8, further comprising determining the data throughput target based on a buffered-data quantity corresponding to the selected mobile terminal.

10. A scheduling subsystem for scheduling sub-carriers in an Orthogonal Frequency Division Multiplexing (OFDM) communication system, comprising:

an interference determination module configured to determine one or more sub-channel interference levels; and

an allocation processor configured to control the interference determination module and to;

for each of two or more threshold interference levels, identify one or more sub-carrier groups composed of contiguous sub-carriers corresponding to sub-channels having interference levels below the threshold interference level;

calculate an estimated data throughput for each of the identified sub-carrier groups in view of a selected mobile terminal; and

allocate at least one of the identified sub-carrier groups to the selected mobile terminal according to the estimated data throughputs.

11. The scheduling subsystem of claim 10, wherein the allocation processor is further configured to determine the two or more threshold interference levels based on the sub-channel interference levels.

12. The scheduling subsystem of claim 10, further comprising a signaling block configured to generate a signaling message for the selected mobile terminal, the signaling message comprising a first parameter identifying a sub-carrier in a first one of the at least one allocated sub-carrier groups and a second parameter indicating the number of sub-carriers in the first one of the at least one allocated sub-carrier groups.

13. The scheduling subsystem of claim 10, wherein the sub-carriers are organized into resource blocks comprising two or more contiguous sub-carriers, and wherein the allocation processor is configured to identify one or more-sub-carrier groups by identifying sub-carrier groups composed of contiguous resource blocks, wherein each of the contiguous resource blocks is composed of sub-carriers corresponding to sub-channels having interference levels below the threshold interference level.

14. The scheduling subsystem of claim 13, further comprising a signaling block configured to generate a signaling message for the selected mobile terminal, the signaling message comprising a first parameter identifying a resource block in a first one of the at least one allocated sub-carrier groups and a second parameter indicating the number of resource blocks in the first one of the at least one allocated sub-carrier groups.

15. The scheduling subsystem of claim 10, wherein the allocation processor is configured to calculate estimated data throughput by selecting one or more modulation formats and coding schemes for the identified sub-carrier group and calculating the estimated data throughput as a function of the selected modulation formats and coding schemes.

16. The scheduling subsystem of claim 10, wherein the allocation processor is configured to allocate an identified sub-carrier group having the highest estimated data throughput to the selected mobile terminal.

17. The scheduling subsystem of claim 10, wherein the allocation processor is configured to allocate two or more of the identified sub-carrier groups having an aggregate estimated data throughput equal to or exceeding a data throughput target for the selected mobile terminal.

18. The scheduling subsystem of claim 17, wherein the allocation processor is further configured to determine the data throughput target based on a buffered-data quantity corresponding to the selected mobile terminal.

19. A method of scheduling sub-carriers in an Orthogonal Frequency Division Multiplexing (OFDM) system, the method comprising:

determining a channel quality metric value for each of a plurality of sub-channels, in view of sub-channel gains for a selected mobile terminal;

for each of two or more threshold levels for the channel quality metric, identifying one or more sub-carrier groups composed of contiguous sub-carriers corresponding to sub-channels having channel quality metric values superior to the threshold level;

calculating an estimated data throughput for each of the identified sub-carrier groups; and

allocating at least one of the identified sub-carrier groups to the selected mobile terminal according to the estimated data throughputs.

20. The method of claim 19, wherein determining a channel quality metric value for each of a plurality of sub-channels comprises estimating a signal-to-interference-plus-noise (SINR) ratio corresponding to the selected mobile terminal for each of the plurality of sub-channels.

21. The method of claim 20, wherein estimating a SINR ratio corresponding to the selected mobile terminal for each of the plurality of sub-channels comprises estimating the SINR ratios using one or more sounding reference signals.

22. The method of claim 20, further comprising determining the two or more threshold levels for the channel quality metric based on the estimated SINR ratios.

23. The method of claim 19, further comprising generating a signaling message for the selected mobile terminal, the signaling message comprising a first parameter identifying a sub-carrier in a first one of the at least one allocated sub-carrier groups and a second parameter indicating the number of sub-carriers in the first one of the at least one allocated sub-carrier groups.

24. The method of claim 19, wherein the sub-carriers are organized into resource blocks comprising two or more contiguous sub-carriers, and wherein identifying one or more sub-carrier groups composed of contiguous sub-carriers corresponding to sub-channels having channel quality metric values superior to the threshold level comprises identifying one or more sub-carrier groups composed of contiguous resource blocks, wherein each of the contiguous resource blocks is composed of sub-carriers corresponding to sub-channels having channel quality metric values superior to the threshold level.

25. The method of claim 24, further comprising generating a signaling message for the selected mobile terminal, the signaling message comprising a first parameter identifying a resource block in a first one of the at least one allocated sub-carrier groups and a second parameter indicating the number of resource blocks in the first one of the at least one allocated sub-carrier groups.

26. The method of claim 19, wherein calculating an estimated data throughput comprises selecting one or more modulation formats and coding schemes for the identified sub-carrier group based on the channel quality metric values and calculating the estimated data throughput as a function of the selected modulation formats and coding schemes.

27. The method of claim 19, wherein allocating at least one of the identified sub-carrier groups to the selected mobile terminal according to the estimated data throughputs comprises allocating an identified sub-carrier group having the highest estimated data throughput to the selected mobile terminal.

28. The method of claim 19, wherein allocating at least one of the identified sub-carrier groups to the selected mobile terminal according to the estimated data throughputs comprises selecting two or more of the identified sub-carrier groups having an aggregate estimated data throughput equal to or exceeding a data throughput target for the selected mobile terminal.

29. The method of claim 28, further comprising determining the data throughput target based on a buffered-data quantity corresponding to the selected mobile terminal.

30. A scheduling subsystem for scheduling sub-carriers in an Orthogonal Frequency Division Multiplexing (OFDM) communication system, comprising:

a channel quality determination module configured to determine a channel quality metric value for each of a plurality of sub-channels, in view of a selected mobile terminal; and

an allocation processor configured to control the channel quality determination module and to;

for each of two or more threshold levels, identify one or more sub-carrier groups composed of contiguous sub-carriers corresponding to sub-channels having channel quality metric values superior to the threshold level;

calculate an estimated data throughput for each of the identified sub-carrier groups; and

allocate at least one of the identified sub-carrier groups to the selected mobile terminal according to the estimated data throughputs.

31. The scheduling subsystem of claim 30, wherein the channel quality determination module is configured to determine channel quality metric values comprising signal-to-interference-plus-noise (SINR) ratios.

32. The scheduling subsystem of claim 31, wherein the channel quality determination module is configured to estimate the SINR ratios using one or more sounding reference signals.

33. The scheduling subsystem of claim 30, wherein the allocation processor is further configured to determine the two or more threshold levels based on the channel quality metric values.

34. The scheduling subsystem of claim 30, further comprising a signaling block configured to generate a signaling message for the selected mobile terminal, the signaling message comprising a first parameter identifying a sub-carrier in a first one of the at least one allocated sub-carrier groups and a second parameter indicating the number of sub-carriers in the first one of the at least one allocated sub-carrier groups.

35. The scheduling subsystem of claim 30, wherein the sub-carriers are organized into resource blocks comprising two or more contiguous sub-carriers, and wherein the allocation processor is configured to identify one or more sub-carrier groups by identifying sub-carrier groups composed of contiguous resource blocks, wherein each of the contiguous resource blocks is composed of sub-carriers corresponding to sub-channels having interference levels below the threshold interference level.

36. The scheduling subsystem of claim 35, further comprising a signaling block configured to generate a signaling message for the selected mobile terminal, the signaling message comprising a first parameter identifying a resource block in a first one of the at least one allocated sub-carrier groups and a second parameter indicating the number of resource blocks in the first one of the at least one allocated sub-carrier groups.

37. The scheduling subsystem of claim 30, wherein the allocation processor is configured to calculate estimated data throughput by selecting one or more modulation formats and coding schemes for the identified sub-carrier group and calculating the estimated data throughput as a function of the selected modulation formats and coding schemes.

38. The scheduling subsystem of claim 30, wherein the allocation processor is configured to allocate an identified sub-carrier group having the highest estimated data throughput to the selected mobile terminal.

39. The scheduling subsystem of claim 30, wherein the allocation processor is configured to allocate two or more of the identified sub-carrier groups having an aggregate estimated data throughput equal to or exceeding a data throughput target for the selected mobile terminal.

40. The scheduling subsystem of claim 39, wherein the allocation processor is further configured to determine the data throughput target based on a buffered-data quantity corresponding to the selected mobile terminal.