Method and apparatus for controlling transmissions of a communications systems

• US 6,493,331 B1
• Filed: 03/30/2000
• Issued: 12/10/2002
• Est. Priority Date: 03/30/2000
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Wallace, Mark, Walton, Jay R., Holtzman, Jack, Antonio, Franklin P.
• Primary Examiner(s): Olms, Douglas
• Assistant Examiner(s): Sam, Phirin
• Application Number:
  US09/539,157
• Time in Patent Office: 985 Days
• Field of Search: 370/329, 370/330, 370/332, 370/333, 370/334, 370/335, 370/341, 370/342, 370/343, 370/344, 370/436, 370/437, 370/441, 370/204, 370/208, 370/210, 370/215, 370/336, 370/345, 370/442, 370/458, 370/478, 370/479, 370/480, 370/498, 375/130, 375/297, 375/317, 375/345, 445/447, 445/450, 445/452, 445/522, 445/69
• US Class Current: 370/341
• CPC Class Codes: H04B 17/336 Signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR]
• CPC Class Codes: H04B 17/382 for resource allocation, admission control or handover
• CPC Class Codes: H04W 52/24 using SIR [Signal to Interference Ratio] or other wireless path parameters
• CPC Class Codes: H04W 52/241 taking into account channel quality metrics, e.g. SIR, SNR, CIR, Eb/lo
• CPC Class Codes: H04W 52/244 Interferences in heterogeneous networks, e.g. among macro and femto or pico cells or other sector / system interference [OSI]
• CPC Class Codes: H04W 52/267 taking into account the information rate
• CPC Class Codes: H04W 52/286 during data packet transmission, e.g. high speed packet access [HSPA]
• CPC Class Codes: H04W 52/343 taking into account loading or congestion level
• CPC Class Codes: H04W 52/346 distributing total power among users or channels
• CPC Class Codes: H04W 72/52 based on load
• CPC Class Codes: H04W 72/542 using measured or perceived quality
• CPC Class Codes: H04W 72/569 of the traffic information

Abstract

In some aspects, each cell in the communications system can be designed to operate in accordance with a set of back-off factors that identify the reductions in peak transmit power levels for the channels associated with the back-off factors. The back-off factors are defined to provide the required power to a large percentage of the users while reducing the amount of interference. In some other aspects, the cells operate using an adaptive reuse scheme that allows the cells to efficiently allocate and reallocate the system resources to reflect changes in the system. A reuse scheme is initially defined and resources are allocated to the cells. During operation, changes in the operating conditions of the system are detected and the reuse scheme is redefined as necessary based on the detected changes. For example, the loading conditions of the cells can be detected, and the resources can be reallocated and/or the reuse scheme can be redefined. In yet other aspects, techniques are provided to efficiency schedule data transmissions and to assign channels to users. Data transmissions can be scheduled based on user priorities, some fairness criteria, system requirements, and other factors. Users are assigned to available channels based on a number of channel assignment schemes. Channel metrics are also provided, which can be used to prioritize users and for channel assignments.

Claims

1. A method for controlling transmissions in a communications system, the method comprising:

determining one or more characteristics of the communications system, including loading probabilities for the communications system;

partitioning available system resources into a plurality of channels;

defining a plurality of back-off factors for the plurality of channels based at least in part on the determined one or more characteristics of the communications system, wherein each channel is associated with a respective back-off factor that identifies a reduction from peak transmit power level, and wherein each back-off factor ranges from zero to one; and

transmitting on the plurality of channels at power levels determined based at least in part on the plurality of back-off factors.

2. A method for controlling transmissions in a communications system, the method comprising:

determining one or more characteristics of the communications system;

partitioning available system resources into a plurality of channels;

defining a plurality of back-off factors for the plurality of channels based at least in part on the determined one or more characteristics of the communications system, wherein each channel is associated with a respective back-off factor that identifies a reduction from peak transmit power level, and wherein each back-off factor ranges from zero to one, wherein the plurality of back-off factors are defined based in part on required outage probabilities; and

transmitting on the plurality of channels at power levels determined based at least in part on the plurality of back-off factors.

3. A method for controlling transmissions in a communications system, the method comprising:

determining one or more characteristics of the communications system;

partitioning available system resources into a plurality of channels;

defining a plurality of back-off factors for the plurality of channels based at least in part on the determined one or more characteristics of the communications system, wherein each channel is associated with a respective back-off factor that identifies a reduction from peak transmit power level, and wherein each back-off factor ranges from zero to one, wherein the plurality of back-off factors are defined based in part on one or more set points selected for the plurality of channels, wherein each set point corresponds to a required C/I for a data transmission, wherein the one or more set points are determined based in part on required outage probabilities; and

transmitting on the plurality of channels at power levels determined based at least in part on the plurality of back-off factors.

4. A method for controlling transmissions in a communications system, the method comprising;

determining one or more characteristics of the communications system;

partitioning available system resources into a plurality of channels;

defining a plurality of back-off factors for the plurality of channels based at least in part on the determined one or more characteristics of the communications system, wherein each channel is associated with a respective back-off factor that identifies a reduction from peak transmit power level, and wherein each back-off factor ranges from zero to one;

transmitting on the plurality of channels at power levels determined based at least in part on the plurality of back-off factors;

estimating a required transmit power level for each of the plurality of channels, wherein the required transmit power level for a particular channel is estimated based on a C/I estimate of a data transmission on the particular channel; and

adjusting the plurality of back-off factors based on the estimated required transmit power levels for the plurality of channels.

5. The method of claim 4, wherein the required transmit power level for the particular channel is further estimated based on a data rate for the data transmission on the particular channel.

6. A method for controlling transmissions in a communications system, the method comprising:

determining one or more characteristics of the communications system;

partitioning available system resources into a plurality of channels;

defining a plurality of back-off factors for the plurality of channels based at least in part on the determined one or more characteristics of the communications system, wherein each channel is associated with a respective back-off factor that identifies a reduction from peak transmit power level, and wherein each back-off factor ranges from zero to one, wherein at least one channel is associated with a back-off factor of one, representative of full transmit power, and remaining channels are associated with back-off factors of less than one; and

transmitting on the plurality of channels at power levels determined based at least in part on the plurality of back-off factors.

7. A method for controlling transmissions in a communications system, the method comprising:

determining one or more characteristics of the communications system;

partitioning available system resources into a plurality of channels;

defining a plurality of back-off factors for the plurality of channels based at least in part on the determined one or more characteristics of the communications system, wherein each channel is associated with a respective back-off factor that identifies a reduction from peak transmit power level, and wherein each back-off factor ranges from zero to one, wherein the plurality of back-off factors are dynamically defined to reflect changes in the communications system; and

transmitting on the plurality of channels at power levels determined based at least in part on the plurality of back-off factors.

8. The method of claim 7, wherein the plurality of back-off factors are dynamically defined to reflect changes in performance requirements in the communications system.

9. A method for controlling transmissions in a communications system, the method comprising:

determining one or more characteristics of the communications system;

partitioning available system resources into a plurality of channels;

defining a plurality of back-off factors for the plurality of channels based at least in part on the determined one or more characteristics of the communications system, wherein each channel is associated with a respective back-off factor that identifies a reduction from peak transmit power level, and wherein each back-off factor ranges from zero to one, wherein the plurality of back-off factors are adaptively defined to approximately match changes in the communications system; and

transmitting on the plurality of channels at power levels determined based at least in part on the plurality of back-off factors.

10. The method of claim 9, wherein the plurality of back-off factors are adaptively defined to approximately match changes in characterization of receiver units in the communications system.

11. The method of claim 9, wherein the plurality of back-off factors are adaptively defined to approximately match changes in loading conditions in the communications system.

12. A method for controlling transmissions in a communications system, the method comprising:

determining one or more characteristics of the communications system;

partitioning available system resources into a plurality of channels;

defining a plurality of back-off factors for the plurality of channels based at least in part on the determined one or more characteristics of the communications system, wherein each channel is associated with a respective back-off factor that identifies a reduction from peak transmit power level, and wherein each back-off factor ranges from zero to one, wherein one or more back-off factors are adjusted based on measured performance, wherein the one or more back-off factors are adjusted based on estimated or measured C/I; and

transmitting on the plurality of channels at power levels determined based at least in part on the plurality of back-off factors.

13. A method for controlling transmissions in a communications system, the method comprising;

determining one or more characteristics of the communications system;

partitioning available system resources into a plurality of channels;

defining a plurality of back-off factors for the plurality of channels based at least in part on the determined one or more characteristics of the communications system, wherein each channel is associated with a respective back-off factor that identifies a reduction from peak transmit power level, and wherein each back-off factor ranges from zero to one, wherein one or more back-off factors are adjusted based on measured performance, wherein the one or more back-off factors are adjusted based on measured frame erasure rates (FERs); and

transmitting on the plurality of channels at power levels determined based at least in part on the plurality of back-off factors.

14. A method for controlling transmissions in a communications system, the method comprising:

determining one or more characteristics of the communications system;

partitioning available system resources into a plurality of channels;

defining a plurality of back-off factors for the plurality of channels based at least in part on the determined one or more characteristics of the communications system, wherein each channel is associated with a respective back-off factor that identifies a reduction from peak transmit power level, and wherein each back-ff factor ranges from zero to one, wherein one or more back-off factors are adjusted based on measured performance, wherein the one or more back-off factors are adjusted based on estimated outage probabilities; and

transmitting on the plurality of channels at power levels determined based at least in part on the plurality of back-off factors.

15. A method for controlling transmissions in a communications system, the method comprising:

determining one or more characteristics of the communications system;

partitioning available system resources into a plurality of channels;

defining a plurality of back-off factors for the plurality of channels based at least in part on the determined one or more characteristics of the communications system, wherein each channel is associated with a respective back-of factor that identifies a reduction from peak transmit power level, and wherein each back-off factor ranges from zero to one, wherein one or more back-off factors are set to zero for selected time durations to eliminate interference on one or more associated channels; and

transmitting on the plurality of channels at power levels determined based at least in part on the plurality of back-off factors.

16. A method for controlling transmissions in a communications system, the method comprising:

determining one or more characteristics of the communications system;

partitioning available system resources into a plurality of channels;

defining a plurality of back-off factors for the plurality of channels based at least in part on the determined one or more characteristics of the communications system, wherein each channel is associated with a respective back-off factor that identifies a reduction from peak transmit power level, and wherein each back-off factor ranges from zero to one, wherein the back-off factor of a particular channel is set to zero if performance of the particular channel is degraded below a particular threshold; and

transmitting on the plurality of channels at power levels determined based at least in part on the plurality of back-off factors.

17. The method of claim 16, wherein the back-off factor of the particular channel is set to zero if a frame erasure rate (FER) exceeds a particular FER threshold.

18. The method of claim 16, wherein the back-off factor of the particular channel is set to zero if an outage probability for the particular channel exceeds a particular value.

19. A method for controlling transmissions in a communications system, the method comprising:

defining a reuse pattern for the communications system, wherein the reuse pattern includes a plurality of cells;

determining one or more characteristics for each cell in the reuse pattern;

partitioning available system resources into a plurality of channels;

defining a plurality of back-off factors for the plurality of channels for each cell in the reuse pattern based at least in part on the determined one or more characteristics, wherein each channel of each cell is associated with a respective back-off factor that identifies a reduction from peak transmit power level, and wherein each back-off factor ranges from zero to one;

transmitting on the plurality of channels from the plurality of cells at power levels determined based at least in part on the associated back-off factors;

estimating effective link margins for the plurality of channels for each cell in the reuse pattern; and

redefining the back-off factors for each cell in the reuse pattern based on the estimated effective link margins.

20. The method of claim 19, wherein the estimating and redefining are performed iteratively until a set of conditions is satisfied.

21. The method of claim 19, wherein the estimating and redefining are performed iteratively until the effective link margins are within a particular threshold value.

22. A method for controlling transmissions in a communications system, the method comprising:

defining a reuse pattern for the communications system, wherein the reuse pattern includes a plurality of cells;

determining one or more characteristics for each cell in the reuse pattern, including carrier-to-noise-plus-interference (C/I) characterization of receiver units in the communications system or loading probabilities for the communications system, or both;

partitioning available system resources into a plurality of channels;

defining a plurality of back-off factors for the plurality of channels for each cell in the reuse pattern based at least in part on the determined one or more characteristics, wherein each channel of each cell is associated with a respective back-off factor that identifies a reduction from peak transmit power level, and wherein each back-off factor ranges from zero to one; and

transmitting on the plurality of channels from the plurality of cells at power levels determined based at least in part on the associated back-off factors.

23. A method for controlling transmissions in a communications system, the method comprising:

defining a reuse pattern for the communications system, wherein the reuse pattern includes a plurality of cells;

determining one or more characteristics for each cell in the reuse pattern;

partitioning available system resources into a plurality of channels;

defining a plurality of back-off factors for the plurality of channels for each cell in the reuse pattern based at least in part on the determined one or more characteristics, wherein each channel of each cell is associated with a respective back-off factor that identifies a reduction from peak transmit power level, and wherein each back-off factor ranges from zero to one, wherein the plurality of back-off factors for each cell are defined based in part on C/I characterization for receiver units in the cell, one or more set points selected for the plurality of channels, required outage probabilities, or a combination thereof; and

transmitting on the plurality of channels from the plurality of cells at power levels determined based at least in part on the associated back-off factors.

24. A method for controlling transmissions in a communications system, the method comprising:

defining a reuse pattern for the communications system, wherein the reuse pattern includes a plurality of cells;

determining one or more characteristics for each cell in the reuse pattern;

partitioning available system resources into a plurality of channels;

defining a plurality of back-off factors for the plurality of channels for each cell in the reuse pattern based at least in part on the determined one or more characteristics, wherein each channel of each cell is associated with a respective back-off factor that identifies a reduction from peak transmit power level, and wherein each back-off factor ranges from zero to one, wherein one or more back-off factors for a particular cell are adjusted based on measured or estimated performance corresponding to measured frame erasure rates (FERs), outage probabilities, or C/Is, or a combination thereof; and

transmitting on the plurality of channels from the plurality of cells at power levels determined based at least in part on the associated back-off factors.

25. A method for operating a plurality of transmitter units in a wireless communications system, the method comprising;

partitioning available system resources into a plurality of channels;

defining a reuse pattern for the communications system, wherein the reuse pattern includes a plurality of cells;

determining one or more characteristics for each cell in the reuse pattern;

allocating a set of channels to each cell in the reuse pattern based at least in part on the determined one or more characteristics for the cell, wherein each cell in the reuse pattern is allocated a respective set of channels that includes one or more channels available for transmission at full power level and one or more channels available for transmission at reduced power levels; and

repeating the determining and allocating to reflect changes in the communications system.

26. A method for operating a plurality of transmitter unit in a wireless communications system, the method comprising:

partitioning available system resources into a plurality of channels;

defining a reuse pattern for the communications system, wherein the reuse pattern includes a plurality of cells;

determining one or more characteristics for each cell in the reuse pattern;

allocating a set of channels to each cell in the reuse pattern based at least in part on the determined one or more characteristics for the cell, wherein one or more channels allocated to a particular cell are temporarily prohibited from transmitting to reduce interference; and

repeating the determining and allocating to reflect changes in the communications system.

27. A method for operating a plurality of transmitter units in a wireless communications system, the method comprising:

partitioning available system resources into a plurality of channels;

defining a reuse pattern for the communications system, wherein the reuse pattern includes a plurality of cells;

determining one or more characteristics for each cell in the reuse pattern;

allocating a set of channels to each cell in the reuse pattern based at least in part on the determined one or more characteristics for the cell, wherein a particular cell transmits on a non-allocated channel for a transmission demand not supportable by the capacity of the allocated set of channels; and

repeating the determining and allocating to reflect changes in the communications system.

28. The method of claim 27, wherein the non-allocated channel is selected based on an estimated performance of the selected channel.

29. The method of claim 28, wherein the non-allocated channel is selected based on an estimated probability of occupancy of the selected channel by neighbor cells.

30. The method of claim 28, wherein the non-allocated channel is selected based on an estimated carrier-to-interference-plus-noise (C/I) achievable on the selected channel.

31. The method of claim 28, wherein the non-allocated channel is selected based on an estimated outage probability for the selected channel.

32. The method of claim 27, wherein one or more channels are reserved for transmissions by a particular cell for a particular time duration.

33. The method of claim 32, wherein neighbor cells are prohibited from transmission on the one or more reserved channels for the particular time duration.

34. A method for providing data transmissions to a plurality of receiver units in a communications system, the method comprising:

defining a reuse scheme to be used for the data transmissions to the plurality of receiver units, wherein the defined reuse scheme identifies a particular reuse pattern, an initial allocation of available system resources, and a set of operating parameters, including;

characterizing one or more parameters of the communications system, and

defining a reuse plan based at least in part on the one or more characterized parameters, wherein the reuse plan identifies the particular reuse pattern and an initial cell reuse layout based on the particular reuse pattern;

transmitting to the plurality of receiver units in accordance with the defined reuse scheme;

evaluating performance of the communications system;

determining whether the evaluated system performance is within particular thresholds; and

if the evaluated system performance is not within the particular thresholds, redefining the reuse scheme.

35. The method of claim 34, wherein characterizing includes determining an interference characterization for the plurality of receiver units in the communications system.

36. The method of claim 34, wherein the one or more parameters are updated periodically to reflect changes in the communications system.

37. The method of claim 34, wherein the defining the reuse scheme further includes

partitioning the available system resources into a plurality of channels, and

allocating a set of channels to each cell in the cell reuse layout based at least in part on the one or more characterized parameters.

38. The method of claim 37, wherein the characterizing includes determining expected probabilities of occupancy for the set of channels allocated to each cell.

39. The method of claim 38, wherein the expected probabilities of occupancy are set to one for uncharacterized channels.

40. The method of claim 37, wherein the defining the reuse scheme further includes

defining a set of back-off factors to be associated with each allocated set of channels.

41. The method of claim 37, wherein the set of operating parameters includes a set of back-off factors for each allocated set of channels.

42. A method for providing data transmissions to a plurality of receiver units in a communications system, the method comprising:

defining a reuse scheme to be used for the data transmissions to the plurality of receiver units, wherein the defined reuse scheme identifies a particular reuse pattern, an initial allocation of available system resources, and a set of operating parameters;

transmitting to the plurality of receiver units in accordance with the defined reuse scheme;

evaluating performance of the communications system, including determining effective link margins, frame erasure rates (FERs), outage probabilities, or average throughputs, or a combination thereof, for a particular cell;

determining whether the evaluated system performance is within particular thresholds; and

if the evaluated system performance is not within the particular thresholds, redefining the reuse scheme.

43. A method for providing data transmissions to a plurality of receiver units in a communications system, the method comprising:

updating a first set of parameters to be used for scheduling the data transmissions;

prioritizing the data transmissions;

assigning the data transmissions to respective available channels based at least in part on priorities of the data transmissions;

updating a second set of parameters to be used for transmitting the data transmissions; and

transmitting on the assigned channels to the plurality of receiver units using the updated second set of parameters.

44. The method of claim 43, wherein the first set of parameters channel occupancy probabilities, loading probabilities, characterization of carrier-to-interference-plus-noise (C/I) of the receiver units, or back-off factors, or a combination thereof.

45. The method of claim 43, wherein the prioritizing includes computing channel metrics for the available channels for each receiver unit using the updated first set of parameters.

46. The method of claim 45, wherein the channel metrics relate to cumulative throughput.

47. The method of claim 46, wherein the cumulative throughput is determined based on realizable or actual data rates.

48. The method of claim 46, wherein the cumulative throughput is determined as a sliding average of realizable or actual data rates over a particular time interval.

49. The method of claim 45, wherein the channel metrics relate to outage probabilities.

50. The method of claim 45, wherein the channel metrics relate to expected achievable carrier-to-interference-plus-noise (C/I).

51. The method of claim 45, wherein the channel metrics is reflective of interference constraint matrices indicative of interference expected from interfering sources.

52. The method of claim 45, wherein the prioritizing further includes

assigning priorities to the data transmissions based in part on the computed channel metrics.

53. The method of claim 52, wherein the prioritizing further includes

upgrading priority of a particular data transmission based at least in part on delays experienced by the data transmission.

54. The method of claim 52, wherein the assigning the data transmissions to respective available channels is achieved base in part on the assigned priorities of the data transmissions and the computed channel metrics.

55. The method of claim 54, wherein successively lower priority data transmissions are assigned to the available channels, starting with the highest priority data transmission.

56. The method of claim 54, wherein successively smaller load data transmissions are assigned to the available channels, starting with the highest load data transmission.

57. The method of claim 43, further comprising:

measuring performance of one or more data transmissions; and

adjusting transmit power levels for the one or more data transmissions based on the measured performance.

58. The method of claim 54, wherein the transmit power levels for the one or more data transmissions are adjusted based on measure frame erasure rate (FER) of the one or more data transmissions.

59. The method of claim 43, further comprising:

estimating required transmit power for a particular data transmission; and

adjusting a data rate of the particular data transmission based at least in part on the estimated required transmit power.

60. The method of claim 43, wherein the assigning is achieved to approximately equalize data rates for the data transmissions.

61. The method of claim 60, wherein the equalized data rates are achieved by assigning two or more channels to data transmissions transmitted at lower data rates.

62. A method for providing data transmissions on a plurality of channels to a plurality of receiver units in a communications system, the method comprising:

computing channel metrics for the plurality of channels for each receiver unit;

prioritizing the data transmissions;

assigning data transmissions to the plurality of channels based on priorities of the data transmissions and the computed channel metrics, wherein the assigning includes;

selecting a data transmission having a highest priority,

assigning the selected data transmission to a channel having a least favorable channel metrics but meeting requirements, and

successively assigning remaining data transmissions, in order of decreasing priorities, to available channels;

transmitting on the assigned channels to the plurality of receiver units; and

upgrading one or more data transmissions to available channels having more favorable channel metrics, including;

selecting a data transmission having a highest priority;

selecting a channel, from a list of available channels, having a most favorable channel metrics; and

reassigning the selected data transmission to the selected channel if the channel metrics associated with the selected channel is more favorable than the channel metrics associated with the original assigned channel.

63. A method for providing data transmissions on a plurality of channels to a plurality of receiver units in a communications system, the method comprising:

defining a plurality of back-off factors for the plurality of channels, wherein the back-off factors identify reduction from peak transmit power level for the respective channels;

assigning the data transmissions to the plurality of channels;

determining required transmit power levels for the data transmissions;

adjusting the plurality of back-off factors in accordance with the determined required transmit power levels;

transmitting the data transmissions on the plurality of channels in accordance with the plurality of adjusted back-off factors; and

computing channel metrics for the data transmissions based at least in part on the plurality of back-off factors, and

wherein the assigning the data transmissions to the plurality of channels is performed based in part on the computed channel metrics.