Uplink scheduling for wireless networks

• US 7,158,804 B2
• Filed: 11/27/2002
• Issued: 01/02/2007
• Est. Priority Date: 11/27/2002
• Status: Active Grant

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Qian, Lijun, Kumaran, Krishnan
• Primary Examiner(s): Anderson, Matthew D.
• Assistant Examiner(s): TRINH, TAN H
• Application Number:
  US10/305,614
• Publication Number:
  US 20040102202A1
• Time in Patent Office: 1,497 Days
• Field of Search: 455/515, 455/500, 455/454, 455/450, 455/452.1, 455/453.3, 455/445, 455/561, 455/453, 455/452.2, 370/210, 370/468, 370/411
• US Class Current: 455/515
• CPC Class Codes: H04B 1/71072 Successive interference cancellation
• CPC Class Codes: H04W 28/14 using intermediate storage
• CPC Class Codes: H04W 52/288 taking into account the usage mode, e.g. hands-free, data transmission, telephone
• CPC Class Codes: H04W 72/54 based on quality criteria

Abstract

Mobiles are sorted by using a first metric and one or more of the sorted mobiles are selected. A second metric is determined using the selected sorted mobiles, and mobiles are selected to transmit during a time period based on the second metric. Multiple embodiments are disclosed using these steps and exact or approximate solutions as to which mobiles should transmit may be determined. By way of example, the first metric may be a weighted marginal rate and the second metric may be an objective function. An uplink proportional fair technique is presented in which, for example, either a single “strong” mobile or a group of “weak” mobiles may be selected to transmit during a single time period. In addition, techniques are presented for determining uplink scheduling when there is partial orthogonality in Walsh codes, modeled by an orthogonality factor, assigned to mobiles. Techniques are also presented for optimal uplink scheduling for uplink mobile transmissions in a single cell with successive interference cancellation.

Claims

1. A method for uplink scheduling in a wireless network, comprising the steps of:

sorting a plurality of mobiles requesting transmission for a given time period based at least in part on a first metric;

selecting one or more of the sorted mobiles;

determining a second metric based on one or more properties of the selected one or more sorted mobiles; and

selecting which mobile or mobiles are to transmit during the time period based on the second metric.

2. The method of claim 1, wherein:

the step of sorting the plurality of mobiles further comprises sorting the plurality of mobiles according to values of the first metric;

the step of selecting one or more of the sorted mobiles further comprises selecting a sorted mobile with a best value of the first metric, wherein the selected sorted mobile has not been previously selected;

the step of selecting which mobile or mobiles are to transmit during a time period based on the second metric further comprises the step of performing, until the second metric decreases, the step of selecting a sorted mobile with a best value of the first metric and the step of determining a second metric; and

the step of selecting which mobile or mobiles are to transmit further comprises the step of selecting the sorted mobiles that did not cause the second metric to decrease.

3. The method of claim 1, further comprising the step of sending, to the mobile or mobiles selected to transmit, a message indicating permission to transmit.

4. The method of claim 1, further comprising the step of determining a rate of transmission for each of the mobiles selected to transmit during the given time period.

5. The method of claim 1, wherein the first metric comprises a weighted marginal rate and wherein the second metric comprises an objective function.

6. The method of claim 5, wherein weights used in the weighted marginal rate comprise at least one of queue length and delay.

7. The method of claim 5, wherein the weighted marginal rate comprises peak received power for a mobile, wherein the peak received power is related to maximum transmit power for a mobile, and wherein the maximum transmit power for a mobile is received from a mobile or estimated.

8. The method of claim 5, wherein at least one mobile has a lower transmission rate limit, an upper transmission rate limit, or both the lower and the upper transmission rate limits, wherein the weighted marginal rate is proportional to a rate function, and wherein the rate function is limited by any transmission rate limit for the at least one mobile.

9. The method of claim 5, further comprising the steps of (1) performing the steps of sorting, selecting one or more of the sorted mobiles, determining, and selecting which mobile or mobiles are to transmit for each of a plurality of fixed values, wherein each of the fixed values corresponds to a weighted marginal rate and a value of an objective function, and (2) selecting a best value of an objective function corresponding to one of the plurality of fixed values.

10. The method of claim 9, wherein each of the fixed values is a cumulative normalized signal to noise ratio (NSNR) and wherein the step of selecting a best value for an objective function further comprises the step of selecting an objective function having a largest value of the plurality of objective functions corresponding to the plurality of fixed values.

11. The method of claim 5, wherein:

the weighted marginal rate is based on a weight for a mobile, a highest normalized signal to noise ratio (NSNR) of the mobile, and a transmission rate for the mobile occurring when the mobile transmits at the highest NSNR; and

the objective function is a sum for all mobiles of a product of a weight for a mobile and the transmission rate of the mobile.

12. The method of claim 5, further comprising the steps of:

determining a plurality of fixed values meeting a predetermined criterion, wherein each two of the plurality of fixed values defines an interval, and wherein there are a plurality of intervals;

for each interval, performing the steps of sorting a plurality of mobiles, selecting one or more of the sorted mobiles, determining a second metric, and selecting which mobile or mobiles are to transmit; and

selecting a best value for an objective function from the intervals.

13. The method of claim 12, wherein each fixed value comprises a cumulative normalized signal to noise ratio (NSNR) and wherein the predetermined criterion comprises the condition that the weighted marginal rate for a mobile matches the weighted marginal rate for a different mobile.

14. The method of claim 5, wherein:

the weighted marginal rate is based on a queue length of a mobile, a transmission rate of the mobile assuming no interference from other mobiles, and a peak received power for the mobile; and

the objective function is based on a sum of a product of a transmission rate for each mobile assuming interference from selected sorted mobiles and a queue length for each mobile.

15. The method of claim 5, wherein:

the step of sorting a plurality of mobiles comprises the step of sorting a plurality of mobiles in decreasing order of weighted marginal rate while assuming no interference between mobiles;

the step of selecting one or more sorted mobiles further comprises the step of selecting a mobile having a highest weighted marginal rate, wherein the selected mobile has not been previously selected;

the step of determining a second metric further comprises determining a value for the objective function, wherein the objective function incorporates interference from all selected sorted mobiles; and

the step of selecting which mobile or mobile are to transmit further comprises the steps of (1) performing the steps of selecting a mobile having a highest weighted marginal rate and determining a value for the objective function until the objective function begins to decrease and (2) selecting the sorted mobiles that did not cause the objective function to decrease.

16. The method of claim 15, wherein each weighted marginal rate is based on a queue length of a mobile, a transmission rate of a mobile assuming no interference between mobiles and a peak received power of a mobile, and wherein the objective function is based on the sum of a product of queue length for a mobile and a transmission rate of a mobile assuming interference from selected sorted mobiles.

17. The method of claim 15, wherein each weighted marginal rate is based on a transmission rate of a mobile assuming no interference from other mobiles and an average transmission rate of a mobile, and wherein the objective function is based on a sum of a transmission rate for each mobile assuming interference from sorted mobiles used to determine the objective function.

18. The method of claim 1, wherein the first metric is a weight and the second metric is an objective function, wherein an orthogonality factor is between zero and one-half, the orthogonality factor specifying a fraction of power transmitted to other mobiles that appears as direct interference to a particular mobile.

19. The method of claim 18, wherein:

the method further comprises the steps of determining an upper limit, inflection point and critical tangent, separating mobiles into two classes based on the upper limit, inflection point, and critical tangent, and performing, for a number of fixed values, the steps of selecting one or more of the sorted mobiles and determining a second metric; and

the step of selecting which mobile or mobiles are to transmit further comprises the steps of selecting a best value of an objective function for the plurality of fixed values and selecting which mobile or mobiles are to transmit based on the objective function corresponding to the best value and a set of sorted mobiles corresponding to the objective function corresponding to the best value.

20. The method of claim 1, wherein the second metric is an objective function, the step of sorting a plurality of mobiles further comprises separating mobiles into groups based on the first metric, wherein a first group comprises mobiles having values of the fist metric above a predetermined value and a second group comprises mobiles having values of the first metric below a predetermined value, wherein the step of determining a second metric comprises the steps of determining a value of the objective function for all mobiles in the second group and determining a value for the objective function for each of the mobiles in the first group, and wherein the step of selecting which mobile or mobiles are to transmit further comprises the steps of selecting a highest value of the values for the objective functions and determining the mobile or mobiles corresponding to the highest value.

21. The method of claim 20, wherein the first metric comprises at least one of average signal to interference ratio (SIR), data rate, and received power.

22. An apparatus for uplink scheduling in a wireless network, comprising:

a memory; and

at least one processor, coupled to the memory, and operative to;

sort a plurality of mobiles requesting transmission for a given time period based at least in part on a first metric;

select one or more of the sorted mobiles;

determine a second metric using the selected one or more sorted mobiles; and

select which mobile or mobiles are to transmit during the time period based on the second metric.

23. An article of manufacture for uplink scheduling in a wireless network, comprising a machine readable medium containing one or more programs which when executed implement the steps of:

sorting a plurality of mobiles requesting transmission for a given time period based at least in part on a first metric;

selecting one or more of the sorted mobiles;

determining a second metric using the selected one or more sorted mobiles; and

selecting which mobile or mobiles are to transmit during the time period based on the second metric.

24. A method for uplink scheduling in a wireless network using successive interference cancellation (SIC), the method comprising the steps of:

fixing a decoding order based on queue length for at least two mobiles of a plurality of mobiles; and

decoding the at least two mobiles based on the fixed decoding order.

25. The method of claim 24, wherein the decoding order is based on increasing order of queue length.

26. The method of claim 24, wherein each mobile transmits at maximum power.

27. The method of claim 24, further comprising the steps of determining a transmission rate for each mobile and informing each mobile of the determined transmission rate for the mobile.

28. The method of claim 24, wherein each mobile transmits at rates given by R=f(γ

_i), where R_i is a rate for a mobile, γ

_i is a signal to interference ratio (SIR) for a mobile and f(γ

₁) is a function of the SIR.

29. The method of claim 28, wherein f(γ

_i)=β

log(1+γ

_i) and wherein β

is a bandwidth.

30. The method of claim 24, wherein the at least two mobiles are all of the plurality of mobiles.

31. A method for uplink scheduling in a wireless network using successive interference cancellation (SIC), the method comprising the steps of:

classifying any mobiles having a property above a predetermined threshold as being first mobiles and any mobiles below the predetermined threshold as being second mobiles;

decoding information from the first mobiles with a first decoding method;

subtracting interference from the first mobiles; and

decoding information from the second mobiles with a second decoding method, wherein the step of subtracting interference is performed prior to the step of decoding information from the second mobiles, and wherein the first and second decoding methods are different.

32. The method of claim 31, wherein the property comprises at least one of a probability of being correctly decoded, a received power, and a received signal to interference ratio.

33. The method of claim 31, wherein the first method is selected from at least one of a method using power order to provide decoding order and a method using queue length to provide decoding order, and wherein the second method is multi-user detection.

34. The method of claim 31, wherein each mobile transmits at maximum power.

35. The method of claim 31, further comprising the steps of determining a transmission rate for each mobile and informing each mobile of the determined transmission rate for the mobile.