METHODS AND SYSTEMS FOR SCHEDULING IN A VIRTUAL MIMO COMMUNICATION ENVIRONMENT

• US 20110211462A1
• Filed: 05/09/2011
• Published: 09/01/2011
• Est. Priority Date: 01/20/2006
• Status: Active Grant

• Current Assignee: Malikie Innovations Limited (Key Patent Innovations Limited)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Wu, Jianming, Tong, Wen, Zhu, Peiying, Jia, Ming
• Granted Patent: US 8,867,330 B2
• Time in Patent Office: Days
• US Class Current: 370/248
• CPC Class Codes: H04B 7/0452 Multi-user MIMO systems
• CPC Class Codes: H04B 7/0613 using simultaneous transmission H04B7/0686 takes precedence
• CPC Class Codes: H04J 11/003 at the transmitter transmission to multiple receive units in multiple input multiple output [MIMO] H04B7/0452; transmit antenna weighting H04B7/0615
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/0222 Estimation of channel variability, e.g. coherence bandwidth, coherence time, fading frequency
• CPC Class Codes: H04L 5/001 the frequencies being arranged in component carriers
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04L 5/0037 Inter-user or inter-terminal allocation
• CPC Class Codes: H04L 5/0051 of dedicated pilots, i.e. pilots destined for a single user or terminal
• CPC Class Codes: H04L 5/0075 Allocation using proportional fairness
• CPC Class Codes: H04W 72/0446 Resources in time domain, e.g. slots or frames
• CPC Class Codes: H04W 72/121 for groups of terminals or users
• CPC Class Codes: H04W 72/1268 of uplink data flows
• CPC Class Codes: H04W 72/54 based on quality criteria
• CPC Class Codes: H04W 72/541 using the level of interference
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

A system and method for scheduling cooperative uplink transmissions a virtual multiple input multiple output (MIMO) wireless communication environment are provided. More specifically, both random and channel aware orthogonal scheduling techniques for identifying a sub-set of N mobile terminals to provide cooperative uplink transmissions for each transmit time interval are provided.

Claims

1. A method of scheduling uplink transmissions, comprising:

scheduling a plurality of mobile terminals for virtual multiple input multiple output (MIMO) operation;

monitoring a measure of throughput for each mobile terminal of the plurality of mobile terminals;

determining that a measure of throughput for at least one mobile terminal fails to meet a minimum throughput criterion; and

scheduling the at least one mobile terminal for single input multiple output (SIMO) operation.

2. A method of scheduling uplink transmissions, comprising:

scheduling a plurality of mobile terminals for virtual multiple input multiple output (MIMO) operation;

monitoring at least one respective uplink transmission parameter for each mobile terminal of the plurality of mobile terminals;

determining that the at least one respective uplink transmission parameter for at least one mobile terminal fails to meet a transmission quality criterion; and

scheduling the at least one mobile terminal for single input multiple output (SIMO) operation.

3. A method as defined in claim 2, wherein the at least one respective uplink transmission parameter is a measure of long term signal to noise ratio (SNR).

4. A method of scheduling uplink transmissions for a plurality of mobile terminals, comprising:

scheduling mobile terminals of the plurality of mobile terminals having a velocity greater than a predetermined threshold velocity using random user scheduling;

monitoring at least one respective uplink transmission parameter for each mobile terminal of the plurality of mobile terminals having a velocity less that the predetermined threshold velocity;

scheduling mobile terminals of the plurality of mobile terminals having respective uplink transmission parameters that meet the transmission quality criterion for virtual multiple input multiple output (MIMO) operation; and

scheduling mobile terminals of the plurality of mobile terminals having respective uplink transmission parameters that fail to meet a transmission quality criterion for single input multiple output (SIMO) operation.

5. A method as defined in claim 4, comprising periodically repeating the steps of claim 4 for each of a plurality of successive time intervals.

6. A method as defined in claim 4, wherein each mobile terminal of the plurality of mobile terminals is initially scheduled using random user scheduling before performing the steps of claim 4.

7. A method as defined in claim 4, wherein each mobile terminal of the plurality of mobile terminals is initially scheduled for virtual MIMO operation before performing the steps of claim 4.

8. A method as defined in claim 4, wherein the step of monitoring the at least one respective uplink transmission parameter comprises determining a channel transfer function.

9. A method as defined in claim 4, wherein the respective uplink transmission parameters are deemed to fail to meet the transmission quality criterion when a predetermined proportion of sub-carriers in sub-channels assigned to the uplink transmissions for a mobile terminal experience interference exceeding a predetermined interference level.

10. A method as defined in claim 4, wherein the step of scheduling the mobile terminals for virtual MIMO operation comprises scheduling the mobile terminals using channel aware orthogonal scheduling (CAOS).

11. An apparatus for scheduling uplink transmissions, comprising:

at least one network interface; and

a control system associated with the at least one network interface and configured to;

schedule a plurality of mobile terminals for virtual multiple input multiple output (MIMO) operation;

monitor a measure of throughput for each mobile terminal of the plurality of mobile terminals;

determine that a measure of throughput for at least one mobile terminal fails to meet a minimum throughput criterion; and

schedule the at least one mobile terminal for single input multiple output (SIMO) operation.

12. An apparatus for scheduling uplink transmissions, comprising:

at least one network interface; and

a control system associated with the at least one network interface and configured to;

schedule a plurality of mobile terminals for virtual multiple input multiple output-(MIMO) operation;

monitor at least one respective uplink transmission parameter for each mobile terminal of the plurality of mobile terminals;

determine that the at least one respective uplink transmission parameter for at least one mobile terminal fails to meet a transmission quality criterion; and

schedule the at least one mobile terminal for single input multiple output (SIMO) operation.

13. An apparatus as defined in claim 12, wherein the at least one respective uplink transmission parameter is a measure of long term signal to noise ratio (SNR).

14. An apparatus for scheduling uplink transmissions, comprising:

at least one network interface; and

a control system associated with the at least one network interface and configured to;

(i) schedule mobile terminals having a velocity greater than a predetermined threshold velocity using random user scheduling;

(ii) monitor at least one respective uplink transmission parameter for each mobile terminal having a velocity less that the predetermined threshold velocity;

(iii) schedule mobile terminals having respective uplink transmission parameters that meet the transmission quality criterion for virtual multiple input multiple output (MIMO) operation; and

(iv) schedule mobile terminals having respective uplink transmission parameters that fail to meet a transmission quality criterion for single input multiple output (SIMO) operation.

15. An apparatus as defined in claim 14, wherein the control system is further adapted to periodically repeat steps (i) through (iv) for each of a plurality of successive time intervals.

16. An apparatus as defined in claim 14, wherein the control system is further configured to initially schedule all of the mobile terminals using random user scheduling before performing steps (i) through (iv) of claim 14.

17. An apparatus as defined in claim 14, wherein the control system is further configured to initially schedule all of the mobile terminals for virtual MIMO operation before performing steps (i) through (iv) of claim 14.

18. An apparatus as defined in claim 14, wherein the control system is further configured to determine a channel transfer function in order to monitor the at least one respective uplink transmission parameter.

19. An apparatus as defined in claim 14, wherein the respective uplink transmission parameters are deemed to fail to meet the transmission quality criterion when a predetermined proportion of sub-carriers in sub-channels assigned to the uplink transmissions for a mobile terminal experience interference exceeding a predetermined interference level.

20. An apparatus as defined in claim 14, wherein the control system is further configured to schedule mobile terminals for virtual MIMO operation using channel aware orthogonal scheduling (CAOS).

21. An apparatus for scheduling cooperative uplink transmissions comprising:

at least one network interface; and

a control system associated with the at least one network interface and configured to;

determine channel transfer functions for a plurality of sub-carriers for each of a plurality of mobile terminals served by a base station;

identify a select group of mobile terminals from the plurality of mobile terminals based on orthogonality of the channel transfer functions; and

assign at least one sub-channel comprising ones of the plurality of sub-carriers to the select group of mobile terminals to be simultaneously used by each mobile terminal in the select group of mobile terminals.

22. An apparatus as defined in claim 21 wherein the control system is further adapted to determine the orthogonality of the channel transfer functions for ones of the plurality of mobile terminals in each of a plurality of potential groups including the select group.

23. An apparatus as defined in claim 22 wherein the control system is further adapted to determine an average orthogonality value ( D) for each of the plurality of potential groups based on the equation:

24. An apparatus as defined in claim 22 wherein the control system is further adapted to:

select a first mobile terminal from the plurality of mobile terminals based on round-robin scheduling; and

select one of the plurality of potential groups including the first mobile terminal as the select group based on the orthogonality of the channel transfer functions for the ones of the plurality of mobile terminals in each of the plurality of potential groups.

25. An apparatus as defined in claim 22 wherein the control system is further adapted to select one of the plurality of potential groups based on proportional fairness scheduling.

26. An apparatus as defined in claim 25 wherein the control system is further adapted to:

determine proportional fairness values for the plurality of potential groups, each of the proportional fairness values being a sum of ratios of transmission rates and average throughputs for mobile terminals in an associated one of the plurality of potential groups; and

select one of the plurality of potential groups as the group of mobile terminals based on the proportional fairness values for the plurality of potential groups.

27. An apparatus as defined in claim 22 wherein the control system is further adapted to:

for each one of the plurality of mobile terminals, identify at least one group including the one of the plurality of mobile terminals from the plurality of potential groups based on the orthogonality of the channel transfer functions for the ones of the plurality of mobile terminals in each of the plurality of potential groups including the one of the plurality of mobile terminals; and

select the select group from the at least one group for each of the plurality of mobile terminals based on proportional fairness scheduling.

28. An apparatus as defined in claim 27 wherein the control system is further adapted to:

determine proportional fairness values for the at least one group for each of the plurality of mobile terminals, each of the proportional fairness values being a sum of ratios of transmission rates and average throughputs for mobile terminals in an associated one of the at least one group for each of the plurality of mobile terminals; and

select one of the at least one group for each of the plurality of mobile terminals as the select group based on the proportional fairness values for the at least one group for each of the plurality of mobile terminals.

29. An apparatus as defined in claim 21 wherein the control system is further adapted to assign the at least one sub-channel via downlink transmission.

30. An apparatus as defined in claim 21 wherein the control system is further adapted to assign the at least one sub-channel to the select group of mobile terminals to be simultaneously used by each mobile terminal in the select group of mobile terminals during a common uplink transmit time interval.

31. An apparatus as defined in claim 30 wherein the control system is further adapted to repeat the steps of determining, identifying, and assigning for a plurality of uplink transmit time intervals.

32. An apparatus as defined in claim 21 wherein the control system is further adapted to instruct one of the plurality of mobile terminals to artificially rotate a phase of sub-carrier waveforms transmitted by the one of the plurality of mobile terminals in order to improve the orthogonality of the channel transfer functions for the one of the plurality of mobile terminals with at least one other of the plurality of mobile terminals.

33. An apparatus as defined in claim 21 wherein the cooperative uplink transmissions are Orthogonal Frequency Division Multiplexing (OFDM) transmissions.

34. An apparatus as defined in claim 21 wherein the cooperative uplink transmissions are Single-Carrier Frequency Division Multiple Access (SC-FDMA) transmissions.

35. An apparatus for scheduling cooperative uplink transmissions comprising:

at least one network interface; and

a control system associated with the at least one network interface and configured to;

group a plurality of mobile terminals into either a first group or a second group; and

schedule ones of the plurality of mobile terminals in the first group for virtual multiple input multiple output (MIMO) operation and ones of the plurality of mobile terminals in the second group for 1×

N diversity operation, wherein N is greater than 1.

36. An apparatus as defined in claim 35 wherein the control system is further configured to:

a) select a first mobile terminal from the plurality of mobile terminals based on round-robin scheduling;

b) if the first mobile terminal is in the first group,

i) select at least one additional mobile terminal from the plurality of mobile terminals, the first mobile terminal and the at least one additional mobile terminal forming a group of mobile terminals to provide a cooperative uplink transmission; and

ii) assign at least one sub-channel comprising a plurality of sub-carriers to the group of mobile terminals to be simultaneously used by each mobile terminal in the group of mobile terminals; and

c) if the first mobile terminal is in the second group, assign et least one sub-channel comprising a plurality of sub-carriers to the first mobile terminal to be used by the first mobile terminal for 1×

N diversity operation.

37. An apparatus as defined in claim 36 wherein the control system is further configured to randomly select the at least one additional mobile terminal from the plurality of mobile terminals.

38. An apparatus as defined in claim 36 wherein the control system is further configured to:

determine channel transfer functions for a plurality of sub-carriers for each of the plurality of mobile terminals; and

identify the at least one additional mobile terminal based on orthogonality of the channel transfer functions for the first mobile terminal and the channel transfer functions for the at least one additional mobile terminal.

39. An apparatus for scheduling cooperative uplink transmissions comprising:

at least one network interface; and

a control system associated with the at least one network interface and configured to;

a) identify a group of mobile terminals to provide a cooperative uplink transmission by randomly selecting at least one of the group of mobile terminals; and

b) assign at least one sub-channel, comprising a plurality of sub-carriers to the group of mobile terminals to be simultaneously used by each mobile terminal in the group of mobile terminals.

40. An apparatus as defined in claim 39 wherein the control system is further configured to:

select a first mobile terminal based on round-robin scheduling; and

randomly select at least one additional mobile terminal, such that the first mobile terminal and the at least one additional mobile terminal form the group of mobile terminals.

41. An apparatus as defined in claim 39 wherein the control system is further configured to:

randomly group a plurality of mobile terminals into a plurality of potential groups; and

select one of the plurality of potential groups as the group of mobile terminals based on proportional fairness scheduling.

42. An apparatus as defined in claim 39 wherein the control system is further configured to:

determine proportional fairness values for the potential groups, each of the proportional fairness values being a sum of ratios of transmission rates and average throughputs for mobile terminals in an associated one of the potential groups; and

select one of the plurality of potential groups as the group of mobile terminals based on the proportional fairness values for the potential groups.