SYSTEMS AND METHODS FOR INTERFERENCE MITIGATION IN HETEROGENEOUS NETWORKS

• US 20130310058A1
• Filed: 09/27/2012
• Published: 11/21/2013
• Est. Priority Date: 05/17/2012
• Status: Active Grant

• Current Assignee: Tahoe Research Limited (f/k/a Learndale Limited) (Vector Capital Corporation)
• Original Assignee: Intel Corporation
• Inventors: Ibrahim, Ahmed S., Makled, Esraa A., Elgebaly, Hani H., Darwish, Ahmed M.
• Granted Patent: US 8,805,394 B2
• Time in Patent Office: Days
• US Class Current: 455/452.1
• CPC Class Codes: H04B 17/27 for locating or positioning the transmitter
• CPC Class Codes: H04B 7/024 Co-operative use of antennas of several sites, e.g. in co-ordinated multipoint or co-operative multiple-input multiple-output [MIMO] systems
• CPC Class Codes: H04L 5/0073 Allocation arrangements that take into account other cell interferences for intercell interference mitigation or co-ordination in orthogonal multiplex systems H04J11/005
• CPC Class Codes: H04W 52/143 Downlink power control
• 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 52/265 taking into account the quality of service QoS
• CPC Class Codes: H04W 72/00 Local resource management
• CPC Class Codes: H04W 72/541 using the level of interference
• CPC Class Codes: H04W 84/045 using private Base Stations, e.g. femto Base Stations, home Node B
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

Disclosed systems and methods mitigate interference in heterogeneous networks. Embodiments include adaptive or selective inter-cell interference coordination, adaptive multi-user zero forcing, adaptive power, and/or combinations of the foregoing. Techniques may be used to favor one group of users (e.g., femto users or macro users) over another. Certain embodiments focus quality of service (QoS) improvements on a first group of users, while using constraint processes to provide a threshold QoS for a second group of users.

Claims

1. A method for interference mitigation in a heterogeneous network including one or more femto cells within a macro cell coverage area, the method comprising:

transmitting, at a femto station, wireless communication signals using a plurality of femto station resources to communicate with at least one femto user equipment (UE) within a femto coverage area of the femto station;

detecting, at the femto station, a macro UE operating within the femto coverage area;

in response to detecting the macro UE, shutting off a first portion of the femto station resources and transmitting the wireless communication signals using a second portion of the femto station resources, wherein the first portion of the femto station resources are a source of interference to the macro UE.

2. The method of claim 1, wherein detecting the macro UE operating within the coverage area of the femto station comprises:

receiving, at the femto station, a message from the macro UE indicating that power of a first signal received by the macro UE from a macro station is lower than power of a second signal received from the femto station.

3. The method of claim 1, wherein detecting the macro UE operating within the coverage area of the femto station comprises:

measuring a first power of a first signal received at the femto station from the macro UE;

receiving, at the femto station, a message from a macro station indicating a second power of a second signal received at the macro station from the macro UE; and

determining that the first signal is greater than the second signal, the determination indicating that the macro UE is detected within the coverage area of the femto station.

4. The method of claim 1, wherein detecting the macro UE operating within the coverage area of the femto station comprises:

receiving a location message, at the femto station, indicating a geographic location of the macro UE; and

determining that the geographic location of the macro UE is within the coverage area of the femto station.

5. The method of claim 4, wherein the location message is received from the macro UE.

6. The method of claim 4, wherein the location message is received from a macro station.

7. The method of claim 1, further comprising:

selectively adjusting a percentage of the plurality of femto station resources included in the first portion that are shut off as a function of desired capacity available to the at least one femto UE versus a desired improvement in a quality of service provided to the macro UE.

8. The method of claim 7, wherein increasing the percentage of the plurality of femto station resources included in the first portion decreases the capacity available to the at least one femto UE.

9. The method of claim 1, wherein one or more of the plurality of femto station resources included in the first portion comprise at least one of a time resource block and a frequency resource block.

10. The method of claim 1, further comprising:

determining that the macro UE is no longer operating within the femto coverage area; and

in response to the determination, turning on the first portion of the femto station resources to transmit the wireless communication signals using both the first portion and the second portion of the femto station resources.

11. The method of claim 1, wherein the at least one femto UE is associated with a closed subscription group (CSG) that grants access to communicate through the femto station, and wherein the macro UE is not associated with the CSG and is not granted access to communicate through the femto station.

12. The method of claim 1, further comprising:

setting a first transmission power of the femto station;

at the first transmission power, measuring a quality of service (QoS) for the at least one femto UE within the femto coverage area;

comparing the measured QoS for the at least one femto UE with a first target QoS; and

incrementally increasing the power of the femto station from the first transmission power to a second transmission power at which the first target QoS is met for each of the at least one femto UE within the femto coverage area.

13. The method of claim 12, further comprising, before each incremental increase in the power of the femto station:

measuring a QoS for the macro UE detected within the femto coverage area;

comparing the measured QoS for the macro UE with a second target QoS; and

in response to determining that the second target QoS is satisfied for the macro UE, allowing the incremental increase in the power of the femto station.

14. The method of claim 1, further comprising:

setting a first transmission power of the femto station;

at the first transmission power, measuring a quality of service (QoS) for the macro UE detected within the femto coverage area;

comparing the measured QoS with a first target QoS; and

decrementing the power of the femto station from the first transmission power to a second transmission power at which the first target QoS is met for the macro UE within the femto coverage area.

15. The method of claim 14, further comprising, before each decrement in the power of the femto station:

measuring a QoS for the at least one femto UE within the femto coverage area;

comparing the measured QoS for the at least one femto UE with a second target QoS; and

in response to determining that the second target QoS is satisfied for the at least one femto UE within the femto coverage area, allowing the decrement in the power of the femto station.

16. A machine readable storage medium having stored thereon instructions, which when executed by a processor, cause the processor to perform a method for interference mitigation in a heterogeneous mobile communications network including a first transceiver within a coverage area of a second transceiver, the method comprising:

shutting off a percentage of resources used by the first transceiver to communicate with one or more first communication devices associated with a subscription group, wherein shutting off the percentage of resources reduces interference with one or more second communications devices that are not associated with the subscription group; and

varying the percentage of resources that are shut off based on a desired throughput capacity available to the one or more first communication devices to communicate through the first transceiver versus a desired improvement in communication between the one or more second communication devices and the second transceiver.

17. The machine readable storage medium of claim 16, the method further comprising allowing only cell edge users of the second communication devices to schedule resources of the second transceiver corresponding to the shut off resources of the first transceiver.

18. The machine readable storage medium of claim 16, wherein increasing the percentage of resources that are shut off decreases the capacity available to the one or more first communication devices to communicate through the first transceiver.

19. The machine readable storage medium of claim 16, wherein the shut off percentage of resources comprises at least one of a time resource block and a frequency resource block.

20. The machine readable storage medium of claim 16, the method further comprising:

setting a first transmission power of the first transceiver;

at the first transmission power, measuring a quality parameter for the one or more first communication devices;

comparing the measured quality parameter with a threshold quality value; and

incrementally increasing the power of the first transceiver from the first transmission power to a second transmission power at which the threshold quality parameter value is exceeded for each of the one or more first communication devices.

21. The machine readable storage medium of claim 16, the method further comprising:

setting a first transmission power of the first transceiver;

determining that a first quality parameter for the one or more first communication devices does not meet a first threshold quality value at the first transmission power and that a second quality parameter for the one or more second communication devices meets a second threshold quality value at the first transmission power; and

in response to the determination, increasing the power of the first transceiver from the first transmission power to a second transmission power so as to increase the first quality parameter of the one or more first communication devices without reducing the second quality parameter of the one or more second communication devices below the second threshold quality value.

22. The machine readable storage medium of claim 16, the method further comprising:

setting a first transmission power of the first transceiver;

at the first transmission power, measuring a quality parameter for the one or more second communication devices;

comparing the measured quality parameter with a threshold quality value; and

decrementing the power of the first transceiver from the first transmission power to a second transmission power at which the threshold quality parameter value is exceeded for each of the one or more second communication devices.

23. The machine readable storage medium of claim 16, the method further comprising:

setting a first transmission power of the first transceiver;

determining that a first quality parameter for the one or more second communication devices does not meet a first threshold quality value at the first transmission power and that a second quality parameter for the one or more first communication devices meets a second threshold quality value at the first transmission power; and

in response to the determination, decreasing the power of the first transceiver from the first transmission power to a second transmission power so as to increase the first quality parameter of the one or more second communication devices without reducing the second quality parameter of the one or more first communication devices below the second threshold quality value.

24. A machine readable storage medium having stored thereon instructions, which when executed by a processor, cause the processor to perform a method method for interference mitigation in a heterogeneous network including one or more femto cells within a macro cell coverage area, the method comprising:

detecting, at a femto station, a macro user equipment (UE) operating within a femto coverage area of the femto station; and

in response to detecting the macro UE;

estimating a transmission channel toward the detected macro UE;

calculating an orthogonal transmission channel to the estimated transmission channel; and

beamforming, using multiple antennas of the femto station, a transmission of a signal from the femto station according to the orthogonal transmission channel to reduce or minimize the transmission toward the detected macro UE.

25. The machine readable storage medium of claim 24, wherein the beamforming comprises multiplying the signal by a null space matrix according to the orthogonal transmission channel.

26. The machine readable storage medium of claim 24, wherein estimating the transmission channel toward the detected macro UE comprises determining a direction of an uplink channel received from the detected macro UE.

27. The machine readable storage medium of claim 24, wherein detecting the macro UE operating within the coverage area of the femto station comprises:

receiving, at the femto station, a message from the macro UE indicating that power of a first signal received by the macro UE from a macro station is lower than power of a second signal received from the femto station.

28. The machine readable storage medium of claim 24, wherein detecting the macro UE operating within the coverage area of the femto station comprises:

measuring a first power of a first signal received at the femto station from the macro UE;

receiving, at the femto station, a message from a macro station indicating a second power of a second signal received at the macro station from the macro UE; and

determining that the first signal is greater than the second signal, the determination indicating that the macro UE is detected within the coverage area of the femto station.

29. The machine readable storage medium of claim 24, wherein detecting the macro UE operating within the coverage area of the femto station comprises:

receiving a location message, at the femto station, indicating a geographic location of the macro UE; and

determining that the geographic location of the macro UE is within the coverage area of the femto station.

30. The machine readable storage medium of claim 29, wherein the location message is received from the macro UE.

31. The machine readable storage medium of claim 29, wherein the location message is received from a macro station.

32. The machine readable storage medium of claim 24, the method further comprising:

determining that the macro UE is no longer operating within the femto coverage area; and

in response to the determination, transmitting the signal from the femto station in the direction of the estimated transmission channel previously avoided by the beamforming.

33. The machine readable storage medium of claim 24, the method further comprising:

setting a first transmission power of the femto station for communicating with at least one femto UE within the coverage area of the femto station;

at the first transmission power, measuring a quality of service (QoS) for the at least one femto UE within the femto coverage area;

comparing the measured QoS with a target QoS; and

incrementally increasing the power of the femto station from the first transmission power to a second transmission power at which the target QoS is met for each of the at least one femto UE within the femto coverage area.

34. The machine readable storage medium of claim 33, the method further comprising constraining an overall increase in the power of the femto station so as to maintain a desired QoS for the detected macro UE.

35. The machine readable storage medium of claim 24, the method further comprising:

setting a first transmission power of the femto station for communicating with at least one femto UE within the coverage area of the femto station;

at the first transmission power, measuring a quality of service (QoS) for the macro UE detected within the femto coverage area;

comparing the measured QoS with a target QoS; and

decrementing the power of the femto station from the first transmission power to a second transmission power at which the target QoS is met for macro UE within the femto coverage area.

36. The machine readable storage medium of claim 35, the method further comprising constraining an overall decrease in the power of the femto station so as to maintain a desired QoS for the at least one femto UE within the coverage area of the femto station.

37. A mobile communication system comprising:

a first communication node to transmit first signals to a first group of mobile communication devices in a first coverage area; and

a plurality of second communication nodes within the first coverage area, each of the plurality of second communication nodes to transmit second signals to a second group of mobile communication devices in respective second coverage areas, each of the second coverage areas being smaller than, and at least partially within, the first coverage area;

wherein each of the plurality of second communication nodes is configured to;

determine that a measured quality of service (QoS) parameter of one of the first group and the second group is below a predetermined threshold; and

in response to the determination, adjust its transmission power to satisfy a QoS constraint of the other group.

38. The system of claim 37, wherein the predetermined threshold corresponds to a QoS of the second group, wherein the QoS constraint corresponds to the first group, and wherein each of the plurality of second communication nodes is further configured to:

set the transmission power to a minimum operation power;

detect the presence of a mobile communication device of the first group that is within its corresponding second coverage area;

determine that a QoS parameter of the detected mobile communication device of the first group is greater than the QoS constraint for the first group; and

based on the determination, increment the transmission power until the QoS constraint is satisfied.

39. The system of claim 38, wherein each of the plurality of second communication nodes is configured to detect the presence of the mobile communication device of the first group by receiving power from the mobile communication device of the first group.

40. The system of claim 38, wherein each of the plurality of second communication nodes is further configured to:

before determining that the QoS parameter of the detected mobile communication device of the first group is greater than the QoS constraint for the first group, determine that the transmission power has not reached a predetermined maximum power.

41. The system of claim 37, wherein the predetermined threshold corresponds to a QoS of the first group, wherein the QoS constraint corresponds to the second group, and wherein each of the plurality of second communication nodes is further configured to:

set the transmission power to a predetermined operation power;

detect a QoS parameter of each mobile communication device in the second group that is within its corresponding second coverage area;

determine that the detected QoS parameters for each mobile communication device in the second group are greater than the QoS constraint for the second group; and

based on the determination, decrement the transmission power until the QoS constraint is satisfied.

42. The system of claim 41, wherein each of the plurality of second communication nodes is further configured to:

before determining that the detected QoS parameters for each mobile communication device in the second group are less than the QoS constraint for the second group, determine that the transmission power has not reached a predetermined minimum power.

43. The system of claim 37, wherein each of the plurality of second communication nodes is further configured to:

shut off a percentage of its time or frequency resources used to communicate with the second group of mobile communication devices,

wherein the percentage varies according to a target throughput capacity for the second group versus a target interference reduction for the first group, and

wherein any of the first group of mobile communication devices are allowed to communicate with the first communication node using the time or frequency resources shut off by the plurality of second communication nodes.

44. The system of claim 37, wherein each of the plurality of second communication nodes is further configured to:

shut off a percentage of its time or frequency resources used to communicate with the second group of mobile communication devices,

wherein the percentage varies according to a target throughput capacity for the second group versus a target interference reduction for the first group, and

wherein only cell edge users of the first group of mobile communication devices are allowed to communicate with the first communication node using the time or frequency resources shut off by the plurality of second communication nodes.

45. The system of claim 37, wherein each of the plurality of second communication nodes is further configured to:

detect a mobile communication device of the first group of mobile communication devices within the second coverage area of the corresponding second coverage area; and

in response to detecting the mobile communication device of the first group, shut off a percentage of its time or frequency resources used to communicate with the second group of mobile communication devices,

wherein the percentage varies according to a target throughput capacity for the second group versus a target interference reduction for the first group.

46. The system of claim 45, wherein each of the plurality of second communication nodes is further configured to detect the mobile communication device of the first group by detecting a highest received power as being that received from the detected mobile communication device of the first group.

47. The system of claim 45, wherein each of the plurality of second communication nodes is further configured to detect the mobile communication device of the first group by receiving location information indicating that the mobile communication device of the first group is currently located in a same building as the particular second communication node.

48. The system of claim 37, wherein each of the plurality of second communication nodes is further configured to:

detect a mobile communication device of the first group of mobile communication devices within the second coverage area of the corresponding second coverage area;

in response to detecting the mobile communication device of the first group;

estimate a transmission channel toward the detected mobile communication device of the first group;

calculate an orthogonal transmission channel to the estimated transmission channel; and

multiply its transmitted signal by a null space matrix based on the orthogonal transmission channel to reduce or minimize the interference of the transmitted signal with the detected mobile communication device of the first group.

49. The system of claim 48, wherein each of the plurality of second communication nodes is further configured to:

detect the mobile communication device of the first group within the second coverage area by detecting an uplink signal transmitted by the mobile communication device of the first group.

50. An apparatus for wireless communications comprising:

a plurality of time or frequency resources for wireless communication with a first user equipment (UE); and

a processor configured to;

shut off a percentage of time or frequency resources to avoid interfering with communication between a second UE and a base station; and

selectively adjust a transmission power to improve a quality of service (QoS) parameter for at least one of the first UE and the second UE.

51. The apparatus of claim 50, wherein the processor is configured to adaptively shut off the percentage of time or frequency resources in response to detecting the second UE within a predetermined transmission coverage area.

52. The apparatus of claim 50, wherein the processor is configured to selectively vary the percentage of shut off time or frequency resources based on a desired throughput capacity available to the first UE versus a desired improvement in communication between the second UE and the base station.

53. The apparatus of claim 50, wherein the processor is further configured to incrementally increase the transmission power to improve the QoS parameter of the first UE, and wherein an amount of total increase is constrained by a threshold QoS for the second UE.

54. The apparatus of claim 50, wherein the processor is further configured to decrease the transmission power to improve the QoS parameter of the second UE, and wherein a total amount of decrease is constrained by a threshold QoS for the first UE.

55. A machine readable storage medium having stored thereon instructions, which when executed by a processor, cause the processor to perform a method comprising:

transmitting, from a transceiver, wireless communication signals using a plurality of resources to communicate with a first user equipment (UE) within a coverage area of the transceiver;

detecting, at the transceiver, a second UE operating within the coverage area;

in response to detecting the second UE, shutting off a portion of the resources to reduce interference to the second UE.

56. The machine readable storage medium of claim 55, the method further comprising:

setting a first transmission power of the transceiver;

at the first transmission power, measuring a quality of service (QoS) for the first UE within the coverage area;

comparing the measured QoS for the first UE with a first target QoS; and

incrementally increasing the power of the transceiver from the first transmission power to a second transmission power at which the first target QoS is met for the first UE within the coverage area.

57. The machine readable storage medium of claim 56, the method further comprising, before each incremental increase in the power of the transceiver:

measuring a QoS for the second UE detected within the coverage area;

comparing the measured QoS for the second UE with a second target QoS; and

in response to determining that the second target QoS is satisfied for the second UE, allowing the incremental increase in the power of the transceiver.

58. The machine readable storage medium of claim 55, the method further comprising:

setting a first transmission power of the transceiver;

at the first transmission power, measuring a quality of service (QoS) for the second UE detected within the coverage area;

comparing the measured QoS with a first target QoS; and

decrementing the power of the transceiver from the first transmission power to a second transmission power at which the first target QoS is met for the second UE.

59. The machine readable storage medium of claim 58, the method further comprising, before each decrement in the power of the transceiver:

measuring a QoS for the first UE within the coverage area;

comparing the measured QoS for the first UE with a second target QoS; and

in response to determining that the second target QoS is satisfied for the first UE within the coverage area, allowing the decrement in the power of the transceiver.