Systems and methods for interference mitigation in heterogeneous networks

• US 9,294,254 B2
• Filed: 06/30/2014
• Issued: 03/22/2016
• 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., Elgebaly, Hani H., Makled, Esraa, Darwish, Ahmed M.
• Primary Examiner(s): Doan, Kiet
• Application Number:
  US14/319,709
• Publication Number:
  US 20140315567A1
• Time in Patent Office: 631 Days
• Field of Search: 455/456.1, 455/445, 455/446, 455/438, 455/440, 455/522, 455/450, 455/405, 455/436, 455/452.1, 455/435.1, 455/562.1, 370/331, 370/335
• US Class Current: 1/1
• 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 non-transitory 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 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 a macro transmission channel toward the macro UE, wherein a measured first signal power of a macro UE received at the femto station is greater than a second signal power of the macro UE received at a macro station, the second signal power indicated in a message received by the femto station; and

in response to detecting the macro UE;

estimating the macro transmission channel toward the detected macro UE;

calculating an orthogonal transmission channel to the estimated macro transmission channel, the orthogonal transmission channel calculated to reduce or minimize a femto transmission interfering with the macro transmission channel; and

selecting the orthogonal transmission channel for the femto transmission;

determining a beamformed signal for the femto transmission to reduce or minimize transmission toward the detected macro UE;

beamforming, using multiple antennas of the femto station, the femto transmission from the femto station according to the orthogonal transmission channel and beamformed signal to reduce or minimize the femto transmission interfering with the detected macro UE.

2. The non-transitory machine readable storage medium of claim 1, wherein the beamforming comprises multiplying the signal by a null space matrix according to the orthogonal transmission channel.

3. The non-transitory machine readable storage medium of claim 1, wherein estimating the transmission channel toward the detected macro UE comprises determining a direction of an uplink channel received from the detected macro UE.

4. The non-transitory machine readable storage medium 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.

5. The non-transitory machine readable storage medium of claim 1, wherein detecting the macro UE operating within the coverage area of the femto station comprises:

measuring the measured first signal 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 the measured second signal 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.

6. The non-transitory machine readable storage medium 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.

7. The non-transitory machine readable storage medium of claim 6, wherein the location message is received from the macro UE.

8. The non-transitory machine readable storage medium of claim 6, wherein the location message is received from a macro station.

9. The non-transitory machine readable storage medium of claim 1, 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 macro transmission channel previously avoided by the beamforming.

10. The non-transitory machine readable storage medium of claim 1, 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.

11. The non-transitory machine readable storage medium of claim 10, 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.

12. The non-transitory machine readable storage medium of claim 1, 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.

13. The non-transitory machine readable storage medium of claim 12, 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.