Methods Radio Network Nodes and User Equipment for Alleviating Interference in a Radio Communication Network

• US 20160014791A1
• Filed: 03/14/2013
• Published: 01/14/2016
• Est. Priority Date: 03/14/2013
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: KAZMI, Muhammad, LIU, Jinhua
• Granted Patent: US 10,165,579 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H04B 7/2656 for structure of frame, burst
• CPC Class Codes: H04W 24/08 Testing, supervising or monitoring using real traffic
• CPC Class Codes: H04W 52/243 taking into account interferences
• CPC Class Codes: H04W 52/365 Power headroom reporting
• CPC Class Codes: H04W 72/0446 Resources in time domain, e.g. slots or frames
• CPC Class Codes: H04W 72/21 in the uplink direction of a wireless link, i.e. towards the network
• CPC Class Codes: H04W 72/27 between access points
• CPC Class Codes: H04W 72/541 using the level of interference
• CPC Class Codes: H04W 72/542 using measured or perceived quality

Abstract

Methods and radio network nodes (BS1, BS2) for alleviating interference on downlink radio signals in a victim User Equipment, UE (T1, T2), caused by uplink transmission from an aggressor UE (T2, T1). The interference occurs during a flexible subframe in which the direction of signal transmission is variable between uplink and downlink in different radio frames. A first radio network node (BS1) detects (4:1) that a first UE (T1) that is served by the first radio network node (BS1) is one of the victim and aggressor UEs. The first radio network node (BS1) identifies (4:2) a second radio network node (BS2) employing a subframe scheme such that uplink transmission from the aggressor UE may overlap at least partly with downlink reception in the victim UE during the flexible subframe. The first radio network node (BS1) sends (4:3) a notification to the second radio network node, indicating that the first UE is served by the first radio network node. The second radio network node (BS2) is thereby triggered to execute (4:5) an interference mitigation action for alleviating the interference when serving a second UE (T2) being the other one of the victim and aggressor UEs.

Claims

1. A method, performed by a first radio network node in a radio communication network where subframes are transmitted in pre-determined positions within radio frames, wherein the first radio network node employs a subframe scheme where at least one of the pre-determined positions is allocated to a flexible subframe in which the direction of signal transmission is variable between uplink and downlink from one radio frame to another, for triggering mitigation of interference on downlink radio signals received by a victim User Equipment, UE, in a victim cell, said interference being caused by transmission of uplink radio signals from an aggressor UE in an aggressor cell during the flexible subframe, the method comprising:

detecting that a first UE, being one of the victim and aggressor UEs, is served by the first radio network node,

identifying a second radio network node which employs a subframe scheme such that an uplink transmission from the aggressor UE potentially overlaps at least partly with downlink reception at the victim UE during the flexible subframe, and

sending a notification to the identified second radio network node, the notification indicating the flexible subframe and the first UE being served by the first radio network node, to trigger the second radio network node to execute an interference mitigation action for alleviating said interference when a second UE, being the other one of the victim and aggressor UEs, is served by the second radio network node during the flexible subframe.

2. A method according to claim 1, wherein the subframe scheme employed by the second radio network node comprises a flexible subframe that overlaps at least partly in time with the flexible subframe of the first radio network node.

3. A method according to claim 1, wherein the notification is sent after determining that a level of said interference during the flexible subframe is higher than a threshold based on measurements of signals communicated to or from the first UE.

4. A method according to claim 1, wherein the first UE is detected when it is located in a cell border region of the first radio network node adjacent to a cell of the second radio network node.

5. A method according to claim 4, wherein the cell border region is determined based on measurements of path loss between UEs served by the first radio network node and the first radio network node.

7. A method according to claim 5, wherein the determination of the cell border region is further based on additional measurements regarding the UEs served by the first radio network node, the additional measurements comprising measurements of at least one of:

power headroom, transmit power, received signal strength, angle/direction of arrival, timing advanced, and one way propagation delay.

11. A method according to claim 1, wherein a set of neighbouring radio network nodes are identified which employ a direction of signal transmission during the flexible subframe that is opposite to the direction of signal transmission employed by the first radio network node during the flexible subframe, and further comprising sending the notification to one or more radio network nodes in the set of identified neighbouring radio network nodes.

12. A method according to claim 1, wherein when the first UE is the aggressor UE transmitting uplink radio signals with data during the flexible subframe, the first radio network node executes an interference mitigation action for alleviating said interference, the interference mitigation action comprising at least one of:

scheduling low data rate to the first UE in the uplink,

decreasing transmission power of the first UE,

using a more robust modulation scheme for the first UE,

using a more robust coding scheme for the first UE, and

using a more robust transport format for the first UE.

6. (canceled)

8-10. -10. (canceled)

13. A first radio network node in a radio communication network where subframes are transmitted in pre-determined positions within radio frames, the first radio network node being configured to employ a subframe scheme where at least one of the pre-determined positions is allocated to a flexible subframe in which the direction of signal transmission is variable between uplink and downlink from one radio frame to another, and to trigger mitigation of interference on downlink radio signals received by a victim User Equipment, UE, in a victim cell, said interference being caused by transmission of uplink radio signals from an aggressor UE in an aggressor cell during the flexible subframe, the first radio network node comprising:

a detecting unit configured to detect that a first UE, being one of the victim and aggressor UEs, is served by the first radio network node,

an identifying unit configured to identify a second radio network node which employs a subframe scheme such that an uplink transmission from the aggressor UE potentially overlaps at least partly with downlink reception at the victim UE during the flexible subframe, and

a sending unit configured to send a notification to the identified second radio network node, the notification indicating the flexible subframe and the first UE being served by the first radio network node, to trigger the second radio network node to execute an interference mitigation action for alleviating said interference when a second UE, being the other one of the victim and aggressor UEs, is served by the second radio network node during the flexible subframe.

15. A first radio network node according to claim 13, wherein the sending unit is further configured to send the notification after it has been determined that a level of said interference during the flexible subframe is higher than a threshold based on measurements of signals communicated to or from the first UE.

16. A first radio network node according to claim 13, wherein the detecting unit is further configured to detect the first UE when it is located in a cell border region of the first radio network node adjacent to a cell of the second radio network node.

17. A first radio network node according to claim 16, wherein the detecting unit is further configured to determine the cell border region based on measurements of path loss between UEs served by the first radio network node and the first radio network node.

19. A first radio network node according to claim 17, wherein the detecting unit is further configured to determine the cell border region based on additional measurements regarding the UEs served by the first radio network node, the additional measurements comprising measurements of at least one of:

power headroom, transmit power, received signal strength, angle/direction of arrival, timing advanced, and one way propagation delay.

23. A first radio network node according to claim 13, wherein the identifying unit is further configured to identify a set of neighbouring radio network nodes which employ a direction of signal transmission during the flexible subframe that is opposite to the direction of signal transmission employed by the first radio network node during the flexible subframe, and the sending unit is further configured to send the notification to one or more radio network nodes in the set of identified neighbouring radio network nodes.

24. A first radio network node according to claim 13, wherein the first radio network node comprises a mitigation unit configured to, when the first UE is the aggressor UE transmitting uplink radio signals with data during the flexible subframe, execute an interference mitigation action for alleviating said interference, the interference mitigation action comprising at least one of:

scheduling low data rate to the first UE in the uplink,

decreasing transmission power of the first UE,

using a more robust modulation scheme for the first UE,

using a more robust coding scheme for the first UE, and

using a more robust transport format for the first UE.

14. (canceled)

18. (canceled)

20-22. -22. (canceled)

25-32. -32. (canceled)

33. A second radio network node in a radio communication network where subframes are transmitted in pre-determined positions within radio frames, wherein a first radio network node in the radio communication network employs a subframe scheme where at least one of the pre-determined positions is allocated to a flexible subframe in which the direction of signal transmission is variable between uplink and downlink from one radio frame to another, the second radio network node being configured to alleviate interference on downlink radio signals received by a victim User Equipment, UE, in a victim cell, said interference being caused by transmission of uplink radio signals from an aggressor UE in an aggressor cell during the flexible subframe, the second radio network node comprising:

a receiving unit configured to receive a notification from the first radio network node, the notification indicating that an uplink transmission from the aggressor UE potentially overlaps at least partly with downlink reception in the victim UE during the flexible subframe, and that a first UE, being one of the victim and aggressor UEs, is served by the first radio network node,

a detecting unit configured to detect that a second UE, being the other one of the victim and aggressor UEs, is served by the second radio network node,

a logic unit configured to select an interference mitigation action for the detected second UE based on the received notification, and

a mitigating unit configured to execute the selected interference mitigation action.

37. A second radio network node according to claim 33, wherein the selected interference mitigation action comprises at least one of:

scheduling the second UE on an interference protected radio resource, and

avoiding to schedule the second UE during the flexible subframe.

instructing the second UE to apply multiple loop downlink channel filtering or multiple loop downlink link adaptation,

increasing transmission power,

using a more robust modulation scheme,

using a more robust coding scheme,

using a more robust transport format scheme, and

instructing the second UE to use a more robust receiver.

39. A second radio network node according to claim 33, wherein when the second UE is the aggressor UE sending uplink radio signals with data during the flexible subframe, the selected interference mitigation action comprises at least one of:

instructing the second UE to reduce its transmission power.

sending a notification to the second UE to instruct the second UE to execute an interference mitigation action.

34-36. -36. (canceled)

38. (canceled)

40-42. -42. (canceled)

43. A User Equipment, UE, configured to be served by a serving radio network node in a radio communication network where subframes are transmitted in pre-determined positions within radio frames, wherein at least one of the serving radio network node and a neighbouring radio network node in the radio communication network employs a subframe scheme where at least one of the pre-determined positions is allocated to a flexible subframe in which the direction of signal transmission is variable between uplink and downlink from one radio frame to another, and configured to alleviate interference on downlink radio signals received by a victim UE in a victim cell, said interference being caused by transmission of uplink radio signals from an aggressor UE in an aggressor cell during the flexible subframe, the UE comprising:

a receiving unit configured to receive a notification from the serving radio network node which notification indicates that the UE is one of the victim and aggressor UEs, and

an executing unit configured to execute an interference mitigation action based on the received notification.

44. A UE according to claim 43, wherein the executing unit is configured to execute the interference mitigation action by any of:

decreasing transmission power when the notification indicates that the UE is the aggressor UE, and

selecting a more robust receiver when the notification indicates that the UE is the victim UE.