INTRA CELL INTERFERENCE MITIGATION IN A WIRELESS NETWORK EMPLOYING RELAY NODES

• US 20140029507A1
• Filed: 04/01/2011
• Published: 01/30/2014
• Est. Priority Date: 04/01/2011
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Dimou, Konstantinos, Hiltunen, Kimmo
• Granted Patent: US 9,485,008 B2
• Time in Patent Office: Days
• US Class Current: 370/315
• CPC Class Codes: H04B 7/15528 Control of operation parameters of a relay station to exploit the physical medium
• CPC Class Codes: H04B 7/15564 Relay station antennae loop interference reduction
• CPC Class Codes: H04W 24/10 Scheduling measurement reports ; Arrangements for measurement reports
• CPC Class Codes: H04W 72/541 using the level of interference
• CPC Class Codes: H04W 84/047 using dedicated repeater stations

Abstract

A method and relay node (RN) in a wireless communications network for controlling downlink transmissions to User Equipments (UEs) being served by the RN. An RN transceiver circuit requests each UE to measure and report a Reference Signal Received Power (RSRP) and a UE total downlink interference. An RN receiver circuit receives and forwards the reported RSRP and UE total downlink interference for each UE. An RN processing and control circuit measures an RN total downlink interference; determines which UEs are closely located to the RN based on the reported RSRP of each UE; creates a UE-list with UEs determined to be closely located to the RN and which experience UE total downlink interference similar to the measured RN total downlink interference; determines whether the measured RN total downlink interference exceeds an RN interference threshold; and if so, controls the downlink transmissions to the UEs in the created UE-list.

Claims

1. A method in a Relay Node (RN) for controlling downlink transmissions to User Equipments (UEs) being served by the RN in a wireless communications network, the method comprising:

requesting each of said UEs to measure and report a Reference Signal Received Power, (RSRP) and a UE total downlink interference;

measuring a RN total downlink interference;

determining which UEs are closely located to the RN based on each of the reported RSRP;

creating a UE-list with UEs determined to be closely located to the RN and for which a difference between the measured UE total downlink interference and the measured RN total downlink interference does not exceed a difference threshold (Th_—

2);

determining whether the measured RN total downlink interference exceeds a RN interference threshold; and

when the measured RN total downlink interference exceeds the RN interference threshold, controlling the downlink transmissions to the UEs in the created UE-list.

2. The method according to claim 1, wherein requesting each of said UEs to measure and report the RSRP and the UE total downlink interference comprises requesting each of UEs to measure and report at least one of:

RSRP;

interference experienced from a donor base station;

interference experienced from another macro base station; and

interference experienced from other relay nodes.

3. The method according to claim 1, wherein measuring the RN total downlink interference is performed during a same instance as a UE performs the UE total downlink interference measurement.

4. The method according to claim 1, wherein measuring RN total downlink interference comprises measuring at least one of:

interference experienced from a donor base station;

interference experienced from another macro base station; and

interference experienced from other relay nodes.

5. The method according to claim 1, wherein determining which UEs are closely located to the RN comprises determining which of the UEs has a reported RSRP which exceeds a RN RSRP threshold.

6. The method according to claim 1, wherein when determining whether the measured RN total downlink interference exceeds the RN interference threshold reveals that the RN total downlink interference does not exceed the RN interference threshold, the method further comprises:

measuring a new RN total downlink interference; and

determining whether the measured new RN total downlink interference exceeds the RN interference threshold.

7. The method according to claim 6, wherein measuring a new RN total downlink interference and determining whether the measured new RN total downlink interference exceeds the RN interference threshold is repeated until the RN total downlink interference is determined to exceed the RN interference threshold or until a predefined time period has passed.

8. The method according to claim 1, wherein controlling the downlink transmissions to the UEs in the created UE-list comprises:

comparing the number of UEs in the UE-list with the number of UEs which are determined to be closely located to the RN or with a total number of served UEs; and

controlling the downlink transmissions to the UEs in the created UE-list, based on a result from the comparison.

9. The method according to claim 1, wherein controlling the downlink transmissions to the UEs in the created UE-list comprises:

reporting RN downlink total interference to a donor base station; and

receiving instructions, in response to the reporting, from the donor base station on how to control the downlink transmissions to the UEs in the created UE-list.

10. The method according to claim 1, wherein controlling the downlink transmissions to the UEs in the created UE-list comprises at least one of:

suspending downlink transmissions to UEs in the UE-list for a predefined time period;

decreasing output power from the RN towards UEs in the UE-list for a predefined time period;

requesting an increased amount of downlink resources for allocation from a donor base station; and

allocating a fewer number of slots for downlink transmission from the RN to UEs in the UE-list.

11. The method according to claim 1, wherein the measured UE total downlink interference and RN total downlink interference comprise UE total downlink in-band interference and RN total downlink in-band interference.

12. A relay node (RN) for controlling downlink transmissions to User Equipments (UEs) being served by the RN in a wireless communications network, the RN comprising:

a transceiver circuit configured to request each of said UEs to measure and report a Reference Signal Received Power, (RSRP) and a UE total downlink interference;

a receiver circuit configured to receive and forward the reported RSRP and UE total downlink interference for each of said UEs; and

a processing and control circuit configured to;

measure a RN total downlink interference;

determine which UEs are closely located to the RN, based on the reported RSRP of each of said UEs;

create a UE-list with UEs determined to be closely located to the RN and for which a difference between the measured UE total downlink interference and the measured RN total downlink interference does not exceed a difference threshold (Th_—

2);

determine whether the measured RN total downlink interference exceeds a RN interference threshold; and

when the measured RN total downlink interference exceeds the RN interference threshold, control the downlink transmissions to the UEs in the created UE-list.

13. The relay node according to claim 12, wherein the transceiver circuit is configured to request each of said UEs to measure and report at least one of:

RSRP;

interference experienced from a donor base station;

interference experienced from another macro base station; and

interference experienced from other relay nodes.

14. The relay node according to claim 12, wherein the processing and control circuit is configured to measure the RN total downlink interference during a same instance as a UE performs a UE total downlink interference measurement.

15. The relay node according to claim 12, wherein the measured RN total downlink interference comprises at least one of:

interference experienced from a donor base station;

interference experienced from another macro base station; and

interference experienced from other relay nodes.

16. The relay node according to claim 12, wherein the processing and control circuit is configured to determine which UEs are closely located to the RN by determining which of the UEs has a reported RSRP which exceeds a RN RSRP threshold.

17. The relay node according to claim 12, wherein the processing and control circuit is configured to determine when the RN total downlink interference does not exceed the RN interference threshold, and further:

measure a new RN total downlink interference; and

determine whether or not the measured new RN total downlink interference exceeds the RN interference threshold.

18. The relay node according to claim 17, wherein the processing and control circuit is configured to measure a new RN total downlink interference and determine whether the measured new RN total downlink interference exceeds a RN interference threshold repeatedly until the RN total downlink interference is determined to exceed the RN interference threshold or until a predefined time period has passed.

19. The relay node according to claim 12, wherein the processing and control circuit configured to control the downlink transmissions to the UEs in the created UE-list is further configured to:

compare the number of UEs in the UE-list with the number of UEs which are determined to be closely located to the RN or with a total number of served UEs; and

control the downlink transmissions to the UEs in the created UE-list based on a result from the comparison.

20. The relay node according to claim 12, wherein the processing and control circuit configured to control the downlink transmissions to the UEs in the created UE-list is further configured to:

report RN total downlink interference to a donor base station; and

receive instructions, in response to the reporting of RN total downlink interference, from the donor base station on how to control the downlink transmissions to the UEs in the created UE-list.

21. The relay node according to claim 12, wherein the processing and control circuit is configured to control the downlink transmissions to the UEs in the created UE-list by at least one of:

suspending downlink transmissions to UEs in the UE-list for a predefined time period;

decreasing output power from the RN towards UEs in the UE-list for a predefined time period;

requesting an increased amount of downlink resources for allocation from a donor base station; and

allocating fewer number of slots for downlink transmission from the RN to UEs in the UE-list.

22. The relay node according to claim 12, wherein the measured UE total downlink interference and RN total downlink interference comprise UE total downlink in-band interference and RN total downlink in-band interference, respectively.

23. The relay node according to claim 12, wherein the processing and control circuit is configured to additionally control downlink transmissions to all served UEs or to all UEs determined to be closely located to the RN.