METHODS AND APPARATUS TO SUPPORT INTERFERENCE MANAGEMENT IN MULTI-TIER WIRELESS COMMUNICATION SYSTEMS

• US 20110116480A1
• Filed: 11/11/2010
• Published: 05/19/2011
• Est. Priority Date: 11/13/2009
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Seol, Ji-Yun, Jang, Jaehyuk, CHO, Young Bo, Josiam, Kaushik, Pi, Zhouyue, Ramakrishna, Sudhir, Li, Ying
• Granted Patent: US 8,989,086 B2
• Time in Patent Office: Days
• US Class Current: 370/332
• CPC Class Codes: H04W 28/04 Error control
• CPC Class Codes: H04W 4/06 Selective distribution of broadcast services, e.g. multimedia broadcast multicast service [MBMS]; Services to user groups; One-way selective calling services
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management
• 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

When a subscriber station (SS) encounters interference caused an interfering base station (BS), the interference can be mitigated regardless of whether the interfering base station is a CSG-Closed BS or whether the SS is connected to a serving BS. If the SS is not connected to a serving BS and cannot access the interfering BS, the SS will signal the interfering BS directly to request the interfering BS to perform IM. If the SS is a legal user, and conditions to initiate IM are met, the interfering BS will perform IM until conditions to terminate IM are met. If the SS is connected to a serving BS, the serving BS will request the interfering BS to perform or terminate interference mitigation (IM) on behalf of the SS if certain conditions are satisfied.

Claims

1. A Closed Subscriber Group (CSG) base station (BS) capable of performing interference mitigation (IM) in a wireless communications network, the CSG BS comprising:

a wireless communication unit configured to communicate with subscriber stations (SSs); and

a controller coupled to the wireless communication unit and configured to;

directly receive a ranging purpose indication in a ranging request message from a non-member SS through the wireless communication unit, and

selectively perform an IM from among predetermined IM methods comprising at least one of;

reducing transmission power locally and changing from a CSG-Closed status to a CSG-Open status, if the CSG BS is in the CSG-Closed status.

2. The CSG BS of claim 1, wherein the ranging purpose indication indicates that the non-member SS is experiencing a femto interference.

3. The CSG BS of claim 1, wherein the controller is further configured to determine whether conditions to initiate IM are met and perform the IM when the conditions to initiate IM are met, the conditions to initiate IM comprising at least one of:

the request to initiate IM indicates exceptional non-member access to the CSG BS;

the non-member SS has been verified as a non-member of the CSG BS and a legal system user;

the non-member SS has reported to the CSG BS all the base stations it can find and their respective signal strengths;

the CSG BS is an interfering BS that causes the non-member SS to be unable to connect to any accessible BS; and

the CSG BS has the highest signal strength among all interfering BSs.

4. The CSG BS of claim 1, wherein the controller is further configured to terminate the IM when conditions to terminate IM are met, the conditions to terminate IM comprising at least one of:

a timer for the IM has expired;

the non-member SS moving away from the CSG BS;

the non-member SS handing over to another BS;

the non-member SS has determined that a signal strength of an accessible BS is higher than a first threshold for at least a first threshold duration;

the non-member SS has determined that a signal strength of the CSG BS is lower than a second threshold for at least a second threshold duration;

the non-member SS has determined that the signal strength of the CSG BS is lower than the signal strength of the accessible BS by a third threshold for at least a third threshold duration; and

the non-member SS has determined that the signal strength of the CSG BS is not the highest among scanned BSs for at least a fourth threshold duration.

5. A Closed Subscriber Group (CSG) base station (BS) capable of performing interference mitigation (IM) in a wireless communications network, the CSG BS comprising:

a wireless communication unit configured to communicate with subscriber stations (SSs); and

a controller coupled to the wireless communication unit and configured to;

directly receive a ranging purpose indication in a ranging request message from a non-member SS through the wireless communication unit, and

change the CSG BS from a CSG-Closed status to a CSG-Open status, if the CSG BS is in the CSG-Closed status,

wherein the ranging purpose indication indicates that the SS is experiencing a femto interference, and

wherein the CSG-Closed status of the CSG BS does not allow non-member SSs to access the CSG BS.

6. For use in a wireless communications network, a Closed Subscriber Group (CSG) base station (BS) capable of performing interference mitigation (IM), the CSG BS comprising:

a wireless communication unit configured to communicate with subscriber stations (SSs); and

a controller coupled to the wireless communication unit and configured to;

receive a ranging request message from a non-member SS through the wireless communication unit, the ranging request message comprising a ranging purpose indication, and

perform an IM if conditions to initiate IM are met.

7. The CSG BS of claim 6, wherein the conditions to initiate IM comprise at least one of:

the request to initiate IM indicates exceptional non-member access to the CSG BS;

the non-member SS has been verified as a non-member of the CSG BS and a legal system user;

the non-member SS has reported to the CSG BS all the base stations it can find and their respective signal strengths;

the CSG BS is an interfering BS that causes the non-member SS to be unable to connect to any accessible BS; and

the CSG BS has the highest signal strength among all interfering BSs.

8. The CSG BS of claim 6, wherein the controller is further configured to receive at least one scanning report from the non-member SS to determine whether the conditions to initiate IM are satisfied.

9. The CSG BS of claim 6, wherein the controller is further configured to perform the IM by at least one of:

if the CSG BS is in a CSG-Closed type, changing from the CSG-Closed type to a CSG-Open type such that the non-member SS is allowed to access the CSG BS, wherein when the CSG BS is in the CSG-Closed type, non-member SSs are not allowed to access the CSG BS;

allowing the non-member SS to temporarily access the CSG BS, wherein the non-member SS is served at a lower priority than member SSs while the CSG BS allows the temporary access;

adjusting a downlink transmission power; and

changing a frequency allocation.

10. The CSG BS of claim 6, wherein the ranging purpose indication indicates that at least one of:

the non-member SS is requesting the CSG BS to perform the IM, and the non-member SS is experiencing a CSG BS interference.

11. The CSG BS of claim 6, wherein the controller is further configured to terminate the IM when conditions to terminate IM are met.

12. The CSG BS of claim 11, wherein the conditions to terminate IM comprise at least one of:

a timer for the IM has expired;

the non-member SS moving away from the CSG BS;

the non-member SS handing over to another BS;

the non-member SS has determined that a signal strength of an accessible BS is higher than a first threshold for at least a first threshold duration;

the non-member SS has determined that a signal strength of the CSG BS is lower than a second threshold for at least a second threshold duration;

the non-member SS has determined that the signal strength of the CSG BS is lower than the signal strength of the accessible BS by a third threshold for at least a third threshold duration; and

the non-member SS has determined that the signal strength of the CSG BS is not the highest among scanned BSs for at least a fourth threshold duration.

13. The CSG BS of claim 12, wherein the timer is adjustable according to at least one of:

an IM type, a velocity of the non-member SS, and at least one scanning report received from the non-member SS.

14. The CSG BS of claim 6, wherein the controller is further configured to perform IM by negotiating IM attributes with a network entity through at least one of a backhaul and a self-organizing network server.

15. The CSG BS of claim 6, wherein the controller is further configured to receive a request to initiate a coordinated IM from a serving BS that is negotiating on behalf of the non-member SS when the non-member SS is connected to the serving BS.

16. For use in a wireless communications network, a method in a Closed Subscriber Group (CSG) base station (BS) for performing interference mitigation (IM), the method comprising:

receiving a ranging request message from a non-member SS through a wireless communication unit, the ranging request message comprising a ranging purpose indication; and

performing an IM if conditions to initiate IM are met.

17. The method of claim 16, wherein the conditions to initiate IM comprise at least one of:

the request to initiate IM indicates exceptional non-member access to the CSG BS;

the non-member SS has been verified as a non-member of the CSG BS and a legal system user;

the non-member SS has reported to the CSG BS all the base stations it can find and their respective signal strengths;

the CSG BS is an interfering BS that causes the non-member SS to be unable to connect to any accessible BS; and

the CSG BS has the highest signal strength among all interfering BSs.

18. The method of claim 16, further comprising receiving at least one scanning report from the non-member SS to determine whether the conditions to initiate IM are satisfied.

19. The method of claim 16, further comprising performing the IM by at least one of:

if the CSG BS is in a CSG-Closed type, changing from the CSG-Closed type to a CSG-Open type such that the non-member SS is allowed to access the CSG BS, wherein when the CSG BS is in the CSG-Closed type, non-member SSs are not allowed to access the CSG BS;

allowing the non-member SS to temporarily access the CSG BS wherein the non-member SS is served at a lower priority than member SSs while the CSG BS allows the temporary access;

adjusting a downlink transmission power; and

changing a frequency allocation.

20. The method of claim 16, wherein the ranging purpose indication indicates that at least one of:

the non-member SS is requesting the CSG BS to perform the IM, and the non-member SS is experiencing a CSG BS interference.

21. The method of claim 16, further comprising terminating the IM when conditions to terminate IM are met.

22. The method of claim 21, wherein the conditions to terminate IM comprise at least one of:

a timer for the IM has expired;

the non-member SS moving away from the CSG BS;

the non-member SS handing over to another BS;

the non-member SS has determined that a signal strength of an accessible BS is higher than a first threshold for at least a first threshold duration;

the non-member SS has determined that a signal strength of the CSG BS is lower than a second threshold for at least a second threshold duration;

the non-member SS has determined that the signal strength of the CSG BS is lower than the signal strength of the accessible BS by a third threshold for at least a third threshold duration; and

the non-member SS has determined that the signal strength of the CSG BS is not the highest among scanned BSs for at least a fourth threshold duration.

23. The method of claim 22, wherein the timer is adjustable according to at least one of an IM type, a velocity of the non-member SS, and at least one scanning report received from the non-member SS.

24. The method of claim 16, further comprising performing the IM by negotiating IM attributes with a network entity through at least one of a backhaul and a self-organizing network server.

25. The method of claim 16, further comprising receiving a request to initiate a coordinated IM from a serving BS that is negotiating on behalf of the non-member SS when the non-member SS is connected to the serving BS.

26. For use in a wireless communications network, a serving base station (BS) capable of supporting interference mitigation (IM) when a subscriber station (SS) encounters interference, the serving BS comprising:

a wireless communication unit configured to communicate with SSs; and

a controller coupled to the wireless communication unit and configured to;

request an interfering BS to perform IM when, based on a scanning report for IM initiation, the SS is unable to handover to any neighboring BS and conditions for IM initiation are met, and

request the interfering BS to terminate the IM when, based on a scanning report for IM termination, conditions for IM termination are met.

27. The serving BS of claim 26, wherein the controller is further configured to communicate with the interfering BS through a backhaul for at least one of requesting the interfering BS to perform the IM and requesting the interfering BS to terminate the IM.

28. A method in a serving base station (BS) for supporting interference mitigation (IM) when a subscriber station (SS) being served by the BS encounters interference, the method comprising:

requesting an interfering BS to perform IM when, based on a scanning report for IM initiation, the SS is unable to handover to any neighboring BS and conditions for IM initiation are met; and

requesting the interfering BS to terminate the IM when, based on a scanning report for IM termination, conditions for IM termination are met.

29. The method of claim 28, wherein at least one of requesting the interfering BS to perform the IM and requesting the interfering BS to terminate the IM is performed by communicating with a backhaul.

30. For use in a wireless communications network, a subscriber station capable of supporting interference mitigation (IM) when encountering interference, the subscriber station comprising:

a receiver configured to receive messages from base stations;

a transmitter configured to transmit messages to base stations; and

a controller coupled to the receiver and the transmitter and configured to;

if the subscriber station is connected to a serving BS, send a first scanning report to the serving BS to initiate IM with an interfering BS when handover to another BS is not possible and trigger conditions to send scanning report for IM initiation are met, and

if the subscriber station is not connected to any BS, send a ranging request comprising a ranging purpose indication to the interfering BS to initiate the IM when handover to the interfering BS is not possible and trigger conditions to signal the interfering BS for IM initiation are met.

31. The subscriber station of claim 30, further comprising a memory configured to store a local whitelist that identifies closed subscriber groups (CSGs) to which the subscriber station is a member,

wherein the controller is further configured to indicate in the scanning report whether the interfering BS is a CSG BS that belongs to at least one of the CSGs in the local whitelist.

32. The subscriber station of claim 30, wherein the controller is further configured to:

if the subscriber station is connected to the serving BS, send a second scanning report to the serving BS to terminate the IM with the interfering BS when trigger conditions to send scanning report for IM termination are met.

33. A method in a subscriber station for supporting interference mitigation (IM) when encountering interference in a wireless communication network, the method comprising:

if the subscriber station is connected to a serving BS, sending a first scanning report to the serving BS to initiate IM with an interfering BS when handover to another BS is not possible and trigger conditions to send scanning report for IM initiation are met; and

if the subscriber station is not connected to any BS, sending a ranging request comprising a ranging purpose indication to the interfering BS to initiate the IM when handover to the interfering BS is not possible and trigger conditions to signal the interfering BS for IM initiation are met.

34. The method of claim 33, further comprising:

storing a local whitelist that identifies closed subscriber groups (CSGs) to which the subscriber station is a member; and

indicating in the scanning report whether the interfering BS is a CSG BS that belongs to at least one of the CSGs in the local whitelist.

35. The method of claim 33, further comprising:

if the subscriber station is connected to the serving BS, sending a second scanning report to the serving BS to terminate the IM with the interfering BS when trigger conditions to send scanning report for IM termination are met.