Method and apparatus for reducing inter-cell interference

• US 9,559,798 B2
• Filed: 10/23/2013
• Issued: 01/31/2017
• Est. Priority Date: 10/25/2012
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Nuss, Ziv, Apelewicz, Tuvia
• Primary Examiner(s): Nguyen, Phuongchau Ba
• Application Number:
  US14/435,166
• Publication Number:
  US 20160127069A1
• Time in Patent Office: 1,196 Days
• Field of Search: 370/252, 370/311, 370/315, 370/277, 370/329, 455/422.1, 455/446, 455/414.1, 455/423, 455/424, 455/448, 455/453, 455/456.1, 455/501, 455/63.1, 375/267
• US Class Current: 1/1
• CPC Class Codes: H04J 11/005 of intercell interference
• CPC Class Codes: H04J 11/0053 using co-ordinated multipoint transmission/reception co-ordinated antenna or beam-forming aspects H04B7/022
• CPC Class Codes: H04L 1/1812 Hybrid protocols; Hybrid automatic repeat request [HARQ]
• CPC Class Codes: H04W 16/10 Dynamic resource partitioning
• CPC Class Codes: H04W 36/0061 of neighbour cell information
• CPC Class Codes: H04W 72/541 using the level of interference
• CPC Class Codes: H04W 84/042 Public Land Mobile systems, e.g. cellular systems
• CPC Class Codes: H04W 84/045 using private Base Stations, e.g. femto Base Stations, home Node B

Abstract

A method is described for reducing interferences in a wireless network, by: identifying cells which experience more interference than others; identifying a group of PRBs that their transmissions are subjected to moire interference than other concurrent transmissions; identifying UEs associated with the group of PRBs, and determining whether the location of the UEs is at the cells'"'"' edges; selecting a pair of UEs where one member is located at a first cell'"'"'s edge and the other is located either (i) at a second cell, not included within a neighbors'"'"' list of the first cell, or (ii) at the core or remote edge of a second cell. In case (i), the second cell is introduced to the first cell neighbors'"'"' list, and in case (ii) the other UE is falsely defined as a UE located at the near second cell'"'"'s edge. Then, ICIC procedure is invoked for that pair of UEs.

Claims

1. A method for reducing interferences in a wireless communication network comprising a plurality of wireless cells, the method comprising steps of:

(a) identifying one or more of the plurality of wireless cells which experience more interference than a remainder of the plurality of wireless cells;

(b) identifying at least one group of allocated radio resources for transmission to or from the one or more identified wireless cells, wherein transmissions made while utilizing the at least one identified group of allocated radio resources are characterized as being subjected to more interference than concurrent transmissions made while utilizing other groups of allocated radio resources for transmission to or from the one or more identified wireless cells;

(c) for each of the at least one identified group of allocated radio resources, identifying two or more user equipments (UEs) utilizing that group of allocated radio resources and determining whether a location of at least one of the UEs is at an edge of a wireless cell at which the at least one of the UEs is provided with communication services;

(d) selecting one pair of UEs from among the identified two or more UEs, wherein a current location of one member of the one pair of UEs is at an edge of a first wireless cell associated with the one member and a current location of another member of the one pair of UEs is either;

i) located at a second wireless cell which is currently not included in a neighbors'"'"' list of the first wireless cell, or

ii) located at a second wireless cell which is adjacent to the first wireless cell, as long as the other UE member is located away from an edge of the second wireless cell, which is located adjacent to an edge of the first wireless cell;

(dl) for a selected pair of UEs in which another UE member is located at a second wireless cell currently not included of a neighbors'"'"' list of the first wireless cell, including the second wireless cell in the neighbors'"'"' list of the first wireless cell;

(d2) for a selected pair of UEs in which another UE member is located at a second wireless cell adjacent to the first wireless cell but away from an edge of the second wireless cell, which is adjacent to an edge of the first wireless cell, falsely defining the other member as being a UE located at the edge of the second wireless cell, which is adjacent to an edge of the first wireless cell; and

(e) invoking an Inter-cell interference coordination procedure involving the selected pair of UEs, to reduce inter-cell interferences.

2. The method of claim 1, wherein step (a) is triggered when a number of successful hybrid automatic repeat request (HARQ) events associated with a given wireless cell divided by a sum of successful and unsuccessful HARQ events associated with said given wireless cell is less than an average HARQ success rate for the wireless cells included in a cluster of wireless cells to which the given cell belongs, minus a pre-defined factor, wherein the predefined factor is a function of a standard deviation of successful HARQ events divided by a sum of successful and unsuccessful HARQ events associated with the wireless cells of the cluster.

3. The method of claim 1, wherein step (c) further comprises:

retrieving information which relates to Radio Resource Control (RRC) Connection Setup for a plurality of UEs; and

based on the information retrieved, determining one or more UEs connected to a most interfered base station and one or more UEs associated with a most interfered group of allocated radio resources.

4. The method of claim 1, wherein the step of determining whether a location of at least one UE of the identified two or more UEs is at the edge of the wireless cell at which the at least one of the UE is provided communication services is based upon retrieving at least one of a time adjustment (TA) value and a received signal strength power (RSSP) value for each of the identified two or more UEs and comparing each of the at least one of the retrieved TA value and RSSP value for each of the identified two or more UEs to a respective at least one of a predetermined threshold TA value and a predetermined threshold RSSP value, wherein, for a given identified UE, if at least one of the retrieved RSSP value for the given identified UE is less than the predetermined threshold RSSP value, then the given identified UE is determined to be located at the cell edge.

5. The method of claim 1, wherein step (dl) further comprises utilizing Radio Resource Control (RRC) Connection Setup information of a given UE for the selected pair of UEs in order to identify wireless cells that are not currently included in the neighbors'"'"' list of the first wireless cell, wherein the identified wireless cells comprise UEs that are associated with the at least one identified group of allocated radio resources being subjected to more interference.

6. The method of claim 5, wherein step (dl) further comprises comparing at least one of a time adjustment (TA) value and a received signal strength power (RSSP) value associated with each UE connected to a wireless cell which is not currently included in the neighbors'"'"' list of the first wireless cell to a respective at least one of a predetermined threshold TA value and a predetermined threshold RSSP value and if, for a given UE, a respective at least one of the TA value for the given UE is less than the predetermined threshold TA value and the RSSP value for the given UE is less than the predetermined threshold RSSP value, determining that the given UE is located at a cell edge of a wireless cell which is not currently included in the neighbors'"'"' list of the first wireless cell.

7. The method of claim 6, wherein step (dl) further comprises identifying, from among one or more UEs determined to be located at an edge of a respective wireless cell which is not currently included in the neighbors'"'"' list of the first wireless cell, which of the one or more UEs are associated with the at least one identified group of allocated radio resources being subjected to more interference.

8. The method of claim 1, wherein step (e) comprises invoking an Inter-cell interference coordination (ICIC) procedure between the first and second wireless cells that are defined as being neighboring cells even if the second wireless cell is not included in the neighbors'"'"' list of the first wireless cell prior to carrying out step (d1).

9. The method of claim 1, wherein step (e) comprises invoking an Inter-cell interference coordination (ICIC) procedure between the first and second wireless cells even if one UE of the identified two or more UEs is currently located at a core of a wireless cell providing communication services to the one UE.

10. The method of claim 1, further comprising steps of:

monitoring high interference indicator messages sent by a plurality of wireless cells, wherein each high interference indicator message for a given wireless cell comprises a list of groups of radio resources'"'"' allocations that are scheduled for cell edge UEs associated with the given wireless cell; and

storing groups of radio resources'"'"' allocations associated with each of a given wireless cell together with an identity of for a given wireless cell from which a high interference indicator message was sent and a timestamp indicating a time at which the high interference indicator message was sent.

11. The method of claim 10, wherein step (d2) is carried out based on information that relates to stored information regarding groups of radio resources'"'"' allocations, an identity of a given wireless cell associated with each group and a timestamp associated with each group.

12. The method of claim 1, wherein if by following step (c) it is determined that the at least one group of allocated resources of the at least one identified group of allocated radio resources are not associated with UEs located at a cell edge, determining an identity of each of the UEs that are connected to a wireless cell and which are associated with the at least one group of allocated resources of the at least one identified group of allocated radio resources.

13. The method of claim 12, further comprising a step of comparing at least one of a time adjustment (TA) value and a received signal strength power (RSSP) value associated with each UE connected to an adjacent neighboring wireless cell, to a respective at least one of a predetermined threshold TA value and a predetermined threshold RSSP value and if, for a given UE, a respective at least one of the TA value for the given UE is less than the predetermined threshold TA value and the RSSP value for the given UE is greater than the predetermined threshold RSSP value, determining that the UE is located at a cell core of the adjacent neighboring wireless cell.

14. The method of claim 13, further comprising a step of identifying the one or more adjacent neighboring wireless cells that comprise identifications of cell core UEs connected thereto and that are associated with one or more identified group of allocated radio resources being subjected to more interference.

15. The method of claim 14, further comprising a step of conveying a high interference indicator message to all of the identified one or more adjacent neighboring wireless cells that comprise identifications of cell core UEs connected thereto and that are associated with one or more identified group of radio resources being subjected to more interference, wherein the group of allocated radio resources which are found to be associated with a cell core UE are falsely identified for the adjacent neighboring wireless cells as being a group of allocated radio resources associated with a cell edge to enable invoking an inter-cell interference coordination procedure to reduce inter-cell interferences.

16. The method of claim 1, further comprising a step of inducing a change in a tilt of an antenna associated with at least one of the first wireless cell and the second wireless cell.

17. A controller to reduce interferences in a wireless communication network comprising a plurality of wireless cells, wherein the controller is configured to:

(a) identify one or more of the plurality of wireless cells which experience more interference than a remainder of the plurality of wireless cells;

(b) identify at least one group of allocated radio resources transmitted to or from the one or more identified wireless cells, wherein transmissions made while utilizing the at least one identified group of allocated radio resources are characterized as being subjected to more interference than concurrent transmissions made while utilizing other groups of allocated radio resources for transmission to or from the one or more identified wireless cells;

(c) for each of the at least one identified group of allocated radio resources, identify two or more user equipments (UEs) utilizing that group of allocated radio resources and determine whether a location of at least one of these UEs is at an edge of a wireless cell at which the at least one of the UEs is provided with communication services;

(d) select one pair of UEs from among the identified two or more UEs, wherein a current location of one member of the one pair of UEs is at an edge of a first wireless cell associated with the one member and a current location of another member of the one pair of UEs is either;

i) located at a second wireless cell which is currently not included in a neighbors'"'"' list of the first wireless cell, or

ii) located at a second wireless cell which is adjacent to the first wireless cell, as long as the other UE member is located away from an edge of the second wireless cell, which is located adjacent to an edge of the first wireless cell;

(dl) for a selected pair of UEs in which another UE member is located at a second wireless cell currently not included of a neighbors'"'"' list of the first wireless cell, include the second wireless cell in the neighbors'"'"' list of the first wireless cell;

(d2) for a selected pair of UEs in which another UE member is located at a second wireless cell adjacent to the first wireless cell but away from an edge of the second wireless cell, which is adjacent to an edge of the first wireless cell, falsely define the other member as being a UE located at the edge of the second wireless cell, which is adjacent to an edge of the first wireless cell; and

(e) invoke an Inter-cell interference coordination procedure involving the selected pair of UEs to reduce inter-cell interferences.