AUTOMATIC HANDOVER OSCILLATION CONTROL

• US 20100273487A1
• Filed: 04/28/2009
• Published: 10/28/2010
• Est. Priority Date: 04/28/2009
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Gunnarsson, Fredrik, Alonso-Rubio, Jose
• Granted Patent: US 8,331,936 B2
• Time in Patent Office: Days
• US Class Current: 455/436
• CPC Class Codes: H04W 36/385 of the core network

Abstract

A method and apparatus are provided for use in a cellular radio communication system for adjusting a handover parameter. Information is collected regarding actual handovers that have occurred between one or more pairs of cells as well as handover failures. The collected handover information is processed to determine a handover oscillation rate or a handover cost associated with the cell pair. If the handover performance is determined to be acceptable, the determined handover oscillation rate or the determined handover cost is compared with a predetermined target handover oscillation rate or a predetermined target handover cost, respectively. One or more handover parameters associated with at least one of the cells in the cell pair is adjusted based on the comparison.

Claims

1. A method for use in a cellular radio communication system for adjusting a handover parameter, comprising:

collecting information regarding actual handovers that have occurred between one or more pairs of cells;

processing the collected handover information to determine a handover performance associated with the cell pair;

determining whether the determined handover performance satisfies a handover performance setting, and if so, processing the collected handover information to determine a handover oscillation rate or a handover cost associated with the cell pair;

comparing the determined handover oscillation rate or the determined handover cost with a predetermined target handover oscillation rate or a predetermined target handover cost, respectively; and

adjusting one or more handover parameters associated with at least one of the cells in the cell pair based on the comparison.

2. The method of claim 1, further comprising:

if the determined handover performance does not satisfy the handover performance setting, then refraining from adjusting the one or more handover parameters or reverting to the one or more handover parameters prior to adjustment.

3. The method in claim 1, wherein the handover performance is a handover failure rate or a handover success rate.

4. The method in claim 3, further comprising comparing the handover performance to a threshold.

5. The method in claim 1, wherein the comparison includes determining a difference between the determined handover oscillation rate and the target handover oscillation rate or between the determined handover cost and the target handover cost, and wherein the adjusting includes adjusting one or more handover parameters associated with at least one of the cells in the cell pair to reduce the difference.

6. The method of claim 1, wherein the comparison includes determining whether the determined handover oscillation rate exceeds the target handover oscillation rate, and if so, adjusting the one or more handover parameters associated with at least one of the cells in the cell pair to delay or prevent a handover of a call connection from the at least one cell.

7. The method of claim 1, wherein the information includes a time duration that a UE connection remains at one of the cells in the cell pair after the UE connection is handed over from the other of the cells in the cell pair.

8. The method of claim 7, wherein the information includes a direction of each handover that has actually occurred between one or more pairs of cells.

9. The method of claim 8, wherein the information is stored as a cumulative distribution function or as a histogram.

10. The method of claim 8, wherein the information regarding handovers is stored in memory.

11. The method of claim 1 carried out in a distributed fashion at each of multiple radio network nodes.

12. The method of claim 1 carried out in a centralized fashion at a central node in communication with a radio network node associated with the one or more cells.

13. The method of claim 1, wherein the one or more handover parameters includes one or both of a handover margin parameter and a time-to-trigger a handover parameter.

14. The method of claim 13, wherein one or both of the handover margin parameter and the time-to-trigger a handover parameter is based on one or more of the following:

a frequency specific offset of a frequency of a handover candidate cell, a cell specific offset of the handover candidate cell, a frequency specific offset of the frequency of a serving cell, a cell specific offset of the serving cell, a hysteresis parameter, and an offset parameter.

20. The apparatus of claim 14, wherein the electronic data processing circuitry is arranged to:

determine whether the determined handover oscillation rate exceeds the target handover oscillation rate, and if so, adjust the one or more handover parameters associated with at least one of the cells in the cell pair to delay or prevent a handover of a call connection from the at least one cell.

21. The apparatus of claim 14, wherein the information includes a time duration that a UE connection remains at one of the cells in the cell pair after the UE connection is handed over from the other of the cells in the cell pair.

23. The apparatus of claim 20, wherein the information is stored as a cumulative distribution function or as a histogram.

24. The apparatus of claim 14, wherein the cellular radio communication system includes a radio access network with multiple radio base stations, and wherein the apparatus is included in each radio base station.

25. The apparatus of claim 14, wherein the cellular radio communication system includes a radio access network with multiple radio base stations and a central node in communication with the radio network, wherein the apparatus is included in the central node.

26. The apparatus of claim 14, wherein the electronic data processing circuitry includes call duration timing circuitry configured to monitor call duration times for calls handed over to one of the cells in a cell pair until those calls are handed over to another cell.

27. The apparatus of claim 14, wherein the one or more handover parameters includes one or both of a handover margin parameter and a time-to-trigger a handover parameter.

28. The apparatus of claim 25, wherein one or both of the handover margin parameter and the time-to-trigger a handover parameter are based on one or more of the following:

a frequency specific offset of a frequency of a handover candidate cell, a cell specific offset of the handover candidate cell, a frequency specific offset of the frequency of a serving cell, a cell specific offset of the serving cell, a hysteresis parameter, and an offset parameter.

15. Apparatus for use in a cellular radio communication system, comprising:

a memory for storing information regarding actual handovers that have occurred between one or more pairs of cells; and

electronic data processing circuitry arranged to;

process the collected handover information to determine a handover performance associated with the cell pair;

determine whether the determined handover performance satisfies a handover performance setting, and if so, process the handover information from the memory to determine a handover oscillation rate or a handover cost associated with the cell pair;

compare the determined handover oscillation rate or the determined handover cost with a predetermined target handover oscillation rate or a predetermined target handover cost, respectively; and

regulate one or more handover parameters associated with at least one of the cells in the cell pair based on the comparison.

16. The apparatus of claim 15, wherein the electronic data processing circuitry is arranged to:

refrain from adjusting the one or more handover parameters or revert to the one or more handover parameters prior to adjustment if the determined handover performance not satisfy the handover performance setting.

17. The apparatus in claim 16, wherein the handover performance is a handover failure rate or a handover success rate.

18. The apparatus in claim 17, wherein the electronic data processing circuitry is arranged to compare the handover performance to a threshold.

19. The apparatus of claim 15, wherein the electronic data processing circuitry is arranged to:

determine a difference between the determined handover oscillation rate and the target handover oscillation rate or between the determined handover cost and the target handover cost, and

adjust one or more handover parameters associated with at least one of the cells in the cell pair to reduce the difference.

22. The apparatus of claim 19, wherein the information includes a direction of each handover that has actually occurred between one or more pairs of cells.