Method and system for cell selection/reselection taking into account congestion status of target cell in a mobile communication system

• US 20060035662A1
• Filed: 08/11/2005
• Published: 02/16/2006
• Est. Priority Date: 08/11/2004
• Status: Abandoned Application

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Jeong, Kyeong-In, Lee, Kook-Heui
• Application Number:
  US11/201,172
• Publication Number:
  US 20060035662A1
• Time in Patent Office: Days
• US Class Current: 455/525
• CPC Class Codes: H04W 48/06 based on traffic conditions

Abstract

A method and system for ensuring continuous service reception at a UE for each access class by carrying out cell selection/reselection taking into account the congestion status of a target cell in a mobile communication system. The method and system takes into account the congestion status of a target cell, and the UE selects/reselects the target cell of which the access class barred list indicates the access class of the UE as not barred. For cell selection/reselection, the UE can refer to the access class barred list of the target cell all the time, or only when it is necessary to access the network for a specific service indicated by an upper layer.

Claims

1. A cell selection method in a user equipment (UE) in a mobile communication system, comprising the steps of:

measuring a radio strength of a cell being a candidate for cell selection;

determining whether the radio strength satisfies a predetermined threshold;

receiving system information including an access class barred list from a Node B that manages the cell if the radio strength satisfies the threshold; and

selecting the cell according to the access class barred list.

2. The cell selection method of claim 1, further comprising the step of:

determining whether to perform the step of selecting the cell by referring to cell status information and information about a public land mobile network (PLMN) to which the cell belongs in the system information.

3. The cell selection method of claim 1, further comprising the step of:

selecting a cell for an emergency service if no cells to be measured for cell selection exist or if the access class barred list indicates that the cell is not accessible to the UE.

4. A cell reselection method in a user equipment (UE) in a mobile communication system, comprising the steps of:

measuring radio strengths of cells being candidates for cell reselection;

determining whether the radio strengths satisfy a predetermined threshold;

prioritizing to rank cells that satisfy the threshold;

receiving system information including an access class barred list from a Node B managing a cell that satisfies the threshold and ranks highest; and

selecting the cell if the system information allows the UE to select the cell and the access class barred list does not indicate that the cell is not accessible to the UE.

5. The cell reselection method of claim 4, further comprising the step of:

determining whether to perform the step of selecting the cell by referring to cell status information and information about a public land mobile network (PLMN) to which the cell belongs in the system information.

6. The cell reselection method of claim 4, further comprising the steps of:

selecting a cell with a second highest ranking if the system information does not allow the UE to select the cell; and

receiving system information from a Node B that manages the cell with the second highest ranking.

7. The cell reselection method of claim 4, further comprising the step of:

selecting a cell for an emergency service if no cells exist as candidates for cell reselection.

8. A cell selection method in a user equipment (UE) that distinguishes a plurality of service domains for cell selection in a mobile communication system, comprising the steps of:

measuring a radio strength of a cell being a candidate for cell selection;

determining whether the radio strength satisfies a predetermined threshold;

receiving system information including access class barred lists for the service domains from a Node B that manages the cell if the radio strength satisfies the threshold; and

selecting the cell if the access class barred lists indicate that the cell is accessible to the UE in the service domains.

9. The cell selection method of claim 8, further comprising the step of:

determining whether to perform the step of selecting the cell by referring to cell status information and information about a public land mobile network (PLMN) to which the cell belongs in the system information.

10. The cell selection method of claim 8, wherein the service domains comprise a circuit service (CS) domain and a packet service (PS) domain.

11. The cell selection method of claim 10, further comprising the steps of:

determining whether there is a cell which an access class barred list of the CS domain indicates as accessible in the CS domain if no cells to be measured for cell selection exist or if no cells are accessible in all of the service domains; and

selecting the cell accessible in the CS domain.

12. The cell selection method of claim 11, further comprising the steps of:

determining whether there is a cell which an access class barred list of the PS domain indicates as accessible in the PS domain in the absence of a cell accessible in the CS domain; and

selecting the cell accessible in the PS domain.

13. The cell selection method of claim 12, further comprising the step of:

selecting a cell for an emergency service if the access class barred lists indicate no cells as accessible in one of the PS domain and the CS domain.

14. A cell reselection method in a user equipment (UE) that distinguishes a plurality of service domains for cell reselection in a mobile communication system, comprising the steps of:

measuring radio strengths of cells being candidates for cell reselection;

determining whether the radio strengths satisfy a predetermined threshold;

prioritizing to rank cells that satisfy the threshold;

receiving system information including access class barred lists for the service domains from a Node B managing a cell with a highest ranking among the prioritized cells; and

selecting the cell if the access class barred lists indicate the cell as accessible in all of the service domains.

15. The cell reselection method of claim 14, further comprising the step of:

determining whether to perform the step of selecting the cell by referring to cell status information and information about a public land mobile network (PLMN) to which the cell belongs in the system information.

16. The cell reselection method of claim 14, wherein the service domains comprise a circuit service (CS) domain and a packet service (PS) domain.

17. The cell reselection method of claim 16, further comprising the steps of:

selecting a cell with a second highest ranking if the system information does not allow the UE to select the cell or if the access class barred lists indicate the cell as not accessible in all of the service domains; and

receiving system information from a Node B that manages the cell with the second highest ranking.

18. The cell reselection method of claim 17, further comprising the steps of:

determining whether there is a cell of which the access class barred list of a service domain with an existing radio access bearer (RAB) indicates as accessible in the absence of the cell with the second highest ranking; and

selecting the cell.

19. The cell reselection method of claim 18, further comprising the steps of:

determining whether there is a cell of which the access class barred list of the CS domain indicates as accessible in the absence of a cell accessible in the service domain with the existing RAB; and

selecting the cell.

20. The cell reselection method of claim 18, further comprising the steps of:

determining whether there is a cell of which the access class barred list of the PS domain indicates as accessible in the absence of a cell accessible in the CS domain; and

selecting the cell.

21. The cell reselection method of claim 20, further comprising the step of:

selecting a cell for an emergency service in the absence of a cell accessible in one of the CS and PS domains according to access class barred lists of the cell.

22. A cell reselection method in a user equipment (UE) that distinguishes a plurality of service domains for cell reselection in a mobile communication system, comprising the steps of:

receiving an indication indicating starting of a service in one of the service domains from an upper layer;

determining whether the access class barred list of the indicated service domain indicates a serving cell as accessible;

measuring radio strengths of cells being candidates for cell reselection if the serving cell is not indicated as accessible;

determining whether the radio strengths satisfy a predetermined threshold;

prioritizing to rank cells that satisfy the threshold;

receiving system information including access class barred lists for the plurality of service domains from a Node B managing a cell with a highest ranking among the prioritized cells; and

selecting the cell if the access class barred list of the indicated service domain indicates the cell as accessible.

23. The cell reselection method of claim 22, further comprising the step of:

determining whether to perform the step of selecting the cell by referring to cell status information and information about a public land mobile network (PLMN) to which the cell belongs in the system information.

24. The cell reselection method of claim 22, further comprising the step of:

maintaining the serving cell in the absence of a cell that satisfies the threshold.

25. The cell reselection method of claim 22, further comprising the steps of:

selecting a cell with a second highest ranking if the system information does not allow the UE to select the cell or if the access class barred list of the indicated service domain indicates the cell as not accessible; and

receiving system information from a Node B that manages the cell with the second highest ranking.

26. The cell reselection method of claim 22, further comprising the steps of:

determining whether the UE has a radio access bearer (RAB) connection in a service domain other than the indicated service domain; and

selecting the cell if the UE has the RAB connection in the service domain and the access class barred lists of all the service domains indicate the cell as accessible.

27. The cell reselection method of claim 26, further comprising the steps of:

comparing a service associated with the RAB with the service in the indicated service domain if the UE has the RAB connection in the service domain and if the access class barred lists of all the service domains indicate the cell as not accessible; and

selecting a cell of which the access class barred list of the indicated service domain indicates the cell as accessible if the service in the indicated service domain has a higher priority level than the service associated with the RAB.

28. The service reselection method of claim 27, further comprising the step of:

maintaining the serving cell if the service in the indicated service domain does not have a higher priority level than the service associated with the RAB.

29. The service reselection method of claim 22, further comprising the step of:

accessing the indicated service domain in the serving cell if the access class barred list of the indicated service domain of the serving cell indicates the serving cell as accessible.

30. A mobile communication system comprising:

a user equipment (UE) for measuring radio strengths of cells being candidates for cell reselection, determining whether the radio strengths satisfy a predetermined threshold, prioritizing to rank cells that satisfy the threshold, receiving system information including access class barred lists for a plurality of service domains from a Node B managing a cell with a highest ranking among the prioritized cells, and selecting the cell if the access class barred lists indicate the cell as accessible in all of the service domains; and

at least one Node B for managing at least one cell that the UE can access wirelessly and for transmitting the system information to the UE.

31. The mobile communication system of claim 30, wherein if no cells are accessible in all of the service domains, the UE is configured to determine whether there is a cell of which the access class barred list of at least one service domain indicates the cell as accessible, and select the cell in the presence of a cell accessible in the at least one service domain.

32. The mobile communication system of claim 30, wherein in the absence of a cell accessible in the at least one service domain, the UE is configured to select a cell for an emergency service.

33. The mobile communication system of claim 30, wherein the UE is configured to determine whether there is a cell of which the access class barred list of a service domain indicated for starting of a service by an upper layer indicates the cell as accessible, and select the cell in the presence of a cell accessible in the indicated service domain.

34. The mobile communication system of claim 30, wherein in the absence of a cell accessible in all of the service domains, the UE is configured to determine which service has a higher priority level between the service indicated by the upper layer and a service associated with an existing radio access bearer (RAB), determine whether there is a cell of which the access class barred list of a service with the higher priority level indicates the cell as accessible, and select the cell in the presence of the cell accessible in the service domain of the higher-priority service.