Storing of neighbour cell information for rapid recovery in case of handover failure

• US 8,886,193 B2
• Filed: 04/01/2011
• Issued: 11/11/2014
• Est. Priority Date: 05/11/2010
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Lindoff, Bengt, Dimou, Konstantinos, Muller, Walter
• Primary Examiner(s): Brandt, Christopher M
• Application Number:
  US13/696,190
• Publication Number:
  US 20130059587A1
• Time in Patent Office: 1,320 Days
• Field of Search: 455/336, 370/331
• US Class Current: 455/436
• CPC Class Codes: H04W 36/0058 Transmission of hand-off measurement information, e.g. measurement reports
• CPC Class Codes: H04W 36/0072 of resource information of target access point
• CPC Class Codes: H04W 36/0079 in case of hand-off failure or rejection
• CPC Class Codes: H04W 36/00835 Determination of neighbour cell lists
• CPC Class Codes: H04W 36/0085 Hand-off measurements

Abstract

This disclosure teaches a method and apparatus for radio link failure recovery by a User Equipment (UE). The example UE includes one or more controllers that are configured to store cell access information for a target cell that is the target for an impending handover from a serving cell, and for a backup cell that is selected by the UE from among a set of neighboring cells that includes the target cell. Advantageously, in case the handover to the target cell fails, the one or more controllers are configured to retrieve the cell access information stored for the backup cell and to use that information for re-establishing connection in the backup cell. The UE selects the backup cell, for example, as the neighboring cell other than the target cell having the strongest signal conditions with respect to the UE.

Claims

1. A method in a User Equipment (UE) of radio link failure recovery comprising:

selecting a backup cell from among a set of neighbouring cells that includes a target cell, wherein the backup cell is not the target cell and is to be used for reconnecting to a cellular telecommunication network in case an impending handover of the UE from a serving cell to the target cell fails;

storing cell access information for the target and backup cells, said cell access information providing the UE with information needed for establishing a connection to the cellular telecommunication network in either the target cell or the backup cell; and

if the handover to the target cell fails, using the stored cell access information to reestablish connection with the cellular telecommunication network in the backup cell.

2. The method of claim 1, wherein the cell access information comprises random access channel information, including synchronization information for the backup cell.

3. The method of claim 1, wherein storing the cell access information comprises storing a master information block (MIB) transmitted for the backup cell, where the MIB comprises at least one of:

configuration information for a Physical Hybrid Automatic Repeat Request Indicator Channel (PHICH) in the backup cell; and

configuration and system frame number information enabling the UE to receive signaling on a Physical Downlink Control Channel (PDCCH) in the backup cell, and thereby enabling the UE to retrieve information provided in system information blocks (SIBs) transmitted in the backup cell.

4. The method of claim 1, further comprising measuring signal conditions for the serving and neighbouring cells before and/or in conjunction with the handover being attempted from the serving cell to the target cell.

5. The method of claim 4, wherein measuring signal conditions includes performing cell searching with respect to the neighbouring cells and determining at least one of Reference Signal Received Power (RSRP) and Reference Signal Received Quality (RSRQ) for the neighbouring cells.

6. The method of claim 1, further comprising selecting the backup cell from among the neighbouring cells, not including the target cell, based on signal conditions measured by the UE for the neighbouring cells in advance of or in conjunction with the handover being attempted from the serving cell to the target cell.

7. The method of claim 1, further comprising determining an amount of cell access information to be stored, based on a provided quality of service.

8. The method of claim 1, further comprising storing the cell access information in a Random Access Memory (RAM) in the UE.

9. The method of claim 1, further comprising selecting the backup cell as the neighbouring cell other than the target cell having the strongest signal conditions with respect to the UE.

10. The method of claim 1, further comprising determining an amount of cell access information to store for the backup cell in dependence on the type of communication service being provided to the UE, where the amount of cell access information stored determines whether a recovery speed for the provided service is optimized or a bandwidth of the provided service is optimized.

11. A user equipment (UE) comprising:

a transceiver configured to receive signals from and transmit signals to one or more base stations in a cellular telecommunication network; and

one or more controllers operatively associated with the transceiver and configured to;

select a backup cell from among a set of neighbouring cells that includes a target cell, wherein the backup cell is not the target cell and is to be used for reconnecting to a cellular telecommunication network in case an impending handover of the UE from a serving cell to the target cell fails;

store cell access information for the target and backup cells, said cell access information providing the UE with information needed for establishing a connection to the cellular telecommunication network in either the target cell or the backup cell; and

if the handover to the target cell fails, use the stored cell access information to reestablish connection with the cellular telecommunication network in the backup cell.

12. The UE of claim 11, wherein the cell access information comprises random access channel information, including synchronization information for the backup cell.

13. The UE of claim 11, wherein the stored cell access information comprises a master information block (MIB) transmitted for the backup cell, where the MIB comprises at least one of:

configuration information for a Physical Hybrid Automatic Repeat Request Indicator Channel (PHICH) in the backup cell; and

configuration and system frame number information enabling the UE to receive signaling on a Physical Downlink Control Channel (PDCCH) in the backup cell, and thereby enabling the UE to retrieve information provided in system information blocks (SIBs) transmitted in the backup cell.

14. The UE of claim 11, further comprising a monitoring unit configured to measure signal conditions for the serving and neighbouring cells before and/or in conjunction with the handover being attempted from the serving cell to the target cell.

15. The UE of claim 14, wherein the UE is configured to perform cell searching with respect to the neighbouring cells and determine, via said monitoring unit, at least one of Reference Signal Received Power (RSRP) and Reference Signal Received Quality (RSRQ) for the neighbouring cells.

16. The UE of claim 11, wherein the one or more controllers are configured to select the backup cell from among the neighbouring cells, not including the target cell, based on signal conditions measured by the UE for the neighbouring cells in advance of or in conjunction with the handover being attempted from the serving cell to the target cell.

17. The UE of claim 11, wherein the one or more controllers are configured to determine an amount of cell access information to be stored, based on a provided quality of service.

18. The UE of claim 11, wherein the one or more controllers are configured to store the cell access information in a Random Access Memory (RAM) in the UE.

19. The UE of claim 11, wherein the one or more controllers are configured to select the backup cell as the neighbouring cell other than the target cell having the strongest signal conditions with respect to the UE.

20. The UE of claim 11, wherein the one or more controllers include a communication controller that is configured to send a handover measurement report to the cellular telecommunication network upon the handover being triggered, said handover measurement report including signal conditions measured by the UE for the serving and neighbouring cells, and is further configured to store the cell access information, and wherein the one or more controller include a radio link failure recovery controller that is configured to retrieve the stored cell access information for use in reestablishing the connection to the cellular telecommunication network in the backup cell.

21. The UE of claim 11, wherein the one or more controllers are configured to determine an amount of cell access information to store for the backup cell in dependence on the type of communication service being provided to the UE, where the amount of cell access information stored determines whether a recovery speed for the provided service is optimized or a bandwidth of the provided service is optimized.