Access procedure for call re-establishment
An access procedure for call re-establishment is provided. In a first method, a mobile station, in at least some instances of detecting radio link failure, attempts call re-establishment on multiple cells concurrently. In a second method, a mobile station performs a first random access channel procedure when the mobile station is not aware of at least two cells with enabled call re-establishment, and performs a second random access channel procedure when the mobile station is aware of at least two cells with enabled call re-establishment.
1. A method in a mobile station, the method comprising:
in at least some instances of detecting radio link failure, attempting call re-establishment on multiple cells concurrently;
wherein attempting call re-establishment on multiple cells concurrently comprises transmitting a request for call re-establishment to a first cell and then transmitting a request for call re-establishment to a second cell without first waiting to see if there is a positive response to the request for call re-establishment to the first cell.
2. The method of claim 1 comprising:
performing received signal level measurements for a set of cells;
selecting the multiple cells based at least on received signal level measurements taken on the set of cells.
3. The method of claim 1 further comprising:
determining a set of candidate cells according to a first criteria or criterion;
selecting the multiple cells from the set of candidate cells according to a second criteria or criterion.
4. The method of claim 3 wherein:
determining a set of candidate cells according to a first criteria or criterion comprise:
performing received signal level measurements for a set of cells;
including in the set of candidate cells a cell of the set of cells with a highest averaged received signal level;
including in the set of candidate cells at least one cell of the set of cells with a next highest average received signal levels.
5. The method of claim 3 wherein:
determining a set of candidate cells according to a first criteria or criterion comprise:
performing received signal level measurements for a set of cells;
including in the set of candidate cells a cell of the set of cells with a highest averaged received signal level;
including in the set of candidate cells at least one cell of the set of cells with a next highest average received signal levels if the next highest average received signal level is within a defined amount of the highest average received signal level.
6. A method in a mobile station, the method comprising:
in at least some instances of detecting radio link failure, attempting call re-establishment on multiple cells concurrently;
determining a set of candidate cells according to a first criteria or criterion;
selecting the multiple cells from the set of candidate cells according to a second criteria or criterion;
wherein selecting the multiple cells from the set of candidate cells according to a second criteria or criterion comprises selecting the multiple cells subject to at least one of:
a first requirement that call re-establishment for a candidate cell may only be requested if the mobile station has a set of parameters required to perform cell reselection to the candidate cell, the candidate cell is suitable, and call re-establishment is allowed;
a second requirement that the timing of expected corresponding responses from the multiple cells is such that the mobile station will be able to receive a response on a first candidate cell of the multiple cells notwithstanding monitoring for a response from a second candidate cell of the multiple cells.
7. The method of claim 1 wherein:
in at least some instances of detecting radio link failure, attempting call re-establishment on multiple cells concurrently comprises:
transmitting a respective at least one request for call re-establishment to each of at least one cell;
in the event no positive response is received to any of the respective at least one request for call re-establishment to each of at least one cell, concurrently transmitting a respective at least one request for call re-establishment to each of at least two cells.
8. The method of claim 7 wherein transmitting a respective at least one request for call re-establishment to each of at least one cell consists of transmitting one request for call re-establishment to one cell.
9. The method of claim 3 further comprising:
ranking the candidate cells using a ranking scheme;
using the ranking scheme to select the multiple cells.
10. The method of claim 9 wherein the ranking scheme is a function of at least one of:
received signal quality;
received signal strength;
received signal strength proximity for multiple cells;
timing of first available opportunity to transmit a request for call re-establishment to a given cell.
11. The method of claim 1 wherein:
attempting call re-establishment on a cell comprises transmitting a Channel Request message with cause code Call Re-establishment on a Random Access Channel of the cell.
12. The method of claim 1 wherein attempting call re-establishment on a cell comprises:
attempting to receive a CCCH (common control channel) of the cell.
13. The method of claim 12 further comprising:
if one or more Immediate Assignments on the CCCH of any of the cells to which Channel Request was transmitted are received, proceeding with further steps to complete re-establishment.
14. The method of claim 13 wherein proceeding with further steps to complete re-establishment comprises proceeding with further steps to complete call re-establishment with the cell from which an earliest of said one or more Immediate Assignment messages was received.
15. A mobile station configured to implement the method of claim 1 .
16. A computer readable medium having computer executable instructions stored thereon which when executed by a mobile station cause the mobile station to execute the method of claim 1 .
17. A method in a mobile station comprising:
performing a first random access channel procedure when the mobile station is not aware of at least two cells with enabled call re-establishment;
performing a second random access channel procedure when the mobile station is aware of at least two cells with enabled call re-establishment.
18. The method of claim 17 wherein the second random access channel procedure is any procedure that allows attempts to be made on multiple cells sooner than allowed by the first random access channel procedure.