Method for inter-radio access technology cell reselection
A method for performing cell reselection first determines a current cell selection quality value. The cell selection quality value is compared to a predetermined threshold. Measurements of neighboring cells are taken if the cell selection quality value is less than or equal to the predetermined threshold. Measurements can be taken of intra-frequency cells, inter-frequency cells, and inter-radio access technology cells. If a neighboring cell is found that is better than the current cell based on the measurements, then the better neighbor cell is reselected to.
1. A method for performing cell reselection implemented in a wireless transmit receive unit (WTRU), the method comprising:
receiving priority information in a current cell associated with a current radio access technology (RAT), the priority information indicating a cell priority of an inter-RAT cell associated with a candidate RAT relative to the current cell associated with the current RAT;
determining to perform quality measurements of the inter-RAT cell associated with the candidate RAT on a first condition that the inter-RAT cell associated with the candidate RAT has a higher priority than the current cell associated with the current RAT; and
determining to perform quality measurements of the inter-RAT cell associated with the candidate RAT on a second condition that:
the inter-RAT cell associated with the candidate RAT does not have a higher priority than the current cell associated with the current RAT, and
a cell selection value of the current cell is less than or equal to a predetermined threshold.
2. The method of claim 1 , wherein at least one of: the current cell or the inter-RAT cell is a long term evolution (LTE) cell in an evolved universal terrestrial radio access network (E-UTRAN).
3. The method of claim 1 , wherein the priority information includes frequency information for the inter-RAT cell.
4. The method of claim 1 , further comprising reselecting to the inter-RAT cell based on the quality measurement.
5. The method of claim 1 , further comprising:
reselecting to the inter-RAT cell based on a signal strength measured for the inter-RAT cell being greater than a configured threshold for a predetermined period of time on condition that it is determined that the inter-RAT cell associated with the candidate RAT has a higher priority than the current cell associated with the current RAT.
6. The method of claim 1 , wherein the priority information is received via dedicated signaling.
7. The method of claim 1 , wherein the priority information is received via broadcast signaling.
8. The method of claim 1 , further comprising determining an order for measuring a plurality of cells associated with a plurality of RATs based on the priority information.
9. The method of claim 1 , further comprising:
reselecting to the inter-RAT cell based at least in part on there being no cells in a higher priority RAT that meet cell reselection requirements on condition that it is determined that the inter-RAT cell associated with the candidate RAT does not have a higher priority than the current cell associated with the current RAT.
10. The method of claim 1 , further comprising:
reselecting to the inter-RAT cell based at least in part on the inter-RAT cell being higher ranked than the current cell on condition that it is determined that the inter-RAT cell associated with the candidate RAT does not have a higher priority than the current cell associated with the current RAT.
11. A wireless transmit receive unit (WTRU) comprising:
a receiver; and
a processor configured to:
receive priority information in a current cell associated with a current radio access technology (RAT), the priority information indicating a cell priority of an inter-RAT cell associated with a candidate RAT and relative to the current cell associated with the current RAT; and
determine to perform quality measurements of the inter-RAT cell associated with the candidate RAT on a first condition that the inter-RAT cell associated with the candidate RAT has a higher priority than the current cell associated with the current RAT; and
determine to perform quality measurements of the inter-RAT cell associated with the candidate RAT based on a second condition that:
the inter-RAT cell associated with the candidate RAT does not have a higher priority than the current cell associated with the current RAT, and
a cell selection value of the current cell is less than or equal to a predetermined threshold.
12. The WTRU of claim 11 , wherein at least one of: the current cell or the inter-RAT cell is a long term evolution (LTE) cell in an evolved universal terrestrial radio access network (E-UTRAN).
13. The WTRU of claim 11 , wherein the priority information includes frequency information for the inter-RAT cell.
14. The WTRU of claim 11 , wherein the processor is further configured to reselect to the inter-RAT cell based on the quality measurement.
15. The WTRU of claim 11 , wherein the processor is further configured to reselect to the inter-RAT cell based on a signal strength measured for the inter-RAT cell being greater than a configured threshold for a predetermined period of time on condition that it is determined that the inter-RAT cell associated with the candidate RAT has a higher priority than the current cell associated with the current RAT.
16. The WTRU of claim 11 , wherein the priority information is received via dedicated signaling.
17. The WTRU of claim 11 , wherein the priority information is received via broadcast signaling.
18. The WTRU of claim 11 , wherein the processor is further configured to determine an order for measuring a plurality of cells associated with a plurality of RATs based on the priority information.
19. The WTRU of claim 11 , wherein the processor is further configured to reselect to the inter-RAT cell based at least in part on there being no cells in a higher priority RAT that meet cell reselection requirements on condition that it is determined that the inter-RAT cell associated with the candidate RAT does not have a higher priority than the current cell associated with the current RAT.
20. The WTRU of claim 11 , wherein the processor is further configured to reselect to the inter-RAT cell based at least in part on the inter-RAT cell being higher ranked than the current cell on condition that it is determined that the inter-RAT cell associated with the candidate RAT does not have a higher priority than the current cell associated with the current RAT.