Power-aware selection of radio access technology

1. A method of operating a multi-mode wireless communications device, comprising:

selecting a desired operating mode from a plurality of possible operating modes including at least an idle mode, a user-initiated speech mode and a network-initiated speech mode;

scanning one or more frequency bands to determine a set of available radio access technologies that support the desired operating mode;

for each radio access technology (RAT), determining RAT-specific system parameters including a discontinuous cycle parameter and RAT-specific operating conditions;

determining an energy consumption metric as a function of the discontinuous cycle parameter for the desired operating mode and the RAT-specific operating conditions; and

selecting a preferred RAT requiring the lowest energy consumption by the device based on the energy consumption metric for the desired operating mode, wherein said selecting of the preferred RAT is a function of the desired operating mode.

2. The method of claim 1 , wherein the RAT-specific operating conditions include a RAT-specific path loss and wherein evaluating RAT-specific system parameters and RAT-specific operating conditions includes evaluating said RAT-specific path loss.

3. The method of claim 1 , wherein the discontinuous cycle parameter is a discontinuous reception (DRX) cycle parameter.

4. The method of claim 1 , wherein the discontinuous cycle parameter is a discontinuous transmission (DTX) cycle parameter.

5. The method of claim 1 , wherein the RAT-specific system parameters for one or more RATs include a cell deployment density and wherein determining an energy consumption metric comprises determining the energy consumption metric as a function of the cell deployment density.

6. The method of claim 1 , further comprising determining a mobility parameter for the mobile wireless communications device, and wherein determining the energy consumption metric is further based on the mobility parameter.

7. The method of claim 1 , wherein the RAT-specific system parameters for one or more RATs include a RAT-specific frequency band.

8. The method of claim 7 , wherein determining an energy consumption metric comprises calculating a RAT-specific transmitter energy consumption estimate as a function of the RAT-specific frequency band and determining the energy consumption metric as a function of the RAT-specific transmitter energy consumption estimate.

9. The method of claim 8 , further comprising determining a data throughput requirement for the desired operating mode, and wherein calculating a RAT-specific transmitter energy consumption estimate comprises calculating the RAT-specific transmitter energy consumption estimate as a function of the data throughput requirement.

10. The method of claim 1 , wherein the desired operating mode is an idle mode, and wherein selecting a preferred RAT comprises identifying the available RAT requiring the lowest energy consumption in the idle mode and selecting that RAT for idle-mode camping, and further comprising camping on the preferred RAT.

11. The method of claim 10 , wherein the preferred RAT is different from a current RAT, the method further comprising de-registering from the current RAT and registering at the preferred RAT, before camping on the preferred RAT.

12. The method of claim 1 , wherein the desired mode is a mobile-initiated speech mode, and wherein selecting a preferred RAT comprises identifying the available RAT requiring the lowest energy consumption in the mobile-initiated speech mode and selecting that RAT for cell reselection, and further comprising initiating a cell reselection to the preferred RAT.

13. The method of claim 12 , wherein initiating a cell reselection to the preferred RAT comprises de-registering from a current RAT and registering at the preferred RAT.

14. The method of claim 1 , wherein the desired mode is a network-initiated speech mode, and wherein selecting a preferred RAT comprises identifying the available RAT requiring the lowest energy consumption in the network-initiated speech mode and selecting that RAT, and further comprising requesting an inter-RAT handover to the selected RAT.

15. The method of claim 1 , wherein the desired mode is an ongoing voice call, further comprising: when the preferred RAT is different from a RAT currently used by the multi-mode wireless communication device such that an inter-RAN handover would be required, determining whether the preferred RAT offers an improvement in energy consumption that meets a threshold requirement, and selectively requesting an inter-RAT handover based on that determination.

16. A multi-mode wireless communications device for operation with a plurality of radio access technologies (RATs), comprising:

a multi-mode radio section configured to scan one or more frequency bands to determine a set of available RATs supporting a desired operating mode and to determine one or more RAT-specific operating conditions; and

a control section configured to:

select the desired operating mode from a plurality of possible operating modes including at least an idle mode, a user-initiated speech mode and a network-initiated speech mode;

determine RAT-specific system parameters including a discontinuous cycle parameter and the RAT-specific operating conditions for each available RAT;

determine an energy consumption metric as a function of the discontinuous cycle parameter for the desired operating mode and the RAT-specific operating conditions; and

select the RAT requiring the lowest energy consumption by the device for the desired operating mode based on the energy consumption metric, as a function of the desired operating mode.

17. The multi-mode wireless communications device of claim 16 , wherein the one or more RAT-specific operating conditions include a RAT-specific path loss.

18. The multi-mode wireless communications device of claim 16 , wherein the control section comprises a look-up table comprising energy consumption parameters associated with the desired operating mode and with the available RATs, and wherein the control section is configured to evaluate the RAT-specific system parameters and the RAT-specific operating conditions using the energy consumption parameters.

19. The multi-mode wireless communications device of claim 18 , wherein the control section is further configured to update the energy consumption parameters in the look-up table responsive to a software upgrade adding or modifying an access technology capability.

20. The multi-mode wireless communications device of claim 16 , wherein the control section is further configured to determine a mobility parameter for the mobile wireless communications device, and wherein the control section is configured to evaluate the RAT-specific system parameters and the RAT-specific operating conditions using the mobility parameter.

21. The multi-mode wireless communications device of claim 16 , wherein the RAT-specific system parameters include a RAT-specific frequency band, and wherein the control section is configured to calculate a RAT-specific transmitter energy consumption requirement for each RAT as a function of the RAT-specific frequency band and to evaluate the RAT-specific system parameters and the RAT-specific operating conditions using the RAT-specific transmitter energy consumption requirement.

22. The multi-mode wireless communications device of claim 16 , wherein the control section is further configured to initiate access to the preferred RAT.

23. The multi-mode wireless communications device of claim 22 , wherein the control section is configured to initiate access to the selected RAT by initiating a cell-reselection to the preferred RAT.

24. The multi-mode wireless communications device of claim 22 , wherein the control section is configured to initiate access to the selected RAT by requesting an inter-RAT handover to the preferred RAT.