Methods and apparatus for use in initiating vertical handover based on comparative evaluation of WLAN and WWAN signal qualities

1. A method in a mobile communication device for use in initiating vertical handover of a voice or a data call between a wireless local area network (WLAN) and a wide area wireless network (WWAN), the method comprising:

performing communication operations for maintaining the voice or the data call via the WLAN or the WWAN;

during the voice or the data call:

identifying a WLAN signal quality value of signals with the WLAN;

identifying a WWAN signal quality value of signals with the WWAN;

calculating a signal indicator value from both of the WLAN and WWAN signal quality values by calculating a comparative evaluation between the relative WLAN and the WWAN signal quality values;

wherein calculating the signal indicator value is based on a ratio of the WLAN and the WWAN signal quality values; and

wherein the initiating the vertical handover of the voice or the data call between the WLAN and the WWAN is in response to changes in the ratio over time; and

initiating vertical handover of the voice or the data call between the WLAN and the WWAN based on the signal indicator value.

2. The method of claim 1 , further comprising: wherein calculating the comparative evaluation further comprises finding a difference between the WLAN signal quality value and the WWAN signal quality value; and

wherein the initiating the vertical handover for the voice or the data call between the WLAN and the WWAN is further in response to changes in the difference over time.

3. The method of claim 1 , wherein the WWAN comprises a cellular telecommunications network.

4. The method of claim 1 , wherein the WLAN comprises an IEEE 802.11 network.

5. The method of claim 1 , wherein the WLAN signal quality comprises a WLAN radio signal strength indicator (RSSI) value and the WWAN signal quality comprises a WWAN RSSI value.

6. The method of claim 1 , further comprising:

wherein the performing the communication operations comprises performing the communication operations for maintaining the voice or the data call via the WLAN; and

wherein the initiating the vertical handover comprises initiating vertical handover of the voice or the data call from the WLAN to the WWAN based on the comparative evaluation of WLAN and WWAN signal quality values.

7. The method of claim 1 , further comprising:

wherein the performing the communication operations comprises performing the communication operations for maintaining the voice or the data call via the WWAN; and

wherein the initiating the vertical handover comprises initiating vertical handover of the voice or the data call from the WWAN to the WLAN based on the comparative evaluation of WLAN and WWAN signal quality values.

8. The method of claim 1 , which is embodied as computer instructions stored in a non-transitory computer readable medium and executable by one or more processors of the mobile device for performing the method.

9. The method of claim 1 , further comprising:

obtaining signal strength measurements of the WWAN taken at different times during a period of time;

obtaining signal strength measurements of the WLAN taken at different times during the period of time; and

calculating the signal indicator value over the period of time;

wherein the initiating the vertical handover of the voice or the data call between the WLAN and the WWAN is in response to an increasing or decreasing trend in the signal indicator value over time.

10. The method of claim 1 , wherein said initiating the vertical handover for the voice or the data call between the WLAN and the WWAN is further in response to the signal indicator value being greater than a predetermined threshold.

11. A mobile communication device, comprising:

one or more processors;

a WLAN transceiver coupled to the one or more processors and being operative for communications with a wireless local area network (WLAN);

a WWAN transceiver coupled to the one or more processors and being operative for communications with a wireless wide area network (WWAN);

the one or more processors being operative to:

perform communication operations for maintaining a voice or a data performing communication operations for maintaining the voice or the data call via the WLAN or the WWAN;

during the voice or the data call:

identify a WLAN signal quality value of signals with the WLAN,

identify a WWAN signal quality value of signals with the WWAN,

calculate a signal indicator value from both of the WLAN and WWAN signal quality values by calculating a comparative evaluation between the WLAN and the WWAN signal quality values,

wherein said calculating of the signal indicator value is based on a ratio of the WLAN and the WWAN signal quality values, and wherein said initiating the vertical handover of the voice or the data call between the WLAN and the WWAN is in response to changes in the ratio over time; and

initiate vertical handover of the voice or the data call between the WLAN and the WWAN based on the signal indicator value.

12. The mobile communication device of claim 11 , wherein said calculating of the comparative evaluation further comprises finding a difference between the WLAN signal quality value and the WWAN signal quality value, and

wherein said initiating the vertical handover for the voice or the data call between the WLAN and the WWAN is further in response to changes in the difference over time.

13. The mobile communication device of claim 11 , wherein the WWAN comprises a cellular telecommunications network.

14. The mobile communication device of claim 11 , wherein the WLAN comprises an IEEE 802.11 network.

15. The mobile communication device of claim 11 , wherein the WLAN signal quality comprises a WLAN radio signal strength indicator (RSSI) value and the WWAN signal quality comprises a WWAN RSSI value.

16. The mobile communication device of claim 11 , wherein the one or more processors are further operative to perform communication operations by performing the communication operations for maintaining the voice or the data call via the WLAN, and initiate the vertical handover by initiating vertical handover of the voice or the data call from the WLAN to the WWAN based on the comparative evaluation of WLAN and WWAN signal quality values.

17. The mobile communication device of claim 11 , wherein the one or more processors are further operative to perform the communication operations by performing the communication operations for maintaining the voice or the data call via the WWAN, and initiate the vertical handover by initiating vertical handover of the voice or the data call from the WWAN to the WLAN based on the comparative evaluation of WLAN and WWAN signal quality values.

18. The mobile communication device of claim 11 , wherein the one or more processors are further operative to:

obtain signal strength measurements of the WWAN taken at different times during a period of time;

obtain signal strength measurements of the WLAN taken at different times during the period of time; and

calculate the signal indicator value over the period of time;

wherein the initiating the vertical handover of the voice or the data call between the WLAN and the WWAN is in response to an increasing or decreasing trend in the signal indicator value over time.