Reducing power consumption in a mobile communication device in response to motion detection

1. A method of reducing power consumption in a mobile communication device that includes a transceiver module and that is proximate to a wireless local area network (WLAN) having a multitude of wireless access points, the method comprising:

passively receiving first and second WLAN beacon signals from each of a plurality of selected access points;

determining, from the first beacon signals, a first received signal strength indicator (RSSI) value for each of the selected access points;

determining, from the second beacon signals, a second RSSI value for each of the selected access points;

calculating, for each of the selected access points, a variation between the first and second RSSI values for the selected access point;

comparing each variation in RSSI values with a predetermined value to detect motion of the device;

ascertaining whether the number of variations in RSSI values that exceeds the predetermined number is greater than a trigger number, wherein the trigger number indicates a minimum number of the selected access points from which motion of the device is detected; and

selectively enabling the transceiver module in response to the ascertaining.

2. The method of claim 1 , wherein the transceiver module broadcasts probe signals when enabled and does not broadcast any signals when disabled.

3. The method of claim 1 , wherein the selectively enabling comprises:

enabling the transceiver module if the number of variations that exceed the predetermined value is greater than or equal to the trigger number; and

disabling the transceiver module if the number of variations that exceed the predetermined value is less than the trigger number.

4. The method of claim 1 , further comprising:

dynamically adjusting the predetermined value in response to changes in an environment surrounding the device.

5. A mobile communication device for communicating with a wireless local area network (WLAN) having a multitude of wireless access points, the device comprising:

a transceiver to passively receive first and second WLAN beacon signals from each of a plurality of selected access points; and

a processor, coupled to the transceiver, to:

determine, from the first beacon signals, a first received signal strength indicator (RSSI) value for each of the selected access points;

determine, from the second beacon signals, a second RSSI value for each of the selected access points;

calculate, for each of the selected access points, a variation between the first and second RSSI values for the selected access point;

compare each variation in RSSI values with a predetermined value to detect motion of the device;

ascertain whether the number of variations in RSSI values that exceeds the predetermined number is greater than a trigger number, wherein the trigger number indicates a minimum number of the selected access points from which motion of the device is detected; and

selectively enable the transceiver in response to the ascertaining.

6. The device of claim 5 , wherein the transceiver is to broadcast probe signals when enabled and does not broadcast any signals when disabled.

7. The device of claim 5 , wherein the processor, when selectively enabling the transceiver, is to:

enable the transceiver if the number of variations that exceed the predetermined value is greater than or equal to the trigger number; and

disable the transceiver if the number of variations that exceed the predetermined value is less than the trigger number.

8. The device of claim 5 , wherein the processor is to further:

dynamically adjust the predetermined value in response to changes in an environment surrounding the device.

9. A mobile communication device that includes a transceiver module and that is proximate to a wireless local area network (WLAN) having a multitude of wireless access points, the device comprising:

means for passively receiving first and second WLAN beacon signals from each of a plurality of selected access points;

means for determining, from the first beacon signals, a first received signal strength indicator (RSSI) value for each of the selected access points;

means for determining, from the second beacon signals, a second RSSI value for each of the selected access points;

means for calculating, for each of the selected access points, a variation between the first and second RSSI values for the selected access point;

means for comparing each variation in RSSI values with a predetermined value to detect motion of the device;

means for ascertaining whether the number of variations in RSSI values that exceeds the predetermined number is greater than a trigger number, wherein the trigger number indicates a minimum number of the selected access points from which motion of the device is detected; and

means for selectively enabling the transceiver module in response to the ascertaining.

10. The device of claim 9 , wherein the transceiver module broadcasts probe signals when enabled and does not broadcast any signals when disabled.

11. The device of claim 9 , wherein the means for selectively enabling comprises:

means for enabling the transceiver module if the number of variations that exceed the predetermined value is greater than or equal to the trigger number; and

means for disabling the transceiver module if the number of variations that exceed the predetermined value is less than the trigger number.

12. The device of claim 9 , further comprising:

means for dynamically adjusting the predetermined value in response to changes in an environment surrounding the device.