Reducing WLAN Power Consumption on a Mobile Device Utilizing a Cellular Radio Interface

• US 20110211511A1
• Filed: 02/26/2010
• Published: 09/01/2011
• Est. Priority Date: 02/26/2010
• Status: Active Grant

• Current Assignee: Malikie Innovations Limited (Key Patent Innovations Limited)
• Original Assignee: Blackberry Limited
• Inventors: Kholaif, Ahmad, Barbu, Ion, Bakthavathsalu, Krishna Kumar, Mendahawi, Nayef
• Granted Patent: US 8,195,251 B2
• Time in Patent Office: Days
• US Class Current: 370/311
• CPC Class Codes: H04W 4/80 Services using short range communication, e.g. near-field communication [NFC], radio-frequency identification [RFID] or low energy communication
• CPC Class Codes: H04W 48/18 Selecting a network or a communication service
• CPC Class Codes: H04W 52/02 Power saving arrangements in wired systems H04L12/12; signaling of mobile application services, e.g. low battery notifications H04W4/20
• CPC Class Codes: H04W 52/0254 detecting a user operation or a tactile contact or a motion of the device
• CPC Class Codes: H04W 88/06 adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A system and method of reducing the WLAN power consumption and limiting battery drain of a mobile communications device is provided. The mechanism continuously monitors for changes in the WLAN and cellular signal strength and modifies the WLAN profile scanning activity accordingly. By monitoring for changes, transitions can be detected which indicate the location of the mobile device (i.e., indoor or outdoor). An increase in cellular signal strength and a decrease in WLAN signal strength indicates the user is transitioning outdoors where WLAN coverage may be limited. To reduce battery power consumption, background scanning is suspended or its frequency significantly lowered. Moving indoors is indicated by a decrease in cellular signal strength and an increase in WLAN signal strength. Background/Connectivity scanning frequency is increased to provide shorter time-to-connect to WLAN Networks for the user within the WLAN coverage area.

Claims

1. A method of determining the location of a mobile device incorporating cellular and WLAN radio subsystems, the method comprising:

calculating a cellular/WLAN signal quality ratio in accordance with data received from the cellular subsystem and the WLAN subsystem; and

determining an indoor or outdoor location for the mobile device in accordance with the change over time of the cellular/WLAN signal quality ratio.

2. The method according to claim 1, further comprising reducing scanning frequency if an outdoor location is determined, thereby reducing WLAN subsystem power consumption.

3. The method according to claim 1, further comprising increasing scanning frequency if an indoor location transition is determined and if matching WLAN networks are present in the device saved WLAN profile list.

4. The method according to claim 1, wherein if the WLAN subsystem is in a connected state then determining an indoor or outdoor location comprises:

reading a first WLAN signal quality indication for a currently connected WLAN from the WLAN subsystem, and reading a first cellular signal quality indication from the cellular subsystem and calculating a first cellular/WLAN signal quality ratio therefrom;

waiting a predetermined time period;

reading a second WLAN signal quality indication for a currently connected WLAN from the WLAN subsystem and a second cellular signal quality indication from the cellular subsystem and calculating a second cellular/WLAN signal quality ratio therefrom; and

detecting an indoor to outdoor transition in accordance with the first and second cellular signal quality indications.

5. The method according to claim 1, wherein if the WLAN subsystem is in an unconnected state then determining an indoor or outdoor location comprises:

reading from the WLAN subsystem a first WLAN signal quality indication for a strongest WLAN signal detected, and reading a first cellular signal quality indication from the cellular subsystem and calculating a first cellular/WLAN signal quality ratio therefrom;

waiting a predetermined time period;

triggering a WLAN passive scanning and confirming the same previously detected WLAN signal;

reading a second WLAN signal quality indication for a currently connected WLAN from the WLAN subsystem and a second cellular signal quality indication from the cellular subsystem and calculating a second cellular/WLAN signal quality ratio therefrom; and

detecting an outdoor to indoor transition in accordance with the first and second cellular signal quality indications.

6. A method of reducing power consumption of a mobile device incorporating a cellular and Wireless Local Area Network (WLAN) subsystems, the method comprising:

monitoring changes in signal strength measurements received from the cellular and WLAN subsystems; and

modifying a power scheme of the WLAN subsystem in accordance with the changes.

7. The method according to claim 6, wherein WLAN profile background scanning is reduced if the changes indicate increasing cellular subsystem signal strength measurements and decreasing WLAN subsystem signal strength measurements, thereby reducing power consumption of the mobile device.

8. A method of reducing power consumption of a mobile device incorporating a cellular and Wireless Local Area Network (WLAN) subsystems, the method comprising:

calculating a cellular/WLAN signal quality ratio in accordance with data received from the cellular subsystem and the WLAN subsystem;

determining an indoor to outdoor or outdoor to indoor transition for the mobile device in accordance with the change over time of the cellular/WLAN signal quality ratio; and

if an indoor to outdoor transition is determined, setting the mobile device to perform WLAN scanning at a lower frequency thereby reducing WLAN power consumption.

9. The method according to claim 8, wherein the cellular/WLAN signal quality ratio is calculated using a strongest WLAN signal from among those detected.

10. The method according to claim 8, wherein the cellular/WLAN signal quality ratio is calculated using a signal from a currently connected WLAN.

11. The method according to claim 8, further comprising if an indoor to outdoor transition is determined setting an outdoor location for the mobile device.

12. The method according to claim 8, further comprising if an outdoor to indoor transition is determined setting an indoor location for the mobile device.

13. The method according to claim 8, wherein if the WLAN subsystem is in a connected state then determining an indoor or outdoor transition comprises:

reading a first WLAN signal quality indication for a currently connected WLAN from the WLAN subsystem, and reading a first cellular signal quality indication from the cellular subsystem and calculating a first cellular/WLAN signal quality ratio therefrom;

waiting a predetermined time period;

reading a second WLAN signal quality indication for a currently connected WLAN from the WLAN subsystem and a second cellular signal quality indication from the cellular subsystem and calculating a second cellular/WLAN signal quality ratio therefrom; and

detecting an indoor to outdoor transition in accordance with the first and second cellular signal quality indications.

14. The method according to claim 8, wherein if the WLAN subsystem is in an unconnected state than determining an indoor or outdoor transition comprises:

reading from the WLAN subsystem a first WLAN signal quality indication for a strongest WLAN signal detected, and reading a first cellular signal quality indication from the cellular subsystem and calculating a first cellular/WLAN signal quality ratio therefrom;

waiting a predetermined time period;

triggering a WLAN passive scanning and confirming the same previously detected WLAN signal;

reading a second WLAN signal quality indication for a currently connected WLAN from the WLAN subsystem and a second cellular signal quality indication from the cellular subsystem and calculating a second cellular/WLAN signal quality ratio therefrom; and

detecting an outdoor to indoor transition in accordance with the first and second cellular signal quality indications.

15. The method according to claim 8, wherein the indoor to outdoor transition is determined by detecting decreasing WLAN signal Received Signal Strength Indicator (RSSI) with an increasing cellular signal RSSI.

16. The method according to claim 8, wherein the outdoor to indoor transition is determined by detecting an increasing WLAN signal Received Signal Strength Indicator (RSSI) with a decreasing cellular signal RSSI.

17. A mobile communications device, comprising:

a Wireless Local Area Network (WLAN) subsystem;

a cellular subsystem;

a memory;

a processor coupled to the one or more radio circuits and the memory, the processor operative to

calculate a cellular/WLAN signal quality ratio in accordance with data received from the cellular subsystem and the WLAN subsystem;

determine an indoor to outdoor or outdoor to indoor transition for the mobile device in accordance with the change over time of the cellular/WLAN signal quality ratio; and

if an indoor to outdoor transition is determined, set the mobile device to perform WLAN background scanning at a lower frequency thereby reducing WLAN subsystem power consumption.

18. The mobile communications device according to claim 17, wherein the indoor to outdoor transition is determined by detecting decreasing WLAN signal Received Signal Strength Indicator (RSSI) with an increasing cellular signal RSSI.

19. The mobile communications device according to claim 17, wherein the outdoor to indoor transition is determined by detecting an increasing WLAN signal Received Signal Strength Indicator (RSSI) with a decreasing cellular signal RSSI.

20. A computer program product for reducing power consumption in a mobile device, the computer program product comprising:

a computer usable medium having computer usable code implemented therewith, the computer usable program code comprising;

computer usable code configured for calculating a cellular/WLAN signal quality ratio in accordance with data received from a cellular subsystem and a WLAN subsystem;

computer usable code configured for detecting an outdoor transition for the mobile device in accordance with the change over time of the cellular/WLAN signal quality ratio; and

computer usable code configured for setting the mobile device to perform WLAN background scanning at a lower frequency, if an outdoor transition is detected, thereby reducing WLAN subsystem power consumption.