MULTI-RADIO HANDOVER MANAGER SYSTEM AND ALGORITHMS FOR HETEROGENEOUS WIRELESS NETWORKING

• US 20120315905A1
• Filed: 06/07/2011
• Published: 12/13/2012
• Est. Priority Date: 06/07/2011
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Zhu, Jing, Agerstam, Mats
• Granted Patent: US 8,805,374 B2
• Time in Patent Office: Days
• US Class Current: 455/436
• CPC Class Codes: H04W 36/14 Reselecting a network or an air interface
• CPC Class Codes: H04W 36/36 by user or terminal equipment
• CPC Class Codes: H04W 88/06 adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals

Abstract

A multi-radio handover manager and supporting algorithms are disclosed. The multi-radio handover manager (MRHM) minimizes the “on” time of one radio when the other radio is connected to the Internet. The MRHM also prevents unnecessary inter-RAT (radio access technologies) WLAN-to-WWAN handovers in a “multi-AP” WLAN, where intra-RAT WLAN-to-WLAN (layer 2) roaming is possible. The MRHM minimizes the impact of IP address changes due to WWAN-to-WLAN handover on an active TCP/IP session. And, the MRHM optimizes its handover-triggering algorithm based on traffic and environment.

Claims

1. A mobile device, comprising:

a wireless local area network (WLAN) radio to connect to a WLAN, enabling the multi-radio mobile device to access the Internet;

a wireless wide area network (WWAN) radio to connect to a WWAN, also enabling the multi-radio mobile device to access the Internet;

a plurality of parameters of the mobile device, wherein the parameters are established when the mobile device is initialized;

a handover manager to;

turn off the WLAN radio after turning on the WWAN radio;

or

turn off the WWAN radio after turning on the WLAN radio.

2. The mobile device of claim 1, wherein the WLAN radio further:

sends a WLAN status report to the handover manager, wherein the WLAN status report comprises;

a service set identifier (SSID) of a WLAN access point (AP) to which the mobile device is connected;

a basic SSID of the connected WLAN AP;

a WLAN RSSI of the connected WLAN AP;

a maximum RSSI of all the neighboring WLAN APs sharing the same SSID as the WLAN AP;

a multiple access point status, indicating whether multiple APs exist or not; and

a connection status, indicating whether the WLAN radio is connected to an AP or not.

3. The mobile device of claim 1, wherein the WWAN radio further:

sends a WWAN status to the handover manager, wherein the WWAN status report comprises;

a network name of a WWAN base station to which the WWAN is connected;

a base station cell identifier of the connected WWAN base station;

a connection status, indicating whether the WWAN radio is connected to the WWAN base station or not; and

a radio idle indicator, indicating whether the WWAN radio is actively transmitting or receiving traffic.

4. The mobile device of claim 1, wherein the handover manager turns off the WLAN radio after turning on the WWAN radio by:

receiving a WLAN status report from the WLAN radio, from which the handover manager confirms that the connected WLAN radio is a multiple access point WLAN, in which neighboring access points share the same service set identifier (SSID) as the WLAN radio;

confirming that the received signal quality indicator (RSSI) in the WLAN status report is below a threshold value obtained from the plurality of parameters;

sending a scan command to the WLAN radio to obtain a measured received signal strength indicator (RSSI) of the WLAN radio; and

confirming that the maximum RSSI is below a WLAN handover threshold value, wherein the WLAN handover threshold value is one of the plurality of parameters obtained from the mobile device;

sending a WWAN ON command to the WWAN radio so that the WWAN radio is turned on.

5. The mobile device of claim 4, wherein the handover manager turns off the WLAN radio after turning on the WWAN radio by:

starting a handover countdown timer after the WWAN ON command has been sent to the WWAN radio; and

sending a WWAN OFF command to the WWAN radio to turn off the WWAN radio if the WWAN radio does not get connected by the time the handover countdown timer expires.

6. The mobile device of claim 1, wherein the handover manager turns off the WWAN radio after turning on the WLAN radio by:

confirming that the mobile device is connected to a WWAN base station specified by the base station identifier (BSID) from the WWAN status report and has been connected for longer than a time period specified by a WWAN mobility time, wherein the WWAN mobility timer is one of the plurality of parameters available to the handover manager;

confirming that the WWAN radio is “

idle”

;

confirming that the currently connected WWAN base station is on the WWAN white list;

sending a WLAN ON command to the WLAN radio and start the handover countdown timer; and

confirming that the WLAN radio gets connected and the RSSI of the WLAN radio exceeds the sum of a WLAN handover RSSI threshold and a WLAN handover RSSI margin before the handover countdown timer expires.

7. The mobile device of claim 1, further comprising:

a WWAN white list consisting of a list of WWAN base stations in which a successful handover to a WLAN access point has previously been made within a predetermined number of days.

8. The mobile device of claim 7, wherein the WWAN white list is updated according to the following criteria:

the WWAN base station ID from a WWAN status report is added to the WWAN white list if the WLAN radio is connected within a multi-radio handover time limit after the WLAN ON command is issued to the WLAN radio, wherein the multi-radio handover timer is one of the plurality of parameters; and

the WWAN base station ID is removed from the WWAN white list if the WLAN radio is not connected within a WWAN white list timer time limit after the WLAN ON command is issued to the WLAN radio, wherein the WWAN white list timer is one of the plurality of parameters.

9. The mobile device of claim 2, further comprising:

a WLAN handover RSSI threshold optimization program to update the WLAN handover RSSI threshold used by the handover manager, wherein the WLAN handover RSSI threshold is one of the plurality of parameters, the program comprising;

a decision block to compare a signal threshold parameter S(x), the signal threshold parameter being specific to the SSID of the connected AP, denoted as x, to the WLAN signal strength measurement obtained following a scan of the WLAN radio, wherein the decision block generates an outcome, D;

an observation block to generate a result indicator, R, based on the outcome, D, from the decision block, under four different conditions;

a cognition block to update the signal threshold parameter, S(x), based on the result indicator, R, received from the observation block; and

a database to store historical handover data as well as the latest signal strength threshold for each known S(x).

10. The mobile device of claim 1, further comprising:

a traffic type optimization procedure to adjust the received signal strength threshold based on whether real-time traffic is active in the mobile device.

11. The mobile device of claim 9, further comprising:

a low RSSI threshold optimization program to minimize false alarms; and

a high RSSI threshold optimization program to ensure a successful handover;

wherein the low RSSI threshold optimization program is executed when real-time traffic is not present and the high RSSI threshold optimization program is executed when no real-time traffic is present.

12. A multi-radio handover manager executable by a processor in a multi-radio mobile device, the mobile device comprising at least one wireless local area network (WLAN) radio and at least one wireless wide area network (WWAN) radio, the multi-radio handover manager comprising:

a WLAN-to-WWAN handover procedure;

a WWAN-to-WLAN handover procedure;

a list of parameters received from the multi-radio mobile device during initialization of the mobile device; and

a WWAN white list.

13. The multi-radio handover manager of claim 12, further comprising:

a WLAN RSSI threshold optimization;

a traffic type optimization;

a WLAN RSSI low threshold optimization; and

a WLAN RSSI high threshold optimization.

14. The multi-radio handover manager of claim 13, the WLAN-to-WWAN handover procedure comprising:

receiving a WLAN status report from the WLAN radio, from which the handover manager confirms that the connected WLAN radio is a multiple access point WLAN, in which neighboring access points share the same service set identifier (SSID) as the WLAN radio;

confirming that the received signal quality indicator (RSSI) in the WLAN status report is below a threshold value obtained from the plurality of parameters;

sending a scan command to the WLAN radio to obtain a measured received signal strength indicator (RSSI) of the WLAN radio; and

confirming that the maximum RSSI is below a WLAN handover threshold value, wherein the WLAN handover threshold value is one of the plurality of parameters obtained from the mobile device;

sending a WWAN ON command to the WWAN radio so that the WWAN radio is turned on.

15. The multi-radio handover manager of claim 14, the WLAN-to-WWAN handover procedure further comprising:

starting a handover countdown timer after the WWAN ON command has been sent to the WWAN radio; and

sending a WWAN OFF command to the WWAN radio to turn off the WWAN radio if the WWAN radio does not get connected by the time the handover countdown timer expires.

16. The multi-radio handover manager of claim 13, the WWAN-to-WLAN handover procedure comprising:

confirming that the mobile device is connected to a WWAN base station specified by the base station identifier (BSID) from the WWAN status report and has been connected for longer than a time period specified by a WWAN mobility time, wherein the WWAN mobility timer is one of the plurality of parameters available to the handover manager;

confirming that the WWAN radio is “

idle”

;

confirming that the currently connected WWAN base station is on the WWAN white list;

sending a WLAN ON command to the WLAN radio and start the handover countdown timer; and

confirming that the WLAN radio gets connected and the RSSI of the WLAN radio exceeds the sum of a WLAN handover RSSI threshold and a WLAN handover RSSI margin before the handover countdown timer expires.

17. The multi-radio handover manager of claim 13, further comprising:

a WWAN white list consisting of a list of WWAN base stations in which a successful handover to a WLAN access point has previously been made within a predetermined number of days.

18. The multi-radio handover manager of claim 17, wherein the WWAN white list is updated according to the following criteria:

the WWAN base station ID from a WWAN status report is added to the WWAN white list if the WLAN radio is connected within a multi-radio handover time limit after the WLAN ON command is issued to the WLAN radio, wherein the multi-radio handover timer is one of the plurality of parameters; and

the WWAN base station ID is removed from the WWAN white list if the WLAN radio is not connected within a WWAN white list timer time limit after the WLAN ON command is issued to the WLAN radio, wherein the WWAN white list timer is one of the plurality of parameters.

19. The multi-radio handover manager of claim 13, further comprising:

a WLAN handover RSSI threshold optimization program;

a traffic type optimization procedure to adjust the received signal strength threshold based on whether real-time traffic is active in the mobile device;

20. The multi-radio handover manager of claim 13, further comprising:

a WLAN RSSI low threshold optimization program; and

a WLAN RSSI high threshold optimization program.