Wireless Link Quality Monitoring

• US 20150350933A1
• Filed: 05/30/2014
• Published: 12/03/2015
• Est. Priority Date: 05/30/2014
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Chhabra, Kapil, Travostino, Franco, Mannemala, Chaitanya, Boodnnavar, Veerendra
• Granted Patent: US 9,591,497 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H04W 24/04 Arrangements for maintaining operational condition
• CPC Class Codes: H04W 36/305 Handover due to radio link failure control signalling for hand-off failure H04W36/0079
• CPC Class Codes: H04W 76/18 Management of setup rejection or failure
• CPC Class Codes: H04W 76/19 Connection re-establishment
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

Wi-Fi link health monitoring by a wireless device. Signal strength (e.g., RSSI) of a Wi-Fi link may be monitored. If the signal strength is low, further link quality metrics may be monitored. If it is determined that health of the Wi-Fi link is poor based on monitoring signal strength and other link quality metrics, roaming to a different Wi-Fi network may be performed, the Wi-Fi link may be disconnected, and/or an application processor of the wireless device may be woken.

Claims

1. A method for a wireless device to monitor Wi-Fi link quality, the method comprising:

establishing a Wi-Fi link;

monitoring RSSI of the Wi-Fi link;

determining that RSSI of the Wi-Fi link has fallen below a first RSSI threshold based on monitoring RSSI of the Wi-Fi link;

enabling monitoring a plurality of link quality metrics based on determining that RSSI of the Wi-Fi link fell below the first RSSI threshold;

determining that a potential link failure event has occurred based on monitoring the plurality of link quality metrics;

inducing traffic on the Wi-Fi link in response to determining that a potential link failure event has occurred;

determining a failure rate of the induced traffic;

if the failure rate of the induced traffic is higher than a failure rate threshold, triggering disconnection of the Wi-Fi link.

2. The method of claim 1, wherein the plurality of link quality metrics comprise two or more of:

transmit failures at a media access control (MAC) layer;

beacon losses at the MAC layer;

firmware-generated packet losses at the MAC layer;

gateway address resolution protocol (ARP) renewal failures;

domain name resolution failures;

transmission control protocol (TCP) socket establishment failures; and

TCP timeouts.

3. The method of claim 1,

wherein a plurality of potential link failure events are defined at the UE based on the plurality of link quality metrics.

4. The method of claim 3, wherein the plurality of potential link failure events comprise one or more of:

a transmit packet error rate (PER) higher than a first PER threshold over a first period of time for at least a frame threshold number of transmit frames for MAC and/or firmware-generated packets;

a beacon packet loss rate higher than a beacon packet loss rate threshold;

gateway ARP failure;

greater than a socket failure threshold number of TCP socket establishment failures;

greater than a timeout threshold number of timeouts on established sockets;

greater than a DNS failure threshold number of DNS failures.

5. The method of claim 1,

wherein inducing traffic on the Wi-Fi link comprises attempting to ping a serving gateway over the Wi-Fi link,

wherein determining the failure rate of the induced traffic comprises determining a proportion of ping timeouts to ping attempts.

6. The method of claim 1,

wherein triggering disconnection of the Wi-Fi link comprises initiating a disconnection timer and attempting to roam to a different Wi-Fi access point until successful or until expiration of the disconnection timer if one or more alternate Wi-Fi access points are available.

7. The method of claim 1,

wherein triggering disconnection of the Wi-Fi link comprises disconnecting from a Wi-Fi access point providing the Wi-Fi link immediately if no alternate Wi-Fi access points are available.

8. The method of claim 1, the method further comprising:

determining that RSSI of the Wi-Fi link has risen above a second RSSI threshold based on monitoring RSSI of the Wi-Fi link;

disabling monitoring the plurality of link quality metrics based on determining that RSSI of the Wi-Fi link rose above the second RSSI threshold,

wherein the second RSSI threshold is greater than the first RSSI threshold.

9. A wireless user equipment (UE) device configured to monitor link quality of a Wi-Fi link according to a plurality of link quality monitoring states and state transitions, comprising:

a radio; and

a processing element operably coupled to the radio;

wherein UE is configured to;

initially consider the Wi-Fi link to be in a first link quality state;

transition the Wi-Fi link to a second link quality state if RSSI of the Wi-Fi link falls below a first RSSI threshold;

monitor a plurality of network stack statistics for potential Wi-Fi link failure events while in the second link quality state;

transition the Wi-Fi link to a third link quality state if a potential Wi-Fi link failure event is detected while in the second link quality state;

probe the Wi-Fi link by inducing traffic on the Wi-Fi link while in the third link quality state;

transition the Wi-Fi link to a fourth link quality state if probing the Wi-Fi link while in the third link quality state results in failure of the induced traffic and if one or more alternate Wi-Fi access point (AP) candidates are available;

initiate a disconnection timer and attempt to roam to an alternate Wi-Fi AP of the one or more alternate Wi-Fi AP candidates while in the fourth link quality state;

transition the Wi-Fi link to a fifth link quality state if attempting to roam to an alternate Wi-Fi AP while in the fourth link quality state is not successful at expiration of the disconnection timer, wherein the fifth link quality state is a Wi-Fi disconnected state; and

transition the Wi-Fi link to the fifth link quality state if probing the Wi-Fi link while in the third link quality state results in failure of the induced traffic and if no alternate Wi-Fi AP candidates are available.

10. The UE of claim 9, wherein the UE is further configured to:

transition the Wi-Fi link from any of the second, third, or fourth link quality state to the first link quality state if RSSI of the Wi-Fi link rises above a second RSSI threshold, wherein the second RSSI threshold is higher than the first RSSI threshold.

11. The UE of claim 9, wherein the UE is further configured to:

transition the Wi-Fi link from any of the second, third, or fourth link quality state to the first link quality state if roaming to an alternate Wi-Fi AP is performed.

12. The UE of claim 9, wherein the UE is further configured to:

remove a Wi-Fi network used by the Wi-Fi link from auto-join consideration if the Wi-Fi link enters the fourth or fifth link quality state.

13. A method for a Wi-Fi chipset in a wireless user equipment (UE) device to monitor link quality of a Wi-Fi link while an application processor of the UE is in a sleep mode, the method comprising:

monitoring RSSI of the Wi-Fi link;

monitoring one or more additional link quality metrics if RSSI of the Wi-Fi link falls below a first RSSI threshold;

determining, based on monitoring RSSI of the Wi-Fi link and the one or more additional link quality metrics, whether or not the Wi-Fi link is reliable;

providing an indication to the application processor of the UE if it is determined that the Wi-Fi link is not reliable.

14. The method of claim 13,

wherein RSSI is monitored in a first manner if RSSI of the Wi-Fi link falls below the first RSSI threshold, wherein RSSI is monitored in a second manner if RSSI of the Wi-Fi link rises above a second RSSI threshold,

wherein the second RSSI threshold is higher than the first RSSI threshold, wherein a difference between the first RSSI threshold and the second RSSI threshold induces a hysteresis in manner of monitoring RSSI of the Wi-Fi link.

15. The method of claim 14, wherein monitoring RSSI in the first manner comprises waking to monitor Wi-Fi beacons at a higher frequency than when monitoring RSSI in the second manner.

16. The method of claim 14,

wherein a different RSSI threshold for Wi-Fi roaming is used when monitoring RSSI of the Wi-Fi link in the first manner than when monitoring RSSI of the Wi-Fi link in the second manner.

17. The method of claim 14, the method further comprising:

coordinating with a Wi-Fi access point of the Wi-Fi link to increase a delivery traffic indication message (DTIM) interval for the UE when monitoring RSSI of the Wi-Fi link in the second manner.

18. The method of claim 13, wherein the one or more additional link quality metrics comprise one or more of:

transmit packet error rate (PER) of internally generated frames;

results of active Wi-Fi link probing;

beacon reception failure rate.

19. The method of claim 13, the method further comprising:

receiving an indication from the application processor to notify the application processor if the Wi-Fi link is not reliable,

wherein said monitoring RSSI of the Wi-Fi link, monitoring one or more additional link quality metrics, determining whether or not the Wi-Fi link is reliable, and providing the indication to the application processor are performed in response to the indication to notify the application processor if the Wi-Fi link is not reliable.

20. The method of claim 13, wherein RSSI of the Wi-Fi link is performed based on receiving Wi-Fi beacons from a Wi-Fi access point of the Wi-Fi link, wherein the method further comprises:

modifying wake up times for beacon reception for earlier waking to monitor RSSI of the Wi-Fi link based on the application processor being in the sleep mode.