Methods and systems for low power reconnection

1. A method comprising:

entering, by a first device, a wake up mode from a sleep mode;

obtaining, by the first device, in response to entering the wake up mode, stored information indicating a wireless channel previously used to communicate with a second device, the first device to monitor for a beacon frame from the second device, through the wireless channel previously used to communicate with the second device indicated by the stored information;

receiving, by the first device, the beacon frame from the second device, through the wireless channel previously used to communicate with the second device indicated by the stored information; and

transmitting, by the first device to the second device, an association frame in response to receiving the beacon frame,

wherein the second device is an access point (AP) and the first device is a non-AP station (STA),

wherein the stored information indicating the wireless channel includes a frequency band of the wireless channel and timing of a previous communication between the first device and the second device,

wherein the first device and the second device are configured to resume wireless communication without channel scanning.

2. The method of claim 1 , wherein the association frame allows the second device to perform association with the first device to resume wireless communication.

3. The method of claim 1 , wherein the stored information further indicates a target beacon transmission time of the second device.

4. The method of claim 3 , further comprising:

predicting, by the first device according to the stored information, a first time at which the second device is scheduled to transmit the beacon frame, wherein the first device enters the wake up mode at a second time before the predicted first time.

5. The method of claim 1 , further comprising:

generating the stored information based on the wireless channel previously used to communicate with the second device.

6. The method of claim 1 , wherein the first device comprises a head wearable device, and the second device comprises a soft access point.

7. A first device comprising:

a wireless interface configured to communicate with a second device through a wireless communication link; and

one or more processors coupled to the wireless interface, the one or more processors configured to:

cause the wireless interface to enter a wake up mode from a sleep mode,

obtain, in response to entering the wake up mode, stored information indicating a wireless channel previously used to communicate with the second device, the first device to monitor for a beacon frame from the second device, through the wireless channel previously used to communicate with the second device indicated by the stored information,

cause the wireless interface to receive the beacon frame from the second device, through the wireless channel previously used to communicate with the second device indicated by the stored information, and

cause the wireless interface to transmit an association frame to the second device, in response to receiving the beacon frame,

wherein the second device is an access point (AP) and the first device is a non-AP station (STA),

wherein the stored information indicating the wireless channel includes a frequency band of the wireless channel and timing of a previous communication between the first device and the second device,

wherein the first device and the second device are configured to resume wireless communication without channel scanning.

8. The first device of claim 7 , wherein the association frame allows the second device to perform association with the first device to resume wireless communication.

9. The first device of claim 7 , wherein the stored information further indicates a target beacon transmission time of the second device.

10. The first device of claim 9 , wherein the one or more processors are configured to:

predict, according to the stored information, a first time at which the second device is scheduled to transmit the beacon frame, and

cause the wireless interface to enter the wake up mode at a second time before the predicted first time.

11. The first device of claim 7 , wherein the one or more processors are configured to generate the stored information based on the wireless channel previously used to communicate with the second device.

12. The first device of claim 7 , wherein the first device comprises a head wearable display, wherein the second device comprises a soft access point.

13. A first device comprising:

a wireless interface configured to communicate with a second device through a wireless communication link; and

one or more processors coupled to the wireless interface, the one or more processors configured to:

determine a time period,

cause the wireless interface to perform, within a listening interval of the second device, a plurality of switches between a wake up mode and a sleep mode periodically according to the time period, until an association is completed with the second device to resume wireless communication of data, and

cause, for each switch to the wake up mode from the sleep mode according to the time period, the wireless interface to transmit an association frame to the second device according to stored information indicating a wireless channel previously used to communicate with the second device, the association frame to establish the wireless communication link with the second device,

wherein the second device is an access point (AP) and the first device is a non-AP station (STA),

wherein the stored information indicating the wireless channel includes a frequency band of the wireless channel and timing of a previous communication between the first device and the second device,

wherein the first device and the second device are configured to resume wireless communication without channel scanning.

14. The first device of claim 13 , wherein the second device is configured to switch between another wake up mode and another sleep mode of the second device, wherein the second device is configured to receive the association frame while the second device is in the another wake up mode during the listening interval.

15. The first device of claim 14 , wherein the one or more processors are configured to determine the time period to allow at least one switch to the wake up mode from the sleep mode to occur while the second device is in the another wake up mode.

16. The first device of claim 14 , wherein the second device is configured to receive the association frame, while bypassing use of beacon frames.

17. The first device of claim 13 , wherein the one or more processors are configured to cause, for each switch to the wake up mode from the sleep mode according to the time period, the wireless interface to transmit the association frame to the second device through the wireless channel previously used to communicate with the second device indicated by the stored information.