Systems and methods for indicating buffered data at an access point using an embedded traffic indication map
View Patent ↗Stations in standby mode periodically wake up to check for buffered data at the access points. Traditionally, the information is available by checking the periodic beacon frame for a traffic indication map (TIM). Unfortunately, the length of beacons has steadily increased with the progression of the various wireless standards requiring stations to wake up for longer periods to merely check for buffered data. Several approaches are disclosed which address this shortcoming, including the broadcast of TIM frames, the partial reception of beacon frames and the use of an embedded TIM frame within a beacon frame.
1. A method for retrieving buffered data from an access point, the method comprising:
waking up from a standby mode at a predetermined time relative to a delivery traffic indication map (DTIM) target beacon transmission time (TBTT);
receiving, after the waking up, a traffic indication map (TIM) frame not disposed within a beacon frame at the predetermined time;
retrieving the buffered data in response to an indication by a partial virtual bitmap within the TIM frame;
re-entering the standby mode after the retrieving;
wherein the TIM frame is received prior to a DTIM beacon frame.
2. The method of claim 1 , wherein the TIM frame is one of a control frame and a management action frame.
3. The method of claim 1 , wherein the predetermined time is determined according to one of a previous beacon frame and a probe response.
4. The method of claim 1 , wherein the predetermined time precedes the DTIM TBTT by an estimated length of the TIM frame plus a short interframe space (SIFS).
5. The method of claim 4 , wherein the estimated length of the TIM frame is equal to a minimum, an average or a maximum size of the TIM frame.
6. The method of claim 1 , wherein the TIM frame further comprises a check beacon field for indicating a critical or significant change in a subsequent beacon frame.
7. The method of claim 6 , further comprising waking up after re-entering the standby mode to receive a subsequent beacon frame if the check beacon field indicates the critical or the significant change in the subsequent beacon frame.
8. The method of claim 1 , wherein the TIM frame is received prior to only the DTIM beacon frame and not prior to other beacon frames.
9. A wireless device for retrieving buffered data from an access point, the wireless device comprising:
a processor;
a memory comprising instructions causing the processor to:
wake up from a standby mode at a predetermined time relative to a delivery traffic indication map (DTIM) target beacon transmission time (TBTT);
receive, after the wake up, a traffic indication map (TIM) frame not disposed within a beacon frame at the predetermined time;
retrieve the buffered data in response to an indication by a partial virtual bitmap within the TIM frame;
re-enter the standby mode after retrieving the buffered data;
wherein the TIM frame is received prior to a DTIM beacon frame.
10. The wireless device of claim 9 , wherein the TIM frame is one of a control frame and a management action frame.
11. The wireless device of claim 9 , wherein the predetermined time is determined according to one of a previous beacon frame and a probe response.
12. The wireless device of claim 9 , wherein the predetermined time precedes the DTIM TBTT by an estimated length of the TIM frame plus a short interframe space (SIFS).
13. The wireless device of claim 12 , wherein the estimated length of the TIM frame is equal to a minimum, an average or a maximum size of the TIM frame.
14. The wireless device of claim 9 , wherein the TIM frame further comprises a check beacon field for indicating a critical or significant change in a subsequent beacon frame.
15. The wireless device of claim 14 , wherein the instructions cause the processor to wake up after re-entering the standby mode to receive a subsequent beacon frame if the check beacon field indicates the critical or the significant change in the subsequent beacon frame.
16. The wireless device of claim 9 , wherein the TIM frame is received prior to only the DTIM beacon frame and not prior to other beacon frames.
17. An access point comprising:
a processor;
a wireless network interface device;
a memory comprising instructions causing the processor to:
cause the wireless network interface device to transmit a traffic indication map (TIM) frame at a predetermined time relative to a delivery TIM (DTIM) target beacon transmission time (TBTT);
wherein the TIM frame is:
not disposed within a beacon frame; and
received prior to a DTIM beacon frame.
18. The access point of claim 17 , wherein the TIM frame is one of a control frame and a management action frame.
19. The access point of claim 17 , wherein the TIM frame comprises one or more partial virtual bitmap fields indicative of the access point having buffered data awaiting transmission to one or more wireless devices.
20. The access point of claim 17 , wherein the predetermined time precedes the DTIM TBTT by an estimated length of the TIM frame plus a short interframe space (SIFS).
21. The access point of claim 20 , wherein the estimated length of the TIM frame is equal to a minimum, an average or a maximum size of the TIM frame.
22. The access point of claim 17 , wherein the TIM frame further comprises a check beacon field for indicating a critical or significant change in a subsequent beacon frame.
23. The access point of claim 20 , wherein the TIM frame is received prior to only the DTIM beacon frame and not prior to other beacon frames.