Systems and methods for indicating buffered data at an access point using a traffic indication map broadcast
First Claim
Patent Images
1. A method for indicating buffered data comprising:
- periodically broadcasting a traffic indication map (TIM) frame outside a beacon frame;
said TIM frame comprising a bitmap control field comprising an offset and a partial virtual bitmap field indicative of the stations having buffered data awaiting; and
wherein the broadcasting takes place at a predetermined time, wherein the predetermined time is a target beacon transmission time (TBTT) plus an offset, and wherein the offset is a negative number with a magnitude equal to the minimum, average or maximum size of the TIM frame plus a short interframe space (SIFS).
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Abstract
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.
82 Citations
28 Claims
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1. A method for indicating buffered data comprising:
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periodically broadcasting a traffic indication map (TIM) frame outside a beacon frame; said TIM frame comprising a bitmap control field comprising an offset and a partial virtual bitmap field indicative of the stations having buffered data awaiting; and wherein the broadcasting takes place at a predetermined time, wherein the predetermined time is a target beacon transmission time (TBTT) plus an offset, and wherein the offset is a negative number with a magnitude equal to the minimum, average or maximum size of the TIM frame plus a short interframe space (SIFS). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for indicating buffered data comprising:
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periodically broadcasting a traffic indication map (TIM) frame outside a beacon frame; said TIM frame comprising a bitmap control field comprising an offset and a partial virtual bitmap field indicative of the stations having buffered data awaiting; and wherein the broadcasting takes place at a predetermined time, wherein the TIM frame comprises a check beacon indication, and wherein the check beacon indication comprises means for indicating a critical change in the beacon frame. - View Dependent Claims (12)
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13. A method for indicating buffered data comprising:
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periodically broadcasting a traffic indication map (TIM) frame outside a beacon frame; said TIM frame comprising a bitmap control field comprising an offset and a partial virtual bitmap field indicative of the stations having buffered data awaiting; and wherein the broadcasting takes place at a predetermined time, wherein the TIM frame comprises a check beacon indication, and wherein the check beacon indication comprises means for indicating a significant change in the beacon frame. - View Dependent Claims (14)
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15. A method in a station for retrieving buffered data from an access point comprising:
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waking up at a predetermined time; receiving a traffic indication map (TIM) frame having a partial virtual bitmap and a check beacon indication; if the partial virtual bitmap is indicative that the access point has buffered data for the station, receiving the buffered data; and if the check beacon indication indicates a critical or significant change in a beacon frame, receiving the beacon frame. - View Dependent Claims (16, 17, 18)
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19. An access point comprising:
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a processor; a wireless network interface device; and a memory comprising instructions; said instructions causing the processor to cause the wireless network interface device to broadcast a traffic indication map (TIM) frame outside a beacon frame at a predetermined time; and said TIM frame comprising a bitmap control field comprising an offset and a partial virtual bitmap field indicative of the stations having buffered data awaiting; wherein the predetermined time is a target beacon transmission time (TBTT) plus an offset or a delivery traffic indication time (DTIM) TBTT plus an offset, wherein the offset is announced in a beacon frame, a probe response or both, and wherein the offset is a negative number with a magnitude equal to the minimum, average or maximum size of the TIM frame plus a short interframe space (SIFS). - View Dependent Claims (20, 21, 22)
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23. An access point comprising:
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a processor; a wireless network interface device; and a memory comprising instructions; said instructions causing the processor to cause the wireless network interface device to broadcast a traffic indication map (TIM) frame outside a beacon frame at a predetermined time; and said TIM frame comprising a bitmap control field comprising an offset and a partial virtual bitmap field indicative of the stations having buffered data awaiting; wherein the TIM frame comprises a check beacon indication, comprising a means for indicating a critical change in the beacon frame, a means for indicating a significant change in the beacon frame, or both.
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24. An access point comprising:
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a processor; a wireless network interface device; and a memory comprising instructions; said instructions causing the processor to cause the wireless network interface device to broadcast a traffic indication map (TIM) frame outside a beacon frame at a predetermined time; and said TIM frame comprising a bitmap control field comprising an offset and a partial virtual bitmap field indicative of the stations having buffered data awaiting; wherein the TIM frame comprises a check beacon indication, comprising a first counter which is incremented after each critical change in the beacon frame, a second counter which is incremented after each significant change in the beacon frame, or both.
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25. A station for retrieving buffered data from an access point comprising:
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a processor; a wireless network interface device; and a memory comprising instructions; said instructions causing the processor to wake-up at a predetermined time and to cause the wireless network interface device to receive a traffic indication map (TIM) frame from an access point having a partial virtual bitmap and a check beacon indication; if the partial virtual bitmap is indicative that the access point has buffered data for the station, to receive the buffered data; and if the check beacon indication indicates a critical or significant change in a beacon frame, to receive the beacon frame. - View Dependent Claims (26, 27, 28)
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Specification