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Operation in Light Sleep Mode

Operation in Light Sleep Mode. Authors:. Date: 2009-03-05. Abstract. The presentation provides solutions to reduce the power consumption of the peer mesh STAs of the light sleep mode mesh STA. Light Sleep Mode Mesh STA in MBSS. Behavior of mesh STA Operates in light sleep mode

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Operation in Light Sleep Mode

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  1. Operation in Light Sleep Mode Authors: Date: 2009-03-05 Jarkko Kneckt, Nokia

  2. Abstract The presentation provides solutions to reduce the power consumption of the peer mesh STAs of the light sleep mode mesh STA. Jarkko Kneckt, Nokia

  3. Light Sleep Mode Mesh STA in MBSS • Behavior of mesh STA • Operates in light sleep mode • Listens to the Beacons of its peer mesh STA • Transmits a peer trigger frame to initiate a peer service period for data transmission • Behavior of beaconing mesh STA • Behavior is the same regardless of power management mode • If there is buffered frames, it will indicate it in its beacon • Stay in Awake state until peer service period is completed Jarkko Kneckt, Nokia

  4. Analysis • The beaconing mesh STA has no means to return to Doze state if the peer mesh STA does not transmit a trigger frame • This leads to extra power consumption in beaconing mesh STA • Solution is to have Request-To-Trigger frame • All neighboring MPs may transmit freely traffic • The traffic transmission will not block the triggering of the peer service period • EDCA TXOP and frame aggregation may be used without restrictions Jarkko Kneckt, Nokia

  5. Request to Trigger • Enables possibility for beaconing device to enter doze state if the other device is not well behaving • Improves power efficiency • The following slides introduce examples of the Request to Trigger frame use Jarkko Kneckt, Nokia

  6. Normal Operation of Request to Trigger Frame (1/2) Request to Trigger frame Request to Trigger frame Beacon Time mesh STA-A 2. 3. 1. ? Time mesh STA-B 1. TIM element in transmitted Beacon indicates buffered traffic to mesh STA-B, mesh STA –B is not able to receive the Beacon and goes to Doze state 2. Mesh STA A transmits Request to trigger frame and Mesh STA-B is not available to receive the frame 3. Mesh STA A retransmits Request to trigger frame and Mesh STA-B is not available to receive the frame. Mesh STA A goes to Doze state. Jarkko Kneckt, Nokia

  7. Normal Operation of Request to Trigger Frame (2/2) Request to Trigger frame Beacon Time mesh STA-A 2. 1. 3. RX RX Trigger frame Time mesh STA-B 1. TIM element in transmitted Beacon indicates buffered traffic to mesh STA-B, mesh STA –B may retrieve the buffered traffic from mesh STA-A and initiate peer service period 2. Mesh STA A transmits Request to trigger frame and Mesh STA-B acknowledges the frame. The transmitted Request-to-Trigger frame provides knowledge that triggering is expected. 3. Mesh STA-A sends a trigger frame to retrieve the buffered traffic from mesh STA-A and to initiate peer service period Jarkko Kneckt, Nokia

  8. Triggering after Request to Trigger Frame is ‘in Transmission’ Request to Trigger frame Data frame EOSP =1 RX Beacon Time mesh STA-A 2. 3. 5. 1. 4. RX Trigger frame RX RX Time mesh STA-B 1. TIM element in transmitted Beacon indicates buffered traffic to mesh STA-B, mesh STA –B may retrieve the buffered traffic from mesh STA-A and initiate peer service period 2. Mesh STA A does not get a trigger frame from mesh STA B and puts Request to trigger frame into transmission 3. Mesh STA A transmits a trigger frame to Mesh STA-B. 4. Mesh STA-A transmits buffered frames to mesh STA-B. Among these frames the Request to Trigger frame may be transmitted, but it does not cause any action in mesh STA-B. Please note that mesh STA-A may also remove the request-to-trigger frame from transmission 5. The peer service period is terminated after the last transmitted frame with EOSP bit set to 1. Jarkko Kneckt, Nokia

  9. The Request to Trigger Frame without Ack (1/2) Request to Trigger frame Request to Trigger frame Beacon Time mesh STA-A 2. 3. 4. 1. 5. ? ? RX Trigger frame Trigger frame Time mesh STA-B 1. TIM element in transmitted Beacon indicates buffered traffic to mesh STA-B, mesh STA –B may retrieve the buffered traffic from mesh STA-A and initiate peer service period 2. Unlikely event occurs. Mesh STA A transmits Request to trigger frame and Mesh STA-B is not able to receive the frame 3. Very unlikely event occurs. Mesh STA A retransmits Request to trigger frame and Mesh STA-B is not able to receive the frame 4. Mesh STA-A may try to retrieve the buffered traffic from mesh STA-A and initiate peer service period, but mesh STA-B is no longer available. No Peer Service Period is triggered between mesh STA-A and mesh STA-B 5. After the retransmissions of the Trigger frame, the mesh STA-B may go to doze state Jarkko Kneckt, Nokia

  10. The Request to Trigger Frame without Ack (2/2) • In the event of missing both Request-to-Trigger frames is very unlikely, because: • Request-to-Trigger frames will be mainly transmitted to one or two mesh STAs to request peer service period triggering • Request-to-Trigger frames are short, so they are likely transmitted in robust modulation and coding scheme • If the network is congested, the power save is not likely used due to transmissions and receptions to/from other peerings Jarkko Kneckt, Nokia

  11. CIDs 437 and 949 Solutions Do not Match with 802.11s D2.07 The comments are solved by using the Request to Trigger frame. Jarkko Kneckt, Nokia

  12. Appendix, Simple Estimation of the Power Save Obtained through the Use of Request-to-Trigger Frame Jarkko Kneckt, Nokia

  13. Assumptions of the Estimation • Assumptions: • Beaconing mesh STA has indicated buffered traffic to light sleep mode mesh STA, but has not received a trigger frame • Mesh STA transmit one TIM beacon between 100ms • Mesh STA transmits one DTIM beacon between 500ms • Awake Window period duration 10 ms • Mesh STAs have ½ beacon period offset as shown, i.e. opportunity to trigger service periods repeats between 50ms or 250 ms • The Request-to-Trigger frame will be transmitted 20 ms after the beacon frame Mesh STA-A Time Mesh STA-B Time ½of the Beacon period Jarkko Kneckt, Nokia

  14. Estimation of the Power Save Obtained through the Use of Request-to-Trigger Frame • The table lists beaconing mesh STA operation time in Awake and doze power states • The estimation assumes that trigger frame will not be received • If trigger frame will be received, the time in Awake and Doze state will be the same in all modes in granularity of 1 ms Jarkko Kneckt, Nokia

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