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Enhancement of Low Power Medium Access STAs

Date: July, 2012. Enhancement of Low Power Medium Access STAs. Date: 2012-07-12. Authors:. Low Power Medium Access [1]. A low power STA doesn’t need to listen to TIM. It can send PS-Poll any time. The AP receives PS-Poll will respond ACK or buffered data frame to the low power STA.

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Enhancement of Low Power Medium Access STAs

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  1. Date: July, 2012 Enhancement of Low Power Medium Access STAs Date: 2012-07-12 Authors: Liwen Chu Etc.

  2. Low Power Medium Access [1] A low power STA doesn’t need to listen to TIM. It can send PS-Poll any time. The AP receives PS-Poll will respond ACK or buffered data frame to the low power STA. Date: July, 2012 Beacon ACK BU=1 Data Beacon PS Poll Doze Awake Time Doze Example with buffered data frames in AP Beacon ACK BU=0 Beacon PS Poll Doze Awake Time Doze Example without buffered data frames in AP

  3. Optimization 1: STA’s Low Power Capability Indication A STA can indicate its low power operation when it associates with the AP. A Low Power Indication bit can added to STA’s extended Capabilities or other IEs. The AP can use this information to do some optimization operation when it allocates AIDs, creates TIM etc. The AIDs of low power STAs are allocated to different beacon interval. This can decrease collisions. The AIDs of low power STAs are at the edge of AID set in the beacon interval. This can decrease TIM length. The AP will not to send TIM indication for the low power STAs. Date: July, 2012 AIDs for low power STAs xxxxxxxxx………..xxxxxxxxxx AID319 Group 5 AID set AID256

  4. Optimization 2: Distributed Low Power Medium Access In a smart-grid BSS or sensing BSS, almost all STAs are low power STAs. Low power STAs July wake up at the same time to poll the AP. This July creates more collisions. Solution: the STAs poll the AP in different time: An AP proposes different offset, period to each STA through association procedure or other management frames. Each STA requests offset period of its polling. The AP accepts or rejects the request. The STA should follow the negotiated polling time. It July also poll the AP in other time per its situation (e.g. sensing result ready etc). The AP July transmit unicast management frame as downlink frame after receiving the trigger frame. Such management frame can be used as timing, management synchronization. Date: July, 2012

  5. Optimization 2: PS-Poll Distribution A low power STA negotiates the offset, period (sleepinterval) of its polling through association or management frames. The offset is relative to the group TBTT following the negotiation. The period is GroupInterval*M (e.g. M=1, 2, 3…). A low power STA should finish its PS-Poll Sequence before the following TBTT. Date: July, 2012 Group n TBTT Group n TBTT Group n TBTT GroupInterval (in BI) TBTT TBTT offset STAj PS-Poll Period Low power STAj in Group n negotiates offset and period of PS-Poll transmission. STAj shall wake up to send PS-Poll.

  6. Reference [1] 11-12/127r1, Low Power Medium Access. Date: July, 2012

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