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Method by which stations operating in power save mode in wireless LAN systems transmit and receive frames, and apparatus for supporting same

  • US 9,491,700 B2
  • Filed: 01/30/2013
  • Issued: 11/08/2016
  • Est. Priority Date: 02/10/2012
  • Status: Expired due to Fees
First Claim
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1. A method of transmitting and receiving a frame performed by a first station (STA) that operates in a power save mode in a wireless local area network (WLAN) system, comprising:

  • receiving a traffic indication map (TIM) element including a bitmap sequence, wherein the bitmap sequence includes a first bit indicating that a buffered frame for the first STA exists and a second bit indicating that a buffered frame for a second STA exists;

    setting a back-off timer for the first STA based on a bit index of the first bit and the second bit, wherein the back-off timer for the first STA is a value of at least one slot time, wherein if the bit index of the first bit is lower than the bit index of the second bit, a value of the back-off timer for the first STA is higher than a value of a back-off timer for the second STA, wherein if the bit index of the first bit is higher than the bit index of the second bit, a value of the back-off timer for the first STA is lower than a value of a back-off timer for the second STA;

    acquiring a channel access authority based on at least one slot time, wherein each slot time is a time when a channel is kept in an idle state for a channel access of the first STA;

    transmitting a PS (power save)-poll frame requesting a transmission of the buffered frame for the first STA to an access point (AP); and

    receiving a response frame from the AP in response to the PS-poll frame,wherein a length of the each slot time is set to be larger than a transmission time of the PS-poll frame.

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