Changes between Version 20 and Version 21 of 802.11/MAC/Lower/Retransmissions


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Timestamp:
May 5, 2015, 4:00:33 PM (9 years ago)
Author:
chunter
Comment:

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  • 802.11/MAC/Lower/Retransmissions

    v20 v21  
    130130  ''The LRC for an MPDU ... and the SLRC shall be incremented every time transmission of a MAC frame of length greater than dot11RTSThreshold fails ... . This LRC and the SLRC shall be reset when a MAC frame of length greater than dot11RTSThreshold succeeds ... .''
    131131
    132 The failure to receive an ACK for the long MPDU causes both the LRC and and the SLRC to increment.  The increment operation on the SLRC causes the CW to increase to its next value. When the ACK is received in the second attempt, the CW is reset to its minimum value according to '''''Excerpt B of Section 9.3.3 of 802.11-2012''''' from [#ExampleS.1 Example S.1].
     132The failure to receive an ACK for the long MPDU causes both the LRC and and the SLRC to increment.  The increment operation on the SLRC causes the CW to increase to its next value. When the ACK is received in the second attempt, the CW is reset to its minimum value according to '''''Excerpt B of Section 9.3.3 of 802.11-2012''''' from [#ExampleS.1 Example S.1]. The SLRC is also reset to zero, but the reasons behind this involve going deeper than the 2012 publication of the standard. There is actually an acknowledged error in the 2012 publication. Specifically,
     133
     134    '''''Excerpt E of Section 9.3.3 of 802.11-2012'''''
     135
     136  <strike>The SSRC shall be reset to 0 when a CTS frame is received in response to an RTS frame, when a BlockAck frame is received in response to a BlockAckReq frame, when an ACK frame is received in response to the transmission of a frame of length greater than dot11RTSThreshold containing all or part of an MSDU or MMPDU, or when a frame with a group address in the Address1 field is transmitted. The SLRC shall be reset to 0 when an ACK frame is received in response to transmission of a frame containing all or part of an MSDU or MMPDU of , or when a frame with a group address in the Address1 field is transmitted.</strike>
    133137
    134138== Example L.3 ==
     
    147151Furthermore, '''''Excerpt A from 9.3.3 of 802.11-2012'''' in [#ExampleS.1 Example S.1] applies here as well, so the contention window immediately increases to 31 after the post-RTS timeout. The second attempt of the first MPDU begins with a new RTS transmission. When a CTS is received in response to that RTS, the following excerpt instructs our behavior:
    148152
    149   '''''Excerpt E from 9.3.3 of 802.11-2012'''''
     153  '''''Excerpt F from 9.3.3 of 802.11-2012'''''
    150154
    151155  '' The SSRC shall be reset to 0 when a CTS frame is received in response to an RTS frame ... .''