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Definitions of ACK and CTS Timeout

Definitions of ACK and CTS Timeout. Sunghyun Choi Philips Research USA sunghyun.choi@philips.com. Definitions of ACK & CTS Timeout. In 802.11-1999, they are mentioned in the text while the actual value is never defined in the text. The values are defined in the SDL in Annex C

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Definitions of ACK and CTS Timeout

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  1. Definitions of ACK and CTS Timeout Sunghyun Choi Philips Research USA sunghyun.choi@philips.com S. Choi, Philips

  2. Definitions of ACK & CTS Timeout • In 802.11-1999, they are mentioned in the text while the actual value is never defined in the text. • The values are defined in the SDL in Annex C • TGe decided not to use Annex C as the reference. • Therefore, TGe needs to define them in the text accordingly. S. Choi, Philips

  3. According to 802.11-1999 • Annex C, p. 346 ACKTimeout = SIFS + ACK Transmission Duration + SlotTime • Annex C, p. 348 CTSTimeout = SIFS + ACK Transmission Duration + SlotTime • “ACK Transmission Duration” is determined based on the PHY rate expected based on the rules in 9.6. • ACK length = CTS length S. Choi, Philips

  4. Problem with Current Definitions • The transmitter of an MPDU or an RTS does not need to wait for the whole ACK or CTS transmission time as defined in certain cases • When CCA stays idle after an MPDU or an RTS for PIFS, it implies that the MPDU or RTS was not received by the receiver correctly. • We can define two different values for ACK/CTS Timeout depending on the situation! (See the resolution of Comment #1805 in 02/084r9) S. Choi, Philips

  5. New Definition • After the transmission of an MPDU (or RTS), ACK Timeout (or CTS Timeout) will be: • PIFS when CCA stays idle during the following PIFS interval • SIFS + ACK Transmission Duration + SlotTime when CCA becomes busy within the following PIFS interval S. Choi, Philips

  6. Normative Text • In Clause 9.2.8, add the following at the end of the third paragraph: ACKTimeout is determined by PIFS if no PHY-CCA.indication(busy) is detected from the PHY during a period with a duration of (aSIFSTime + aSlotTime) starting at the PHY-TXEND.confirm. ACKTimeout is determined by (aSIFSTime + ACK_Time + aSlotTime) if PHY-CCA.indication(busy) is detected from the PHY during a period with a duration of (aSIFSTime + aSlotTime) starting at the PHY-TXEND.confirm, where ACK_Time is the transmission duration of an ACK frame at the PHY rate determined according to the rule found in Clause 9.6. S. Choi, Philips

  7. Normative Text • In Clause 9.2.5.7, add the following the first and second paragraphs: The source STA shall wait CTSTimeout amount of time without receiving a CTS before concluding that the RTS failed. CTSTimeout is determined by PIFS if no PHY-CCA.indication(busy) is detected from the PHY during a period with a duration of (aSIFSTime + aSlotTime) starting at the PHY-TXEND.confirm. CTSTimeout is determined by (aSIFSTime + CTS_Time + aSlotTime), where CTS_Time is the transmission duration of a CTS frame at the PHY rate determined according to the rule found in Clause 9.6, if PHY-CCA.indication(busy) is detected from the PHY during a period with a duration of (aSIFSTime + aSlotTime) starting at the PHY-TXEND.confirm. S. Choi, Philips

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