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| --- This message came from the IEEE 802.11 Working Group Reflector ---
Hi Jianlin, Further to Adrian’s response, 1) The intention is that if, and only if, the medium is idle when the packet is presented to be transmitted, then the STA need only wait DIFS and if the medium is still idle, the STA may transmit. I agree that that the text is not crystal clear on this, but this is what the rule is for idle medium. My submission 16/0221r1 is attempting to get the description clearer. I think that if the text is clear then the diagram is probably OK. 2) CWmin is 7. This is 8 values, 0 to 7. Now the initial value represents CW - 1, or CW = 7+1 = 8. The next value would be CWx2 - 1, or 8x2 -1 = 15. The figure 10-14 is supposed to make this clear but agreed it may not immediately be clear that CWmin = CW -1. Hope this helps Graham From: *** IEEE stds-802-11 List *** [mailto:STDS-802-11@xxxxxxxx] On Behalf Of Stephens, Adrian P --- This message came from the IEEE 802.11 Working Group Reflector --- Hello Jainlin, Please see below... Best Regards, Adrian P STEPHENS Tel: +44 (1793) 404825 (office) Tel: +1 (971) 330 6025 (mobile) ---------------------------------------------- Intel Corporation (UK) Limited Registered No. 1134945 (England) Registered Office: Pipers Way, Swindon SN3 1RJ VAT No: 860 2173 47 -----Original Message----- --- This message came from the IEEE 802.11 Working Group Reflector --- All, I have questions on two MAC figures in Draft P802.11REVmc_D5.0 (and early versions). Any explanation is appreciated. 1) Figure 10-4: Some IFS relationships In statement "Immediate access when Medium is idle >= DIFS or AIFS[i]", should >= be >? Because >= indicates two cases: > or =. The case > is no problem, but case = may violate backoff rule. Because with =, a STA can wait for DIFS or AIFS[i], then immediately access medium even after busy medium (since medium is already idle for DIFS or AIFS[i] time). [Adrian P Stephens] There are two different uses for DIFS (and likewise AIFS): 1. If an MSDU arrives for transmission when the medium has been idle for >= DIFS 2. To precede a backoff time of random() x slot duration “Immediate access”, IMHO, applies to the first case, and the equals sign is appropriate. See 1289.43 (REVmc D5.0). This is distinct from backoff. 2) Figure 10-13: Example of exponential increase of CW Should the initial CW value (i.e., CWmin value) be 8 instead of 7? Because if CW = 7 for initial attempt, it means CWmin = 7. Then for the first retransmission, CW should be CWmin x 2 - 1 = 7 x 2 - 1 = 13, and for the second retransmission, CW should be 7x2x2-1 = 27, ... [Adrian P Stephens] Please see 1288.62: “The set of CW values shall be sequentially ascending integer powers of 2, minus 1” Jianlin Guo Mitsubishi Electric Research Labs Cambridge, MA, USA _______________________________________________________________________________ If you wish to be removed from this reflector, do not send your request to this reflector - it will have no effect. Instead, go to http://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-11 and then press the LEAVE button. If there is no LEAVE button here, try http://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-11-RO. Further information can be found at: http://www.ieee802.org/11/Email_Subscribe.html _______________________________________________________________________________ _______________________________________________________________________________ If you wish to be removed from this reflector, do not send your request to this reflector - it will have no effect. Instead, go to http://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-11 and then press the LEAVE button. If there is no LEAVE button here, try http://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-11-RO. Further information can be found at: http://www.ieee802.org/11/Email_Subscribe.html _______________________________________________________________________________ If you wish to be removed from this reflector, do not send your request to this reflector - it will have no effect. Instead, go to http://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-11 and then press the LEAVE button. If there is no LEAVE button here, try http://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-11-RO. Further information can be found at: http://www.ieee802.org/11/Email_Subscribe.html _______________________________________________________________________________ |