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| --- 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
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