[Ns-developers] questions and patch
francesco.gringoli at ing.unibs.it
Wed Jan 18 00:35:04 PST 2006
On Jan 18, 2006, at 07:17, mathieu lacage wrote:
> Maybe it woul be worth asking the 802.11 commitee for a
> clarification. I don't care that much though.
I think for the moment that if we agree on that we can ask later.
>>> number of packets in TXOP1:
>>> TXOP1 transmission:
>> Uhm, what is the first ACK? Do you mean (ACK+PKT1) is a single
> no, it is the ACK for CFPOLL1. If you don't send it, the QAP thinks
> the TXOP is not used and switches to the next TXOP.
Mathieu, I'm not sure on that: your code too sends just a single
packet after the POLL with data, if this is available. In the draft
ACK+DATA is ok. My doubt was on the lack of a SIFS between ACK and PKT1.
>> I would remove the last SIFS and if N1 is the maximum number of
>> "nominal" packet QSTA1 can send inside its TXOP, I will say that
>> TXOP1 must contain [ CFPOLL+SIFS+(N1-1)*(PKT+SIFS+ACK+SIFS)
>> +PKT_N1 +SIFS+ACK ]
>> Hence we can fix
>> However (this is the key point) to calculate the CFP duration we
>> have to add PIFS between every consecutive TXOPs plus a PIFS at
>> the end of the CFP. Only if we calculate CFP duration in this way
>> everything is ok. Imagine what happens if we don't count the
>> PIFS: if we have a lot of backlogged traffic in all stations,
>> every one will not send QOSNULL since there is no time. The last
>> station however will never be polled because the m_txopTimer
>> always added up PIFS to the TXOP and if the CFP=TXOP1+TXOP2+TXOP3
>> +... all the added PIFSs have consumed time that should be
>> granted to last station. Then it has no time to complete the TXOP
>> inside the CFP.
> yes, hence my suggestion to add PIFS somewhere :)
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