1. Access during an MCCAOP by mesh STAs that are not the MCCAOP owner
Month Year
doc.: IEEE yy/xxxxr0
Access during an MCCAOP by mesh STAs that are not the MCCAOP owner
Date: November 10, 2010
Authors:
Alexander Safonov, IITP RAS
Alexander Safonov, IITP RAS

2. Month Year
doc.: IEEE yy/xxxxr0
Abstract
According to the draft 7.02, an MCCA enabled mesh STA shall not initiate its transmissions within MCCAOPs owned by other STAs
But the STA can easily initiate its transmission before the MCCAOP, no matter how much time left before the MCCAOP beginning
This rule causes a problem: however MCCA enabled mesh STAs declare that they respect MCCAOPs owned by other STAs, it fact they do not, as their EDCA TXOPs still may overlap with MCCAOPs owned by others
The value of MCCA diminishes because of this problem
The problem can be solved by adding one more paragraph to the draft, which is proposed in this submission
Alexander Safonov, IITP RAS
Alexander Safonov, IITP RAS

3. Problem Statement
Although MCCA capable mesh STAs are not allowed to start their transmissions within MCCAOPs owned by others, they are allowed to start transmissions shortly before the MCCAOPs. So, MCCAOP and EDCA TXOPs may overlap
This may lead to: 1)MCCA TXOP truncation or 2) collisions, in case of hidden stations
Alexander Safonov, IITP RAS

4. Possible solution 1
Just before its packet transmission, a station checks whether it has enough time to send this packet before the next MCCAOP
i.e. the station checks the inequality: TDATA+TSIFS+TACK < tMCCA - current_time where tMCCA is the MCCAOP start time
If OK, the STA starts its transmission
If NOT OK, the STA defers its transmission and starts new round of the backoff procedure after the MCCAOP is finished
Alexander Safonov, IITP RAS

5. Possible solution 2
Just before its packet transmission, a station checks whether it has enough time to send this packet before the next MCCAOP
i.e. the station checks the inequality: TDATA+TSIFS+TACK < tMCCA - current_time where tMCCA is the MCCAOP start time
If OK, the STA starts its transmission
If NOT OK, the STA defers its transmission and starts new round of the backoff procedure immediately
Alexander Safonov, IITP RAS

6. Possible normative text covering both solution 1 and solution 2
Add the following text after the first sentence of the second paragraph of clause 9.9a in IEEE s_D7.02 “When a MCCA enabled mesh STA obtains an EDCA TXOP, the STA shall not start its transmission if the TXOP cannot be finished before the start of an MCCAOP corresponding to a reservation in its neighborhood MCCAOP times. Instead, the STA shall defer the transmission and initiate another backoff procedure with the same value of CW.”
Alexander Safonov, IITP RAS

7. Strawpoll
Should the normative text in the previous slide be considered for inclusion in the current draft?
Yes:
No:
Abstain:
Alexander Safonov, IITP RAS

8. Acknowledgement
The proposal was made in the framework of ICT FP7 project FLAVIA
Alexander Safonov, IITP RAS