Re: [6tisch] Questions on TSCH CSMA-CA retransmission algorithm in IEEE 802.15.4-2015

[Yasuyuki Tanaka <[e-mail]>]

Thank you, Fabrice!

> the backoff window is selected randomly between 0 and 2^BE-1. 

According to you, the term of "the backoff window" seems to be used as the retransmission backoff or the retransmission backoff wait. If so, I was confused by a sentence in the third paragraph of the section, "A successful transmission in a shared link resets the backoff window to the minimum value."

What is "reset" or the minimum value...?

Perhaps, the backoff window there is meant (2^BE - 1) and its minimum value is (2^macMinBe - 1).

> dedicated links > no collision / no backoff. 
> You transmit it without delay 
> (NB: you may have the first transmission during a shared link, and its retransmission in a dedicated one)

Yes, that how it works.

> If I understand correctly the standard, in that case, the dedicated link should not impact the BE value: the next packet will be picked in the queue, and transmitted with the same BE value as previously. 

Hmm, what if that next packet is not acknowledged in the first attempt? 

Will it use the *same* BE value in the following retransmission as perviously or use macMinBe as described in the standard, which could be different from the BE value used previously...?

> "NB is the number of times the CSMA-CA algorithm was required to back off while attempting the current transmission"

Aha, I see; then we need "NB=0" just after the "Retransmission?" box ;-)

> I have also the same doubts as you for the figure 6.6….

It'd be great if someone is woking on revising the figure... (>_<)

Best,
Yatch