Hi Tero,
Thank you for the clear explanation!!
I check Figure 6-5 and Figure 6-6 that you referred. Indeed, there is
no distinction on a sending frame between unicast or broadcast.
Now I've got synchronized. :-)
Best,
Yatch
On 2016/11/16 4:05, Tero Kivinen wrote:
Yasuyuki Tanaka writes:
In this sense, the purpose of macNodeAddress is only to make something
like a priority cell for outgoing frames to a certain MAC address
other than the broadcast address. And, we cannot allocate a cell
exclusively used for sending broadcast frames. I wish IEEE
802.15.4-2015 could elaborate what is expected to do with
macNodeAddress... Everybody may have no confusion about these things
except me...
We had long discussion about that when 802.15.4-2015 revision was
being made, and we tried to clear things as much as possible, but as
people also had bit different things what 4e meant it was bit hard...
With regard to Link Options or Cell Options, I believe I have the same
understanding as Tero's. I'm relieved here. :-) But, I have one thing
I want to confirm about this.
If a cell is "shared", this means that there is a possibility of
contention or collision as you mentioned. This attribute, shared or
not, is orthogonal to which type of communication, unicast and/or
broadcast, to be done, isn't it?
Yes. The 802.15.4-2015 [1] CSMA-CA algorithms (section 6.2.5.1) state
machines Figure 6-5 and TSCH CSMA-CA retransmission algorithm (section
6.2.5.3) Figure 6-6 do not make difference whether the slot is
broadcast or not. It just have steps "Wait for next TX link to
destination" and that can be either broadcast link or link only for
it. The shared bit affects the next step which is "Dedicated Link?" /
"Shared slot?" questions.
[1] http://standards.ieee.org/getieee802/download/802.15.4-2015.pdf
Therefore, in theory, we may have a dedicated (non-shared) TX cell
whose macNodeAddress is the broadcast address.
Yes. I.e. you are the only one allowed to send to that link, but there
are multiple listeneres in there. So, as it does not have shared bit
on, there will not be other transmitters, but there can be multiple
listeners on it.
In this case, a node having such a TX cell is supposed to be the
unique sender in its neighborhood. We may also have a shared TX cell
whose macNodeAddress is a unicast address. In this case, more than
one pairs of devices could share such a cell for their
communication.
Yes.
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