[riot-devel] Implementing a new MAC protocol for IEEE 802.15.4

Oleg Hahm oliver.hahm at inria.fr
Tue May 12 14:28:39 CEST 2015

Hi Daniel!

> >PAN coordinators are only required for the beacon enabled mode in IEEE
> >802.15.4. 6LoWPAN, for instance, does not require this mode (I'm not even sure
> >if it is supported by the spec) and thus, there is no need for a PAN
> >coordinator or star topology.
> That's unfortunately not the case. Please refer to the specs [1] at Section
> 5.3, especially the second paragraph. According to the specification a PAN
> coordinator is always required, even in "Mesh" topology where it may get
> dynamically elected.

Ok, I was imprecise here. You still have a pan coordinator but it has another
role and it's not really important for the MAC protocol any more (if I'm not
completely mistaken). At least, it is not a single point of failure any more,
so I fail to see how this is a problem.
> It get's even better ( Peer-to-peer data transfers):
> >In a peer-to-peer PAN, every device may communicate with every other
> >device in its radio sphere of
> >influence. In order to do this effectively, the devices wishing to
> >communicate will need to either receive
> >constantly or synchronize with each other. In the former case, the device
> >can simply transmit its data using
> >unslotted CSMA-CA. In the latter case, other measures need to be taken in
> >order to achieve synchronization.
> >Such measures are beyond the scope of this standard.
> As receiving all the time is no option because of energy consumption you
> need some kind of synchronization. but that's "[...] beyond the scope of
> this standard". Thank you IEEE.
> That's why I don't aim to be compatible with IEEE 802.15.4-2006 in terms of
> the MAC-layer. Either I have a PAN coordinator or it advises me to do what I
> want.

Well, if the spec tells you to do what you want (inside the boundaries of this
spec), then you can to what you want and be still 802.15.4 compliant.

Unix is user friendly... its just selective about who its friends are.
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