Hi Oleg,
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.
It get's even better (5.5.2.3 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.
Best regards,
Daniel Krebs
[1]
https://openwsn.atlassian.net/wiki/download/attachments/688143/ieee802154-2006.pdf
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