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 (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. 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. Cheers, Oleg -- Unix is user friendly... its just selective about who its friends are.
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