Randy Turner writes: > Hi All, > Just re-confirming an assumption — from a TSCH perspective, slot > scheduling assumes any single transmission “cannot” exceed a slot > boundary —
Yes. IEEE Std. 802.15.4-2015 requires that "The transmission of frames and the associated Ack frames need to be completed at least one SIFS time before the end of the ATI", and ATI (allowed transmission interval) is specified for TSCH as "TSCH timeslot: start and end time defined the macSlotframeHandle, macTimeslot and macTsTimeslotLength". (section 6.7.5 of 802.15.4-2015). > if transmissions require a certain amount of time, then the slot > width is increased to deal with this ( or possibly increase the TX > bit rate if possible ) In practice no. Yes, you could recreate the network with new parameters, but in practice you need to decide parameters beforehand, and those parameters will then limit what you can do. For example dynamically changing the timeslot length would not really work in TSCH, as there is no way to syncronize that change throughout the network, and devices sleeping would get out of sync if they do not see the beacon announcing new parameters. If such feature would be needed, I think you need to tear down the network and recreate it if you want to change any core parameters in the TSCH network. You can add new slots and add new slotframe descriptors, but changing existing ones are harder. The 802.15.4-2015 do warn you about this: (section 6.2.6.1): Each timeslot allows enough time for a pair of devices to exchange a frame and an acknowledgment. It is possible, although usually undesirable, to define a timeslot that is not long enough for a pair of devices to exchange a maximum length frame and an Ack frame. So it is better to decide the required parameters before you start the network and stick with them.... -- [email protected] _______________________________________________ 6tisch mailing list [email protected] https://www.ietf.org/mailman/listinfo/6tisch
