I can only speak to T1 and my methodology in the linked document...but... Micaz and other 2420 radio devices have a hardware level ACK which may improve the failure detection rate without turning on the software ACK. The mica2, on which I did my main testing does not have the hdw level, so if you want any indication of a packet's getting through you have to use the sft ACK. This is _not_ the default, and in fact even when enabled they are not passed through to the pc-host without making a mod to TOSBase as I did. It does reduce the total message throughput, but in most WSN cases (especially low power) one is not running at maximum.
Look at the code refed in my doc for a usage example. In general one should get one ACK for each successful message and none for unsuccessful ones. However you can miss the ACK for a success and so you need to implement a sequence number mechanism of some kind at the user level to really be sure. I don't know if there is a retry mechanism in T1, but I think there is a packet interface of some kind in T2 that does retries. Otherwise it's up to the user. MS João Paulo Amaro da Costa Luz Carneiro wrote: > Hi all, > > Low Power Listening TEP recommends sending duplicate packets and > enabling acknowledgements while this > http://www.etantdonnes.com/Motes/report_mica2/ > concludes PRR is higher when acknowledgments are disabled. Can > someone explain? > About the acknowledgement mechanismand how do ACKs work in tinyos2/WSNs: > Does the system automatically retransmits when the ACKs aren't received? > How does a node knows how many ACKs it should receive? > Is it enabled or disabled by default, and how to change configurations? > Thanks, regards. > > Joao > _______________________________________________ > Tinyos-help mailing list > Tinyos-help@millennium.berkeley.edu > https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help -- Platform: WinXP/Cygwin TinyOS version: 1.x, Boomerang Programmer: MIB510 Device(s): Mica2, MicaZ, Tmote Sensor board: homebrew _______________________________________________ Tinyos-help mailing list Tinyos-help@millennium.berkeley.edu https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
