Re: [6tsch] report flow contents

[Qin Wang <[e-mail]>]

Hi Diego,

I understand, theoretically, dynamic allocation may have some advantages in
terms of increasing reliability. But, in the channel hopping network, it is
challenge for a node to catch up the channel hopping sequence change in its
neighbors. Thus, I think, if updating channel hopping sequence, it could be
better to do it in network wide. What do you think?

Thanks
Qin


On Fri, Sep 13, 2013 at 11:28 PM, Prof. Diego Dujovne <
[e-mail]> wrote:

> Qin,
>       I think frequency blacklisting on a node-pair basis (either
> centralized or distributed) would
> break the schedule matrix structure, which overrides narrowband
> interference by channel hopping.
> If frequencies are blacklisted on all slots, that would waste
> resources. Narrowband interference
> can harm the link locally, but the same frequency may be
> interference-free in other parts of
> the net.
>       The dynamic allocation I propose was only an example. If you
> have 16 frequencies
> and 2 of them have interference, and the channel offset is sequential,
> you may loose 2 packets
> every 16. Am I right on this?
>
> Thoughts?
>
>                                                       Diego
>
>
> 2013/9/13 Qin Wang <[e-mail]>du>:
> > Thomas,
> >
> > I agree with you that it is not clear what is the advantage and
> disadvantage
> > of adaptive channel hopping in reality.
> >
> > In mind, based on the per-frequency report, PCE can do two things: (1)
> > update channel hopping sequence is a frequency is really bad network
> wide;
> > (2) avoid use some bad channel when it runs cell allocation algorithm.
>  The
> > two things happen in PCE, so, will not make negative impact on the
> network.
> > Thought?
> >
> > Thanks
> >
> > Qin
> >
> >
> >
> >
> > On Fri, Sep 13, 2013 at 10:46 PM, Thomas Watteyne
> > <[e-mail]> wrote:
> >>
> >> Qin, Diego,
> >>
> >> My 2 cents. I agree with you that it would be nice for the PCE to be
> able
> >> to get some per-channel information. Although adaptive channel hopping
> (i.e.
> >> selectively blacklisting frequencies for a specific bundle) is
> appealing in
> >> principle, it's unclear (at least to me) whether the gains clearly
> outweigh
> >> the overhead (complexity, signalign traffic) one has to pay to
> coordinate
> >> this [1-5].
> >>
> >> My opinion is that we should enable both metrics averages over all
> >> channels, and per-channel metrics. In some configurations, one can
> imagine
> >> gathering the former by default, and querying for the latter on specific
> >> occasions. Having the option of gathering per-channel information does
> >> enable us to be future-proof against future adaptive channel hopping
> >> algorithm.
> >>
> >> For sure, this makes for a great question: how do a pair of motes and
> the
> >> PCE have to communicate to enable adaptive channel hopping on that
> link? The
> >> answer to that might directly impact the application payload formats we
> have
> >> are talking about. Is this something you be interested in looking
> further
> >> into?
> >>
> >> Thomas
> >>
> >> [1] A Decentralized Scheduling Algorithm for Time Synchronized Channel
> >> Hopping. Andrew Tinka, Thomas Watteyne, Kris Pister, Alexandre M. Bayen.
> >> ICST Transactions on Mobile Communications and Applications, 11(7-9).
> >> European Union Digital Library link. doi:10.4108/icst.trans.mca.2011.e5.
> >> September 2011.
> >> [2] A Decentralized Scheduling Algorithm for Time Synchronized Channel
> >> Hopping. Andrew Tinka, Thomas Watteyne, Kris Pister. International
> >> Conference on Ad Hoc Networks (ADHOCNETS), Victoria, BC, Canada, 18-20
> >> August 2010.
> >> [3] Mitigating Multipath Fading Through Channel Hopping in Wireless
> Sensor
> >> Networks. Thomas Watteyne, Steven Lanzisera, Ankur Mehta, Kris Pister.
> IEEE
> >> International Conference on Communications (ICC), Cape Town, South
> Africa,
> >> 23-27 May, 2010.
> >> [4] Feasibility Analysis of Controller Design for Adaptive Channel
> >> Hopping. Branko Kerkez, Thomas Watteyne, Mario Magliocco, Steven Glaser,
> >> Kris Pister. First International Workshop on Performance Methodologies
> and
> >> Tools for Wireless Sensor Networks (WSNPerf), Pisa, Italy, 23 October
> 2009.
> >> [5] Reliability Through Frequency Diversity: Why Channel Hopping Makes
> >> Sense. Thomas Watteyne, Ankur Mehta, Kris Pister. Sixth ACM
> International
> >> Symposium on Performance Evaluation of Wireless Ad Hoc, Sensor, and
> >> Ubiquitous Networks (PE-WASUN), Tenerife, Canary Islands, Spain, 26-30
> >> October 2009.
> >>
> >> On Fri, Sep 13, 2013 at 7:23 AM, Prof. Diego Dujovne
> >> <[e-mail]> wrote:
> >>>
> >>> Hello Qin,
> >>>               I think that a per-frequency report will help the PCE
> >>> to decide which frequency to use, and maybe temporarily
> >>> black-list them. For example, a dynamic scheme may include
> >>> sampling the blacklisted frequencies every X minutes to re-enable
> >>> them once the interference has disappeared.
> >>>              This will require the node to refresh the RSSI
> >>> and LQI values in a opportunistic way (every time the a cell
> >>> uses that frequency) to save energy.
> >>>
> >>> Any thoughts?
> >>>
> >>>                             Diego
> >>
> >>
> >> _______________________________________________
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> >>
> >
> >
> > _______________________________________________
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>
>
>
> --
> DIEGO DUJOVNE
> Académico Escuela de Ingeniería en Informática y Telecomunicaciones
> Facultad de Ingeniería UDP
> www.ingenieria.udp.cl
> (56 2) 676 8125
>