Re: [6tsch] report flow contents

[Qin Wang <[e-mail]>]

Hi Pouria,

In the centralized case, I believe PCE will take care everything you
mentioned. That means internal-interference caused by other neighboring
communication should not be the contributor to low link quality of a cell.
Thus, I think PCE will use per-cell report to adjust over-provision of
cells. For example, when PCE found a bundle of cells can not achieve
required BW, PCE may assign more cells.

Make sense?
Qin


On Sat, Sep 14, 2013 at 12:45 AM, <[e-mail]> wrote:

> Dear All,
> Regarding to the Xavi's report list, I found "per-cell" reports for each
> node (in addition to potential "per-frequency" and "per-neighbor" reports)
> in the list. I have the following concerns,
> (1) In the centralized management approach, what is the gain of reporting
> the statistics "per-cell"? Per-cell information will be used to evaluate
> the potential internal-interference caused by other neighboring
> communication. Am I right? Shouldn't the PCE, take care of allocation of
> cells (either dedicated or shared cells)? I mean, shouldn't the PCE take
> care of not allocating (re-using) the dedicated cell to two different
> pairs? Shouldn't the PCE take care of allocating the shared cell to the
> limited number of transmitters?
> (2) For sure, in the "per-frequency" and "per-neighbor" reports, each node
> has a limited number of frequencies (i.e. 11-26 in 2.4GHz) and a maximum
> number of linked-neighbors to report. However, in reporting "per-cell",
> what is the maximum number of cells defined for a node? (We might also
> consider the dense traffic scenarios).
> Am I missing anything?
> Best Wishes,
> Pouria
>
> -----Original Message-----
> From: [e-mail] [mailto:[e-mail]] On Behalf Of
> Prof. Diego Dujovne
> Sent: Friday, September 13, 2013 5:29 PM
> To: Qin Wang
> Cc: Thomas Watteyne; 6TSCH
> Subject: Re: [6tsch] report flow contents
>
> 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]>:
> > 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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> >> [e-mail]
> >> https://www.ietf.org/mailman/listinfo/6tsch
> >>
> >
> >
> > _______________________________________________
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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
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