Re: [6tsch] report flow contents

[Qin Wang <[e-mail]>]

Hi Pouria and Diego,

I think the "link-by-link" adaptive channel hopping mechanism of ISA100.11a
AND cell over-provision mechanism of 6top can be used together. Make sense?

Thanks
Qin


On Mon, Sep 16, 2013 at 8:56 AM, <[e-mail]> wrote:

> Hi Diego,
>
> ISA100.11a considers the adaptive channel hopping on a link-by-link basis,
> in addition to traditional blacklisting on the whole network. This
> mechanism is described as following:
>
> "Additionally, a device may autonomously treat transmit links on
> problematic channels as idle, thus reducing unnecessary interference and
> wasted energy on channels with a history of poor connectivity. A device
> skipping links in this manner should periodically test the links to verify
> that they remain problematic. Such selective channel utilization can be
> disabled by the system manager on a link-by-link basis, through the
> attribute dlmo.Link[].Type.SelectiveAllowed. [1]"
>
> In this scheme, the sender/receiver consider the poor channel as idle. The
> sender and receiver (on the poor edge) will still follow the defined
> hopping pattern and they will not conflict with the rest of the network.
> Potential Drawbacks: 1/16 of the resources might be wasted on that edge,
> but the poor channel of that edge will be skipped, locally.
> Important Strength: The overhead of this scheme is low.
>
> Best wishes,
> puoria
>
> 1. IEC 62734: Industrial communication networks - Fieldbus specifications
> - Wireless systems for industrial automation: process control and related
> applications - ISA100.11a.
>
> -----Original Message-----
> From: [e-mail] [mailto:[e-mail]] On Behalf Of
> Prof. Diego Dujovne
> Sent: Friday, September 13, 2013 9:07 PM
> To: Qin Wang
> Cc: Thomas Watteyne; 6TSCH
> Subject: Re: [6tsch] report flow contents
>
> Hi Qin,
>           On the centralized case, changing the channel hopping sequence
> (and thus blacklisting the channels with interference) on the whole
> network, and not in a peer basis is not efficient in terms of channel
> usage. Let me explain this with an
> example:
>
> Let's say there is are 4 nodes: A, B, C and D. A and B are interfered only
> on channel 4 by an external source, while C and D listen interference only
> on channel 8. If I disable channel 4 and 8 by blacklisting both channels
> from the hopping sequence, A and B won't be able to use channel 8 and C and
> D won't be able to use channel 4, both interference free between them.
>
> On the distributed case, if two nodes are already connected and if both
> detect a interfered channel they will (someway) agree to blacklist that
> channel from the hopping sequence. But we have not arrived to this case yet
> on 6TiSCH.
>
> On the other side, if we blacklist by changing the hopping sequence, a
> node talking to different neighbours will have different channel hopping
> sequences. And this increases complexity too.
>
> I don't have an answer (just questions) on how to reduce the probability
> of using an interfered channel, but it seems that the current tsch scheme
> does not allow a simple way to blacklist channels unless it is done
> network-wide. To sum up, I'm worrying about reducing channel diversity.
>
> Thoughts?
>
>                                                          Diego
>
>
>
>
>
>
> 2013/9/13 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]>:
> >> > 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
> >> >>
> >> >>
> >> >> _______________________________________________
> >> >> 6tsch mailing list
> >> >> [e-mail]
> >> >> https://www.ietf.org/mailman/listinfo/6tsch
> >> >>
> >> >
> >> >
> >> > _______________________________________________
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> >> > https://www.ietf.org/mailman/listinfo/6tsch
> >> >
> >>
> >>
> >>
> >> --
> >> DIEGO DUJOVNE
> >> Académico Escuela de Ingeniería en Informática y Telecomunicaciones
> >> Facultad de Ingeniería UDP www.ingenieria.udp.cl
> >> (56 2) 676 8125
> >
> >
>
>
>
> --
> 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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