Re: [6tsch] report flow contents

"Prof. Diego Dujovne" <diego.dujovne@mail.udp.cl> Fri, 13 September 2013 15:28 UTC

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Date: Fri, 13 Sep 2013 12:28:34 -0300
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From: "Prof. Diego Dujovne" <diego.dujovne@mail.udp.cl>
To: Qin Wang <qinwang@berkeley.edu>
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Cc: Thomas Watteyne <watteyne@eecs.berkeley.edu>, 6TSCH <6tsch@ietf.org>
Subject: Re: [6tsch] report flow contents
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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 <qinwang@berkeley.edu>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
> <watteyne@eecs.berkeley.edu> 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
>> <diego.dujovne@mail.udp.cl> 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