Re: [6tsch] blacklisting (was "report flow contents")
Qin Wang <qinwang@berkeley.edu> Mon, 16 September 2013 21:34 UTC
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Date: Tue, 17 Sep 2013 05:34:03 +0800
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From: Qin Wang <qinwang@berkeley.edu>
To: Thomas Watteyne <watteyne@eecs.berkeley.edu>
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Cc: 6TSCH <6tsch@ietf.org>
Subject: Re: [6tsch] blacklisting (was "report flow contents")
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Hi Thomas, I fully agree with you. + 2 more comments. (1) Network wide blacklisting can be used to avoid some frequencies occupied by other networks in the same area. (2) Per-link blacklisting can be used when overprovision is applied. For example, we need the bandwidth from nodeA to nodeB is 15 cells per slotframe. Assume it is known that channel-22 is very bad, and others are in good condition. Then, we can schedule 16 cells in one slotframe, and skip channel-22 every time when encountering it. What do you think? Thanks Qin On Tue, Sep 17, 2013 at 2:16 AM, Thomas Watteyne <watteyne@eecs.berkeley.edu > wrote: > *[changed thread subject from 'report flow contents' to 'blacklisting > (was "report flow contents")']* > > All, > > Great discussion! > > Allow me to sum up. > > Problem statement: > > - At 2.4GHz, 16 orthogonal frequencies are available. > - "blind" channel hopping exploits frequencies diversity by hopping on > all 16 frequencies > - because of interference and multi-path fading, some frequencies > exhibit a worse Packet Delivery Ratio (PFD) than others > - if because of interference, it is possible that same set of > frequencies are "bad" in the whole network > - if because of multi-path fading, the set of "bad" frequencies is > different for every pair of neighbor nodes > > Network-wide blacklisting: > > - goal: prevent all nodes in the network to use a given frequency > - decision can be made by PCE after receiving statistics, or > administratively by operator configuration > - different mechanisms to blacklist a channel: > - modify the hopping pattern to include the same frequency twice > and remove another one. Can be done on-the-fly. > - consider there are only 15 frequencies, and build a schedule with > 15 channel offsets. Needs to be done before network starts (or long process > of "freeing-up" one channel offset) > - efficiency is limited since: > - because of multi-path fading, a "bad" channel might not be bad > for all bundles > - limits frequency diversity > > Per-link blacklisting: > > - goal: prevent a bundle (i.e. two neighbors scheduled to communicate) > to use a given frequency > - decision can be made based on the per-frequency statistics gathered > (packet counters and/or RSSI/LQI) > - problem: > - changing the hopping pattern for a single bundle can create > interference with other bundles since collisions are possible if hopping on > different sets of frequencies. > - solution (used by ISA100): > - cancel a scheduled communication if that communication happens on > the blacklisted channel > - note that this will reduce the bandwidth of that bundle by 1/16, > so needs possibly to be combined with adding 1/16 more cells to that bundle. > > Did I miss something? > > Thomas > > > On Mon, Sep 16, 2013 at 9:35 AM, <P.Zand@utwente.nl> wrote: > >> Hi Qin, >> >> "Link-by-link" adaptive channel hopping in ISA is used by a node to >> select the best frequencies for its further communication with its >> particular neighbor. >> And, cell over-provision (i.e. the combination of "channel offset" and >> "slot" info used for communication with a particular neighbor), might be >> used for evaluating the internal interference and BW requirements between >> two neighbors. Am I right? >> >> Best wishes, >> Pouria Zand >> >> On Sep 16, 2013, at 4:34 PM, "Qin Wang" <qinwang@berkeley.edu> wrote: >> >> 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, <P.Zand@utwente.nl> 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: 6tsch-bounces@ietf.org [mailto:6tsch-bounces@ietf.org] 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 <qinwang@berkeley.edu>: >>> > 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 >>> > <diego.dujovne@mail.udp.cl> 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 <qinwang@berkeley.edu>: >>> >> > 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 >>> >> >> >>> >> >> >>> >> >> _______________________________________________ >>> >> >> 6tsch mailing list >>> >> >> 6tsch@ietf.org >>> >> >> https://www.ietf.org/mailman/listinfo/6tsch >>> >> >> >>> >> > >>> >> > >>> >> > _______________________________________________ >>> >> > 6tsch mailing list >>> >> > 6tsch@ietf.org >>> >> > 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 >>> _______________________________________________ >>> 6tsch mailing list >>> 6tsch@ietf.org >>> https://www.ietf.org/mailman/listinfo/6tsch >>> >> >> > > _______________________________________________ > 6tsch mailing list > 6tsch@ietf.org > https://www.ietf.org/mailman/listinfo/6tsch > >
- Re: [6tsch] blacklisting (was "report flow conten… Thomas Watteyne
- [6tsch] blacklisting (was "report flow contents") Thomas Watteyne
- Re: [6tsch] blacklisting (was "report flow conten… Qin Wang