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Z-wave jamming problem


binoxGTS

Question

Hello,

I have strong reasons to believe  the HC3 that I am administering is getting jammed from time to time. There are periods when it works ok, and periods when I have big delays or it doesn't work at all.

I have a Z-wave Sniffer and today I caught something strange which looks like jamming . In that period my commands were  delayed or not executed at all.

My HC3  Home ID is D68BCAE6 the rest of ID's are very strange and all in a very short interval. 

Do you know about similar cases? 

 

 

 

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If you have a lot of non zwave plus devices, based on series 300 chipset, then what you see is "beaming" which normally is used to wake up FLIRS devices. But those old devices can BEAM for no good reason at al. The total length of a beam is 1.1 seconds. Any device trying to transmit at the same time will indeed be "jammed" and you will see CRC errors and routing issues.

 

On small networks (say up to 20 nodes) this can go undetected, the 1 second delays might be unfrequent and acceptable.

 

It is rarely discussed on the public forum but a few users talked to me about this and came to the same conclusion.

 

You can try to lower the traffic but ultimately replacing the "offending device" with a zwave plus variant is what I recommend.

 

Warning! Do not jump to conclusions, the device that is causing the trouble is not the device sending the beam.

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  • The sistem is big, around 200 devices but most of all (or maybe all of them ) are fibaro zwave+ devices.

    From what I understand in those 4 photos during only 2-3 seconds a lot of different zwave controllers lunched wake up beam messages. 

    I posted only 2-3 seconds of z-sniffer logs, but it lasted several minutes.

    It is hard to believe that in the range of this HC3 there are so many different z-wave controllers. 

    If those messages were launched by my HC3 or by one of my devices I think all should have the same Home ID, am I getting this wright?

     

     

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    2 minutes ago, binoxGTS said:

    The sistem is big, around 200 devices

    That is really big. I consider everything beyond 100 Z-Wave devices to be in the "requires attention" zone, and apparently you think the same because you are able to show Zniffer logs... that is good.

     

    3 minutes ago, binoxGTS said:

    most of all (or maybe all of them ) are fibaro zwave+ devices.

    Please do check the non-zwave devices anyway, I can tell you a little story. A friend of mind had several "roller shutter" devices. When he tried to control all devices at ones, the network could freeze for 1 minute. When the commands got spaced out by several seconds, the "jamming was better but still not 100% OK because the roller shutter sends position and power updates.

     

    So although we were dealing with only a few devices (from the top of memory, maybe 5) the "disturbance" was quite spectacular.

     

    7 minutes ago, binoxGTS said:

    It is hard to believe that in the range of this HC3 there are so many different z-wave controllers. 

    Yes, well, "Zniffer" is only listening to a signal, it makes almost no judgement about WHAT it hears. If it misses the start or stop of a packet, or 2 transmitters interfere, it registers garbage.

     

    Carefully positioning the Zniffer may help but even then interpretation of what you see is challenging

     

    For exampl, if a data packet contains this:

     

    55555555...

     

    or

     

    AAAAAAA...

     

    it means you have the "preamble" of the packet in the data. The preamble should not be visible, it is a sequence of 1010101... bits repeated to synchronise the receiver

     

    If you want to know more I can find the (public) document that describes various Z-Wave packets like the "beam" and "direct" and "ack" messages

     

    If I were you, I would focus on what happened right before the "jamming" started, so any packets before BEAM or before "Routed Errors", It might point to a certain device.

     

    I would like to offer some help but last time I've analysed a similar situation, it took me 12 hours to find cause and effect. At the moment I do not have 12 hours...

     

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    @petergebruers you raise a good point about clashing of signals when activating multiple devices. If you had a "goodnight" scene that switched off multiple (10+) Dimmer2's, would you recommend putting a two second delay between each activation? I assume the Home Centre queues up zwave messages that are to be sent, but from what you wrote, the problem is usually the number of messages coming back to the controller?

     

    Also, were the devices that your friend had Qubino Shutters??

     

     

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    7 hours ago, Tim__ said:

    @petergebruers you raise a good point about clashing of signals when activating multiple devices.

    Thanks. It is a rather complex issue though because Z-Wave has "Listen Before Talk" logic but that does not always work. This is really low level RF stuff and much of the phenomena, I have to explain them buy guessing how stuff works. 

     

    Another devious thing I forgot to mention is "Explorer Frames". Those are broadcasts sent when devices think they have no valid route to the destination and they can appear on large saturated networks. They do not always mean trouble but sometimes they make a device learn a long and "silly" route. Especially when part of the network is "BEAM-ing"

     

    7 hours ago, Tim__ said:

    If you had a "goodnight" scene that switched off multiple (10+) Dimmer2's, would you recommend putting a two second delay between each activation?

    When I started 10 years ago on HC2 it was definitely a wise thing to put in 150-250 ms or a bit more when sending a "salvo" of commands. IIRC it was even an official recommendation by Fibaro.

     

    Again, the details are somewhat devious, it is not always the sending that causes trouble, it is also the devices reporting back. Keeping some separation

     

    I haven't seen many complaints lately, I speculate that transition to HC3 and newer, Z-Wave Plus devices with better radios and protocols have helped. Also, old devices only do 9.6/40 kbit per second while all Z-Wave Plus devices also support 100 kbit/s

     

    Still, it makes sense to reduce reporting (for your database) and avoid sending data (eg repeatedly sending "on") that isn't needed.

     

    A few years ago I wrote a scene to help people to set parameters on some (known) spamming devices, I think it still works

     

     

    It is unmaintained because imho newer devices have better defaults, and I do own those newer modules and cannot test them

     

    7 hours ago, Tim__ said:

    Also, were the devices that your friend had Qubino Shutters??

    IIRC they were FGRM-222 so the model before the Roller Shutter 3 but I cannot find it in my notes, so, yeah, Qubino is possible because based on my observations it is 99% related to the "protocol version" of the module.

     

    If you go to "Devices" on your HC3, then pick a module, go to the "advanced" tab and have a look at Z-Wave version, for example:

     

    Z-Wave version: 3.52

     

    In my notes I talk a lot about the 3.52 as being "problematic" in the context of BEAMing, but it is likely that other 3.X may cause issues as well

     

    I bought mine in 2013-14 and after that the modules got hardware-upgraded to Z-Wave Plus.

     

    For sake of completeness: I cannot judge that from the screenshots but BEAMing is expected if the user has FGT-001 or Z-Wave Door Locks based on FLiRS, you can send data to them as if they were mains powered but to do that the protocol has to send a BEAM...

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  • Thank you all for  discussion and suggestions. 

    I understand now that what may seem jamming could be communication errors due to problematic modules generating high traffic.

    I also want to explain why I am thinking at jamming. The HC3 is installed in a villa located inside of a gated community where are living many foreign officials.

    On the villa just across the alley lives some important foreign official which is heavily guarded by special services from my country and from his country also. He has 2 pole type antennas on the villa, around 2-3m long, probably for some special communications. 

    I know that special communication should normally not interfere with public radio channels but those frequencies are different from region to region and I don't know what frequency they use.

    I also know that special services sometimes use jammers to make sure no "surprise device" can be triggered remotely along their route.

     

    If you were in my place how would you make sure the problem is caused by problematic modules/controller or there are indeed interferences with nearby radio transmissions?

     

     

     

     

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    29 minutes ago, binoxGTS said:

    If you were in my place how would you make sure the problem is caused by problematic modules/controller or there are indeed interferences with nearby radio transmissions?

    This is definitely not my field of expertise, but I want to speculate and give an option...

     

    Occam's Razor: "the simplest explanation is likely to be the most correct explanation"

     

    - you have a very large network. Beyond 50 nodes I recommend Zniffer (like you have) because without it you will be chasing ghosts. I know a few people with > 100 nodes and they use multiple controllers which can help depending a bit on the layout of your house

    - Zniffer sees lots of hexadecimal AAAA and 5555 in packets which means some modules are able to transmit data. This is not the "jamming signal", a real jamming signal is wideband and would be ramdom noise

    - Zniffer still decodes some Z-Wave Packets - so the jamming would be weak

    - You have periods of normal operation, then maybe 1 minute of disturbances. I am guessing that "jamming" would go on for much longer periods. But then again, I have not seen many "spy movies"

     

    I understand what you are saying and indeed the idea of "jamming" or some sort of external noise hitting the 868 MHz band is not impossible. I have noticed reports of alarm systems operating in the 868 range causing issues, but that is maybe 1 or 2 cases in 10 years. Those systems are low power so should be close to your Z-Wave network to cause problems.

     

    Here is an idea. I own a Software Defined Radio and it is capable of visualising analog radio signals in the 30-900MHz range (some have even wider range).

     

    I have used it to "listen" to my Z-Wave network before we got instructions to make a REAL Z-Wave sniffer

     

    This is a starting point: 

    Please login or register to see this link.

     

    That was in 2015. The software is free and still exists, it is called "SDR# (SDRSharp)"

     

    I cannot recommend hardware because I'have not followed the evolution of SDR, all I can say is that prices start at about 30 EUR and such a basic device would probably do the job.

     

    What would you use this SDR for. Simply put: observe a band of a few MHz around 868 MHz. If your Z-Wave network goes crazy and you see a rather narrow peak, then 99% certain it is a bunch of Z-Wave modules transmitting. If you see a broad spectrum over several 100s kHz or more then it is a transmitter, and possibly a jammer. If you install this on your laptop you can find the spot where the signal is strongest.

     

    It is not easy, but doable. I spent several hours investigating "disturbances" like that.

     

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  • Thank you very much for your answer, you are the second person who recommends trying with a SDR, so I guess I need to get one :)

    My other big concern is that I used ZW3 engine for each the remeshing function is not available yet ( neither in web interface or installer app).

    The HC3 was moved inside the house at some point and some of the battery powered modules were enrolled near the HC3 ( for faster enrollment) and then moved to their final position (I planned to do a network remesh  which was available at that moment but I didn't know it was not working)

    Normally I should make a network re-mesh but I can't. 

    Do you know if I do "reconfigure device" the meshing of that device will be redone?  A fibaro support guy said it wont, the fibaro trainer said it would...

     

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