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  1. #71
    gashead's Avatar
    gashead is offline Admin Verified: Best Accent Ever(Tm)
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    I don't want to seem bullish here, but......

    Wireless control is a stupid idea.

    In professional shows at least, far too many variables and unsafe if I'm honest.

    This demonstrates the Lazyness of the industry today, those who think it's a hassle running cables should be forced to tour for 2+ years with Multiple gas heads and plumbing, some heavy mains and distro.

    Thou shall also be made to empty the supply hoses of the remaining water after the gig for talking such rubbish.



    Nige.

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  2. #72
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    TBH Nige as to whether wireless is possible and safe, I see 2 different things.

    Wireless certainly has some issues to overcome to ensure it's reliable. I'm not convinced it isn't possible, but equally not convinced that it is. I think there are possibilities to explore...

    Safety, as I see it, comes not down to the wireless delivery, but how the DAC handles a lost or scrambled signal. I don't see any reason why wireless should be any less safe than wired as it's not the delivery that matters but the the processing. Does wired never lose signal or suffer interference? It might not be as prone, but I find it hard to believe it never happens. If you have a logic that on loss of signal or receipt of a partial or scrambled signal reverts to a safe state (whatever that may be eg loop from the last known good signal entered into the memory or total blackout), and that logic exists on it's own circuit, then safety shouldn't be at question.

  3. #73
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    Bah, you're running a wired estop already (RIGHT???), run ethernet too. Hell, run wired AND wireless ethernet (which is what I do). Use the wireless connection during setup to dial in the projectors on stage and then switch to wired control for the show. easy peasy. In fact, why not run multi-conductor cable and do it all through a single run?

    Don't run your show on wireless... c'mon.

  4. #74
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    Standard wireless is something I have some experience in running. Using tje 802.11x standard will not do when running in a crouded enviroment. It does not matter if you have your SSID all to your self. It is a matter of how many other devices sharing the same channel, and you have no controll over this.


    Quote Originally Posted by m0f View Post
    One of the big problems with 802.11x wireless for this type of application is that it is a standard, and every cell phone out there is using it too. So one could test it thoroughly all day in an empty room and have it working well, fill the room with 20000 people and 20000 cell phones trying to use wifi and latency becomes a huge problem. If ever there were a wireless solution for laser use, I'd think it would have to be a dedicated set of frequencies, and as every country has differing rules on that, and different frequencies in use, it becomes very difficult to accomplish.
    m0f is pointing toward the essence in why, at least, this kind of nettworking should not be used in live shows. One of our customers complains about slow nettwork for data, and poor response. Investigating the issue shows that the location is flooded with WL traffic, and all channels are occupied. There are simply no more room for in the air for the IP-packet to come through. Using topshelf Cisco equipment does not help. Cellphones in use are the biggest problem. Even without connection to a WLAN the unit broadcasts and generates noise. Asking 20000 people shutting down the wlan before the gig starts is not doable. Getting 200 poeple turning off theyr phone inside an airplane, threatning with big fines if they dont, does hardly work.
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  5. #75
    swamidog's Avatar
    swamidog is offline Jr. Woodchuckington Janitor III, Esq.
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    not to mention humans are mostly just weird sacks of rf blocking goo.

    Quote Originally Posted by Datsurb View Post
    Standard wireless is something I have some experience in running. Using tje 802.11x standard will not do when running in a crouded enviroment. It does not matter if you have your SSID all to your self. It is a matter of how many other devices sharing the same channel, and you have no controll over this.




    m0f is pointing toward the essence in why, at least, this kind of nettworking should not be used in live shows. One of our customers complains about slow nettwork for data, and poor response. Investigating the issue shows that the location is flooded with WL traffic, and all channels are occupied. There are simply no more room for in the air for the IP-packet to come through. Using topshelf Cisco equipment does not help. Cellphones in use are the biggest problem. Even without connection to a WLAN the unit broadcasts and generates noise. Asking 20000 people shutting down the wlan before the gig starts is not doable. Getting 200 poeple turning off theyr phone inside an airplane, threatning with big fines if they dont, does hardly work.
    Last edited by swamidog; 09-20-2014 at 09:25.
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  6. #76
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    would LINE OF SIGHT , highly directional , boosted power , antennae push out the interference from mobiles etc ??

    ?
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  7. #77
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    Quote Originally Posted by Lasermad View Post
    would LINE OF SIGHT , highly directional , boosted power , antennae push out the interference from mobiles etc ??
    Not really. The interferers are almost always going to be along the same line of sight as the controller and the laser have to each other, by virtue that the lasers are typically on one side of a crowd and the controller is on the other side. All of those interferers are getting the benefit of that extra receive gain from the directional antennas, and all of them are closer to the laser than the controller, so lots (relatively speaking) of power would be required to overcome that situation to the point that the receiver would not notice or care about the other radios in the path.

    The insurmountable problem with using 802.11 for this purpose is that the 802l.11 media access control layer (MAC), the software that decides when a buffer full of data can be sent, is designed for SHARING THE FREQUENCY. That means your data may not go when it needs to for a real-time application. This is the behavior of CSMA/CA (carrier-sense-multiple-access with collision avoidance, compare to ethernet's csma/cd, where collisions can be detected) and the Distributed Coordination Function of the 802.11 spec. You can overcome this for streaming application by adding buffers, but buffering adds latency to the control link, which I don't think anyone would accept in a production environment.

    Interestingly enough, there is a Point Coordination Function in the 802.11 spec wherein the access point controls who gets to talk when, so theoretically, it should be possible to have a two-member network, one of them being the access point, that could be adapted to a real-time application. However, even under Linux, I have never seen the PCF used. Even if it were available and stable, it would still have to contend with interference from other networks on the same channel. You could write your own firmware, but... once again we are off on a custom engineering path that is not really 802.11.

    802.11 is not suitable for this kind of real-time, low-latency, safety-critical control link. Let's just stop beating that horse.

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