FB4

[tribble]

The very latest high end wireless routers use 2 frequency bands simultaneously and should have low latency due to both their speed and processing power.

It's not all about the processor. The CSMA/CA MAC is just not made for tight latency, low-jitter links. The baseband firmware in these radios is all from the same few OEMs regardless which GUI someone slaps on it, and they are all just good enough for the consumer market. Drivers are updated only when something blatantly fails, otherwise, staff are working on next year's model (or next quarter's model.)

It's entirely possible to make a highly reliable and suitable wireless link for this application, but I wouldn't base it on 802.11, and I suspect it would take more engineering than most expect.

[m0f]

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.

[Pockels]

Wireless in large venues is not a case of sticking in the highest power transmitter/receiver in place that you can lay your hands on. There are too many variables to go into here - Frequency used & distance between projectors and control will have a bearing on the height your RF kit needs to be to avoid Fresnel zone losses. Then there's the question of uni versus omni directional antenna hardware.

On the subject of frequencies, there are papers suggesting that 2.4GHz is more stable than 5 over the same distance.

[White-Light]

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.

It's about to become easier in Europe as there's currently a standardisation of frequencies going on. So in the near future, all European countries should be using the same frequencies for the same purposes.

http://europa.eu/legislation_summari...l24218a_en.htm

I accept the issue with wireless and phones although would they interefere? All they could do surely is detect and try to join the network which would be rejected anyway if it had security implemented such as WAP.

One thought that occurred to me a while ago would be to use a specific frequency within the band allocated to Private Mobile Radio use (walkie talkies if you like!) if the authorities agreed. At most events, PMR wouldn't be in use.

Maybe at large festivals where it was either ethernet could be used instead, or PMR channel selected by the organisers to be as far away from the laser communication channel as possible. One complication is that in the UK at least (not sure about Europe), a PMR license is required.

As very few PMR's are in use and range is limited, the chance of intereference would be low and any competing signal would likely be weak as it would be distant if not at the event itself.

I'm not sure how this would all fit in with the US, but assuming the US uses a different part of the spectrum, the choices would appear to be a dual band product switcheable for EU / US use, or separate product lines for EU / US. I would have thought with the latter, the respective size of each market would make it viable. For non EU / US countries, it might no be viable to have such a product, as each market would be too small to justify the cost.

Would this solution work? I don't know, only Pangolin could evalutate it closely. However, it is food for thought....

[Lasermad]

are you serious WL , can you REALLY imagine trying to explain to O hagen ,or ANY other H&S worth his salt aye its awrite pal , th signal wont in tefere as its LIKELY to be weak , oh and i have told the organizer ( 21 year olds ) to keep on a different channel ! nae worries their 18 year old security guards wont fiddle with their new electronic toys just handed out to them and play on any other channels

Maybe i picked you up wrong WL but it sounds like there's a lot of openings for human error in the scenario you paint so to answer your question , nae chance pal

[White-Light]

I'm just mooting possibilities.

Getting a frequency totally exclusive to laser would be nigh on impossible I fear in a crowded spectrum and even then cross channel interference couldn't be ruled out.

However, isn't there human error in any scenario though?

eg. you can have Ethernet but it can become detached even if you're careful be it through unforeseen equipment failure or human interference.

Surely what's important here is how the DAC (mounted at the laser end) deals with a loss of signal or scrambled signal rather than a 100% guarantee of no loss of signal.

However, also on the subject of interference, when was the last time your digital mobile phone suffered interference?

Yet there are 10's of millions of users out there and probably a few using their mobile at the same time in your area on the same frequency as you are on any given phone call. So there must be ways of mitigating it (not sure how phones achieve it (- encryption, intelligent switching???)

However, as I said above, surely the really important factor is how the DAC deals with it. One way to ensure safety using a Pangolin Wireless connection could be to tie the receiver into the DAC (even if it's a separate module) and use a digital hand shake so 3rd party DAC's couldn't be used with it. That way behaviour on loss of signal becomes predictable if the Pangolin DAC is set up for safety (which pretty much goes without saying on Pangolin gear). I can't see how H&S would be an issue if the behaviour was always guaranteed safe.

[swamidog]

the only safe way for a DAC to handle the loss of a data connection is to stop blasting signals to the laser projector.

do you want to explain to your client that the lasers stopped working because too many little raver kids with pacifiers and led gloves were posting selfies on facebook?

[tribble]

However, also on the subject of interference, when was the last time your digital mobile phone suffered interference?

Every minute of every call anyone is ever on. CDMA and GSM systems are designed to operate every link on the ragged edge of the receiver's Eb/No curves to maximize the number of calls they can carry simultaneously with a given cell infrastructure cost. Errors are frequent but not significant enough that you can't pick out most of what that person who sounds like they're talking from under a kiddie pool filled with jello is saying. The vocoders are lossy, and when a packet gets dropped it doesn't matter much; people don't speak continuously anyway. High-rate low-error digital data links such as would be required for a laser DAC link cannot be operated in the same area of the performance curve. I'm not saying it can't be done; it can, and it has been for other purposes... but it's not simple, and it's not cheap to design.

[White-Light]

the only safe way for a DAC to handle the loss of a data connection is to stop blasting signals to the laser projector.

Are you sure about that, because from memory I'm pretty sure the Qm2000 card pre-loads shows and keeps running from it's memory if the connection to the host PC is lost. I'm sure that was always one of the boasts of the system, that it keeps going even if the PC crashes.

do you want to explain to your client that the lasers stopped working because too many little raver kids with pacifiers and led gloves were posting selfies on facebook?

I'm still not sure how you think this would happen. The clients couldn't log onto your network if you were using a wifi network based solution with a secured network. So that rules out uploading selfies on your network.

The only option for a client to do this, would be if you were very close to a nearby building which had an unsecured wifi network but most clubs are not in residential areas due to planning constraints and businesses never have unsecured networks. Also most home wifi networks in any event are no longer unsecured (not an issue anyway in a non residential area), and any unsecured network would show on the network icon in the control PC's system tray, so you'd be fully aware in the rare event of an unsecured network being within range within the club, in which case you could make the decision to use ethernet.

As for uploading selfies, via 3G / 4G, in the UK 3G uses 2.1Ghz and 800mhz, and 4G uses 1.8Ghz.

WiFi uses 2.5Ghz and 5Ghz, so completely separate.

Couldn't comment on the US.

Every minute of every call anyone is ever on. CDMA and GSM systems are designed to operate every link on the ragged edge of the receiver's Eb/No curves to maximize the number of calls they can carry simultaneously with a given cell infrastructure cost. Errors are frequent but not significant enough that you can't pick out most of what that person who sounds like they're talking from under a kiddie pool filled with jello is saying. The vocoders are lossy, and when a packet gets dropped it doesn't matter much; people don't speak continuously anyway. High-rate low-error digital data links such as would be required for a laser DAC link cannot be operated in the same area of the performance curve. I'm not saying it can't be done; it can, and it has been for other purposes... but it's not simple, and it's not cheap to design.

Well it's clear you know a lot more about mobile telecoms than I do.

I must admit though, that maybe I just never notice it, but in the UK call quality is very interference free on the face of it. The only real time you get aberrations or drop outs is on the move, but that's down to coverage and physical terrain rather than interference. Sit in eg a coffee shop with good coverage with lots of other people on the phone, and call quality appears to remain perfect (albeit slightly tinny which no doubt is down to low data rates designed to accommodate high call traffic volumes on the network).

[Lasermad]

I think my real point was , its ok for us hobbyist to play but when it comes to commercial products , dealing in hope and possibles wont work , im surprised you suggested it .. only defined and definates are available to commercial products