802.11

[fluppet]

Presumably the 0.3s latency is dominated by the internet latency and the bandwidth taken up by the video signal (unless its a completely different frequency). For the purposes of running a local connection Id expect latency to be a few milliseconds, especially if the machine isnt tied up with trying to run Windows as well. (Linux isnt all that well suited either, although theres a bit more control and there are pseudo RTOS variants - Im tempted to see if BeOS has any WiFi drivers).

Trying to run a video signal back the other way (especially if something is playing with inter-frame compression, which is inherently laggy) is bound to cause havoc!

A commendable effort (Id seen the posts before), but its practicality or lack thereof isnt indicative of the result of using the same technology locally.

Ignoring for a minute the question of whether its a good idea, is there any technical reason this shouldnt be considered?

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Fluppet

[jim]

I didnt meant to disparage the idea, I think its well worth looking into. It could provide many advantages over the current radio control options.

[fluppet]

Sorry Jim - I was a bit more defensive than I meant to be because I wanted to make it clear to other readers that two different things were being discussed.

Obviously 802.11 has overheads in comparison to a simpler system, but as you say it does have advantages once youve already got a control system of the appropriate complexity. (Its a sledgehammer to crack a nut, but if youve already got the sledgehammer and youve got a nut to crack...)

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Fluppet

[friet]

Gents,

It wouldnt work in an arena environment. Not enough transmitting power and reception sensitivity. You have to know that WiFi only works well within certain parameters ie. in your home...and not inside a steel cage buzzing with signals....hell it doesnt even work properly in some homes...(eg. when the floors/ceilings are made of fortified concrete..full of iron).

But I would like a way to do two way communication with our robots...eg. for telemetry, health status, etc.

cheers,

Frank

[fluppet]

Whoops - sorry, Id half written a reply to Frank, then failed to post it.

I have to say Ive never had a reception problem with 802.11b (with the base station wedged behind large metal boxes), although my house is hardly huge. Ill take your word for it that the arena is too noisy, but on paper the range is good enough, and the fail-back to slower modes should degrade gracefully. Id have expected it to kind of cope (if not at full rate), but if youve tried it and it doesnt then Im certainly not going to argue. It would be embarrassing to find a signal doesnt get through the railings at Debenham, say. (Im sure things could be improved with a high power antenna, but allowing this while disallowing boosted 40MHz antennae seems unreasonable).

40MHz wireless modem it is, then (or the equivalent components). With a bidirectional link, obviously. Now to dig out the part numbers someone suggested to me in the past... (just when £20 of 802.11 cards looked promising).

Incidentally, my feeling is that a lot of fights struggle because of reception problems, and that it might be fairer to try to do some things to the arena to improve reception (pipe the antenna to the middle of the ceiling, add radio-absorbing material to the walls, make the arena a Faraday cage so the equipment outside doesnt interfere, that kind of jazz). Perhaps when people have got rich on their class 1 arenas...

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Fluppet

[roger_plant]

I have just installed 802.11 g on my computers.
The Adsl hub/WAN point is indoors in a wooden portacabin.
Having just taken the laptop for a walk outdoors, I found it worked well up to about 100 metres BUT only when stood still.
As soon as I started to move when the range was greater than 20 metres, the link light when out but came on again soon after I stopped moving.
That does not sound good for controlling a moving robot.

[fluppet]

Thanks for the feedback, Roger! Ive had limited experience (Ive only got a card in one machine, and Ive cunningly misplaced the charger for it...) so Im prepared to believe its a bit flakey. Id expect 802.11b to do a little better than .11g, but not so much so that signs of .11g failing to cope dont bode poorly.

Ill plan to go down the route of hijacking the signal from a normal 40MHz transceiver for now, then.

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Fluppet

[fwsorg]

Would like to discuss this with you on sat Andrew if youre coming to the unofficial social.

Eddy

P.S There was a bluetooth controlled ant at the FeatherWeight Smash 2004. Obviously no good for anything larger, but fun nonetheless.

[stu]

Im starting to wonder about that Eddy.
It was 100% safe and needed a password either side, on the receiver and transmitter, i cant see anything unsafe about it to be honest.

Mr Stu