Peer-to-Peer/Adhoc Radio Network

[beefence]

Hi everyone, we are having an interesting problem that I could use some advice on.

We have 20 seacans, each having its own switch, PLC, HMI and process equipment. Static IP addressing is used, and all IP addresses for all devices in all seacans will be on the same subnet.

Of the 20 seacans, three are chosen and sent to a site together. When on-site, the PLC in each seacan will poll the other 2 PLCs for data. Poll frequency will be less than one/second and bandwidth usage will be low. To allow this PLC-to-PLC polling, we want to network the on-site seacans via radio/access points, essentially creating a single private network on site. All radios need to be able to initiate communication. Sites are small and line of sight should not be an issue.

All radios/access points need to have the same configuration (i.e. no master or slave radios); this will allow seacans to be chosen at random and minimize future radio configuration changes. What we are hoping to accomplish is that when the seacans get to site and are powered up, the adhoc network is formed and they can freely communicate with each other without involvement from field staff.

Finding radios that allow for the creation of an adhoc network has been challenging. We've received quotes for mesh radios and other fancy models, but I can't shake the feeling there is something simple and elegant that can satisfy our requirements. Can anyone recommend a brand or model that could work?

Thanks

 

[IRstuff]

No idea what a "seacan" is, but machts nichts. The critical thing that you've not provided is the distance between the nodes. Is there cell service? Have you considered WiFi, Bluetooth, ZigBee, etc.?

TTFN
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[beefence]

A seacan is a big rectangular metal box that is easily transported by trucks and boats, check out the image below. They're really sturdy and can be used for more temporary or mobile processes like the one we're working on. I saw a drag reducing agent injection skid that was inside a seacan a little while ago, kinda neat.

The distance between the nodes should be less than 100 meters, line of sight shouldn't be a problem. There is cell service and we have Sixnet modems for collection of data from off-site, but I don't think that would be the best solution for our on-site node-to-node communication issues. Could WiFi work without a wireless router? I'm not very familiar with ZigBee, I'll do some research on it.

In the end, if all radio signals can reach all other radios on site and use CSMA/CA for media access control, should they really need a master or hub or other infrastucture to make it work?

 

[DRWeig]

At less than 100 meters, you should be able to employ off-the-shelf single-point wifi adapters. My new LG television made an ad-hoc network with my PC no troubles, and I can chase it down with a laptop from my daughter's house just over 200 meters away. Adding others to the little network is a matter of entering a password once at initial config time. They remember each other.

Try it with two of these: Belkin N300

If you need range boost, wifi repeaters are cheap. You shouldn't need an actual router if you've done your polling software properly.


Best to you,

Goober Dave

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[Noway2]

Finding radios that allow for the creation of an adhoc network has been challenging. We've received quotes for mesh radios and other fancy models, but I can't shake the feeling there is something simple and elegant that can satisfy our requirements. Can anyone recommend a brand or model that could work?

This unit was recommended to me for a similar application, and it is what I used:

http://www.esteem.com/products/195eg-24-ghz-54-mbps.html