[SOLVED] How to fit 1000+ wifi devices into one room?

[TeaTable]

We're developing a smart lamp for growing plants. Each lamp is individually connected to the access point and receives commands from it. Now we're planning to make our lamp fit for big greenhouses and indoor farms. This would mean that there are will be multiple 100 if not more than 1000 devices in one room. How can we make the devices communicate with upstream without connection problems due to limited bandwith?

Strategies that I have come up with but are not satisfying (I guess)

• use mesh network for devices to connect with their neighbours before connecting to upstream
• use LORA (Low Range Wide Area Network, probably has the same downsides as wifi when it comes to big quantities?)
• use wired connections between lamps that are close together

What would you suggest? Does anyone have experience?

 

[lvt]

An access point is only good for 255 connected devices max.

 

[TeaTable]

@lvt That is true only for a subnet mask of 255.255.255.0. Just by using 255.255.0.0 (16 bit) I could already address up to 65’534 devices. The problem relies in bandwith and wifi interference. Any tips for that?

 

[JWNoctis]

I'm not well informed enough to offer any specific advice, but you might want to at least provide some kind of estimation for data bandwidth requirements(How is the lamp controlled? Does the lamp phone home? Just things like serial number and temperature, or live feed from integrated webcam, or something inbetween?), as well as any cost constraints.

It'd be hard for anyone to offer useful insights without at least those.

And whatever you do, please think hard about security. Worst case scenario, those indoors farm or greenhouse deploying your product could be turned into a rave at best, or a thousand-node botnet at worst, in short order.

 

[bill001g]

The IP subnet mask has nothing to do with how many device can connect to a AP. A AP does not use IP addresses it is a layer 2 device it understands only mac addresses.

There are a number of things that limit the number of connected devices.

The most common is the manufacture puts some artificial limit on the device that they feel is valid. Some of these numbers are very small for not real well documented reasons.

There are 2 common technical limits. The radio chipset must keep track of every mac addresses and all they encryption keys so every device needs some memory. The radio chip must also encrypt the data so the more traffic the more cpu power it takes. A bunch of idle devices will take much less cpu that say 2 or 3 watching hd netflix but even completely idle devices need fairly regular traffic to keep the encryption keys valid. So there likely is a point the radio chip would spend all its time polling devices if it got too many.

Now if you are actually manufacturing your own equipment you might be able to get more information from the wifi chipset manufacture about memory and cpu capacity but it is not something I have found that is avaialble to the public, years ago you had to sign NDA agreements to see it and still they limited who could even sign NDA.

Your other problem is going to be wifi is not designed to really run high density stuff. It is a half duplex protocol and to work properly the end devices must be able to hear each other. With that many devices you almost guarantee collision even if you are using different AP.

I suspect a different technology will be best. I know for example the power and water companies use some form of wireless transmitter so they no longer have to read meters. The power one updates every 10 minutes so that is quite a bit of traffic when consider apartment buildings that can have groups of 100s of meters.

This forum is mostly a consumer equipment forum. If you are really going to manufacture a product you have much more ability to contact manufactures of various wireless technology and get assistance. They have sales people who will really want to sell you chips you can place in your product.

 

[TeaTable]

Thanks for your elaborate answer @bill001g ! I will look out for an alternative technology then.

@JWNoctis Yes we thought about that and are using TLS 1.2 and also thinking about flash encryption. You're right that a hacker could turn the whole thing into a botnet :X