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I am developing a device that consists of a base station and several wireless sensor nodes. In application there may be up to 30 of these devices in a laboratory with up to 5 sensor nodes communicating with each base station. The sensors will be sampling and sending data at up to 4kHz at 12bits.

Without developing my own wireless protocol at 915MHz (to get away from busy 2.4GHz) it seems that bluetooth offers the best interference handling (using frequency hopping) of the many 2.4ghz wireless protocols available.

Has anyone had any experience with ~100 bluetooth devices or ~30 piconets operating in the same room?

I have thought about using 6LoWPAN at 915MHz but cannot find any information related to how it would handle the interference my application could cause.

Thanks!

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100 bluetooth devices in the same room doesn't seem sustainable to me. Bluetooth does select channels depending on if they're busy, but the issue is that it needs a minimum of 20 channels, and with that many devices, it might be hard to do. A custom system might be required here. –  Gustavo Litovsky Jan 11 '13 at 3:53
    
Thank you for your thoughts. Do you have any suggestions for the basis of a custom system? –  MButler Jan 13 '13 at 21:43
    
There are many factors that go into designing one. If you think you'll have interference from WiFi, then stick to 900MHz band. Depending on the network topology, you can assign different channels and cut down on interference. Then using time division you can place multiple devices in the same channel. Look around for different wireless sensor network protocols. Hopefully one of them can deliver what you need. Start small and scale from there. –  Gustavo Litovsky Jan 13 '13 at 23:32
    
Yes Wifi will definitely be present so sticking to sub 1ghz protocols is probably wise. Thank you for your suggestions –  MButler Jan 14 '13 at 0:37
    
It seems that 915mhz is only approved for use in region 1 (Americas) en.wikipedia.org/wiki/ITU_region. These devices must be able to be used world wide - Surely we must be able to get away with using 915MHz in the other parts of the world. I know of many 915MHz products that are sold worldwide... –  MButler Jan 14 '13 at 1:06

1 Answer 1

I work in a testing facility that particularly tests phones and infotainment systems; there can be up to 20 different piconets running at the same time.

As you said, Bluetooth is incredible at avoiding interference through the frequency hopping spectrum and data whitening, an additional encryption that Bluetooth uses. From what I recall, the data whitening can only be decrypted with the Bluetooth address of the Master device. I do know that the timing of the hopping is determined by this address.

In summary, it will be unlikely that you encounter interference. If you do, perhaps consider building a large Faraday cage :)

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