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I want to build a small device (beacon) that can send its location (inside of a building) and can receive signals in order to output information on an LED screen. The beacon should communicate with a central unit.
So the device would be pretty similar to a Tile in many ways.

Here's a picture to illustrate the problem:

enter image description here The beacon is currently located in area 1. When pinged, it should either send back its exact coordinates (so that the central unit can calculate that the beacon is positioned in area 1) or the current area id.
Once the beacon is moved, it should of course update its position.
The areas are inside of a building, always rectangular and I can install hardware on site (e.g. on the four emitters in the corners of the rectangles). The side length of the areas is between 1 and 20 meters.

Right now, I am evaluating different possible technologies. The biggest challenge is that I need 2-way communication.

Other requirements:

  • The beacon should have a battery life of several months
  • The beacon should update its location on a regular basis (e.g. once a minute) and on demand (when triggered from the central unit)
  • There can be up to 5,000 beacons in one area at a time. They all have to work simultaneously

RFID
+ Passive (no need for batteries)
+ Cheap
+ Location detection should be fairly easy with "gates"
- Range probably too short for my scenario
- No 2-way communication possible (would need additional module)

Bluetooth
+ Battery life with low energy BT
+ Range should suffice
+ 2-way communication possible
- Not sure how many BT beacons can be connected to the central unit at once (probably not 5,000)
- Not sure how locating the beacon would work (signal strength?)

Wifi
+ Range
+ 2-way communication
+ Connection to thousands of beacons at the same time possible
- Not wure how locating the beacon would work (signal strength?)
- Battery life?

I highly appreciate any recommendations, tips and improvements. Right now, I don't really know which way to take and it would end in a lot of trial and error :)

Thanks so much.

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closed as too broad by Fred, Wasabi, JMac, hazzey, BarbalatsDilemma Apr 22 '17 at 18:07

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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Some thoughts on your options:

RFID, as you stated, likely won't work, most certainly not over 20 meters as low power devices, that's not what it is designed for.

Bluetooth and WiFi would work with signal strength measurement (proximity) and triangulation. The signal strength measurement could lack the desired accuracy, especially if you're in the 1m range. But if accuracy isn't very important, you probably should choose one of those.

As an alternative, I once worked with these RF Modules (low-power, good range, good precision), but 5'000 connections are not possible (if I remember it correctly). Maybe there are other solutions in this direction..

Anyway, sounds like an interesting project. (What do you need 5'000 beacons for?)

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  • $\begingroup$ Thanks - the RF modules seem interesting. The project is to keep track of moving parts in manufacturing. $\endgroup$ – horen Apr 21 '17 at 20:39

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