I am working on an arduino-based robot that might be used in a classroom environment, in which case there could be forty of them in a single room. If I want them to be wireless, what problems might arise that I wouldn't find with just a few systems (e.g. interference)? On the single robot level we were thinking of playing around with nrf, bluetooth, and xbee off-the-shelf systems. What would be the pros and cons of these (and other?) systems in this sort of high density environment?

  • 1
    \$\begingroup\$ If the total payload data rate is not very high you could implement a time-sharing scheme with a master and slave system. The master allocates say 40 time slots, 1 for each individual pair of radios. If the actual data rate is 9600 and each controller sends maybe 4 bytes for control of its robot then a 5msec slot would do and every 200msec the controller gets another crack of the whip. \$\endgroup\$ – Andy aka Sep 26 '13 at 22:40

There are a lot of variables involved. Questions to ask yourself would be:

  1. How many RF channels does the protocol allow?

  2. What is the network topology? Can you get away with multiple masters or peer-to-peer networks? Can a master scan RF channels if a master/slave implementation is needed?

  3. If you are using a off-the-shelf system how many nodes or addresses are allocated to the protocol?

  4. How much data does each protocol allowed to be sent in a packet PLUS the overhead data the protocol needs to send?

  5. How fast do you need to send data?

If you take all of these together you can play a numbers game to see which one would work for your classroom. Maybe a couple of masters with only 10 or 20 devices could get the data rate you need on separate channels?

A quick search on Google shows XBEE has 16 channels and can have a 16 or 64 bit address.

Problems that could arise if these weren't being considered:

  1. Flooded bandwidth
  2. Slower data rate
  3. Not enough addresses for all of the devices (anything over 5 bit addressing should cover it though)
  4. Interference from an outside source such as another network or something like a microwave

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.