RF Line of Sight (Obsticles)

Q&A forumCategory: QuestionsRF Line of Sight (Obsticles)
John Yeoman asked 3 weeks ago

I have a setup where I’m planning on having a base station and multiple rovers.  The rover units will control small autonomous tractor units on my farm.  However, I have several buildings that they will have to work around.  If you have a setup where the rover will need to move on both sides of a building and true line of sight is not possible, what are the options?  

Ardusimple Staff replied 2 weeks ago

Note that the system is able to navigate without corrections will centimeter accuracy for 10-20 seconds, and then slowly starts degrading. If you can make sure your robots never stop behind the “blind spots” it might work.

Alternatively you can use NTRIP and use a technology that doesn’t have problems going through buildings like 4G.

1 Answers
jhnymn2002 answered 2 weeks ago

Not stopping in the blind spots is an option, but one I’d like to avoid.  
My limited understanding of the XBEE radio network is that it is a self forming mesh network where the radios have one of three configurations (End Point, Coordinator, and Router).  In a network with three radios on the same network, the coordinator could talk directly to the end point, but if the end point moved out of range of the coordinator, then if it was within range of the router, it would still get the communication through that leg of the mesh.  I assume in your configured systems, the base station is the coordinator that sets up the network and the rover is the End Point.  I have several questions here?

  1. Is my understanding of the xbee correct?  Please correct me if I got this wrong.
  2. Could one or more Routers be added to the network to fix the line of sight issues and relay the data?
  3. How is the network address set up?  A default ID or a random ID?
  4. If I have a setup like this and my neighbor does as well, how does my modules know which network to connect to?
  5. Is it possible to add additional nodes and messages to the network without disrupting your correction data communication?

Thanks for your time,

Ardusimple Staff replied 2 weeks ago

1. That’s one way of using the XBee radios yes. We use a different configuration which is broadcast only.
2. You could setup this with the impact that your radio-to-radio range would drop, but with the advantage of adding relays. But note that your network throughput will drop and latency will increase.
3. Unfortunately for this I need to address you to the Digi documentation…
4. The modules without an external CPU are “not smart”, i.e. either you tell them to which network to connect to or you build a mesh network, they cannot choose between 2 different networks on their own. To do so you need to add a CPU and take this decision for them.
5. There’s still some bandwidth left in the default configuration for sending RTCM messages yes, but not much.