Author Topic: How many RFM95 LoRa radios can transmit to one receiver?  (Read 2614 times)

akstudios

  • NewMember
  • *
  • Posts: 28
How many RFM95 LoRa radios can transmit to one receiver?
« on: February 22, 2018, 06:14:47 AM »
I have a few Moteino boards with RFM95 modules and I was able to transmit data from one to another using the RadioHead library. I was also able to transmit from two modules to a third one that was programmed to receive data. Did some basic low bitrate setting and experimented with some outdoor tests in the heart of downtown Chicago and got more than 0.5 miles through densely populated buildings and everything in between. I'm sure I can push it more if I play around.

My question is:

Unlike RFM69 modules and the LPL library however (that have node IDs assigned to them), how many LoRa radios can you use to send to a gateway/receiving radio? I don't see any straight forward way of assigning a "node ID" or a "network ID", apart from adding it manually to the data packet itself to differentiate between the data. If I use, let's say 20 radios in a radius of 1 km that all transmit some packets in the air at some interval, would they all go through? Would there be cross-talk or interference? Or is LoRa more designed for communication between two radios only? Is there a hard or soft limit to how many radios you can have talking to one radio (apart from transmit speed and network congestion)? Still new to LoRa, so trying to figure this out.

Thanks!

LukaQ

  • Sr. Member
  • ****
  • Posts: 302
  • Country: si
Re: How many RFM95 LoRa radios can transmit to one receiver?
« Reply #1 on: February 22, 2018, 12:58:49 PM »
How do you now know which is which?

akstudios

  • NewMember
  • *
  • Posts: 28
Re: How many RFM95 LoRa radios can transmit to one receiver?
« Reply #2 on: March 05, 2018, 08:33:26 PM »
LukaQ, my bad, I didn't notice this reply!

I currently identify the nodes by modifying the datapacket. The format I'm using for the packet is like this: i:2,t:23.56,h:45.21

In the above example, I add "i:2" referring to node #2. I change it to "i:43" for node #43. I'm parsing that out in backend. Just wondering if this will scale up to several 20-30 nodes, as I plan on purchasing several Moteinos with the RFM96 chips. The other problem is, what is the "gateway" node ID? All nodes can listen and transmit to all others, so it appears that with lower bandwidth, there would be more traffic and interference as you increase the number of nodes, and consequently, lost packets.

Leonid49

  • NewMember
  • *
  • Posts: 20
  • Country: ua
Re: How many RFM95 LoRa radios can transmit to one receiver?
« Reply #3 on: March 29, 2018, 04:56:31 AM »
Hi akstudios.
Add in Your sketches RHDatagram.h from RadioHead library. This allows You ability to set addresses for the serwer and clients.
See also examples in an RadioHead.examples.rf95.rf95_reliable_datagram_cl ient(or rf95_reliable_datagram_server).
These examples shows how to reach Your goal.
Regards.