Mesh or Point to Multipoint?

I need to get sensor data from each sensor to every other sensor on the network but I am having trouble envisioning how the network is set up. I have selected Digi XBee-PRO® 900HP with dipole antennas.

  1. Each device needs to receive and process the sensor data from every other device.
  2. Nominally, the network will have about 12 devices in 2 clusters (5 and 7) about a mile apart. However, it is possible to have a maximum of 25 devices in 3 clusters with each cluster about one mile from the other clusters.
  3. Each device will have an XBee radio and a MCU to process the data.
  4. Assume that all the devices within a cluster can communicate with each other without a hop.
  5. Assume that one of the devices in each cluster will be mounted high enough to be able to reliably transmit and receive data from the other cluster(s).
  6. The sensor data packet is approximately 70 bytes.
  7. The network needs to be self healing to the extent that individual devices may move between clusters. I would not want to have to reconfigure the network each time a device moves between clusters.
  8. Ideally, each device would be equal to all other devices in hardware and software, other than its node type, address and ID.

My questions are:

A. Since all data is shared, should this be set up as a mesh or point to multipoint? Or something else?
B. Time is critical to this application and ideally, data would be refreshed within one second when set to “run” mode. Are there any tricks to high speed XBee networks?
C. How do I calculate throughput?

I have read the Networking Methods chapter of the 900HP manual several times without seeing a clear path. Any advice would be much appreciated.

If the devices can all communicate with each other, then it doesn’t really matter whether you are using mesh or a P2MP network as they will function the same. However, one thing to note is that the P2MP network has a slower RF data rate of only 10kbps, but the tradeoff is that you get longer range.