Communication architecture with XBee S2C

I am building a project using Xbee ZigBee pro (S2C)

Raspberry Pi acts as a coordinator
TI-based microcontrollers act as ED or Router

For power saving, I am thinking of making all the microcontrollers as ED. So no Router in the network.

1. Realistically, the Router: ED =1:8. Now if I don't have any Router in my network, what is the ratio of Coordinator: ED?

2. How many Router per coordinator in case I decide to do that?

    3. In my project, the coordinator needs to send commands to specific ED, receive data back from ED and needs to determine which ED is the data coming from and/or going to. I understand my cooordinator needs to run in API mode. Does the ED also needs to run in API mode? Or AT mode is enough for the ED in this scenario?
  1. In S2C modules, each Coordinator or Router can have upto 20 child End Devices under it. Check ‘NC’ parameter.

  2. There is no required/defined Coordinator:Router ratio. User sufficient routers that provided good network range and smooth data transfer.

  3. ED can run in AT mode since it need not know source of incoming data and will always respond back to coordinator.

  1. If coordinator wants to know from which ED the message is coming from, then ED also needs to be in API mode, send an ‘tx’ packet in API packet format to the coordinator/router right?

no need. Keep ED in API mode if you want ED to know originator of data payload.