The design involves a single base station that communicates with multiple peripheral units. Peripheral units should be able to communicate back to the base station but are not required to communicate between them.
It would be best if some mechanism exists so that when a peripheral unit tries to send data to the base station while another is sending data it will get into a queue.
The amount of data is not great and not continues, more like bursts of 50 bytes or so once in a few minutes / hours.
The system should be low cost as possible with ranges up to 100m in open space under ideal conditions.
If I could pick a close example from wired bus world I guess it would be I2C where each peripheral has an address.