[seanwitte]

The trick is making sure that only one robot transmits at a time. Assuming the population is known you can assign them each a unique ID. They will broadcast to the whole population a packet that includes the sender, intended recipient(s), and the data. The other robots will wait until its their turn based on their ID and the ID of the last sender. Assume robots A, B, C, and D. B can't send until A does, C can't until B, etc. If a robot transmits and doesn't hear anything from the next it will resend or send a packet to skip the next robot.

An alternative would be to promote one as the master and have it tell the others when its their turn to transmit. Assume robots A, B, C, and D, with A as the master. B, C, and D will not send anything until they receive a request from A. A will iterate through the known population and allow them to send their data in turn. Only one should ever be sending at a time so they can share the same channel. They should all listen to the broadcast packets so they know what the other units are doing.