computer networks – Multiplexing problem

Suppose a shared medium M offers to hosts $A_1 ,A_2 ,…,A_N$ in round-robin fashion an opportunity to transmit one packet; hosts that have nothing to send immediately relinquish M. How does this differ from Statistical multiplexing? How does network utilization of this scheme compare with Statistical multiplexing?

I don’t understand what are the differences between these two schemes as they send on packet-by-packet basis.