When the transceivers on node a and b have already pointed
with each other, link a_b becomes an Actual Link (AL), being
able to transmit data; otherwise, if only their transmitters are
pointed with other, link a_b is a Virtual Link* (VL). Because
the receiver and transmitter at a node are not paired, the resulting
network topology is temporary. While data transmission
need changes, the topology will change as well. Besides, due
to limited antennas at each node, at any time, it should be
satisfied that the input degree u(i) ≤ 1, and the output degree