  Cognitive relaying has been introduced for opportunistic spectrum access
systems by which a secondary node forwards primary packets whenever the primary
link faces an outage condition. For spectrum sharing systems, cognitive
relaying is parametrized by an interference power constraint level imposed on
the transmit power of the secondary user. For sensing-based spectrum sharing,
the probability of detection is also involved in packet relaying control. This
paper considers the choice of these two parameters so as to maximize the
secondary nodes' throughput under certain constraints. The analysis leads to a
Markov decision process using dynamic programming approach. The problem is
solved using value iteration. Finally, the structural properties of the
resulting optimal control are highlighted.
