“…Similarly, the work of [43,44,45,46] targets the energy efficiency of CR users, but they do not consider the PU activity. Also, all of the aforementioned schemes [37,38,39,40,41,42,43,44,45,46] ignores the availability of the channels due to their lack in consideration of PU activity. To illustrate the performance gain of our proposed scheme, we compare the greedy and random schemes with the proposed RF source association and channel-sharing mechanisms [34,47].…”