  Wireless energy harvesting constitutes an effective way to prolong the
lifetime of wireless networks. In this paper, an opportunistic
decode-and-forward cooperative communication system is investigated, where the
energy-constrained relays harvest energy from the received information signal
and the co-channel interference (CCI) signals and then use that harvested
energy to forward the correctly decoded signal to the destination. Different
from conventional relaying system with constant energy supplier, the
transmission power of the energy-constrained relay depends on the available
energy that harvested, which is a random process. Best relay selection that
takes into account all the impacting ingredients on the received signal quality
at the destination is deployed. The exact closed-form expression of the outage
probability is derived, and the optimal value of the energy harvesting ratio
for achieving minimum outage is numerically investigated. In addition, the
impacts of the CCI signals on the system's outage and diversity performances
are analyzed. It is shown that the proposed relaying scheme can achieve full
diversity order equal to the number of relays without the need of fixed power
supplier.
