Abstract —A power allocation and single relay selection scheme is proposed to improve the outage performance for a wireless cooperative network with multiple energy-harvesting relay nodes. The optimization problem is formulated to minimize the system outage probability under the constraints of both relay joint maximum transmit power and individual energy limitation caused by energy-harvesting. By using Lagrange multiplier method and KKT (Karush-Kuhn-Tucker) conditions, the optimal transmit power of multi-relay can be solved. Taking into consideration that single relay is more feasible to implement in practical communication scenarios, a best relay can be selected by calculating the contribution factor of relay nodes. In addition, the lower bound of system outage probability is derived in this paper. Simulation results show that the proposed power allocation and single relay selection scheme can reduce system outage probability efficiently, and verify the conclusion of the lower bound of outage probability.
 
Index Terms—Cooperative communication, Energy-Harvesting, outage probability, power allocation, relay selection