Intelligent water drops based joint subcarrier pairing and power allocation with fairness in cooperative relay networks

In this paper, we propose a joint subcarrier pairing and power allocation (JS2PA) scheme with fairness based on the intelligent water drop (IWD) optimization method for orthogonal frequency division multiple access cooperative relay networks. The proposed scheme consists of a subcarrier pairing and selection al- gorithm and a power allocation algorithm. We first formulate the JS2PA problem as a mixed integer programming problem aiming to maximize the total network utility under the constraints of in- dividual power, subcarrier fairness requirement and pairing. To solve the non-convex JS2PA problem, firstly, we propose a subcar- rier pairing and selection algorithm based on Hungarian method so as to select the appropriate subcarrier pairs for relaying. Sec- ondly, we provide a power allocation algorithm based on the IWD method in which water drops act as the agents to find the optimal power allocation for each node. In particular, to improve the opti- mality of power allocation, we integrate network utility and power requirement into heuristic function to measure the desirability of the IWD selecting the next visiting node. Finally, we conduct sim- ulations to validate the proposed algorithms and the results show that the proposed JS2PA scheme outperforms the existing methods in terms of convergence, total network utility and fairness.