Power Splitting and Virtual Power Allocation for Virtual Cell in Ultra-Dense Networks

In the ultra-dense network scenario, a joint power allocation scheme is proposed to maximize the sum rate of user-centric overlapped virtual cell systems. The optimal power allocation is firstly modeled with hierarchical framework and decomposed into two subproblems: power splitting and virtual power allocation, then it is solved by the alternating iteration between the two subproblems. The power splitting is obtained by an SLNR (signal to leakage plus noise ratio)-based algorithm with the introducing of Lagrangian function, and virtual power allocation is achieved by a binary iterative water-filling algorithm. As the power splitting coefficient takes the form of eigenvector which maximizes SLNR, a balanced effect on signal enhancement and interference reduction is achieved. Simulation results show that the proposed algorithm is superior to conventional power allocation algorithms in performance, as it effectively reduces interference and increases the sum rate of the system.