Power control and resource allocation for capacity improvement in picocell downlinks

In this paper we study the power control of multiuser orthogonal frequency division multiplexing (OFDM) transmissions in a heterogeneous network which features macro user equipments (MUEs) and pico user equipments (PUEs) sharing the same resource blocks (RBs) during downlink. We aim to maximize the sum capacity of PUEs while meeting the performance constraints of MUEs. Because of mutual interference caused by RB reuse, the transmission power of every RB is to be individually controlled, leading to a more complex problem of resource allocation and power control optimization. Our proposed approach is to first reformulate the original mixed integer programming problem into a convex power control problem by dropping the allocation variables. Secondly, we propose a fast and effective power control algorithm to solve the convex problem by exploiting the Karush-Kuhn-Tucker conditions of power control. Finally, we propose a suboptimal resource allocation scheme and present numerical results for performance evaluation.