Two-tier OFDMA cellular cloud-RAN: Joint resource allocation and admission control

We present a joint resource allocation (RA) and admission control (AC) framework for an orthogonal frequency-division multiple access (OFDMA)-based cellular network composed of a macrocell overlaid by small cells in cloud radio access network (C-RAN) architecture. In this framework, the resource allocation problems for both the macrocell and small cells are formulated as optimization problems. The macrocell, being aware of the existence of the small cell tier, maximizes the sum of the interference levels it can tolerate subject to quality-of-service (QoS) constraints. On the other hand, small cells try to maximize the number admitted users while minimizing the total transmit power. Being deployed in a C-RAN architecture, small cells perform RA subject to QoS, interference, and practical fronthaul constraints. Both optimization problems are shown to be mixed integer nonlinear problems (MINLPs) for which, lower complexity algorithms are proposed. Numerical results confirm the importance of the careful selection of the macrocell RA policy. Also, the effect of the fronthaul capacity for small cells and the users QoS requirements are studied.