Robust radio resource allocation for heterogeneous traffic in PD-NOMA-based HCNs

Abstract

In this paper, we formulate a downlink robust resource allocation and Base Station (BS) selection problem in heterogeneous cellular networks based on power domain non-orthogonal multiple access (PD-NOMA). The considered optimization problem maximizes the elastic users weighted sum rate subject to streaming users rate, subcarrier allocation, BS selection, transmit power limitations and successive interference cancellation (SIC) constraints by considering uncertainty in channel state information (CSI). We consider worst case CSI uncertainty. The uncertain CSI is modeled as a summation of its estimated value and an additive error where we suppose that the error is bounded in an uncertainty region. First, we transform the worst case optimization problem into new problem with less computational complexity. Then, we divide the optimization problem into two subproblems, subcarrier allocation with BS selection and power allocation, thereafter, apply an iterative algorithm to find the subcarrier, BS and power allocation solutions alternatively. By numerical experiments, we study the effect of the uncertainty in CSI and simulation results show that PD-NOMA scheme improves the system sum rate.