Resource Allocation in OMA-NOMA based Two-Tier Heterogeneous Networks

In this paper, we investigate the sub-channel assignment and power allocation for a heterogeneous network based on orthogonal multiple access (OMA) - non-orthogonal multiple access (NOMA) scheme. We divide the total bandwidth into OMA and NOMA based sub-channels. Small cell base station (SBS) can use OMA and NOMA sub-channels, and OMA sub-channels are available for macro cell base station (MBS) to interference control with small cell users (SCUs). Our aim is to maximize the total data rate of SCUs in the OMA-NOMA scheme and provide the quality of service for macro cell users (MCUs). To solve the NP-hard optimization, we decompose the introduced problem into two problems: sub-channel and power allocation problems. Then we propose a sub-optimal iterative approach to provide the solutions. In our algorithm, the sub-channel assignment is updated by solving the linear problem, while the power allocation policy is obtained using the Lagrange dual method. The results illustrate that the proposed OMA-NOMA scheme outperforms traditional OMA-based scheme in terms of sum data rate performance.