Resource Allocation Techniques for Non-Orthogonal Multiple Access Systems

Non-orthogonal multiple access (NOMA) has been proposed as a viable multiple access (MA) technique to meet the demanding requirements in fifth-Generation (5G) and beyond wireless networks. Unlike conventional orthogonal multiple access (OMA) techniques, NOMA simultaneously sends signals to multiple users in the same resource block (RB) in time and frequency domains using power-domain superposition coding (SC) at transmitter. Therefore, NOMA has the potential capabilities to serve a large number of devices while significantly improving spectrum efficiency (SE) compared to the conventional MA techniques, which supports massive connectivity of Internet-of-Things (IoT) networks. To introduce additional degrees of freedom, and hence facilitate implementing NOMA in ultra-dense networks, NOMA has been integrated with different key technologies including multiple antenna techniques and conventional OMA techniques. In particular, the combination between multiple-input single-output (MISO) and NOMA, referred to as MISONOMA, is firstly considered in this thesis. In which, different beamforming designs have been proposed for MISO-NOMA system, including global energy efficiency maximization (GEE-Max) design and EE fairness-based designs. In addition, different multi-performance metrics have been also considered in the designs including GEE-SE design and fairness-sum rate design. Due to non-convexity of the formulated optimization problems, different convex relaxation and approximation techniques have been exploited throughout the thesis to approximate the original non-convex problems with convex problems. The performance of the proposed designs has been evaluated through drawing comparisons with that of the existing beamforming designs in the literature. Secondly, the combination of NOMA with OMA scheme has been investigated, particularly, energy harvesting (EH) capabilities of time division multiple access (TDMA) and NOMA system has been considered. In this hybrid TDMA-NOMA system, simultaneous wireless information and power transfer (SWIPT) technique is integrated such that user has the capability to harvest energy and decode information, simultaneously. Simulation results show that EH capabilities of the TDMA-NOMA system outperform that of the conventional TDMA system.