Efficient resource allocation and user association in NOMA-enabled vehicular-aided HetNets with high altitude platforms

The increasing demand for massive connectivity and high data rates has made the efficient use of existing spectrum resources an increasingly challenging problem. Non -orthogonal multiple access (NOMA) is a potential solution for future heterogeneous networks (HetNets) due to its high capacity and spectrum efficiency. In this study, we analyze an uplink NOMA-enabled vehicular -aided HetNet, where multiple vehicular user equipment (VUEs) share the access link spectrum, and a high -altitude platform (HAP) communicates with roadside units (RSUs) through a backhaul communication link. We propose an improved algorithm for user association that selects VUEs for HAPs based on channel coefficient ratios and terrestrial VUEs based on a cachingstate backhaul communication link. The joint optimization problems aim to maximize a utility function that considers VUE transmission rates and cross -tier interference while meeting the constraints of backhaul transmission rates and QoS requirements of each VUE. The joint resource allocation optimization problem consists of three sub -problems: bandwidth allocation, user association, and transmission power allocation. We derive a closed -form solution for bandwidth allocation and solve the transmission power allocation sub -problem iteratively using Taylor expansion to transform a non -convex term into a convex one. Our proposed three -stage iterative algorithm for resource allocation integrates all three sub -problems and is shown to be effective through simulation results. Specifically, the results demonstrate that our solution achieves performance improvements over existing approaches.