Energy efficiency maximization for multi-carrier cooperative non-orthogonal multiple access systems

Driven by massive connections and exponential growth of data in mobile devices, Non-orthogonal mul-tiple access (NOMA) has become a candidate access technology to meet the requirement of Internet of things (IoT) in the future network. The combination of multi-carrier technology and cooperative commu-nication is an efficient solution to significantly improve the energy efficiency of NOMA systems. Hence, we consider the energy efficiency (EE) maximization problem for the multi-carrier cooperative NOMA (MC-C-NOMA) systems with amplifying-and-forward (AF) protocol. As the EE maximization problem is mixed-integer nonlinear programming (MINLP), it is difficult to design the resource allocation algorithm to find the optimal solution. To make the EE maximization problem easier to handle, we decouple the EE maximization problem into sub-channel selection and power allocation sub-problems. First, under each user's minimum data rate and maximum transmit power constraints, a matching algorithm is pro-posed to achieve sub-channel allocation, which first matches the user with the sub-channel. Secondly, the Dinkelbach-like algorithm is used to achieve power allocation. Then, a joint sub-channel selection and power allocation algorithm is proposed to maximize the total energy efficiency (EE) of users in the MC-C-NOMA system. Finally, simulation results are presented to show that the proposed algorithm can achieve higher energy efficiency compared with the existing algorithms.(c) 2022 Elsevier Inc. All rights reserved.