gies combined pose more promising advantages due to the reasons mentioned below [38, 39] 5 NOMA for 5G and Beyond Wireless Networks Increased transmit signal-to-interference-and-noise-ratio (SINR): Apart from its several benefits, higher density of BSs in a HetNet results in increased interfer- ence, thereby reducing SINR at the user. Using NOMA-enabled BSs enables intelligent tracking of different categories of interference, e.g., inter/intra-tier interference and intra-group interference. This effectively increases the SINR at the users. Improved fairness: Fairness among the users is very important for the HetNets, especially when the aim is to study efficient allocation of resource in multi-tier networks. NOMA provides an efficient way to address fairness by giving higher power to user having poor channel condition. Hence, NOMA plays a role of high significance in the HetNets. The role of macroBS is to serve devices such that the power is required to be split equally among them. However, at the macroBS tier, the role changes. The femtoBS tier serves devices with different data needs and therefore requires different power to achieve them. For example, a femtoBS will serve an Internet of Things (IoT) device along with supporting a high-definition video transmission [40]. Such varied requirements call for appropriate power split as well. Therefore, it becomes suitable to apply NOMA at the femtoBS tier in order to enable power splitting which aids in serving multiple devices with varying requirements, whereas NOMA at macroBS tier is not required. Furthermore, one additional usage of NOMA at the femtoBS tier will be due to the applied offloading from the macroBS tier to the femtoBS tier. The femtoBS tier is usually installed in crowded places and therefore poses high chances of being fully loaded with its registered users/devices [34]. When offloading occurs, more users are added to the already loaded femtoBS. Hence to support additional users, femtoBS tier can pair the offloaded user with the existing user appropr