## 3 Scope of This Survey  
The following are the findings of related surveys written by various authors covering different resource management aspects. Most of these research studies have focused on other aspects of resource management that are effectively enhance the network performance. However, to the best of our knowledge and understanding, there has not been a survey that has combined power allocation, user association, mode selection, and spectrum allocation. The proposed paper investigated HetNet resource management schemes for 5G networks and beyond, which each operates under a unique conceptual framework. This article provides a concise overview of the existing survey literature. This article comprehensively reviews resource allocation methods in 5G networks and beyond [67]. In particular, this article introduces the resource allocation methods in ultra-dense for long-term evolution--unlicensed (LTE-U), HetNets, cognitive radio networks (CRNs), cloud radio access networks (C-RANs), D2D, and mmWave networks. Then, the resource allocation problem was classified using a taxonomy based on different methods, techniques, and optimization criteria. Finally, the emerging technologies, problems, and active research are illustrated and require the researchers' attention. In [68], a survey of HetNet resource management approaches is investigated with a focus on the strategies that optimize spectrum allocation with other mechanisms. Power allocation, complexity, fairness, user association, allocated capacity, and interference management are also important issues. These issues are categorized along with the techniques and strategies to handle related problems. For 5G systems, they provided a resource allocation (RA) survey in HetNets that discussed the various network scenarios [69]. Then, the current RA algorithms analysis is presented for the existing works. Finally, difficult problems and emerging areas of study are investigated. In order to address the RA issues of the 6G HetNets, they propose two possible structures for 6G communications: a control-based structure and a learning-based structure. In [70], the authors summarized the key challenges such as resource allocation, user association, power allocation, co-tier interference, and cross-tier interference emerging in 5G HetNets and focused on their importance. They provided a comprehensive review of interference management-based radio resource management methods. They presented a taxonomy for individual and joint methods as a framework for systematically studying the  
Figure 3: Organization of this study. existing approaches in terms of QoS, quality of experience (QoE), energy efficiency (EE), spectrum efficiency (SE), fairness, and coverage probability. Finally, the difficulties and potential benefits of radio resource management in 5G are discussed, and design guidelines with possible opportunities for advanced mechanisms are illustrated. In [71], the features of interference management for 5G networks from the aspect of HetNets and D2D communications are discussed. These aspects are approached through enabling techniques such as coordinated scheduling, coordinated multipoint, and inter-cell interference coordination. In addition, a critical analysis of several pertinent issues, with a focus on their strategies, advantages, and limitations, as well as the future work by the 3 rd Generation Partnership Project (3 GPP) for interference mitigation, is presented. The study in [72] discussed the new radio resource control inactive cases, initial access, registration, and paging strategies. The literature survey also discusses connected state inter-radio access network handover methods and integrated mmWave cells with 5G HetNet. Finally, handover issues, power consumption, signaling overhead, latency, and security were addressed. This issue demonstrated some practical solutions to meet the 5G mobility management need. Approaches in spectrum sensing (SS) for CR were reviewed [73].