## 4 Resource Management in Heterogeneous Network (RM HetNet)
### Spectrum Allocation (SA)
#### 4.4.1 Traditional Band  
Frequency bands for B5G networks are separated into different frequency ranges. The frequency bands are traditionally used by previous standards but have been extended to include potential new spectrum offerings. In [128], the authors developed a utility-based prioritization of the SA algorithm to improve QoS for the cell center users and cell edge users of HetNet. Voronoi tessellation-based cell user categorization reduces the SINR at the instantaneous fluctuation. The user requests should be prioritized according to the utility of the quality of service and the delay-bound budget in terms of improving fairness among users. In the centralized SA method, the designed utility-based SA algorithm optimized the sharing of resources mechanism to satisfy the QoS and delay bound of the users. Utility-based SA algorithm provided a higher quality of service to guaranteed delay-bound and real-time applications managed by cell edge users when compared to conventional scheduling algorithms. The SA algorithm was implemented to improve the throughput, fairness, average delay, and SE of the users and network. The simulation results prove that the designed utility-based SA algorithm offers superior and more effective solutions for the real-time application of cell edge users in HetNets. However, the centralized SA method is presented. Hence, the burden on the BS increased. In [129], the author proposed a joint SA scheme that integrates NOMA and orthogonal multiple access (OMA) modes into a unified strategy. They utilized cooperative bargaining solution concepts to analyze multiple access methods performed together efficiently. The proposed algorithm considered the hybrid OMA-NOMA system platform and was inspired by the Nash bargaining solution and group bargaining solutions. In the suggested method, users within the same channel form a group, and the SA process for BSs and channels follows the OMA mode. The NOMA mode determines which power level to use for users in each group. Traditional Nash bargaining solution is used in OMA mode SA. The NOMA mode operates on the group bargaining solution in both individuals and across groups. The limited SA is managed and distributed at each period to effectively adapt to the current network changes while ensuring consistent system performance. Simulation results demonstrate that the proposed method attains significant performance improvements over other existing two-tier based NOMA spectrum allocation, locally cooperative game, and NOMA-based HetNet SA schemes when the NOMA and OMA exist in the HetNet system. Nevertheless, In the NOMA model, the tradeoff between SA and the power allocation problem is not considered. In [130], the authors developed a genetic algorithm-based energy-efficient SA scheme in downlink orthogonal frequency division multiple access (OFDMA) HetNets. In order to improve the SE of 5G mobile networks, frequency reuse is used. An intractable mixed-integer nonlinear fractional programming problem is formulated to address the EE optimization problem based on coordinated scheduling. To discuss this, they proposed a two-step genetic algorithm-based scheme to address the optimization problem. In the first step, a standard genetic algorithm is used to solve the SE aspect of the power distribution matrix for the resource blocks. The second step is to use the obtained SA matrix and the non-dominated sorting genetic algorithm to evaluate the power distribution matrix. The simulation results showed a tradeoff between EE and throughput. Nonetheless, as the transmitted power increased, the EE and SE decreased accordingly. Figure 8: Spectrum ranges in HetNet. In [131], the authors proposed two frameworks based on auction games and matching theory to accept secondary users into the HetNet efficiently. In this paper, they considered a practical scenario in which primary channels can have a variety of characteristics.