# Interference Challenges and Management in B5G Network Design: A Comprehensive Review
## 4 Interference in B5G Networks
### Heterogeneous Networks
#### 4.1.4 Related Works in HetNet
In [71], the authors investigated the interference management in two-tier downlink HetNets with hotspot centers, where each tier's BSs have varying transmitting powers, deployment densities, and connection reliability. The MBSs' hotspot centers are dispersed uniformly by two homogeneous PPPs. Several distance distributions were derived, including a joint distance distribution between a typical user and cooperative open-access mm-wave SBS, as well as a distance distribution between a typical user and non-cooperative open-access mm-wave SBS. Therefore, expressions for several performance metrics were obtained, which include association probability, SINR coverage probability, and ergodic capacity, under these situations. The numerical result indicated the best ratios of standard deviation for these performance indicators, as well as insights into the deployment of future networks. However, this study did not take into consideration the association probability for a variable number of SBS in each cluster that affects the ergodic capacity and data rate of the proposed system. In [72], the stochastic geometry-based PPP approach was proposed to alleviate the relay-user-interference (RUI) and inter-relay-interference (IRI) between the relay and user link and then enhance the capacity of the system and the data rate of users. The proposed approach considered a multi-hope communication network for the mm-wave frequency band. As well, a full-duplex (FD) relaying model was considered and the locations of the source, relays, and users were modeled as point processes in the spatial domain. Furthermore, the Rayleigh fading channel with NLOS transmission at 28 GHz frequency was considered. The simulation results stated that the proposed scheme not only minimizes the probability of outage but also enhances the probability of success and ergodic capacity of the user, as compared with the traditional multiple antenna UDN models. It was also stated that deploying more Multiple-Input Multiple-Output (MIMO) antenna configurations can boost the probability of success by 6% and the ergodic capacity of the system by 400%. Yet, the users' mobility that increases the power consumption of the proposed approach was not considered in this study. In [73], a novel interference minimization and radio RA management scheme for victim femto-cells (VFCs) was proposed to increase user throughput while decreasing co-tier interference for ultra-dense femtocell networks (UDFNs). The proposed semi-clustering of the victim-cell (SCVC) approach focuses mainly on the status of users either critical or non-critical to categorize VFCs and their aggressors. The proposed scheme was compared with the femtocell cluster-based resource allocation (FCRA) scheme. The simulation results stated that the proposed scheme outperforms the FCRA scheme in terms of critical user mean throughput, victim femtocell capacity, and resource usage percentage by around 185%, 64%, and 31%, respectively. However, the power spectrum efficiency that mitigates the co-tier interference was neglected in this study. The author suggested that SCVC technology can be practiced and evaluated in the future to determine its usefulness for eliminating co-tier interference and optimizing radio resource usage in the next 5G ultra-dense networks. In [74], the authors proposed a multi-metric clustering with differential interference alignment (MMC-DIA) technique to take advantage of small-cell users' performance in a heterogeneous communication environment. The proposed technique operates in two main phases namely clustering formation and differential interference alignment. In the clustering process, sum-rate optimization objective-based clustering of small-cell users is used to maintain communication efficiency. For the comparative analysis, the proposed technique could maximize the SE and sum rate by 6.84% and 11.18%, respectively, along with DoF, regardless of the varying size and transmitting power.