Deployment Challenges and Co-tier Interference Management Techniques for Ultra-dense Femtocell Networks

Network densification is one of the imperative mechanisms expected to enable next generation 5G networks to meet the highly foreseen 1000-fold increase in capacity. In this regard, densification of femtocells is a promising concept to meet growing mobile service requirements and for sustainability of users’ Quality of Service (QoS), especially for hotspots. In this context, this paper first investigates the inter-cell interference scenarios within a typical small femtocell cluster and then discusses the challenges facing femtocell densification in terms of co-tier interference. Moreover, the concept of femtocell classification into different classes is demonstrated. Finally, the article presents a case study where an interference and resource management approach for ultra-dense femtocell networks (UDFNs) is introduced. This proposal organizes the users in each femtocell into two categories, where the first category is for critical users only and the second is for non-critical users. A disjoint cluster is then formed for the first category within each femtocell and its aggressor/s. Moreover, the approach implements a dynamic resource allocation mechanism, based on the status of each user within each femtocell. This mechanism allows ranging from the shared resources for the first category and its aggressor/s, to the frequency reuse one for the second category. The simulation results show that the proposal outperformed one of the prominent related techniques in the literature, namely the X2 with UE support (X2-UEs) for all deployment density scenarios from sparse to ultra-dense. The evaluations were made in regard to the users’ average throughput and the mean capacity of femtocells. The simulation results show that the SCC technique outperformed its counterpart by an average gain of 32.58% for the aforesaid first metric, and an average enhancement of 16.79 Mbps for the later metric compared to only 6.26 Mbps achieved by the X2-UEs.