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Top1. Introduction
In recent years, the massive production of mobile applications has increased the demand on data services. In addition, a great amount of demanded data and voice services is claimed by users positioned in indoor places such as enterprise buildings. Long Term Evolution (LTE), which is a broadband network, provides advanced technical features and services. However, due to the penetration loss and long distance between User Equipment (UE), which is placed in indoor environment, and macrocell, the coverage of macrocell might not be worthy and meet UEs satisfaction. As a result, the notion of Home eNodeB (HeNodeB), also called femtocell or femto base station (FBS), is proposed and introduced to overcome the indoor environment deficiency of signaling. Correspondingly, femtocell entices the wireless industries interests and attentions (Chandrasekhar, Andrews, & Gatherer, 2008; Zhang et al., 2014). Femtocell expands the coverage of indoor environment as well as unloads traffic from macrocell. Femtocells are low power and low cost cellular networks. Also, femtocell can be deployed by the end users. Moreover, it uses licensed spectrum and uses backhaul connection to connect to the operators networks (Chandrasekhar et al., 2008). In addition, femtocell delivers high spectral efficiency, which is one of the features that can be achieved to enhance the UEs throughput.
Orthogonal Frequency Division Multiple Access (OFDMA) is a selected downlink transmission scheme that is introduced by 3GPP LTE. In terms of physical layer, the Physical Resource Block PRB is the basic unit, which is assigned for attached UEs. The critical key issue of deploying femtocell and macrocell coexistence environment is the interference between cells. Due to the co-channel deployment, the interference will be experienced and lead to the systems performance limitation (Lopez-Perez, Valcarce, de la Roche, & Zhang, 2009). Subsequently, a useful approach is desired to mitigate the interference and resolve this challenge especially in dense deployment of femtocells. In femtocell networks, the setting and installment process is done by end users, which is preferable choice to diminish the cost on network operators.
Controlling femtocells power is one of the common methods and techniques that have been suggested to alleviate and avoid interference in heterogeneous networks. The femtocell power is low because it serves and covers limited areas such as residential homes and apartments, even though the dense and unplanned deployment of adjacent femtocells would cause interference among femtocells. Nevertheless, a mechanism for controlling the femtocell power is stimulated to be considered in order to mitigate the effect of interference among adjacent deployed femtocells. Many solutions have been proposed to handle this issue in previous works.