## 1 Introduction  
The rapidly expanding demand for higher bandwidth, coverage and data rate in the mobile network has been a great stimulant to develop system capacity. The overlaid femtocell over macrocell in the heterogeneous network (HetNet) is a promising technology to accomplish the dreams of greater coverage, high efficiency and enhance the capacity of the cellular network. Femtocell is an energy efficient base station also called Femto Base Station (FBS) [1]. The femtocells are specifically designed for an indoor environment to enhance the capacity and quality having coverage of 10-20 m, named femto access point (FAP) [2]. The FAP shares the same licensed frequency spectrum with macrocell as it connected to the mobile operator's network using public infrastructure such as broadband internet backhaul [3]. Traffic offloading from the LTE cellular network is currently a widely used method to manage exponentially increasing data traffic [4]. A femtocell is a promising candidate in this regard, as 45% of the mobile data traffic is offloaded through the femtocell because most of the data traffic originates from the indoor environment [5]. It is expected that, in the near future, indoor environments like schools, airports, homes, and offices will generate 60% and 90% of voice traffic and data traffic, respectively [6]. Although femtocells are deployed in the existing macrocell network to enhance network coverage in an indoor environment, the User Equipments (UEs) connected to them might be indoor or outdoor, depending on their location [7]. One of the attractive features of the femtocell is the access style. Three kinds of access control modes exist for the femtocell, i.e., closed, hybrid and open access modes. In the closed access mode, no other user can access femtocell services except for a Closed Subscriber Group (CSG) [8]. In the hybrid access mode, the CSG is prioritized over all other users, whereas in open access mode, all users i.e., OSG (Open Subscriber Group) can enjoy the service of the femtocell [9; 10]. The access control mode plays an important role in terms of interference, i.e., the Inter-Cell Interference (ICI) is worse in the CSG mode [11]. The overlaid femtocell over macrocell in the two-tier heterogeneous network, where anmacrocell base station (also known eNB), works as a primary system and the Femto Base Station (also known as HeNB) as a secondary system. The two systems share the same frequency spectrum and work in a frequency reuse fashion [12]. The deployment of the femtocell has a massive role to manage interference in the two-tier network [13]. Inadequately deployed femtocell by users has lack of coordination with the macrocell. Normally the operator does not control such femtocells. The inter-cell interference becomes worse when the user deploys the femtocell in an ad-hoc style and moves it from one place to another. This can dramatically deteriorate the performance of the whole system by causing interference to cell edge Macro User Equipment (MUE) [14]. High transmission power of the femtocell enhances indoor coverage area and better signal strength; on the contrary, it causes a great amount of interference to the victim MUE existing in the coverage area of the femtocell. The interference is much worse when the MUE has the lower signal strength from the macrocell as compared to signal power from the femtocell [15]. This type of interference causes severe QoS degradation of the system, packet loss, transmission delay, and communication link failure. Besides the interference, high transmission power increases the atmospheric Carbon Dioxide (CO\({}_{2}\)) concentrations.