## 1 Introduction  
Nowadays, wireless communication systems require a high spectral efficiency and high reliability. The orthogonal frequency division multiplexing (OFDM) technique was developed, because it is one of the schemes which use frequency efficiently within a limited bandwidth [1; 2; 3]. The OFDM technique is robust to the multi-path fading [1]. Therefore, the OFDM technique has been widely applied to various wireless communication systems [2; 3]. In the wireless communication systems, the amount of required traffic and data are increased. In order to satisfy needs, additional network nodes (or transmitting/receiving base station) must generally be built. The system in which the additional network nodes are constructed is the heterogeneous network (HetNet) system [4; 5; 6]. By increasing the number of cells, the traffic per unit area can be increased without increasing the amount of traffic that must be supported per cell. The HetNet system is generally composed of a small cell, new access technologies, and various transmission power schemes of the base station. Also, arrangement of the small cell, such as the pico and femto cell, has advantage of expanding the capacity and cell coverage in the HetNet systems [5]. There are many issues of research on the HetNet. The energy efficiency, analysis of cell coverage and interference mitigation are subjects of research on the HetNet. [PERSON], et al. propose a mechanism that can save energy when multimedia data in HetNet small cell environment are transmitted [7]. An algorithm for cell planning in HetNet to find the optimal number of cell sites subject to QoS requirements was proposed in [8]. [PERSON], et al proposes a tractable heterogeneous cellular network model through the cell coverage analysis [9]. In addition, a power allocation scheme for minimizing energy consumption in heterogeneous networks is proposed in [10; 11]. In other words, the energy efficiency and cell coverage analysis are very important issues in HetNet system. Furthermore, the interference mitigation is a very important topic. Therefore, this paper focuses on interference mitigation. However, the HetNet system can cause complex ICI scenarios, which are an important part of the HetNet system. In this paper, two representative scenarios are considered. The first scenario is the ICI by the signals transmitted from other mobiles in adjacent cell. When the mobile is located at the cell edge, the ICI occurs due to the signal transmitted from other mobiles to the other base station in the adjacent cell. The second scenario is the ICI by the signals transmitted from the base station in the adjacent cell. When the mobile is located in the cell edge, the ICI occurs due to the signal transmitted the base station of the adjacent cell to the other mobile. In the first scenario, because the interference signal is transmitted by the mobile in the adjacent cell, the power of the interference signal is lower than the interference signal transmitted by the base station. However, in the second scenario, because the interference signal is transmitted by the base station in the adjacent cell, the interference signal has high power. Therefore, it greatly affects the performance of the HetNet system. Owing to complex ICI scenarios, the reception performance of the mobile is reduced and consequently the reliability of the wireless communication system is reduced [12; 13]. This paper proposes a scheme to mitigate the interference signal transmitted from the base station among the interference scenarios of the HetNet system. In order to solve complicated ICI scenarios, this paper proposes a CoMP scheme in which the base station cooperates adaptively according to the location of the mobile. The CoMP scheme is a communication technique in which the base stations in adjacent cells cooperate with each other. In the proposed CoMP scheme, the mobile transmits feedback information (including the position, channel state information (CSI), etc.) to all base stations in adjacent cells.