Self-Optimization Technology For Inter-Cell Interference Coordination In LTE-A System

Long Term Evolution Advanced (LTE-A) system adopts frequency reuse scheme. Therefore, subcarriers face serious interference from the subcarriers of the adjacent cells in the same frequency having serious implications on the capacity and performance (especially for the cell edge). Traditional interference coordination technique, as a function of the radio resource management (RRM), is manually configured, aiming to improve the performance of a single cell. With the wireless networks becoming more complex and heterogeneous, network interference problem become even more serious. Therefore, it is vital to introduce interference self-optimizing functions to reduce the disruption to the cell edge users, ensure the quality of service (QoS) of edge users, as well as reduce network operating costs.Fractional frequency reuse (FFR) is an inter-cell interference coordination (ICIC) scheme wherein the whole bandwidth is divided into regions using different frequency reuse factors in OFDMA. However, it is hard to achieve the balance of cell-edge and cell-center user throughput in practice as all base stations (BS) are configured with static transmission power for each sub-band in traditional FFR. To solve this problem, a gradient projection based self-optimizing (GPB-SO) algorithm for ICIC is proposed to adjust transmission power of each subbands set by exchanging the gradient direction information, aiming to maximize the overall network utility. With the simulation results, it is demonstrated that the proposed algorithm not only provides a better tradeoff between spectrum efficiency and cell-edge user throughput, but also increases the system energy efficiency due to interference reduction. In addition, the wide deployment of heterogeneous networks brings new interference problem to wireless communication, especially when the home base station (HeNB) is closed, the macro user equipment (MUE) located near it will suffer severe interference. To solve the above problem, a self-optimizing algorithm is proposed to reduce intra-layer and inter-layer interference through adjusting transmission power of BSs, aiming to improve the overall efficiency of the heterogeneous network. With the simulation results, it is showed that the proposed self-optimizing algorithm can effectively reduce the interference between heterogeneous nodes, as well as improve edge user throughput.