Robust Power Allocation for Femtocell Networks Using Fuzzy Estimation of Dynamic Channel States

Abstract

In this paper, the power control scheme is proposed in the two-tier femtocell network, where the wireless resources are shared with the macrocell and femtocell. Since the communication environment is uncertain and complex, channel state information (CSI) is imperfect. Hence, an effective power control scheme is essential to adapt to the changing communication environment. In the power control scheme, the uncertain CSI is formulated to adapt to the dynamics of the communication environment. Since the channel gain is varied with the changing communication environment, it is crucial for the power control scheme to determine the instantaneous channel gain. The fuzzy logic system (FLS) is proposed to estimate the instantaneous channel gain. The proposed scheme attempts to overcome the limitation of the existing methods which require the channel gain distribution to be assumed. The FLS can capture the dynamics of the changing channel feature using the achievable information in the communication system. Based on the estimation of dynamic channel gain, the power optimal allocation scheme can be developed to satisfy the power level constraint and the transmitting rate requirement. To implement the proposed scheme in real-time environments, an iterative algorithm is developed with a fast convergence speed. The simulation results demonstrate that the proposed scheme is more flexible with uncertain channels when compared with the existing method.