Enhancement of Geometry and Throughput in LTE Femtocells Cognitive Radio Networks

Abstract

The mutual electromagnetic interference among macro users and femto users is a challenge, when femtocells are deployed in LTE and LTE advanced systems. When the used femtocells have a closed access, the macro users, who are indoors or near to the femtocells, are prone to a severe interference from the femto access points especially, in the case of the universal frequency reuse deployment. A power control is an effective way to improve the macro users' geometry at the expense of a drop in the femto users' geometry and capacity. The concept of a cognitive radio is proposed, as a novel approach, to mitigate the interference and improve the macro and femto users' geometry. The system is designed, mathematically analyzed, and simulated considering that the femto users are secondary users for the macro users. The macro users and the femto users' throughputs of the proposed system are estimated. Comparisons among the universal frequency reuse, the power control, and the suggested approach are held. The simulation results validate the efficiency of the proposed system. The average of femto users' throughput in the proposed system is better than the corresponding one employing the universal frequency reuse or the power control, even if only 20 % of the subcarriers are available to be accessed by the femto users. Moreover, the macro users' throughput in the proposed system is better than the corresponding one applying the universal frequency reuse or the power control, even if only 40 % of the subcarriers are available to be accessed by the macro users.