System Design and Performance Analysis of LTE Cognitive Femtocells

Femtocells’ deployment can extend the LTE coverage to include indoor areas. Unfortunately, a mutual electromagnetic interference can occur among the macro cells and femtocells due to the co-channel deployment. Moreover, interference among the femtocells themselves can occur due to utilizing the same subcarriers. The two types of interference can degrade the system performance. Femtocells base station power control can reduce the interference, which affects the macro users at the expense of a drop in the femto users’ geometry and throughput. A cognitive radio is proposed, as a novel approach, to completely eliminate the mutual interference among the macrocells and femtocells. The system is designed, mathematically analyzed, and simulated considering that the femto users are secondary users for the macro users. Analytical and simulation results show that applying the cognitive radio, to improve the system performance, is better than applying power control algorithms. The interference, which occurs among the femtocells, can be eliminated by different techniques. These novel techniques, which can achieve a maximization of the femto users’ geometry, are proposed and illustrated in details.