Downlink power control for interference management in femtocell-macrocell cellular communication network

Deployment of femtocell in macrocell cellular network which forms two-tier femtocell-macrocell cellular network faces more complicated interference problems, since it uses the same licensed frequency spectrum as its macrocell. This paper addresses the interference problems for downlink transmission in such two-tier cellular communication network. In this paper, interference management using power control is proposed in that two-tier network. This paper considers multi-cell cellular network composing of three macrocell systems. Ten femtocells are deployed in each macrocell system. This paper takes worst case for the scenario that is all femtocells and macrocells in downlink transmissions. Simulation for the system without power control was carried out first as a baseline system. Then, two methods of power control called as PC-1 and PC-2 in this paper were explored to reduce the interference effects. The use of two power controls is to take a trade-off, the increasing of quality of service (QoS) in macrocell system while is not degrading much QoS in femtocell system. Both power control methods are based on the estimated Signal to Interference Plus Noise Ratio (SINR). Both of power control methods also ensure that the results of controlled transmitting power will not exceed the maximum or the minimum of allowable transmitting powers. Simulations have been carried out and performance parameter in term of Cumulative Distribution Function (CDF) of SINR have been collected for co-tier (femtocell-femtocell and macrocell-macrocell), cross-tier (femtocell-macrocell and macrocell-femtocell), and the total interferences. The simulation results show that both power control methods outperform the baseline system.