Interference Management Using Power Allocation for Downlink Transmission of Femtocell-Macrocell Ultra Dense Networks

Femtocell is a promising technology to increase network capacity and coverage, especially in indoor areas. It has low power, short range. The Home Base Station/HeNB (Femtocell Base Station) can be installed by users using connection of personal equipment such as laptops, notepads and cell phones, and it is activated by service provider. By deploying femtocells into existing macrocell/microcell areas, the radio resources are shared among femtocells and existing macrocells. However, the sharing of limited available bandwidth frequency licenses cause interference problems between femtocells and/or macrocells. The interference problem becomes more complex when the number of deployed femtocells is many and dense creating a phenomenon of Ultra Dense Network (UDN). To cope with this interference problem, this paper proposes a power allocation method for femtocells deployed in macrocells areas (UDN) at downlink transmissions. In this method the power transmitted at HeNB to each femtocell user is adjusted in such a way as to reduce or increase the transmitted power at HeNB. If the estimated SINR value at current time is less than 20 dB, the power on the HeNB is increased by such a way so SINR is expectedly to be 20 dB for next transmission time. However, if the obtained SINR at current transmission time is more than 20 dB, then the transmission power at the HeNB is reduced so that the SINR value becomes 20 dB for the next transmission time. Extensive simulation has been carried out and the performance parameters in terms of SINR, throughput, and BER have been measured and compared to the baseline system, i.e., the system without power allocation method. The simulation results show that the system that applies power allocation method which is used in the cell edge area is better than the baseline system both in the center and the edge of cells.