Self-adjustment downlink transmission power for femtocells in co-channel deployment in heterogeneous networks

The employment of femtocells has been considered as a promising approach for increasing network capacity and enhancing end users' QoS and throughput as well as low cost and simple deployment. Deploying femtocells is common in indoor environment such as residential buildings comprising adjacent apartments. However, dense deployment of femtocells introduces interference among femtocells and the undesirable influence of interference is incremented among adjacent femtocells. As a result, the performance of the network is diminished. One of the techniques, which is considered to mitigate the impact of the interference, is adjusting transmission power of the femtocells. In this work, a dynamic downlink transmission power of femtocells is proposed. Each femtocell adjusts its transmission power autonomously based on measured cost function unit. The transmission power level of femtocell is constrained by the rate of interference that femtocell produces to adjacent femtocells. A simulation experiment is conducted to validate the efficiency of the proposed scheme compared to other two different approaches. The numerical results show that the proposed scheme can achieve better capacity and also can preferably mitigate the impact of the interference among co-channel deployed femtocells compared to other schemes, which are considered in this work.