Energy-efficient femtocell placement in LTE networks

To enhance battery life of mobile handsets and increase the data rates for indoor users in LTE networks, low power nodes like Femtos are deployed in homes and enterprise buildings. But the optimal placement of Femtos is a challenging task due to heterogeneity in building layouts and co-tier intercell interference. In this work, we focus on reducing the battery power consumption (uplink transmit power) while guaranteeing uplink Signal to Interference plus Noise Ratio (SINR) threshold (USINRTh) and downlink SINR threshold (DSINRTh). We achieve this by placing the Femtos optimally, taking into account wall attenuation factor and interference among Macro and Femto base stations. A two-step optimization model has been formulated: in step one, we formulate a Mixed Integer Programming (MIP) problem yields the optimal positions of the Femtos and meets DSINRTh and USNRTh while also minimizing Femto count and uplink transmission power. In step two, we formulate a Linear Programming (LP) problem with the aim of guaranteeing USINRTh and minimizing the total uplink power, after placing the Femtos in the optimal positions obtained from step one. When compared to center K-means placement scheme, the proposed optimal placement scheme obtained by solving the two-step model registers a significant, 47%, reduction in uplink energy consumption.