Joint placement and power control of LTE Femto Base Stations in enterprise environments

In order to boost the data rate for indoor users, low power nodes like Femto Base Stations (BSs) are deployed in LTE (long term evolution) networks. The placement of Femtos inside enterprise building environments can significantly affect indoor user performance. We consider a system model that takes into account the following parameters: co-channel interference between Femto BSs and Macro BSs, wall attenuation factor and user density in enterprise building environments. We solve joint placement and power control problem by formulating two Mixed Integer Programming (MIP) optimization models: Optimal Constant Threshold Signal to Interference plus Noise Ratio (OptCTSINR) and Optimal Varying Threshold SINR (OptVTSINR), which optimally tune the power of Femto BS, guarantee a certain minimum SINR to users and also minimize the number of Femtos needed for the coverage of enterprise buildings. We then solve these MIP models by utilizing branch and bound framework of CPLEX solver in General Algebraic Modeling System (GAMS) tool. When compared to center K-Means (CKM) clustering based placement scheme, for a given number of Femtos, proposed scheme OptCTSINR results in average SINR improvement of 39% and proposed OptVTSINR outperforms OptCTSINR by 6.7%, respectively.