Power allocation and antenna selection for heterogeneous cellular networks

In this paper, we investigate the system performance of a heterogeneous cellular network consisting of a macro cell and a small cell, where each cell has one user and one base station with multiple antennas. The macro base station (MBS) and the small base station (SBS) transmit their confidential messages to the macro user (MU) and the small user (SU) over their shared spectrum respectively. To enhance the system sum rate (SSR) of MBS-MU and SBS-SU transmission, we propose joint antenna selection combined with optimal power allocation (JAS-OPA) scheme and independent antenna selection combined with optimal power allocation (IAS-OPA) scheme. The JAS-OPA scheme requires to know the channel state information (CSI) of transmission channels and interference channels, while the IAS-OPA scheme only needs to know the CSI of transmission channels. In addition, we carry out the analysis for conventional round-robin antenna selection combined with optimal power allocation (RR-OPA) as a benchmark scheme. We formulate the SSR maximization problem through the power allocation between MBS and SBS and propose iterative OPA algorithms for JAS-OPA, IAS-OPA and RR-OPA schemes, respectively. The results show that the OPA schemes outperform the equal power allocation in terms of SSR. Moreover, we provide the closed-form expression of the system outage probability (SOP) for IAS scheme and RR scheme, it shows the SOP performance can be significantly improved by our proposed IAS scheme compared with RR scheme.