Optimization of two layer macro-pico networks using LTE

The exponential increase in data traffic demand has focused attention on two layer network deployment strategies where low-power pico base-stations are placed within a macro cell coverage area targeting specific capacity demands. Two aspects of such a network are different from a macro-only deployment and are studied in this paper - (i) the choice of antenna geometry and polarization for a non-sectorized pico base-station (ii) the necessity for a macro layer to be silenced to protect users served by a pico layer and receiving severe interference from the macro layer. Our results show that orthogonally polarized arrays are markedly better than co-polarized arrays for pico cells. Also, linear arrays (whether cross- or co-polarized) are better matched to the LTE codebook than circular arrays. To manage interference, silencing a macro for an optimized fraction of time-frequency resources is necessary only when a significant fraction of users are off-loaded from a macro layer to a pico layer in an outdoor pico deployment.