Polarization and Power Optimization for Spectrum Sharing in Cognitive Heterogeneous Cellular Network

Cognitive heterogeneous cellular network (CHCN), comprised of small cells overlaid with macrocells, is a promising topology to fulfill the explosive demand for high-data-rate transmission by employing cognitive radio technologies. In this paper, a joint polarization and power allocation (JPPA) scheme is proposed for spectrum sharing in CHCN. By exploiting spectrum opportunities in polarization and power domains simultaneously, the proposed algorithm jointly optimizes the polarization states and transmitting power of small cell to maximize its downlink capacity subject to its own transmit-power constraint and interference-power constraint of macrocell. Numerical results reveal that the proposed scheme provides capacity and spectrum efficiency improvements compared with polarization-based spectrum sharing and power allocation schemes. In addition, it approaches the performance of the optimal exhaustive search with a much lower computational complexity.