Abstract
In this letter, we consider a cognitive radio network consisting of broadcast satellite service (BSS), high-density fixed-satellite service (HDFSS), and high-altitude platforms (HAPs) systems. The spectrum utilization within a satellite beam coverage is increased by deploying extra HAPs in the pre-determined hot-spot regions to existing cognitive systems in which the BSS and HDFSS share frequency bands. Since the multiple network nodes simultaneously employ the same frequency band, there exists a challenge to efficiently mitigate the interference between them. Therefore, we propose an iterative precoding and band allocation algorithm for multi-antenna HAPs to maximize the network data rate. In addition, we present other low-complexity techniques and compare them through simulation results.