Enabling the implementation of spatial interweave LTE cognitive radio

LTE the latest mobile network standard, is widely adopted and targets high spectral efficiency. Cognitive radio (CR) systems on the other hand enable smart use of wireless resources leading to significant performance and reliability improvement. Accordingly, adopting the LTE specifications in CR it is a reasonable choice to optimized the spectrum utilisation in wireless communications. In this paper, we investigate some issues in the real-time implementation of a TDD (time division duplex) LTE-based spatial interweave (IW) CR. Indeed, the IW-CR requires the channel state information (CSI) to opportunistically exploit spatial holes for cognitive transmissions. Preliminary works have illustrated the possibility to acquire the CSI through the calibration of the channel reciprocity inherent in TDD systems. However, they consider constant radio frequency (RF) filters, which leads to perturbations in the IW-CR. Hence, we propose a new tracking method to tackle the variation in the RF. The whole system is implemented and evaluated on an experimental platform, where the simulation results reveal performance enhancement using this new approach.