Statistically coordinated precoding for the MISO cognitive radio channel

In this work¹, we study a cognitive radio setting consisting of a primary multiple-antenna transmitter (TX) serving a single-antenna primary user (PU) and a secondary multiple-antenna TX serving a secondary user (SU). The main specificity of this work is that we let the primary TX coordinate its transmit strategy with the secondary TX, while considering a realistic channel state information (CSI) scenario where each TX has solely access to the instantaneous knowledge of its direct channel and the statistics of the multi-user channel. This setting gives rise to a Team Decision problem where the TXs aim at cooperating on the basis of individual information. We develop a novel coordination scheme where the TXs coordinate without any exchange of information or any iteration to guarantee the fulfillment of the primary constraint while maximizing the rate of the SU. The coordination is done on the basis of statistical information such that the coordination can be optimized offline. The proposed scheme outperforms conventional schemes from the literature and has low complexity. It can thus be used in settings with low signal processing capabilities and a weak backhaul infrastructure.