Iterative transceiver beamforming of distributed relay networks in cognitive radio networks

This paper investigated the transceiver beamforming problem of multi-pair distributed relay network in a cognitive radio (CR) framework. The goal is to support reliable multi-pair transmissions between secondary users (SU) with assistance of a number of relays, while keeping the total leakage interference on the primary user (PU) under a predefined threshold level. Certain iterative algorithm is proposed to decompose the very difficult original problem into three solvable sub-problems, and after certain number of iteration steps, the obtained transceiver beamformers and relay beamformers can form a group of globally sub-optimal solutions that leads to significant performance enhancement of the secondary network while restricting the leakage interference on PU receiver. Two transmission schemes are considered where the first one only constrain the leakage signal power introduced to PU received, and the second one adds a constraint of the total relay output power. At last, we analyzed the condition, under which the later transmission scheme could be simplified with less computational complexity to solve it.