Signal Space Cognitive Cooperation

In this work, a new transmission scheme, signal space cognitive cooperation, is introduced by applying the idea of signal space diversity in an underlay spectrum sharing decode-and-forward multi-relay cooperative network. In the proposed structure, the secondary source signal is rotated by a certain angle and then the source and the secondary best relay transmit different partial representations (the in-phase and the quadrature components) of the rotated signal. As a consequence, two source signal