Trade-off on spectrum-energy efficiency in cooperative cognitive radio networks

The demand for high throughput at low power consumption requires spectrum efficient as well as energy efficient design in next generation wireless networks. However, spectrum efficiency (SE) and energy efficiency (EE) can not be improved simultaneously. To this aim, in this work, the EE-SE trade-off issue is investigated in a cooperative cognitive radio network (CCRN). The secondary users (SUs) either cooperate in primary user's (PU) transmission when PU is detected active or proceed with their individual transmissions when PU is detected idle. The objective is to study the EE-SE trade-off in terms of cooperative and secondary transmission. A set of optimal values for spectrum sensing (SS) time, final decision threshold, self and cooperative transmission power gains are calculated under the constraints of SU power budget, PU detection probability, SU and PU spectrum efficiency. Numerical results highlight the efficacy of the proposed system and the issue of EE-SE trade-off is clearly demonstrated.