On the Coexistence of Cognitive Radio Systems

摘要

In this paper, we study the coexistence issue of cognitive radio system (CRS) including selfcoexistence among secondary users (SUs) and the coexistence between primay users (PUs) and SUs. The selfcoexistence addresses the sharing of identified spectrum opportunity among SUs. The coexistence between SUs and PUs addresses the interference from SUs to PUs. To parameterize these issues, we first introduce a new parameter named as quality of coexistence (QoC), which is defined as the quality of SU transmission divided by the negative interference to PUs. Assuming the a time slot of spectrum opportunity has been found by multiple SUs, we partition this time slot to multiple SUs to maximize the QoC. This leads to a good spectrum usage among SUs and minimized interference to PUs. It is assumed that the SUs have multiple antennas and employ transmit power control (TPC). Numerical study shows that using the proposed method, the spectrum opportunity can be shared among multiple SUs while giving the minimum interference to the primary users (PUs). Results show that by properly allocation time slots to multiple SUs to share the spectrum opportunity, the QoC factor can be increased by more than 20% which indicates a significant improvement of coexistence not only between SUs and PUs but also among SUs.