30. MIMO-Empowered Secondary Networks for Efficient Spectrum Sharing

Cognitive radio (CR) and multiple-input multiple-output (MIMO) are two independent physical layer technologies that have made significant impact on wireless networks. In particular, CR operates on the channel level to exploit efficiency across spectrum dimension, while MIMO operates within the same channel to exploit efficiency across spatial dimension. In this chapter, we explore MIMO-empowered CR technique to enhance spectrum access in wireless networks. Specially, we study how to apply MIMO-empowered CR for both interweave and underlay paradigms in multi-hop network environment. With MIMO interference cancelation (IC) capability, we first show how multiple secondary links achieve simultaneous transmission on the same channel under the interweave paradigm. Next, we show how secondary networks achieve simultaneously transmission with the primary network on same channel to achieve transparent coexistence under the underlay paradigm. Through rigorous mathematical modeling, problem formulation, and extensive simulation results, we find that MIMO-empowered CR can offer significant improvement in terms of spectrum access and throughput performance under both interweave and underlay paradigms.