Adaptive cooperative transmission and spectrum sharing in MIMO-CCRN

A two-phase spatiotemporal adaptive transmission and spectrum sharing mechanism is designed for multi-input multi-output cooperative cognitive radio network (MIMO-CCRN). By employing cognitive user(s) as relay(s), performance of end-to-end primary transmission is improved. On the other hand, secondary user (SU) can access to the spectrum for its own data transmission simultaneously with the primary, as a reward for assisting the primary's data delivery. With the proposed scheme, multiple SU pairs participate in the data relaying, and share the access authority following a time division multiplexing mode. By joint transmit precoding and receive filtering design, co-channel interference can be appropriately suppressed. Moreover, bottleneck effect in the end-to-end primary link is studied, and an adaptive time slot division scheme is employed as a solution to bottleneck elimination. Simulation results show that the primary spectral efficiency is improved with the assistance of SU(s). Time domain adaptation could effectively enhance the end-to-end performance. Meanwhile, spatiotemporal multiplexing of different types of transmission facilitates the spectral efficiency. As a result, a win-win situation for both the primary and secondary is achieved.