Transmission Strategies for MIMO Overlay Spectrum Sharing

This work studies the coexistence of a single-input and single-output (SISO) primary link and a multiple-input and multiple-output (MIMO) secondary link in the overlay spectrum sharing paradigm. The secondary transmitter has noncausal knowledge of the primary message and codebook, and helps with the primary transmission as a return for the access to the primary spectrum. Two transmission strategies are proposed to maximize the secondary achievable rate while satisfying the primary rate requirement and secondary power constraint, namely, superposition coding in combination with dirty-paper coding (DPC) at the secondary transmitter, and linear precoding with single-stream transmission at the secondary transmitter. For the former, optimal precoding and power allocation is derived; while for the latter, transceiver design is proposed. The performance of the two strategies is evaluated through numerical simulations in terms of achievable secondary rate under different configurations of system parameters.