Combining Eigen-Beamforming and Orthogonal Space-Time Block Coding for Secondary Usage of Spectrum

For a spectrum sharing environment, where an unlicensed (secondary) user coexists with a licensed (primary) user, we study the performance of the multiantenna transmission scheme that combines orthogonal space-time block coding with transmit eigen-beamforming. The objective is to minimize a tight bound on the symbol error rate of the secondary user subject to two practical constraints: maximum transmit power constraint of the secondary user and received interference constraint of the primary user. Here, we consider both peak and average interference constraints. Using the knowledge of channel correlations of the secondary user and perfect channel knowledge (for the peak interference constraint) or the knowledge of channel correlations (for the average interference constraint) of the primary user, we solve the original optimization problem with two constraints by decomposing it into two sub- problems each with a single constraint. Simulation results are presented to show the symbol error rate performance of the secondary user under different channel and interference constraint considerations.