Abstract
This thesis consider a multi-input-multi-output (MIMO) cognitive environment with a multi-antenna primary user (PU) who has the spectrum license and does not cooperate with the cognitive user (CU). This thesis addresses two problems: 1. the robust cognitive transmission subject to the probabilistic interference constraints to the PU, and 2. the robust cognitive receive beamforming subject to the channel uncertainties. The CU transmits the signal opportunistically with constrained interference to the PU on the influence caused by the channel estimation errors at the cognitive system. The probability of the interference from CU to PU exceeding the tolerant threshold is constrained and trades off with spectrum utilization efficiency. With constrained interference to PU, the CU encodes signals on the orthogonal space time block code (OSTBC) s.t. the cognitive system is channel state information only at the receiver (CSIR). On the other hand, the robust receiver is directed against the channel uncertainties between transmitter and receiver caused by training estimation error. In this thesis, we keep the interference from CU to PU under a probabilistic threshold and maximize the spectrum efficiency by minimize the observation duration. Therefore, we analyze the channel uncertainties between CU's transmitter and receiver caused by training error and find the robustness corresponding to the estimation errors. Finally, we simulate the probability of the interference exceeding tolerant threshold at the PU and the BER performance of the CU. From the simulation results, we make sure that the analysis of cognitive scheme is workable.