On the ergodic performance of a simple closed-loop spatial multiplexing architecture

Cognitive radio system shares the frequency spectrum with the license system. As a result, the dramatic improvement of the frequency usage efficiency can be expected. Since the cognitive radio system is independent from the license system, it should recognize the wireless communication parameter of the license system, such as frequency, modulation scheme, and so on. Multiple-input multiple-output (MIMO) system, which can transmit multiple data signals with using single frequency spectrum, is applied to cognitive radio, and thus frequency use efficiency is more significantly improved. In MIMO-cognitive radio system, when new cognitive user tries to use the frequency resource, it is necessary that the new user should detect the number of parallel transmitted symbols which the license user transmit, because the new user should remove the interference signals whose number is the same as that of data symbol transmitted by the license user. In this paper, in MIMO-cognitive radio system, the novel method for recognizing the number of parallel data symbols is proposed.