| Summary: | 碩士 === 國立交通大學 === 電信工程研究所 === 104 === Multiple antenna technique have been considered to further improve spectrum efficiency and link quality of cognitive radio (CR) systems. Employing beamforming at secondary transmitter is one such solution in cognitive radio systems. In order to design CR beamforming, channel state information (CSI) of the cross-tier communication link must be known at the secondary transmitter. In the thesis, we study the problem of the limited feedback of the channel state information (CSI) for the cognitive radio networks. Motivated by the fact that the assumption of perfect CSI feedback requires close coordination between primary and secondary networks such as employing powerful channel coding which may incur excessive signaling overhead, we consider that the primary system can not afford to pay too much overhead. More specifically, assuming that CSI feedback is no longer perfect, then we derive the a posteriori average interference power based on the imperfect feedback CSI. A closed-form formula for the optimal CR beamforming is derived, and the performance of average received signal to noise ratio (SNR) is analytically characterized. Besides, the energy efficient beamforming is also considered on our proposed feedback link. The performance of the proposed scheme can be illustrated throughout the computer simulation.
|
|---|
