| In wireless communication environment, high-speed communications have suffered the limited spectrum resources, time-varying complex wireless environment and other issues. In order to meet the higher data rates, better service quality and greater demands for network capacity, innovative techniques that improve spectral efficiency and transmission reliability are proposed, such as the MIMO technology which uses multiple antennas at the receiver and transmitter. Without increasing bandwidth or transmit power, MIMO systems can improve channel capacity greatly. In the fast moving environment, sometimes receiver cannot get channel state information accurately, but differential space-time coding technology may decode effectively in this condition. In the cognitive radio (CR) system, the cognitive user has been allowed to opportunistically exploit the licensed spectrum, and the overall spectral efficiency will be improved greatly. In this paper, we make three improvements: analysis the possibility of conciliatory for the MIMO technology and the CR system to improve the system capacity and spectral efficiency; utilize the "ABBA" high dimensionality construction principle to construct the distributed differential space-time codes to decrease the coding complexity, and the simulation results show that the BER performance of the DDSTBC is better than the BER performance of the circles; propose the structure of the transmitter and receiver in CR MIMO system. The simulation results show that the BER performance of the DSTBC system is better than uncoded system. |
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