| MIMO precoding algorithms play a very important role both in single-user and multi-user communication systems. By adjusting the phase of transmitting signal, the user can achieve maximum channel capacity for a single-user communication system. For multi-user communication system, precoding algorithm can suppress the interference from other users. The paper mainly studies the robust precoding algorithm for single-user system, joint user scheduling and beamforming algorithm for multi-user system, and joint user selection and precoding algorithm in spectrum sensing system.The precoding algorithms highly rely on the accuracy of channel information. By giving a channel error model and using objective function expectations instead of instantaneous value, this paper derives a closed-form of robust scheme. The simulation results demonstrate that if channel error modeling can make best of the channel correlation and covariance of estimation error, robust algorithm can be better than non-robust algorithm for1～2dB.The joint multi-user scheduling and precoding technology for multi-user transmission system is widely recognized. This paper first analysis two algorithms PU2RC and BCI, and then proposes an improved user scheduling scheme. By ensuring the quality of service of each user as well as the maximum channel capacity of the system, the amount of feedback is not high, and the feedback bit is still lower compared to BCI, gaining a benefit both in throughput and feedback bit.Spectrum sensing technology allows secondary user to access the spectrum of primary user and improves the utilization of the spectrum. This paper proposes a joint user scheduling and precoding algorithm based on limited feedback in this system. Compared with SS-BD algorithm which can pre-cancell the primary user’s suffering interference, the proposed algorithm can have a strong robustness. And the factor such as the size of codebook and the QoS of primary user to the proposed algorithm is simulated. |
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