Lte-Advanced Downlink Feedback Enhancement And Simulation

With the development of LTE standardization, as an important program to improve the system performance, multi-user MIMO has been widely concerned. This thesis mainly researchs on the technology of CQI feedback enhancement in multiuser MIMO. In the existing standards, the CQI of user based on Multiuser MIMO transmission is still calculated in accordance with the single-user MIMO and feedback, the current users do not calculate the interference on the same frequency of pairing users when the users are on multiuser MIMO transmission mode. Therefore, in consideration of the multi-user CQI accuracy and system overhead, reasonable CQI reporting is particularly important. At the same time, combining the calculation strategy of multi-user CQI, it will provide effective support to improve the system performance.This thesis describes the background of TD-LTE, analyzes the existing issues in MU-MIMO transmission, then analyzes the reporting model and calculation method of multi-user MIMO CQI. Based on the above analysis, this thesis puts forward the MU-CQI feedback strategy based on PMI. Further more, through putting forward SU-CQI, MU-CQI hybrid cycle transmission strategy to guarantee system performance and system overhead tradeoff. And the system level simulation platform is built. The simulation results and analysis demonstrate that the proposed scheme can take into account the performance overhead and upgrade of system performance.Secondly, this thesis studies the relationship between the multi-user CQI and channel condition, based on this, the calculation method of estimating multi-user CQI is proposed. According to the CQI of single-user whoes RI is equal to1, combined with channel status report so as to obtain constantly updated the multi user CQI. In this paper, the simulations show the comparison between the proposed scheme and the traditional scheme, the proposed scheme can improve the system performance. Further simulations show the precise multi-user CQI is important for the base station channel estimation.Finally, this thesis summarizes the work of research, and pointes out the direction of future research on feedback enhancement.