本篇論文旨在於調查MU-MIMO架構在通訊系統中的特性及效能分析，我們考量了細胞覆蓋範圍內的主動使用者數量，使用者移動速度及傳輸環境的信噪比。MU-MIMO是下一代多天線架構的熱門議題，相比起SU-MIMO能夠更加的提高空間利用率，多用戶增益及高信噪比環境高吞吐量，而且在硬體設置上因其通道容量不受限於使用者端的天線數，因此使用者端節省設計成本及傳輸耗電量，在基地台天線架構上比起SU-MIMO更適合使用窄間距天線或天線陣列，這是受設備廠商所歡迎的。可惜MU-MIMO並非全能的解決方案，傳輸的優勢伴隨著相應的缺點，空間利用率的提升代表在空間複用上要更加費心地去處理信號相互干擾的問題，多用戶增益提升表示其不適於傳輸在分布使用者量少的環境，在高信噪比環境取得高吞吐量則表示其不適於傳輸在低信噪比環境中，再加上由於多波束成型的使用要求對通道條件的預估需更加準確，造成了MU-MIMO在高通道移動性環境下高度的吞吐量衰減，所幸發展已久的SU-MIMO在特性及傳輸優勢上與MU-MIMO呈現互補關係，SU/MU-MIMO切換系統架構在本篇中即為敘述重點。在下行傳輸排程系統架構中我們考量了服務品質的封包預排，吞吐量的預測，傳輸模式的切換及傳輸效能的優化。在實驗部分我們使用了LTE傳輸標準，針對各種不同的傳輸模式分析其效能及最合適的傳輸環境，展現了不同模式的傳輸環境優勢點作為切換點，之後再設置了LTE-A天線架構的傳輸環境並進行效能分析及評比，效能分析圖證實了不同傳輸模式的環境優勢點，基於環境參數的切換對效能影響是直接而有力的。

The paper investigates the feature and performance evaluation of transmission system based on MU-MIMO strategy. We consider number of active users in coverage area, user mobility and environments SNR. MU-MIMO gained numerous attention of researchers because of the spatial efficiency, multi user diversity gain and fit to transmit in good SNR environments. Moreover, it allows the spatial multiplexing gain at the BS to be obtained without the need for multiple antenna terminals, while power saving and cost is kept on the infrastructure side. In BS antenna configuration, widely spaced antennas reduce the spatial correlation and usually result in good SU-MIMO performance but MU-MIMO is found to perform particularly well in highly correlated antenna setups, which is a promising candidate for practical deployment. Unfortunately, MU-MIMO is not an almighty solution. Spatial efficiency accompanies more processing in interuser interference problem. Multi user diversity gain represents the performance degradation with a decreasing number of users and it will not performs good in low SNR environments. Furthermore, multibeam beamforming demand more accurate CSI, it cause high decadence in high channel speed. We propose a downlink transmission scheduling structure considering QoS scheduling, grouping performance prediction, MIMO mode switching and grouping optimization. In our simulation, we followed LTE SPEC to evaluate the performance and superior environments of different transmission mode and demonstrate appropriate transmission mode switching point. Furthermore, we set up LTE-A antenna configurations and showing the switching mechanism in throughput performance affect is direct and powerful.

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