本篇論文中將處理多細胞聯合傳輸模式下多重輸入多重輸出系統中的用戶排程議題，聯合傳輸為一能將細胞間干擾轉換為有用的訊號以增加細胞邊緣用戶的資料傳輸速度的技術，然而，決定要將哪些用戶使用聯合傳輸來服務是一件很困難的任務，因為對於細胞中心用戶來說，使用聯合傳輸所能帶來的效益是很有限的，一個直覺的方式是分別估測一個用戶在聯合傳輸模式下與非聯合傳輸模式下的 signal-to-interference-plus-noise ratio (SINR)，哪個模式的 SINR 比較高就使用該模式來服務該用戶。在多用戶的情境下，估測兩種傳輸模式下的 SINR 是一件非常不容易的事情，因為基地台對於每個用戶的能量分配以及使用的預編碼方式都會影響到用戶的 SINR 值。在本研究中，我們提出了一個基於隨機矩陣理論的計算方式以估測兩種不同模式下用戶的 SINR 值，接著我們針對聯合傳輸模式下設計了兩種基於系統整合空間分割及多工(Joint Spatial Division and Multiplexing, JSDM)的空間多工方式。在 JSDM 中，用戶被分成兩個群組，不同群組之間的通道空間特性是不重疊的， 同個群組內的用戶們的通道相關矩陣的基底幾乎相同，因為排程在同一個時間槽作傳輸的用戶可能會具有高度的空間相關性(將會導致自由度不足、傳輸資料速度下降)，我們考慮了每個用戶群組的秩狀況並提出了一個基於圖的用戶排程機制，此外我們也修改了廣被使用在等距線性天線陣列的基於 DFT 的波束成形機制，並提出了一個較能涵蓋細胞網路中的扇形區域一個變種的 DFT 波束成形機制。論文中也呈現了廣泛的模擬結果以評估所提出的考慮細胞邊緣用戶之聯合傳輸機制的效能，並與一些既存的方法作了比較。

In this thesis, the problem of determining which user equippments (UE) should be served with multiple-input multiple-output (MIMO) by joint transmission (JT) is addressed. In multi-cell network in the downlink scenarios, JT is a promising technique to enhance the data rate of cell-edge UEs by converting inter-cell interference (ICI) to useful signal. However, whether the UE should be served by JT needs to be carefully determined since the gain of serving the cell-center UEs with JT is marginal. An intuitive method is to estimate the SINR of JT mode and non-JT mode, respectively, of a UE and select the transmission mode with higher SINR. In the multi-user scenario, the estimate of SINR in both transmission modes is non-trivial because both the power allocated to each UE and the precoder structure for inter- ference cancellation depend on which set of UEs is co-scheduled. In this work, we propose a new approach based on random matrix theory (RMT) to estimate the SINR of different trans- mission modes. Then we design two schemes to achieve spatial multiplexing based on joint spatial division and multiplexing (JSDM) in JT mode. In JSDM, UEs are partitioned into different groups, each with disjoint channel supports and the UEs in the same group have approximately the same supports of channel covariance matrices. Since the co-scheduled UEs may be highly spatially correlated, which would decreases the data rate, we proposed a graph-based user scheduling mechanism considering the rank condition of each UE group. We also revisited the discrete Fourier transform (DFT) based beamformer, which is widely used with uniform linear array (ULA) antennas. A variant of DFT beamforming was proposed to better cover the sectored area in the multi-cell environment. Extensive simulation results are presented to evaluate the performance of the proposed cell-edge-aware JT scheme in comparison with some existing approaches.

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