在多傳送接收點的網路中，細胞間的干擾對於提升頻譜效率來說，一直都是一個很大的障礙。為了解決細胞間的干擾問題，3GPP 在 Release 11 中，提出了協調多點的方法，其中下行協調傳輸模式的聯合傳輸，可以透過傳送接收點的共同服務，將干擾的信號源轉為有效的信號源，藉以提升信號能量並且降低細胞間的干擾影響。聯合傳輸又可分成兩種模式，分別是同調聯合傳輸及非同調聯合傳輸。為了簡化系統設計，我們採用較為實際的非同調聯合傳輸，為主要的傳輸模式。過去的論文中，一般都是在探討單天線的聯合傳輸，對於多天線的聯合傳輸研究，比較少有著墨，如果能善加利用多天線的優點，例如多樣性增益及空間多工性增益，可以有效提升系統效能。因此，在非同調的聯合傳輸下，將分別利用不同的傳輸模式，達到多樣性增益及空間多工增益的效果。參與協調的傳送接收點可以進行多層次的傳輸，所以彼此間的層次分配，也是我們會考慮到的要點。除了層次協調外，我們會考慮到系統進行傳輸時的步驟，包含傳送接收點的分群、決定可以接受聯合傳輸的用戶及排程方法，此外，傳送接收點必須進行共同排程，分群可以減少共同排程的複雜度，然而，並不是所有用戶需要接受聯合傳輸，因此我們利用參考訊號的接收能量以及分群的限制，挑選出需要聯合傳輸的用戶。為驗證系統效能，我們採用按照 3GPP的規範所建立的模擬器進行系統層級模擬，模擬結果，將會呈現不同聯合傳輸模式的比較，用以觀察多輸入多輸出的聯合傳輸對於頻譜效率的改善。

In multi-­TRP network, inter-­cell interference (ICI) strictly limits spectral efficiency. Coordinated multi­point (CoMP) is proposed to solve the ICI problem. Joint transmission (JT), which turns the interference signal into useful signal is one of the downlink transmission mode in CoMP. In general, JT is divided into coherent JT and non­-coherent JT. In order to simplify the system design, non­-coherent JT is more practical than coherent JT. In this thesis, the performance of non­-coherent JT with multiple-­input multiple-­output (MIMO) is investigated. The conventional JT mainly focuses on the user equipment (UE) with single antenna and the coordinated base stations (BSs) send the same signal to UE. By leveraging the merits of multiple antennas, such as diversity gain and spatial multiplexing gain, the spectral efficiency would be improve substantially. However, the preferred transmitted data stream of the coordinated BSs might be different so the layer coordination is required in different JT modes. A system ­level study is conducted in this work. First, the clustering method is used to define the co­-scheduled BSs. Because not all the UEs need JT, a decision rule based on reference signal received power (RSRP). Moreover, the scheduling method based on proportional fair scheduling with different clustering method is proposed. The mentioned transmission processes are implemented in a system­ level simulator, which is fully compiled with the 3GPP specification. The simulation results are presented to demonstrate the improvement of spectral efficiency in different JT mode with MIMO.

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