本論文第一部分，我們著重於偏時移領航訊號(PTSP)方法，在領航訊號污染問題與容納的使用者數量之間取得更好的權衡。相較於傳統的時移領航訊號(TSP)方案，我們將領航符元取代領航序列，並允許不同細胞群使用相同的符元區間，雖然導致細胞群之間干擾變強，然而經由增加使用者數量，進而達到提升總傳輸率的目的，並且透過下行鏈路功率控制再進一步的增強性能。模擬結果顯示總傳輸速率在下行鏈路與上行鏈路都能夠有顯著的提升。
在第二部分中，我們則探討整合部分領航訊號重用(FPR)及時移領航訊號(TSP)的結合方案，稱為雙時移領航訊號(DTSP)方案，以減緩全雙工巨量天線系統的領航訊號污染問題。具體而言，將TSP方案應用於雙重細胞的內部和邊緣區域，使得容納的用戶數量加倍。其中基地台為全雙工系統模式，使用導頻符號而不是導頻序列，以用於增加用戶分集增益。模擬結果證實下行鏈路和上行鏈路傳輸率顯著提升，另外數值分析也驗證了模擬的準確性。
第三部分我們探討將一個細胞劃分成多個環的時移導頻(MR-TSP)方案，並且將非重疊時隙分配給不同的環以用於發送導頻。此外，類似於傳統的TSP方案，仍然可以與屬於不同組的小區共享相同的時隙。依據分析和模擬結果，發現細胞分成多環的系統性能夠明顯提升。
最後一部分，我們開發了多小區協同調度(MCCS)算法，以適當地安排用戶完全重用相鄰小區之間的有限正交導頻，從而可以減輕大規模MIMO系統中導頻污染（PC）的影響。為此，定義多小區協作調度索引(COSI)以最大化數據速率，最大化Jain的公平性指數並在其間達到更好的平衡(CMDR、CMMF和CPF COSI表示)。

This dissertation has four parts. The first part we focus on a partial-time-shifted pilot (PTSP) scheme to find a better tradeoff between the user accommodation and orthogonality of pilots for the massive multiple-input multiple-output (MIMO) system. To this end, the pilot symbols rather than the pilot sequences are applied. Also, the neighboring cells are allowed to transmit the pilot signals using the overlapped symbol periods. Despite the stronger interference, the larger user accommodation as well as the near-far effect incurred by using the pilot symbols can contribute to the higher sum transmission rates for both the uplink and downlink cases.
Second, we focuse on a cocktail approach, to delicately integrate the two conventional countermeasures, i.e., the fractional pilot reuse and time-shifted pilots (TSP) schemes, named it dual partial-time-shifted pilot (DTSP) scheme, for the pilot contamination problem in the full-duplex massive multiple-input multiple-output system. Specifically, the TSP scheme is applied to duplicate for the inner and edge regions of a cell such that the number of accommodated users can be doubled. To achieve this, the base station should operate in the full-duplex mode; also, the pilot symbols rather than the pilot sequences are used to attain the user diversity gain. The simulation results verify the accuracy of the numerical analysis and the remarkably boosted sum rate for both the downlink and uplink cases.
For the third part, we develop a general multi-ring TSP (MR-TSP) scheme by dividing a cell into multiple rings; and allocating non-overlapped timeslots to different rings for transmitting pilots. Moreover, similar to the conventional TSP scheme, the same time slots can still be shared with cells belonging to different groups. Based on the analytical and simulation results, it is found that three rings are recommended for the TSP-based pilot contamination schemes.
Finally, we develop the multi-cell cooperative scheduling (MCCS) algorithm to properly arrange users for completely reusing the limited orthogonal pilots among the neighboring cells so that the impact of pilot contamination (PC) in the massive MIMO systems can be alleviated. To this end, the multi-cell cooperative scheduling indexes (COSIs) are defined for maximizing the data rate, maximizing the Jain's fairness index and reach a better tradeoff in-between (which are denoted by CMDR, CMMF and CPF COSIs, respectively).

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