在巨量多輸入多輸出(Massive Multiple-Input Multiple-Output, M-MIMO)蜂巢式網路(cellular network)下，由於分配給領航序列傳輸的時頻資源和通道同調時間都是有限的，因此正交領航序列的數量也是有限的。這使得領航序列在蜂巢式網路中，相鄰的細胞會重複使用，而目標細胞基站的通道估測會受到其他細胞的用戶所傳輸的領航序列造成污染，這種同調干擾就被稱為領航序列污染(Pilot Contamination, PC)。頻率和領航序列的重用導致通道估測干擾，從而降低其性能。因此，PC被認為是多細胞M-MIMO系統的性能瓶頸。
本篇論文基於領航訊號汙染的環境下，著重於兩部分，分別為通道估測與領航序列分配。通道估測主要為了解決，在M-MIMO分時雙工系統並且多細胞多用戶的情況下，存在大量的通道狀態資訊，為了減少基站的負擔，使用一種用於減輕領航訊號污染的通道估測器。此估測器不用假定干擾細胞的大範圍衰減係數，因此通道估測時就不需產生大量的開銷，性能也能夠接近MMSE估測。領航序列分配為了解決領航訊號污染的問題，使用一種新領航序列分配法，基於現有的兩種方法:軟性領航序列重用方案、加權著色圖領航序列分配法。為了符合領航序列互相正交且資源有限的情況，透過重新分配領航序列的方式，達到抑制領航訊號汙染的效果。

Under the Massive Multiple-Input Multiple-Output (M-MIMO) cellular network, since the time-frequency data and channel coherence time allocated to pilot sequence transmission are limited, therefore the number of orthogonal pilot sequences is also limited. This makes the pilot sequence in the cellular network, adjacent cells will be reused, and the channel estimation of the base station of the target cell will be polluted by the pilot sequence transmitted by the users of other cells. This kind of coherent interference is called pilot contamination (PC). The reuse of frequency and pilot sequences leads to interference in the channel estimation, thereby degrading its performance. Therefore, the PC is considered to be the performance bottleneck of the multi-cellular M-MIMO system.
This thesis is based on the environment of pilot signal pollution, focusing on two parts, namely channel estimation and pilot sequence allocation. Channel estimation is mainly to solve the problem. In the case of M-MIMO time-division duplex system and multi-cell multi-user, there is a large amount of channel state information. In order to reduce the burden on the base station, a channel estimation for reducing pilot signal pollution is used. This estimator does not assume a wide range of attenuation coefficients for interfering cells, so channel estimation does not require a large overhead and performance can approach that of MMSE estimation. Pilot sequence allocation is to solve the problem of pilot signal pollution, a new pilot sequence allocation method is used, based on two existing methods: soft pilot sequence reuse scheme and weighted coloring graph pilot sequence allocation method. In order to comply with the situation that pilot sequences are mutually orthogonal and resources are limited, the effect of suppressing pilot signal pollution is achieved by reassigning pilot sequences.

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