巨量天線系統在理想的情況下，能夠藉由龐大天線數量所帶來的自由度消除來自細胞內以及細胞之間的干擾，然而使用非正交領航序列所造成的領航訊號污染問題，使得巨量天線系統的優點將會受到限制。而傳統的時移領航訊號方案能夠藉由將細胞分組，錯開細胞組之間傳送領航訊號的時間來遏止大部分的領航訊號污染，然而這樣的方法同時也嚴重的犧牲細胞能容納的使用者數量。
在本論文中，我們所提出的偏時移領航訊號方法，在領航訊號污染問題與容納的使用者數量之間取得了更好的權衡，因此相較於傳統的時移領航訊號方案，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的干擾變強，然而可容納使用者數量的增加提升了總傳輸速率，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，因此相信本論文能夠有助於巨量天線系統的發展。

By deploying an extremely large number of antennas at base station (BS), the massive multiple-input multiple-output (MIMO) technique can provide sufficient degrees of freedom such that the intra- and inter-cell interference can be thoroughly eliminated. However, this ideal merit is seriously restrained by the well-known pilot contamination problem caused by using the non-orthogonal pilot sequences. Traditionally, the time-shifted pilot (TSP) technique was proposed to partition cells into several groups; and only the cells within the same group are allowed to transmit pilots simultaneously. Unfortunately, using the TSP scheme restricts the number of accommodating users.
In this paper, we aim to find a better tradeoff between the orthogonality of pilots and the number of users by proposing the partial-time-shifted pilot (PTSP) scheme. Specifically, the cells belonging to different groups are allowed to transmit pilot signals using the overlapped symbol intervals. To achieve this, the pilot symbols rather than the pilot sequences are adopted in this paper. Although it can result in the stronger IGI, the larger number of accommodating users can contribute to higher sum rates. Moreover, a well-designed downlink transmission power can further raise the performance enhancement. The simulation results demonstrate the significant sum rate improvements for the downlink and uplink cases, respectively. It is believed that the contributions of this paper can provide helpful information for developing a massive MIMO system.

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