中文摘要
一個新的巨量天線(Massive Multiple Input Multiple Output, Massive MIMO) 陣列被視為5G新無線技術 (New radio, NR) 的核心技術，在基地台裝載大量天線並配合波束成型 (Beamforming) 技術，使得訊號能量集中至用戶端的方向，用戶獲得波束成型增益讓解調能力提升獲得更佳的系統效能。然而，如何讓基地台事先獲知用戶端的地理方向，是現在各公司在標準制定會議中熱烈討論的議題。
目前，各家公司已達成共識採用週期性的波束追蹤，基地台藉由傳輸多個方向參考訊號，用戶經過測量這些參考訊號後，再回報該用戶端接收能量最強的參考訊號的相關資訊給基地台。然而波束追蹤需要基地台消耗大量資源傳輸參考訊號，進而使得整體傳輸速率下降。另一方面在用戶端，又因為需要量測多次的參考訊號也使的用戶端的計算複雜度上升，增加耗電量。因此，本篇提出非週期性的波束追蹤，可拉長波束追蹤的週期，並配合非週期性的波束追蹤，進而解決因為用戶移動造成的波束追蹤失準的問題。
Abstract
A new paradigm dubbed as “Massive-multiple input multiple output array (Massive-MIMO array)” has been regarded as one of the key candidate technologies for 5G new radio (NR). A base-station equipping with a large number of antennas concentrates the transmission signal toward the direction of one user equipment (UE) by the beamforming technology. Obtaining beamforming gain, UE demodulates signal more efficiently and the system has better performance. However, how the base-station has the knowledge of UE’s geometric direction in advance is a serious issue where many companies were engaged in standards meetings.
So far, many companies had agreed that the periodic beam search is the solution. The base-station firstly transmitted multiple beam-formed reference signals (RSs) and each RS was beam-formed to one specific direction decided by base-station. Then, the UE measures those beam-formed RSs and feedbacks favorite beam index to base-station. However, this beam search consumes a lot of RS resource, which leads to low throughput. On the other hand, the UE has more complexity since the UE needs to measure multiple beam-formed RSs which may cause battery consumption. Hence, we propose an aperiodic beam search method in this paper. Our proposal can extend the periodicity of beam search to ease the loading at both base-station and UE sides. The base-station can track the UE’s direction immediately by aperiodic beam search to solve problem of the beam mismatch due to UE’s moving.
關鍵詞(Key Words)
新無線技術 (New Radio；NR)
波束成型 (Beamforming)
全維度多輸入多輸出 (Full-Dimension Multiple Input Multiple Output；FD-MIMO)
通道狀態資訊參考訊號 (Channel State Information-Reference Signal；CSI-RS)
相關檔案: 減低波束搜尋複雜度之非週期性技術(全文)
