第五代毫米波通訊系統下指向性參考信號設計與排程機制

Abstract

毫米波頻帶提供了一個可以支援數億位元傳輸率的新未開發頻帶給無線行動通訊系統。但是毫米波頻帶的通道傳輸物理特性比一般低頻的電波還要脆弱，因此必須使用指向性天線將能量集中在傳輸方向形成波束克服。指向性天線在無線行動通訊系統的使用面臨許多嶄新的挑戰，例如指向性參考信號的設計。指向性參考信號可用作量測通道品質、波束追蹤與裝置移動性管理。在本篇論文中，設計指向性參考信號使之確保整個基地台的參考信號覆蓋範圍且提升參考信號在行動裝置端的頻繁接收率。並且利用指向性參考信號的特性，設計出兼具行動裝置省電與高傳輸流量的排程機制。在這篇論文中透過數學理論分析與電腦數值模擬結果驗證了提出方法比起傳統方法的突出表現。

Millimeter wave (mmWave) frequency bands offer a new frontier for cellular wireless systems to enable multigigabit communication. However, the availability and reliability of mmWave links are significantly limited due to its propagation characteristics. To mitigate the impact of such links and provide uninterrupted network services, the study of changing link condition is important. This paper proposes a reference signal (RS) transmission scheme and RS aware scheduling mechanism for a mmWave cellular system using highly directional antenna beams. The aim of RS is to estimate the channel condition which can be used for various purposes, e.g. initial access, beam alignment, and channel state information (CSI) measurement. In particular, the objective of our RS scheme is to enable efficient RS transmission in terms of RS frequently reception while ensuring a fair number of RS reception at all UEs within cell coverage. In addition, we provide a scheduling mechanism considering directional RS for studying the system throughput. Through theoretical analysis and simulation, we show that the proposed scheme achieves higher efficiency.