60GHz正交分頻多工系統波束形成技術之研究

Abstract

為了可以增加無線通訊系統之資料傳輸速率以及頻譜使用效率，正交分頻多工系統結合波束形成技術的方式已被廣泛的討論。在60GHz的通訊系統下，由於高載波頻率的關係，使得射頻元件的尺寸得以縮小，多天線技術的實現也較為容易，因此使用波束形成技術成為一個可以有效提升效能的方式。應用於正交分頻多工之波束形成技術可以分為逐符碼波束形成(symbol-wise beamforming)、逐子載波波束形成(subcarrier-wise beamforming)和混合型(hybrid)三種。本文中，分別討論逐符碼波束形成以及逐子載波波束形成之優缺點，並針對逐符碼波束形成與混合型的架構提出改進的演算法。近年來，綠能通訊的概念逐漸被重視，因此在最後我們也提出一種新的波束形成方法，在多輸入單一輸出(multi-input single-output, MISO)的系統下，藉由關閉天線元件來提升能量使用的效率。

To increase the wireless communication system data rate and spectrum efficiency, the approach of combining OFDM system with beamforming techniques has been widely discussed. For 60GHz communications systems, due to the high carrier frequency, the size of RF components can be reduced and it makes the realization of MIMO techniques much easier. According to the above reasons, beamforming is an effective way to improve performance. The beamforming techniques used in OFDM include symbol-wise beamforming, subcarrier-wise beamforming and the hybrid type. In this thesis, at first we discuss the properties of symbol-wise and subcarrier-wise beamforming, then we propose improved algorithms for both symbol-wise beamforming and the hybrid type. In recently, green radio communications have become more important, and finally we also propose a new beamforming method to improve the energy efficiency by turning off the antenna elements of MISO-base radio system.