近來由於隨著無線傳輸技術之發展，無線網路在日常生活上的應用範圍越來越廣，隨著許多應用的環境開發，許多機密的資料也藉由無線網路的媒介傳輸，資料中包含的個人身分資料，如銀行帳號、信用卡密碼、個人住家地址與通訊方式等等，在無線網路環境中由於無線傳輸的特性，難以控制存取的對象，所以需要有安全的機制，讓機密性的資料無法被非法使用者獲得。另外，無線應用在於軍事用途中是相當重要的一部分，由於在嚴苛的戰場環境中非常容易受到敵方的干擾以及竊聽機密資訊，因此能夠在戰場中安全及有效的傳遞訊息是主要的安全需求。為了更清楚安全機制的需求，首先我們介紹在於無線傳輸網路的各類型攻擊模式，以及會造成的安全危害。接著依據安全機制的需求，介紹各種安全機制所要滿足的條件。本篇論文研究方向在於，無線通訊網路中建立於實體層(physical layer)的安全機制。由於無線網路中的各種資源的有限性，例如，電力、頻寬以及無線裝置的計算能力等等。因此，在設計安全機制時必須考慮到這些限制，依照安全等級的需求以及使用環境來設計所需的安全機制。我們將存在的安全機制分類為，頻道方法、編碼方法以及傳輸能量控制方法，三種方法。依序介紹在各分類方法中所使用的安全機制，以及能夠預防的攻擊方式；每種方法利用了不同在於實體層的特性或是編碼技術，用以實現在實體層上的安全機制。隨著在無線網路上的應用發展，因此安全機制也日益重要，陸續的有許多在實體層的安全機制被提出，也仍有許多安全技術問題上的需求，值得深入地研究，根據不同的安全環境及安全需求以及各種方法滿足的安全需求。

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