合作式通訊系統利用空間分集改善了通訊品質，然而，惡意中繼點的出現也可能造成系統效能嚴重下降；在這篇論文中，我們考慮兩個中繼點的解碼傳送(Decode and Forward)合作式網路，中繼點採用正交時空區塊編碼(Orthogonal Space Time Block Code)來實現空間分集，並且假設存在著一定機率，中繼點會惡意竄改傳送的符元造成合作的性能嚴重衰減，在過去相關的文獻中，惡意中繼點的偵測需要準確的通道狀態資訊，但是未考慮到惡意中繼的行為對於通道估測的影響，因此我們提出了一種新的偵測惡意行為方案，由於惡意的中繼行為影響了估測的通道及改變了通道原本的統計分佈，所以目的端可藉由比較估測通道的統計分佈來偵測出中繼點是否存在惡意行為，且不需要通道狀態資訊來增強偵測的效能，透過模擬的結果，我們驗證所提出的方案可偵測惡意行為而不需要知道通道資訊，相對於目的端接收訊雜比，只要目的端接收夠多的追蹤符元，就可偵測出惡意的中繼行為。

Cooperative systems exploit spatial diversity to improve communication quality. But system performances could be severely degraded in the existance malicious relay nodes. In this thesis, we consider a two-relay decode-and-forward (DF) cooperative network. Relay nodes adopt Orthogonal Space Time Block Code (OSTBC) to achieve spatial diversity. Assume that relay nodes may misbehave with a certain probability. If a relay is malicious, it will garble transmission signals, resulting in severe damage to system performance. In the literature, detecting malicious relays requires perfect channel state information. However, misbehavior of the relay will first lead to inaccurate channel estimation. Therefore, we propose a novel detecting misbehavior scheme to deal with the dilemma. Since misbehavior of relays influences statistical properties of the estimated channel coefficients, destination can detect misbehaving by comparing the distribution of channel estimates. The most important of all is that we don’t need channel state information to enhance detecting performance. Through simulation results, we verify proposed scheme can detect misbehavior effectively without channel state information. Compared with signal-to-noise ratio, the number of received tracing symbols has more significant impact on detecting misbehavior of the relay.

摘要 i
Abstract ii
第 一 章 簡介 1
第 二 章 文獻探討 4
2.1 單一中繼點之惡意行為偵測 5
2.2 雙中繼點採用追蹤符元之惡意中繼點偵測 9
2.3 總結 14
第 三 章 系統模型 15
第 四 章 通道估測及其統計特性 20
4.1 Case I：假設所有中繼點都遵守合作機制 23
4.2 Case II：假設任一中繼點存在惡意行為 25
4.3 Case III：假設所有中繼點都存在惡意的行為 30
第 五 章 偵測含有惡意行為的中繼節點 32
5.1 步驟1：目的端偵測中繼點為Case II或Case I / Case III 34
5.2 步驟2：目的端偵測中繼點為Case III或Case I 38
第 六 章 模擬結果 42
第 七 章 結論 47
參考文獻 48

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