合作式通訊系統中，訊號源到目的端之間的傳輸藉由中繼端的幫助達到空間多樣性(spatial diversity)，以便抵抗通道衰減。然而，若中繼端出現異常行為或惡意行為，而目的端若沒有察覺而直接使用中繼端傳輸過來的訊號，那麼系統的多樣性增益會大幅降低，導致合作系統性能下降。在本論文中，我們考慮一個中繼端解碼後再傳送(decode and forward, DF)之合作式網路，並且假設存在著一定機率，中繼端會惡意竄改傳輸訊號來破壞合作式系統。我們在論文中討論三種惡意行為的偵測方式，更明確地說，我們採用時序檢測(sequential test)的方式來偵測中繼端行為，若訊號源傳送追蹤符元(tracing symbols)，目的端收到的訊號後，先取出追蹤符元，然後使用對數-概似比值檢測(log-likelihood ratio test)來對追蹤符元進行中繼端行為偵測；若訊號源不傳送追蹤符元，我們會先將目的端經由直接路徑接收資訊進行訊號偵測，然後利用偵測值和中繼端送來的訊號對中繼端行為進行偵測。透過模擬的結果，在一定的錯誤率範圍下，我們使用的方法在高訊雜比時可以有效地減低取樣數，換句話說，在高功率時，目的端不需接收大量的追蹤符元或傳輸訊號，就可以快速偵測出惡意的中繼行為，以降低惡意中繼端造成的傷害。

To combat channel fading, cooperative communication achieves spatial diversity for the transmission between source and destination through the help of relay. However, if the relay behaves abnormally or maliciously and the destination is not aware, the diversity gain of the cooperative system will be significantly reduced, which degrades system performance. In our thesis, we consider an one-relay decode and forward cooperative network, and we assume that the relay may misbehave with a certain probability. If the relay is malicious, it will garble transmission signal, resulting in severe damage to cooperative system. In this work, we discuss three kinds of malicious behavior detection. More specifically, we adopt sequential detection to detect the behavior of relay. If tracing symbols are inserted among the source message, the destination detects malicious after extracting the received tracing symbols. We adopt log-likelihood ratio test to examine these tracing symbols, and then determine the behavior of relay. If the source does not transmit tracing symbols, the destination detects misbehavior according to the received data signal. Furthermore, we employ sequential detection to reduce detection time for a given probabilities of false alarm and miss detection. Through simulation results, for a certain target on probability of errors, our proposed methods can effectively reduce numbers of observations. On the other works, the destination can effectively detect misbehavior of relay, and eliminating the damage causes by malicious relay without requiring large numbers of observations.

論文審定書
致謝................................................................ i
中文摘要............................................................ii
英文摘要........................................................... iii
目錄............................................................... iv
圖次............................................................... vi
表次.............................................................. viii
第 一 章 簡介.......................................................1
第 二 章 相關背景...................................................5
2.1 單一中繼點採用接受訊號相關性之惡意行為偵測.................. 6
2.2 雙中繼點採用追蹤符元之惡意行為偵測........................... 10
2.3 簡單的序列傳感............................................... 15
第 三 章 系統模型..................................................18
3.1 訊號模型..................................................... 18
3.2 中繼端之行為模型............................................. 20
3.3 追蹤符元系統架構............................................. 22
第 四 章 中繼惡意行為的時序偵測....................................23
4.1利用追蹤符元的時序偵測........................................25
4.1.1 中繼端發生自私行為.......................................26
4.1.2 中繼端發生竄改行為........................................27
4.1.3 中繼端發生混合惡意行為....................................28
4.2無追蹤符元的時序檢測......................................... 31
4.2.1 中繼端發生自私行為........................................34
4.2.2 中繼端發生竄改行為........................................34
4.2.3 中繼端發生混合惡意行為....................................35
第 五 章 模擬結果..................................................41
第 六 章 結論與未來研究方向........................................58
參考文獻...........................................................59
附錄................................................................61
附錄 A.......................................................... 61
附錄 B.......................................................... 62
附錄 C.......................................................... 64
附錄 D.......................................................... 65
附錄 E.......................................................... 68

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