近年來，合作式通訊架構解決了將多根天線放置於行動端的困難性。在合作
式通訊模型中，透過只有單根天線中繼端的協助，不僅提供了空間上的多樣性也
提高了整體通訊品質。然而大部分現有的研究只探討改變中繼端協助傳送的方式
來達到更好的通訊品質，因此，首先必須獲得完整的通道狀態資訊。但是，於初
始的情況下並無通道狀態資訊。因此接收端或是中繼端對於獲得通道狀態資訊就
變得非常重要。本篇論文則是於中繼端以放大並傳送的策略下做討論。
探討多個中繼端形成的合作式通訊系統在空間上的多樣性，必須要有縝密且
複雜的協定，並且考慮到中繼端發生違反行為的情況。因此，進行通道估測時必
須要有能強韌抵抗中繼端可能發的違反規則行為。然而現有的研究都是假設所有
中繼端都是完全協助訊號的傳送，相較於本篇論文，合作式通訊系統出現違反行
為的中繼端下設計強韌的通道估測技術，並且更貼切於實際環境，通道之間存在
相關性，也就是，傳送端到中繼端之間以及中繼端到接收端之間的通道存在相關
性，並且中繼端接收到的雜訊同時也存在相關性。總結本篇論文的主要論點，則
是設計強韌的通道估測技術以及訓練序列，抵抗通訊過程中存在違反行為的中繼
端和存在通道相關性的影響。

Recently, the difficulty of placing multiple antennas onto a mobile terminal to exploit more
diversity has been solved by using the cooperative communication technique, in which several
relay nodes with a single antenna partner with each other to serve as virtual multiple antennas
for providing the spatial diversity. Many existing researches in cooperative communication
focuses on designing relay strategies to achieve better communication performance. However,
most of their designs require the channel state information (CSI) being perfectly known. Unfortunately,
CSI is generally unknown in practice. Therefore, before getting benefits brought by
the relay-assisted network, it is necessary to obtain accurate channel state information (CSI)
at the destination or relays. In this thesis, we also consider the training design for channel
estimation in the AF relay network.
The involvement of multiple relay nodes to exploit space diversity in cooperative communications
requires sophisticated and complicated protocols, which poses a difficulty in avoiding
all possible misbehaving relay nodes. Therefore, the channel estimation scheme in cooperative
communication network needs to be robust against the possible relay misbehaviors. However,
most prior works focused on developing channel estimation schemes by assuming perfect relayassisted
communication protocol. By contrast, this work focuses on designing robust channel
estimation schemes to combat the possible presence of the relay misbehaviors. Besides considering
the robust design against relay misbehaviors, this work also considers more general channel
model when designing the training sequence and channel estimation scheme. Specifically, in
contrast to assume independent channels across relays, this thesis considers the correlated channels
in both phases and the correlated noises in the first phase. Overall, the main problem of
this work is to design robust channel estimation and training sequences against relay misbehaviors
when the communication channels within the cooperative network are not restricted to
be independent.

1 Introduction 1
2 System Model 5
3 Training Based Channel Estimation 8
3.1 Linear minimum mean square estimation . . . . . . . . . . . . . . . . . . . . . . 8
3.2 Optimal training design at a correlated channel and noise environment . . . . . 10
3.3 Effect of misbehaving relays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.4 Optimal Training Sequences Design . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.5 Suboptimal Training Sequences Design . . . . . . . . . . . . . . . . . . . . . . . 13
4 Simulation 14
4.1 Parameter Seting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4.2 Quasi-Exhaustive Search . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4.3 The Scenario of 3 Relays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.4 The Scenario of 4 Relays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.5 The Scenario of 5 Relays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
5 Conclusion 27
A Proof of The Mean Square Error in Section 3.3 29

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