臺灣博碩士論文加值系統

在無線式合作通訊網路中，選擇合適的中繼點對於取得良好的結果是一個重要的考量。結果包括錯誤率以及流量等等。中繼點選擇協定也將會影響整個選擇程序的延遲。因此，在延遲和結果中取得良好的平衡是我們所探討的。在本文中，我們提出一個快速中繼點選擇協定。在數個競爭時序中，讓任意個中繼點彼此競爭此通道，依照瞬時的訊雜比來決定競爭通道的強度。以此方式最後能夠快速的選擇出可利用的中繼點。於本文中，我們推導此協定的平均延遲時間以及錯誤率。並經由模擬的結果與機會式選擇比較，我們證明此提出的方法能夠有效的降低選擇時間的延遲，並且於錯誤率中依然擁有良好的結果。

In cooperative wireless network, selecting suitable relay nodes is critical to the achievable gain, including error rate, throughput and so on. The relay selection protocol will also effect the resulting due to the delay in relay selection. How to balance to trade-off between performance improvement and delay penalty thus needs to be carefully addressed. In this thesis, we propose a fast relay selection protocol. We let relay nodes to compete for the channel access during the relay selection phase leading to completely distributed relay selection. The relay nodes utilize instantaneous channel information to decide its action. In this thesis, we derive the expression of average delay time and outage probability. From the numerical results, we demonstrate the proposed scheme can significantly reduce the relay selection time and maintain a low outage probability.

Cover Page . . . . . . . . . . . . . . . . . . . . . . . . i
Chinese Abstract . . . . . . . . . . . . . . . . . . . . ii
English Abstract . . . . . . . . . . . . . . . . . . . . iii
Contents . . . . . . . . . . . .. . . . . . . . . . . . . iv
List of Figures . . . . . . . . . . . . . . . . . . . . . vi
1 Introduction . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Challenges and Problem Statement . . . . . . . . . . . 1
1.2 Thesis Outline . . . . . . . . . . . . . . . . . . . . 2
2 Background and Literature Review . . . . . . . . . . . . 3
2.1 Background . . . . . . . . . . . . . . . . . . . . . . 3
2.1.1 An Introduction of Cooperative Communications . . . 3
2.1.2 An Introduction to Opportunistic Relaying . .. . . . 5
2.2 Literature Review . . . . . . . . . . . . .. . . . . . 7
2.2.1 Relay Selection Criterion . . . . . . . . . . . . . 7
2.2.2 OR-based Cooperative Protocols . . . . . . . . . . . 8
3 Proposed Protocol for Relay Selection . . . . . . . . . 9
3.1 System Model . . . . . . . . . . . . . . . . . . . . . 9
3.2 Description of the Proposed Protocol . . .. . . . . . 10
3.2.1 Selection criterion . . . . . . . . . . . . . . . . 11
3.3 Performance Analysis . . . . . . . . . . . . . . . . 12
3.3.1 Distance Decay . . . . . . . . . . . . . . . . . . 12
3.3.2 Bit Error Rate (BER) . . . . . . . . . . . . . . . 13
3.3.3 Accessing Probability . . . . . . . . . . . . . . . 13
3.3.4 Average Election Time of I.I.D. Channels . . . . . 15
3.3.5 Average Election Time of Non-I.I.D. Channels . . . 16
3.4 Outage Probability . . . . . . . . . . . . . . . . . 16
3.5 Discussions on the Protocol Parameters . . . . . . . 18
4 Simulation Results and Discussions . . . .. . . . . . . 19
4.1 Simulation Model . . . . .. . . . . . . . . . . . . . 19
4.2 Average Relay Election Time . . . . . . . . . . . . . 21
4.2.1 I.I.D. Channels . . . . . . . . . . . . . . . . . . 21
4.3 Comparisons with OR . . . . . . . . . . . . . . . . . 23
4.3.1 Fixed Topology . . . . . . . . . . . . . . . . . . 23
4.3.2 Random Topology . . . . . . . . . . . . . . . . . . 26
4.4 Outage Probability in Random Topology . . . . . . . . 29
5 Conclusion and Future Work . . . . . . . . . . . . . . 34
5.1 Summary of Thesis Contribution . . . . . . . . . . . 34
5.2 Future Work . . . . . . . . . . . . . . . . . . . . . 34
References . . . . . . . . . . . . . . . . . . . . . . . 36
Appendix . . . . .. . . . . . . . . . . . . . . . . . . . 39
Bibliography . . . . . . . . . . . . . . . . . . . . . . 41

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