在傳統合作式通訊中，大部分文獻只考慮單一使用者受到一個或多個中繼站幫忙做轉傳，然而，在實際的應用中包括行動通訊網路的上鏈路與感測網路，會有多個使用者傳送到一個共同接收端的情況發生。在本文中主要探討的問題就是如何在多使用者的情況下選擇哪個中繼站轉傳來達到公平與最好的傳輸效能，一些文獻中有選擇擁有最佳通道的使用者來進行傳輸，也有讓使用者輪流傳輸後再選擇最佳的中繼站幫忙轉傳，但是，前者會造成傳輸不公平的狀況，而後者會產生低傳輸效率與大量功率消耗等問題，為了解決這些問題，我們提出了一個結合使用者排序與選擇中繼站的方法，使用者先輪流傳輸，再根據各使用者達成的平均傳輸率排序，最後中繼站根據使用者的排序與其與接收端的通道品質，決定幫忙轉傳訊號的優先次序。模擬結果顯示，所提出的方法不僅維持公平性，也提升了系統的傳輸效能與降低中繼站的功率消耗。

Existing works on cooperative networks have primarily focused on the scenario with only one source node. However, some practical applications, e.g., uplink cellular networks
or surveillance sensor networks for environment monitoring, may arise such that multiple source nodes transmit to a common destination. In this context, an important problem
is to schedule multiple source transmissions and select a proper relay for each source to perform cooperative retransmission. Some relative works select the source which has the highest source-relay channel gain to transmit in each scheduling instant, and some use round-robin scheduling to let multiple source nodes transmit followed by relay retransmission for each source, regardless their transmission results. However, the former may result in unfair source scheduling, and the latter may not be e cient in terms of time and power consumption. To address these issues, we propose a joint source scheduling and relay selection scheme in this thesis. We use round-robin scheduling to ensure fairness. In addition, the relay which has the superior relay-destination link quality is assigned with a higher priority to assist the source transmission. Simulation results show that the proposed scheme not only maintains fairness but also achieves higher throughput and lower relay power consumption.

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