在合作式通訊中，中繼點合作會消耗傳輸資源，所以需要中繼點選擇機制以達到多樣性增益同時造成的效率損失是可接受的。中繼點選擇機制可分為集中式和分散式。大部分先前的中繼點選擇機制為集中式，其中的單一節點需要知道整個網路的資訊。相反地，分散式機制允許各個節點基於本身的資訊決定要不要參與合作式傳輸。本篇論文提出了兩個利用解調後傳送基於量化式回饋的有限延遲中繼點選擇機制以避免不必要的中繼點合作，在提出的機制中，只有當來源端和目的端之間的直接傳輸失敗時，目的端才會要求中繼點重新傳送來源訊號。此兩種機制中所需要的回饋經過量化以減少多餘的回饋負載。除此之外，中繼點選擇的時間長度是受限且可被控制的，和中繼點的數量也無關。為了評估機制的效能，本篇論文分析了這兩個機制的位元錯誤率和平均傳輸時間。此外，經由模擬來驗證分析的精確度，並分析幾個提出的機制中重要的參數對系統效能的影響。模擬的結果證明系統位元錯誤率效能受到回饋的量化解析度是有限的，本篇論文提出的利用量化回饋與解調後傳送的方法可以有效地利用多樣性增益且非常適合於低複雜度的無線網路。

In cooperative communication, relay cooperation consumes additional resources, hence the relay selection is required to reduce the resource consumption but still achieve diversity gain. Relay selection can be performed in a centralized or a distributed manner. Most prior works adopt centralized selection that requires network-wide information to be available at a single node. On the contrary, distributed selection allows each node to make cooperation decision locally. In this thesis, two distributed relay selection schemes based on demodulate-and-forward (DmF) using destination feedback are proposed to avoid unnecessary relay cooperation, the destination in the proposed schemes asks the relays for retransmission only when the direct source-destination transmission is considered as failed. The feedback required in both schemes is quantized to reduce the redundant feedback load. Furthermore, the duration of the relay selection is limited in a controlled fashion and insensitive to the number of relays. To evaluate the performance of the proposed schemes, both the end-to-end bit error rate (BER) and the average transmission duration are analyzed theoretically. Extensive simulations are conducted to validate the analysis accuracy and to get insights into the impacts of various important system parameters to the proposed distributed relay cooperation schemes. The results suggest that BER performance is less sensitive to the quantization resolution, the proposed methods using quantized feedback and DmF relays can effectively exploit the cooperative diversity gain and thus are very suitable to low-complexity wireless networks.

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