無線網路環境中，變動且不穩定的頻道條件嚴重影響通訊服務的品質。當行動節點遇到嚴重的訊號干擾時，會無法順利將資料傳送出去，導致無法滿足應用程式所需要的服務品質。而干擾的出現，會進一步降低多重躍進網路架構下的效能。IEEE 802.16j是相當受注目的多重躍進網路標準。它藉由中繼站來傳遞基地台與行動節點間的訊息，以提供以下優勢：網路覆蓋範圍的增加，吞吐量及網路能力的提升等等。IEEE 802.16j的排程服務機制會周期性的分配頻寬給整條多重躍進路徑的每一段傳輸。一旦行動節點遇到了不好的無線訊號，則第一段傳輸的失敗，就會導致分配給整條多重躍進路徑的頻寬都被浪費，降低頻寬的使用率。這不僅破壞服務品質的協議，更大大地降低系統的效能。本論文提出一合作式傳遞機制來克服IEEE 802.16j無線訊號固有的不穩定性。也就是說，一個遇到不好之無線訊號的行動節點可以藉由尋找另一個無線訊號良好的行動節點來幫忙傳遞自己的資料到目的地。另外，為了找出一個具有最佳能力條件的合作夥伴，本論文同時提出一動態夥伴選取演算法來達到此目的。模擬的結果根據封包延遲時間，封包延遲時間變化量，系統吞吐量以及封包遺失率來支持本論文所提的方法可以達到更高的效能。

The inherent property of fluctuant channel conditions in the wireless networks influences the Quality-of-Service (QoS) severely. The Mobile Stations (MS) suffering from rigorous interference could not deliver data successfully and fail to achieve the QoS required by the applications. The occurrence of interference would worsen the performance especially in multihop relay networks. IEEE 802.16j is a promising Multihop Relay (MR) networks which enhance coverage, throughput and system capacity of IEEE 802.16e networks by deploying Relay Stations (RS) to relay data between MSs and the Multihop Relay BS (MR-BS). The scheduling services in IEEE 802.16j may allocate the bandwidth periodically without explicit bandwidth request to each hop along the path between the source and the destination. Once the MS encounters low channel quality in access link, the whole resources scheduled for the MS will waste. This not only breaks the QoS agreements but greatly decreases the system performance. In this paper, we propose a cooperative relaying mechanism to overcome the unstable channel conditions in IEEE 802.16j MR networks. Therefore, a user that is currently experiencing bad channels could survive if a cooperative partner with good channels is willing to relay its data to the destination. In order to find out a cooperative partner with best capacity to relay data, we also propose an adaptive partner selection algorithm. Extensive simulations highlight the superiority of the proposed solutions in terms of packet delay, jitter, system throughput, and packet loss rate.

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