在近年來，感知無線電的技術顯著地改善了頻譜效率不佳的機會使得頻譜使用率得以提高。但也因為主要用戶與次要用戶之間不同的權限使得主要用戶端要使用所屬頻譜區段時次要用戶端必須立即空出頻譜資源歸還給主要用戶而導致次要用戶端的網路整體效能受限於頻譜資源的歸還而受到影響，也因此衍生出感知無線電技術所需克服的問題像是頻譜配置與繞徑協定的設計和頻譜換手等問題來減緩網路效能的損失且由於無線網路中的頻道干擾特性也間接地影響了感知無線網路中每一節點頻譜配置的考量。透過選擇強健性高的頻譜可以有效地降低受主用戶端的干擾因而減少網路損毀情形。然而，透過繞徑協定選擇於高穩健性或是最短路徑仍然會導致網路環境上發生擁塞情形。
著重於上面的問題，本篇論文主要提出了於多躍式感知無線網路環境上建置高效率考量且頻道干擾最小化的頻譜配置演算法來避免主用戶端的干擾以及降低於次要用戶端的同頻譜干擾之影響以提高資訊傳輸的穩定性與資料傳輸效率。另外，我們同時提出一套具備負載平衡的繞徑協定來分散流量最大負載情況並且提供高穩健性、低延遲的繞徑來傳輸。
而從實驗結果可以很明顯地看出以本篇論文的結果可以建置出最小化干擾程度頻譜配置策略並且可以有效地降低網路損毀的機率，使得在實驗結果中網路效能皆可以比傳統式無線網路運作架構或是過去研究所提及的方法獲得許多地改善。頻譜配置方法中，我們所提出的TSRMITA方法的平均網路產能優於RCA和CRTCA方法分別有10%~35.2%和15.7%~23.3%的改善幅度。除此之外，我們藉由負載平衡且穩健導向的繞徑協定來與穩健導向的繞徑和最短繞徑的比較過程可以發現到當網路負載情形過高的情況下負載平衡且穩健導向的延遲優於其他兩者的繞徑方法。繞徑選擇方法中，我們所提出的RLBRA方法的延遲時間優於SFA和DAU方法分別有4.4%~16.7%和2.9%~13.5%的改善幅度。

In recent years, cognitive radio technique significantly improves the spectrum utilization efficiency. However, due to the privilege of primary users (PUs,) the network performance of secondary users (SUs) would shrink for returning the occupied spectrum whenever the PU becomes active. Therefore, channel assignment strategies, spectrum handoff methods and routing should be considered thoroughly to avoid the shrinkage of network performance. Besides, the feature of co-channel interference also influences the channel assignment for each node, which is solved by choosing highly robust channel in the existing approach to reduce the occurrence of interference and the probability of network corruption. However, concentrating network load on the highly robust route or the shortest path would cause network congestion.
Based on the issues described above, two-stage robust and minimum interference topology algorithm (TSRMITA) is proposed in the thesis to minimize the co-channel interference between PUs and SUs and to improve the stability of data transmission in multi-hop cognitive radio networks (CRNs). Moreover, we also propose robustness-oriented and load balanced routing algorithm (RLBRA) which distributes maximum load of the network to provide more stable and low total delay route for data transmission.
From simulation results, we can see that TSRMITA outperforms several existing scheme and improves network performance. The average throughput of TSRMITA is superior to RCA and CRTCA by 10-35.2% and 15.7-23.3% improvement, respectively. Additionally, we compare the performance among the proposed routing RLBRA, robustness-oriented routing and shortest path routing. The simulation results show that under the situation of high traffic load, our proposed routing RLBRA has better performance in end-to-end delay than SFA and DAU routing schemes by 4.4-16.7% and 2.9-13.5% improvement, respectively.

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