多跳感知無線網路中考慮路由穩定度之路由與頻道分配最佳化演算法

感知無線網路(Cognitive Radio)能對環境進行觀測，也可以利用其強大的頻道跳躍能力來調整其傳輸參數。因此，感知無線網路可提供無認證的頻道取得(Secondary Access)。如此便可以解決目前頻寬不足、頻寬使用過度集中的問題。但是，感知無線網路必須在得到頻道認證的使用者(Licensed User)出現時，馬上停止對該頻道的使用。這樣的行為會造成未認證使用者(Unlicensed User)的傳輸被中斷，增加封包遺失率，並令路由難以維持。因此，為了減低封包遺失率，讓路由能較穩定的對抗環境的變動，減少頻道交遞(Spectrum Handoff)的機率，我們希望能提供一個在同時決定路由和頻道分配最佳化時，考慮路由之穩定度的演算法。在這篇論文裡，我們考慮多重跳躍、多頻道、多使用者的環境，亦同時考慮使用者之間頻道使用上的干擾和感知無線網路的頻道異質性(Channel Heterogeneity Property)。我們假設每個連線頻道對(link-channel pair)都具有一個機率參數PPU_idle。這個機率參數代表了這條連線頻道對的穩定程度。我們利用此機率來評估每條路由的穩定度。我們同時提供了最佳化演算法和具有線性複雜度的啟發式演算法，並提供所有演算複雜度和NP-Complete的證明。最後，我們透過摸擬顯示我們的啟發式演算法的結果和最佳化的結果是相近的。

關鍵字

感知無線網路；路由穩定度；頻道分配；路由；整數線性規劃；反覆的線性規劃

並列摘要

Cognitive Radio (CR) can observe the environment and adjust its communication parameters with powerful spectrum-agile ability. Thus, CR is proposed to implement secondary access and solve the problem of spectrum-scarcity, fulfilling the growing communication requirement. However, CR needs to withdraw the spectrum quickly when primary users appear. This will interrupt the transmission of secondary users, increase packet loss rates, and make it hard to maintain existing routes. Thus, in order to decrease packet loss rates, make routes robust against fluctuation of spectrum availability, and decrease the occurrence of spectrum handoff, we attempt to find an approach to route and use spectrum which considers the effort of maintaining routes. In this thesis, we consider a multi-hop multi-user multi-channel environment with interference constraints and channel heterogeneity property of CR networks. We assume that each link-channel pair has a probability PPU_idle which represents the probability of successfully transmitting a packet using this link-channel pair without interruption from primary users and use this probability PPU_idle to estimate the effort of maintaining routes. We provide a mechanism to deploy routes and channels so that the aggregate throughput can be maximized when all the constraints and robustness requirement are satisfied. We first divide the optimal problem into two sub-problems. We design an optimal algorithm with exponential time complexity for the first sub-problem, and prove the NP-Completeness of the second sub-problem. Then, we propose two heuristic algorithms with polynomial time complexity to solve these two sub-problems. Simulation results show that solutions obtained by the heuristic algorithms are near-optimal.

並列關鍵字

cognitive radio ； route robustness ； channel allocation ； routing ； integer linear programming ； iterative linear programming

參考文獻

[1] S. Haykin, “Cognitive Radio: Brain-Empowered Wireless Communications,” IEEE J-SAC 2005.

[3] I. F. Akyildiz, W. Y. Lee, M. C. Vuran, and S. Mohanty, ”Next Generation/Dynamic Spectrum Access/Cognitive Radio Wireless Networks: A Survey,” Computer Networks journal (Elsevier), September 2006.

[4] FCC, ET Docket No 03-222 Notice of proposed rule making and order, December 2003.

[7] C. Peng, H. Zheng, and B.Y. Zhao, “Utilization and Fairness in Spectrum Assignment for Opportunistic Spectrum Access,” ACM Mobile Networks and Applications (MONET), 2006.

[8] H. Zheng and C. Peng, “Collaboration and Fairness in Opportunistic Spectrum Access,” Proc. IEEE ICC 2005.

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多跳感知無線網路中考慮路由穩定度之路由與頻道分配最佳化演算法

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