https://scholars.lib.ntu.edu.tw/handle/123456789/122920
標題: | 無線網路中的分散式存取:賽局論與最佳化 Distributed Access in Wireless Networks: Game Theory and Optimization |
作者: | 徐福得 Hsu, Fu-Te |
關鍵字: | 賽局理論;奈許平衡;效能分析;媒介存取控制;最佳化;Game theory;Nash equilibrium;performance analysis;throughput region;power consumption;medium access control (MAC);ALOHA;CSMA;optimization | 公開日期: | 2012 | 摘要: | 在無線網路中,媒介存取控制扮演一個重要的角色。近年來有人發現大多數分散式的媒介存取控制可以找到一個合適的效用函數,然後用一個賽局來解釋其運作。在這篇博士論文中,我們利用賽局與最佳化理論來研究一些分散式存取的問題。我們比文獻中的網路模型更廣泛的考慮捕獲效應與異質性,因此得到一些新的有趣結果與性質。我們也在效能上做了賽局結果與最佳化結果的比較。利用我們這篇論文得到的結果,可以使無線網路中分散式存取的本質更被了解並且提供我們一些設計準則。 如同分散式存取機制的發展過程,我們首先分析一個像阿羅哈(ALOHA)的隨機存取機制。在這網路中的使用者可自行選擇何時要傳送他的資料以及所使用的傳輸能量,我們推導出競爭使用者的賽局結果與合作使用者的最佳結果,並且顯示在一些條件下,賽局結果等同傳統的阿羅哈存取運作,驗證了阿羅哈之類的隨機存取可以用賽局來解釋。 接著,我們考慮一個基於載波偵測多重存取的網路中使用要求傳送╱清除傳送的交換機制。我們提供這網路中能量消耗總量的一個上界。更確切的說,當使用者使用相同的資料傳送長度時,根據要求傳送封包所佔的比例,這個上界可以被流量區域上其中三個點中的一個點所達到。 最後,我們考慮一個結合媒介存取與實體層的設計,被稱做具有通道察覺的阿羅哈存取機制。在這個網路中,每個使用者知道他自己的通道資訊,然後根據通道資訊來存取去達到他的流量要求。我們採用賽局理論在兩種接收模型下去分析這個網路。第一種接收模型叫做訊號與干擾雜訊比的捕獲模型,另一種是能量的捕獲模型。我們的結果顯示在可達到的流量區域內最多有兩個奈許(Nash)平衡點,並且指出在某些情況下,會出現獲得額外的通道資訊不但不會增進效能反而使效能更差的現象,與Braess的謬論類似。這是一個很重要的發現,因為大家普遍認為獲得額外的通道資訊會提升網路的效能。根據我們所知,我們是最先理論推導發現在隨機存取網路會存在類似Braess的謬論。 Medium access control (MAC) plays an important role in wireless networks. It is discovered recently that most MAC protocols for distributed access can be interpreted as a game with appropriate utility functions. In this dissertation, we study some distributed access problems using the tools of game theory and optimization. Our network models taking into account the capture effect and heterogeneity are more general than existing works in the literature, and some new interesting results and properties are revealed. We also make some performance comparisons between the game-theoretic solution and the optimal solution. These will help us understand more about the essence of distributed access in wireless networks and give us some implications on the design principles. Same as the distributed access schemes in wireless network developed in past years, we start by analyzing ALOHA-like random access in which users independently decide when to transmit and which transmission power levels to use. The game-theoretic solution (for noncooperative users) and optimal solution (for cooperative users) are derived. We also show that under certain condition the game-theoretic solution is the conventional ALOHA (using only one power level), verifying the fact that ALOHA-like random access can be interpreted as a game. Then, a simple CSMA-based network with the request-to-send (RTS)/clear-to-send (CTS) handshake mechanism is considered. A tight upper bound of the total power consumption in the network is provided. To be specific, the upper bound can be satisfied by one of three points in the feasible throughput region depending on the RTS fraction when all users use the same length of data transmission period. Finally, we consider a variant of conventional ALOHA called channel-aware ALOHA, which is a joint medium access and physical layer design. In the network, users have the knowledge of their own channel state information (CSI) and utilize a CSI-dependent access scheme to meet their own throughput demands. A game-theoretic approach is employed to analyze this network model under two reception models. One is called the signal to interference plus noise ratio (SINR) capture model; and the other is the power capture model. We show that there are at most two Nash equilibrium points in the feasible region of throughput demands, and point out that under some situations Braess-like paradoxes may occur that the availability of CSI may degrade rather than improve the performance. To the best of our knowledge, our work is the first to show a Braess-like paradox analytically in a random access network. This discovery is important since it was generally believed that the additional availability of CSI should improve the network performance. |
URI: | http://ntur.lib.ntu.edu.tw//handle/246246/252754 |
顯示於: | 電信工程學研究所 |
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ntu-101-F96942059-1.pdf | 23.32 kB | Adobe PDF | 檢視/開啟 |
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