以聯盟賽局理論之合作式感知無線網路功率控制及時間分配

Abstract

在本篇論文，我們以賽局理論的角度來研究合作式感知無線網路功率控制及時間分配。我們考慮一個由多主要服務者(primary service)和多次要服務者(secondary service)所構成的感知無線網路。在此無線網路架構下，主要服務者和次要服務者採取合作式通訊，主要服務者是此賽局的頻譜擁有者，透過主動租借頻帶給次要服務者使用，藉以獲取通訊品質提升；次要服務者藉由協助主要服務者傳輸，換取租借頻帶的時間，得到頻帶使用權。我們以聯盟賽局理論的模型來分析每個玩家之間合作的行為，並轉化為系統的最佳化問題，在符合條件下求得核心解(core)。主要考慮兩種情況，首先是只考慮功率控制，其次是同時考慮功率控制跟時間分配，並分別在兩種情況下對玩家的合作行為做分析。此外，我們在第二種情況下提出演算法，保證可以求得最佳解，而此最佳解符合聯盟賽局中核心解定義，所有玩家會合作形成大聯盟。在模擬中，也比較我們的作法和前人的作法，並在玩家的利益上探討賽局的收斂行為。另外，也分析系統架構下，我們提出的演算法會收斂到核心解，而在此平衡點，對所有玩家都是有利的，所以保證整體系統配置穩定。

In this thesis, we study the problem of power control and time allocation in cooperative cognitive radio networks (CCRNs) from a game theoretic approach. Particularly, we consider a CCRN with multiple primary users (PUs) and multiple secondary users (SUs), where all players exploit cooperative communication. In the game, the spectrum is licensed for PUs, through leasing the spectrum to SUs for a fraction of time in exchange for improving transmission rates. On the other hand, SUs have opportunities to access the spectrum due to assist primary transmission. We apply the coalitional game to model the cooperative interactions among players and we formulate the problem as an optimization problem and achieve the core under certain conditions. We mainly focus on two cases, which the first case only considers power control and the other one considers power control and time allocation problems. We analyze players’ cooperative interactions in the two cases and we propose a novel algorithm to solve the second case. The proposed algorithm is guaranteed convexity and achieves the equilibrium in the core. According to the definition of the core, all the players in the system will form grand coalition. In the simulations, we compare the proposed approach with other approaches and numerically study the players’ payoffs in the coalitional game. Furthermore, we also show that proposed algorithm converges to the core, which guarantees that the payoff allocation is stable in the system.