近十年來所發展的感知無線電技巧性地使用執照頻帶上之頻譜洞以改善頻譜效益。然而, 相較於傳統蜂窩式系統之不同在於各個頻譜洞上所允許的干擾量皆不盡相同, 亦為無線電資源管理增添了一個新的思考維度。因此在感知無線電系統中, 遠近效應或許並非造成不公平的主因。也就是說, 一個靠近基地台的感知無線電終端可能因為使用了現存干擾量較高的頻譜洞而只能使用較小的傳輸功率; 相對地, 一個距離基地台較遠的感知無線電終端或許可以在現存干擾量較低的頻譜洞上採用較大的傳輸功率。在此一情況下, 遠離基地台之感知無線電終端便可能成了較有利的一方, 非一致的干擾限制便成了另一個造成不公平的變因。所以原本被設計於多使用者間分配無線電資源並解決遠近問題的比例式公平排程器在感知無線電系統中便可能扮演了新的角色。此外, 不同於傳統蜂窩式系統中之最大速度導向排程器, 遠近效應所造成之缺陷似乎不再如此嚴重。因此在感知無線電系統中, 我們結合了最大速度導向及比例式公平排程器, 提出了(PF+MR)演算法以加強頻譜使用效率並公平地分配資源給各個感知無線電使用者。
透過模擬結果, 我們發現在我們假設的環境下, 針對不同數量的線上使用者, (PF+MR) 排程器能在維持高公平性下達到相較比例式排程器提高系統的上載數據傳輸率至多達10% 。

我們相信這份論文能在感知無線電系統之排程器設計領域上開啟
新的一頁。

In this decade, cognitive radio (CR) has been proposed to improve the spectrum efficiency by skillfully utilizing the spectrum holes in the license band. However, different from the conventional cellular systems, the allowable interference constraint associated with each spectrum hole adds a new dimension in the radio resource management (RRM). Consequently, the near-far effects may not be the major reason accounted for the possible unfairness in a CR system. That is a CR terminal near the BS may only allow a fewer amount of transmission power using a spectrum hole with a higher interference level, while another far CR terminal may be able to pour transmission power in a spectrum hole with a lower interference level. In this situation, the far CR terminal may benefit and the non-uniform interference constraints become another factor causing the unfairness. As a result, the conventional proportional-fair (PF) scheduler, mainly designed to solve the near-far problem, may now play a new role in the CR systems. Moreover, the major flaw of the max-rate (MR) scheduler resulted from the near-far problem may not be that serious as in the conventional systems. Thus, to take both advantages of the PF and MR schedulers, we combine these two schedulers (PF+MR) to boost the spectrum efficiency and achieve a fair play in the CR systems. Via simulation results, we find that the combining (PF+MR) scheduler can not only attain a 10% improvement at most in terms of uplink capacity but also maintain almost the same fairness performance as the pure PF scheduler. We believe that this thesis opens a new research area of designing the schedulers for the CR systems.

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