感知網路近年來在動態頻譜感知與使用是一個熱門的研究議題。為了保護主要使用者的傳輸，次要使用者在使用主要使用者的頻寬前，必須先偵測其頻寬是否已被佔據以避免發生碰撞。偵測時間的長短隨著要求達到感測過後未被佔據的授權頻道數目不同而異，而系統傳輸量會被傳送時間和可用的傳輸頻道數目兩者影響，要求的傳輸頻道數目越多，感測的頻道數目就需要越多，傳輸時間也隨之越短。本論文研究目標在於找到一個最佳要求的感測過後未被占據的授權頻道數目使得次用使用者的系統傳輸量得到最大化。當環境為多個次要使用者時，我們提出一個分配感測過後未被佔據的授權頻道給所有次要使用者的演算法。
在本論文中，我們也研究在多頻道感知網路系統中，藉由讓不同次要使用者不同時開始傳送訊號來最大化系統的傳輸量。系統一旦感測到一個未被占據的授權頻道後就先讓一個次用使用者進入傳送階段藉此提早開始累積整個系統的傳輸量，故決定次要使用者進入傳送階段的順序是個最佳化的議題。我們也比較以往次用使用者同時開始傳輸的方法和本篇所提出允許讓不同次要使用者不同時開始傳送的方法。最後，模擬結果不僅顯示提出方法的可行性，同時指出，不同參數設定下，最佳使用者傳送順序也將有所不同。

In a cognitive radio (CR) network, the secondary users (SUs) are allowed to utilize the primary channels (PCs) when they are unoccupied. To avoid collision with the primary users, SUs must sense the PCs before transmitting their signals. Conceptually, the number of available channels sensed by the CR network depends on the length of sensing duration. The tradeoff between the length of sensing duration and the detection performance will affect the throughput of the CR network. In this work, we aim to obtain an optimal number of available PCs in order to maximize the overall system throughput of the SU’s network. In a multi-channel multi-user environment, we also propose a channel allocation algorithm to assign the available channels to inhomogeneous SUs.
In this thesis, we also study the problem of throughput maximization for a multi-channel CR network allowing SUs starting their transmissions non-simultaneously. Since the network throughput will be calculated earlier if SUs can transmit signal once a PC is sensed to be available, the transmission order of SUs is an optimization factor. We discuss and compare the simultaneous transmission scheme with the proposed non-simultaneous transmission schemes for throughput maximization in inhomogeneous multi-channel CR networks. Finally, the simulation results not only show that the proposed scheme is feasible but also indicate the transmission order of SUs will be different according to various parameters.

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