在一般網路中D2D 的傳輸方式具有傳輸距離較短以及能源消耗上的優勢，相對
於傳統的蜂巢網路傳輸方式，更能提升網路的效能。然而，由不同種類的溝通連
結所產生的外部干擾以及由同種溝通連結所產生的內部干擾會大幅提升分析整體
網路情形的困難度。在此篇論文中，我們提供一個基地台、使用者都以Poisson
point process 來定位的可追蹤網路模型。在傳輸方面，使用近似的Gamma 衰落，
而Gil-Pelaez Theorem 可以更進一步的幫助我們推導一般性的通道衰落。然後，
也推導出以D2D 連結和蜂巢連結為參考點的覆蓋率公式。以及提出以距離為基
準的模式選擇機制來控制選擇D2D 模式的使用者數量以達到最大的平均資料傳
輸效能。最後結果顯示，這整個模型對於分析D2D 模式選擇是很有幫助的。

The device-to-device (D2D) communication can improve network performance with respect to conventional cellular network because of the short transmission distance and power consumption. However, the inter-interference caused by the different type communication links and the intra-interference caused by the same type communication links enhance the difficulty to analysis the networks. In this paper, we propose a tractable underlaying cellular network model where base-stations (BS), user equipment (UE) and devices are modeled as the points of a Poisson point process. In transmission channel, approximate exponential and gamma fading is considered. Moreover, we can derive general fading case by using Gil-Pelaez Theorem. Then, the closed-form expression of coverage probability performance is derived for both D2D links and cellular links. Furthermore, a distance-based mode selection mechanism is proposed to control the number of UE performing D2D communications to achieve maximum average transmit coverage probability. As a result, this work serves as a powerful and efficient tool for analyzing the effects of D2D mode selection.

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