隨者行動通訊的蓬勃發展，頻譜資源越來越稀少，各種能達到頻譜效益的無線通訊技術因應而生，當中基於傳統蜂窩通訊系統下的裝置間通訊是近年來發展的一項新興技術，藉由和傳統蜂窩用戶共用無線資源的裝置間通訊技術能有效地節省頻譜資源，且當兩終端裝置距離夠近時，不用透過基地台當作轉發的通訊技術即能派上用場，此技術不但能提升無線網路下的系統資料傳輸率，由於裝置之間能直接進行通訊，更能節省傳送端的發射功率；裝置間通訊包含多種模式選擇，其模式切換是依據當時通訊系統內的負載情形或是比較各種模式之間的資料傳輸率，與傳統模式選擇不同，本篇論文藉由考慮通道增益計算通道容量的情況下，用機率式的分析進行模式選擇，由模擬結果得知，筆者提出的模式選擇演算法相較於傳統方式更能提高系統的資料傳輸率。
關鍵字：裝置間通訊、模式選擇、通道容量

Device-to-device (D2D) communication underlaying a cellular network is a promising technology in future wireless networks to improve network capacity and reduce power consumption. Device to device communications enable mobile devices to directly communicate with each other when they are relatively close to each other. We consider the selection of direct or indirect communication path via the base station for D2D communications. Referring to this as the mode selection problem, in this paper we define mode selection rules based on channel capacity. Compare to traditional mode selection method, we add channel fading gain to calculate channel capacity and analysis mode selection with probability. Our results of the proposed method can improve the system sum-rate through mode selection rule for D2D communications.
Keywords - Device to Device Communication, Mode Selection Rules, Channel Capacity

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