本論文著重於LTE下行傳輸實體層依據3GPP Release 12版本定義之標 準規格實現控制區域(Control region)與數據區域(Data region)之傳輸。在文中 將會針對LTE下行鏈路系統做介紹,包括其使用之正交分頻多工(Orthogonal Frequency Division Multiplexing,OFDM)技術、下行鏈路的規格以及調變原 理等。 而本篇論文以軟體定義無線電的方式,實現LTE下行鏈路的發射 機。透過搭載實務軟體定義無線電平台,可以實際即時的在特定的頻段發 設與接收空中的訊號,也可以改變發射及接收增益來觀察訊號在經過空氣 後發生的變化,以及探討訊號的品質評斷系統優劣度等等。;This paper focuses on the transmission of Control Region and Data Region in the LTE downlink physical layer according to the standard speci cations de ned by 3GPP Release 12. In this thesis, we introduce for the LTE downlink system, in- cluding the use of OFDM(Orthogonal Frequency Division Multiplexing)technology, speci cations and uplink modulation and downlink modulation principle, etc. In this thesis, we used Software-de ne-radio to achieve LTE downlink transmitter. By the Software-de ne-radio platform, we can immediatly transmit and receiver signal in the air on some particular band. Also we can change transmit and receive gain to observe the transformation of the signal in the air, discussion on the quality of the signal and system, etc.