隨著無線通訊技術的發展，LTE(Long Term Evolution)在第四代行動通 訊扮演了十分重要的角色。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 與接收機。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 頻段發射與接收在空中的訊號，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。;With the development of wireless communication technology,LTE(Long Term Evolution) plays an important role in the fourth generation of mobile communication technology.In this thesis,we introduce for the LTE downlink system,including the use of OFDM(Orthogonal Frequency Division Multiplexing) technology,speci cations and downlink modulation principle,etc. In this thesis,we used Software-de ne-radio to achieve LTE downlink transmitter and receiver.By the Software-de ne-radio platform,we can immediatly transmit and receive 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.
