基於軟體定義無線電平台之長期演進技術收發機設計與實作

Abstract

近年來Cloud Radio Access Network (Cloud-RAN)被視為基地台架構的演進，有別於上一代的行動通訊網路，其只需將天線及射頻模組建置於服務範圍內，並將大部分的基頻運算以軟體方式集中於基地台的計算平台進行基頻處理、協作運算等，以提高頻譜效益及降低營運成本。在本論文中，以C-RAN為概念，根據3GPP LTE標準，實現以軟體定義無線電(Software Defined Radio)為基礎的基地台以及使用者端系統。 在本論文中，以NI-USRP 2932為射頻模組經過空氣傳送及接收訊號，並在Ubuntu作業系統中以Ettus Research的API及OpenLTE部分功能共同開發軟體收發機，達成了下行及上行雙向通訊的功能，最後再利用多核電腦(multi-cores computer)其可平行執行多執行緒程式的能力和改良收發機的架構以對抗延遲的影響，實現實時的系統。 為驗證系統，結合上述射頻模組及軟體功能，實際展示傳收功能：在下行中，展示了real-time 1.92 MHz、over-the-air的檔案傳輸；在上下行中，亦成功地展示了real-time、over-the-air的雙向通訊，實現了檔案傳輸的功能。藉由展示，證實了軟體定義無線電在LTE收發機的可行性。

Cloud-RAN is viewed as an architecture evolution based on a new base station architecture recently. Unlike conventional communication networks, it just needs to deploy antennas and RF modules in the serving area, and most baseband signal processing is centralized in baseband units using software to increase spectral efficiency and reduce operating costs. In this thesis, based on the concept of C-RAN, we realize the system of basestation and user equipment in physical layer on a software defined radio platform according to LTE standard. We use the NI-USRP 2932 as the transmitter to tansmit RF signal and the receiver to receive RF signal. Also, we utilize the API of Ettus Research and the functions of OpenLTE to develop the software transceiver in the Ubuntu enviromnet. Finally, we use the multi-cores computer that can run multi-threads program parallelly and propose the improved architecute to resist latency to achieve uplink or downlink communication and let real-time be feasible. To verify the system, combining the RF modules and software we developed, we do some demonstrations: In the downlink transmission, we can over-the-air transmit files with 1.92 MHz sample rate. Also, we can transmit files with uplink and downlink both ways. We proved that software defined radio in LTE is workable by demonstration.