This paper proposes a novel approach and apparatus along with its calibration method to use the digital predistortion (DPD) technique in radio-over fiber (RoF) cloud RAN (C-RAN) transmitters that encompass physically spaced central baseband unit (C-BBU) and remote radio head (RRH). The proposed approach requires a calibrated observation path (COP) connecting the RRH to the BBU to mitigate any hardware impairments and distortion using a broadband post-distortion technique. This feedback (FB) link provides on-demand tracking of the change in the downlink (DL) optoelectronic component’s behavior and sends a copy of the radio frequency (RF) output signal to the C-BBU for DPD identification and processing. The proposed technique is experimentally validated using 40 MHz, and 100 MHz LTE-A as DL data signals, while the post-compensation model is built by a 200 MHz LTE-A signal.

中文翻译：

---

使用前和后失真技术对光纤无线云-RAN发射机进行线性化

本文提出了一种新颖的方法和设备及其校准方法，以在包含物理上间隔开的中央基带单元（C-BBU）的无线光纤（RoF）云RAN（C-RAN）发射机中使用数字预失真（DPD）技术和远程无线电头（RRH）。所提出的方法需要使用RRH连接到BBU的校准观测路径（COP），以使用宽带后失真技术减轻任何硬件损伤和失真。该反馈（FB）链接按需跟踪下行（DL）光电组件行为的变化，并将射频（RF）输出信号的副本发送到C-BBU以进行DPD识别和处理。这项提议的技术已使用40 MHz和100 MHz LTE-A作为DL数据信号进行了实验验证，