Open radio access network (ORAN) provides an open architecture to implement radio access network (RAN) of the fifth generation (5G) and beyond mobile communications. As a key technology for the evolution to the sixth generation (6G) systems, cell-free massive multiple-input multiple-output (CF-mMIMO) can effectively improve the spectrum efficiency, peak rate and reliability of wireless communication systems. Starting from scalable implementation of CF-mMIMO, we study a cell-free RAN (CF-RAN) under the ORAN architecture. Through theoretical analysis and numerical simulation, we investigate the uplink and downlink spectral efficiencies of CF-mMIMO with the new architecture. We then discuss the implementation issues of CF-RAN under ORAN architecture, including time-frequency synchronization and over-the-air reciprocity calibration, low layer splitting, deployment of ORAN radio units (O-RU), artificial intelligent based user associations. Finally, we present some representative experimental results for the uplink distributed reception and downlink coherent joint transmission of CF-RAN with commercial off-the-shelf O-RUs.
@article{arxiv.2301.12804,
title = {From ORAN to Cell-Free RAN: Architecture, Performance Analysis, Testbeds and Trials},
author = {Yang Cao and Ziyang Zhang and Xinjiang Xia and Pengzhe Xin and Dongjie Liu and Kang Zheng and Mengting Lou and Jing Jin and Qixing Wang and Dongming Wang and Yongming Huang and Xiaohu You and Jiangzhou Wang},
journal= {arXiv preprint arXiv:2301.12804},
year = {2023}
}