DSP-free remote antenna unit in a coherent radio over fiber mobile fronthaul for 5G mm-wave mobile communication.

Abstract

We propose a novel coherent analog radio over fiber (A-RoF) scheme to realize the generation, separation, and detection of four-independent mm-wave signals with the same carrier frequency on a single-wavelength for 5th generation (5G) mobile communication, and no digital signal processing (DSP) algorithms are required in remote antenna unit (RAU). In baseband unit (BBU), four-independent mm-wave signals are modulated on the two orthogonal polarization states of a single wavelength based on a dual-polarization IQ modulator using the dual single-sideband (SSB) modulation and polarization division multiplexing (PDM) technique. In RAU, a novel carrier polarization rotation module based on the self-polarization stabilization technique is proposed, and thus the four-independent mm-wave signals can be detected by self-coherent detection. Besides, the power fading effect induced by the chromatic dispersion could be overcome thanks to the optical SSB modulation, contributing to the increased coverage. By these means, no DSP algorithms are required in RAU, and the latency of signal processing could be significantly reduced. The experimental results show our proposed scheme could support 38.4 Gbps 16-ary quadrature amplitude modulation (16QAM) signals at 14 GHz over 30 km standard single-mode fiber (SSMF) transmission without DSP, satisfying 3rd Generation Partnership Project (3GPP) requirements. Besides, the measured error vector magnitude (EVM) value of 800 MBaud 16QAM signals at 28 GHz over 50 km SSMF transmission is 12.99%. This research provides a potential solution for the 5G mobile fronthaul.