Extended measurement tests of dual polarization radio over fiber and radio over FSO fronthaul in LTE C-RAN architecture

Abstract

In this paper we present experimental results from extended measurement campaign for an analog dual polarization (DP) radio over fiber and radio over free space optics (FSO) link as part of the cloud mobile network architecture. System utilization with long-term evolution (LTE) test models is described and different link types are evaluated in terms of the error vector magnitude (EVM). Results imply that combined radio over fiber and radio over FSO schemes in combination with Erbium-doped fiber amplifier (EDFA) can provide almost the same performance for a fiber subpart length of between 10 km to 50 km. Moreover, both sub-systems can operate with a high dynamic range and meet the required EVM limit of 9% for 64-quadrature amplitude modulation (QAM) with the minimum optical signal to noise ratio (OSNR) of 24 dB for a 50 km fiber link and a LTE bandwidth 20 MHz. In addition, the combination of 10 km fiber and FSO link is tested under turbulence FSO channel condition showing EVM values below the threshold of 9 % even under a strong turbulence regime.