Experimental Investigation of New Fronthaul Concepts for 5G

The evolution to a centralized radio access network (C-RAN), where multiple base band units (BBU) are co-located to jointly serve multiple remote radio heads (RRH), results in a more efficient use of radio resources [1]. Nevertheless, it also imposes more stringent requirements on the transport network connecting the BBU pool to the RRHs, also known as fronthaul. Especially the increasing demand for higher data rates in the fronthaul challenges current solutions based on protocols like the widespread common public radio interface (CPRI).

In this paper, we investigate two promising approaches to reduce the optical bandwidth utilization in the mobile fronthaul of next-generation cloud radio access networks. We experimentally analyze and compare the performance of an analog radio-over-fiber fronthaul and a new digital fronthaul. The analog system consists of four ?/4-shift DQPSK modulated sub-channels with a data rate of 2.5 Gbit/s each and originates from a custom millimeter-wave system. The digital fronthaul approach utilizes On-Off-Keying (OOK) and is based on 10 Gigabit Ethernet.