Experimental Demonstration of Elastic RF-Optical Networking (ERON) for 5G mm-wave Systems

This paper experimentally demonstrates an elastic RF-Optical C-RAN based on mm-wave MIMO systems. An RF-Optical SBVT in the CO generates 1-GBd signals which are elastically assigned (in time and frequency) by the C-RAN controller to multiple remote antenna units. Introduction The exponential growths in the Internet traffic have continued impressively from one TB/month in 1990 to ten million TB/month in 2014 and is projected to exceed one hundred million TB/month by the year 2020 [1, 2]. The Internet applications have evolved from fixed desktop environments to cloud environments that emphasize ubiquity, mobility, and bandwidth. Future Internet applications are expected to demand even more ubiquity, mobility, and bandwidth through diverse platforms. Today’s wireless networks are typically limited to 1~100 Mb/s connectivity. While fiber optic networks provide 1~100 Tb/s capacity on each singlemode-fiber over thousands of kilometer distances, they are limited to wide area and metro networks, not readily accessible by mobile users. On the other hand, the new elastic optical networking (EON) [3] with coherent optical communications and sliceable bandwidth variable transponders (SBVT) [4] is emerging as a viable platform also for future metro and access networks. EON could then pave the way for nextgeneration 5G systems with a seamless interface between EON and mmWave MIMO technologies. This paper proposes a new elastic RF-photonic communication and networking (ERON) (Fig. 1) architecture that harnesses symbiotic relationships of RF and photonics to bring mobility and high capacity to networks. ERON makes use of three main technologies: (a) RFoptical sliceable bandwidth variable transponders (RFO-SBVT) located at the central offices (COs) generating radio-over-fiber (RoF) signals with variable baud-rate and modulation formats for elastic utilization of wireless and optical networking resources in space-time-frequency domains; (b) mm-wave remote antenna units (RAUs) with optical beam forming capabilities; and (c) spatial division multiplexing multi-inputmulti-output (SDM-MIMO). This architecture assumes to use a functional split eight approach [5] where all the processing is performed at the CO. Under this assumption, the centralized processing and RFO-SBVTs at the CO, together with RAUs with RF-optical processing units (RFOPUs [6]), can implement a photonic hybrid precoding architecture for mm-wave SDM-MIMO systems [7]. Fig. 1 shows how the RFO-SBVT generates WDM RoF signals (each RoF signal is composed of a baseband optical signal plus an Central Office 1 Central Office 2 C-RAN controller RF O -S BV T SDN controller