Key Microwave-Photonics Technologies for Next-Generation Cloud-Based Radio Access Networks

Several key enabling techniques are introduced for next-generation wireless communication systems. Small-cell and cloud-RAN systems have been considered as promising solutions to meet the capacity demand of the future wireless access networks. In addition, utilization of high radio frequency (e.g., millimeter-wave band) is another dimension to expand the spectrum to enhance the throughput. From the network perspective, a high capacity, low latency, and reliable backhaul/fronthaul network is important to support the advanced wireless access techniques. Therefore, microwave-photonics techniques can play an important role in the integrated optical-wireless access systems for next-generation wireless communications. In this paper, we first review several key features and enabling techniques for next-generation 5G wireless communications. Then, we introduce a multiservice small-cell wireless access architecture based on microwave-photonics technologies (cloud radio-over-fiber networks). By combining small-cell cloud-RAN concept with multiband delivery capability in an integrated optical-wireless access system, the proposed architecture can realize high-speed multiservice data transmission in a simplified and flexible way. An in-building cloud radio-over-fiber testbed was demonstrated with real-time WiMAX traffic. Two different approaches of delivering conventional services and future-proof high-data-rate millimeter-wave services in a converged platform are also analyzed and summarized.