Abstract
Future access networks consisting of various transmission media including optical fibers, millimeter-
wave links, etc., would provide broadband connection for many base stations in 5G or beyond 5G
mobile systems. This paper summarizes recent research trends by using a figure of merit to describe
contribution to spectral congestion mitigation. As an example of networks based on convergence of radio
and optical technologies, we focus on radio-over-fiber systems which can offer high-performance
millimeter-wave transmission. Seamless connection between optical and radio signals would play very
important roles in future access networks.
