Contents 1. Introduction
The fifth generation (5G) mobile communication has commendable goals of data capacity enhancement and latency improvement. Many studies proved that to massively deploy small cells with comprehensive coverages can largely enhance wireless transmission efficiencies. [1]–[3] This implies a 5G mobile fronthaul system should employ a point-to-multipoint (PTMP) scheme [4], where a central office (CO) or a baseband unit (BBU) must provide more data capacity and lower power losses to connect massive small cells. Fortunately, fiber communication techniques are capable to meet such requirements with large transmission bandwidth and low power loss natures. Hence, radio-over-fiber (RoF) has become an attractive technique for massive small cell deployment systems. [5]–[7] Most baseband signal processing devices are moved from conventional base stations to the CO or BBU, where remote radio access units (RAUs) complexities are largely reduced. However, the very high carrier frequencies and relative low spectral efficiencies in fiber transmissions vastly increase implementation costs and consume precious spectral resources, which have created huge challenges to make RoF a realistic technology in 5G mobile communications.
