Coexistence and transmission of multiple radios over seamless fiber-wireless systems

In this paper, we present efficient solutions for simultaneous transmission of multiple radio signals over seamless fiber wireless systems, including radio signals in legacy microwave bands and in high frequency bands. At central stations, radio signals can be mapped onto the same optical transport channel using data mapping algorithms and/or subcarrier multiplexing technique. After the fiber transmission, the received signals can be down-converted, digitized, and de-mapped to recover the originally transmitted signals. We present and compare two different methods, including a radio-over-fiber system and optical up-conversion at remote sites and an intermediate-frequency-over-fiber system and an electrical up-conversion at remote sites. We experimentally confirm the suitability of both the transmission methods, and achieve satisfactory performance for all signals, including LTE-advanced, orthogonal frequency-division multiplexing, and filtered-orthogonal frequency-division multiplexing signals. In particular, the latter method can provide a high optical spectral efficiency and low fiber dispersion effect and is suitable for ultra-dense small cell deployment in future mobile networks.