Bandwidth-Efficient Synchronous Transmission of I/Q Waveforms and Control Words via Frequency-Division Multiplexing for Mobile Fronthaul

We propose a novel mobile fronthaul transmission scheme to achieve bandwidth-efficient transmission of both the I/Q waveforms of wireless signals and the control words (CWs) between baseband units (BBUs) and remote radio units (RRUs). Unlike the common public radio interface (CPRI) where the I/Q waveforms and the control words are transmitted as a binary sequence in the time domain, the proposed transmission scheme aggregates multiple wireless signals in the frequency domain and transmits them synchronously with a single-carrier quadrature-amplitude-modulation (QAM) signal that contains the CWs on a single wavelength channel via frequency-division multiplexing. This approach substantially increases the bandwidth efficiency of the mobile fronthaul. Furthermore, we experimentally demonstrate this scheme by transmitting 32 20-MHz LTE signals together with CPRI-compliant CWs, corresponding to a CPRI-equivalent data rate of 39.32 Gb/s, in single optical channel that requires a RF bandwidth of only ~1.6 GHz. After transmission over 5-km standard single-mode fiber (SSMF), the CWs are recovered without error, while the LTE signals are recovered with an error-vector magnitude (EVM) of as low as 3%. This bandwidth-efficient mobile fronthaul technique may find applications in future integrated fiber/wireless access networks to provide ultra-broadband access services.