Fifth-generation new radio millimeter-wave radio signal transmission over a seamless fiber-terahertz mobile fronthaul system for an ultra-dense small cell network.

This Letter demonstrates the transmission of fifth-generation new radio (5G NR) millimeter-wave signals over a seamless fiber-terahertz-wave mobile fronthaul system in the 350 GHz band for an ultra-dense small cell network. The system utilizes a simple optical heterodyne method at the transmitter and direct detection at the receiver. As a proof-of-concept demonstration, we successfully transmitted 256- and 64-quadrature amplitude modulation 5G-NR-compliant signals at 24.2 and 38 GHz over a seamless fiber-terahertz system in the 350 GHz band. The proposed system can provide a simple solution to facilitate the deployment of ultra-dense small cells in high-frequency bands in 5G networks and beyond.

Full-duplex transmission of multi-Gb/s subcarrier multiplexing and 5G NR signals in 39 GHz band over fiber and space.

We propose a stable full-duplex transmission of millimeter-wave signals over a hybrid single-mode fiber (SMF) and free-space optics (FSO) link for the fifth-generation (5G) radio access networks to accelerate the Industry 4.0 transformation. For the downlink (DL), we transmit 39 GHz subcarrier multiplexing (SCM) signals using variable quadrature amplitude modulation (QAM) allocations for multi-user services. As a proof of operation, we experimentally demonstrate the transmission of 3 Gb/s SCM signals (1 Gb/s per user) over a hybrid system consisting of a 10 km SMF and 1.2 m FSO link. For the uplink (UL), satisfactory performance for the transmission of 2.4 Gb/s 5G new radio (NR) signal at 37 GHz over the hybrid system is experimentally confirmed for the first time, to the best of our knowledge. The measured error vector magnitudes for both DL and UL signals using 4/16/64-QAM formats are well below the third generation partnership project (3GPP) requirements. We also further evaluate by simulation the full-duplex transmission over the system in terms of received optical and RF powers and bit error rate performance. A wireless radio distance of approximately 200 m, which is sufficient for 5G small-cell networks, is estimated for both DL and UL direction under the heavy rain condition, based on the available data from Spain. Furthermore, simulation for the DL direction is conducted to verify the superior performance of the system using variable QAM allocation over uniform QAM allocation. Using a variable modulation allocation, up to five users (2 Gb/s per user) can be transmitted over a hybrid 10 km SMF and 150 m FSO link.

Millimeter-wave radio-over-fiber system using optical phase modulation and photonic downconversion for uplink fronthaul transmission.

This Letter proposes a high-performance radio-over-fiber (RoF) system for high-speed and high-fidelity analog waveform transmission of radio signals in the millimeter-wave band in the uplink direction. At the antenna site, the system utilizes a newly fabricated low half-wave voltage broadband phase modulator to convert a millimeter-wave radio signal into an optical signal. At the receiver, by using photonic downconversion and optical filtering technology, a simple direct detection and downconversion of the signal to the microwave band can be achieved simultaneously. As a demonstration of proof of concept, we successfully transmitted a 1024-quadrature amplitude modulation (QAM) narrowband orthogonal frequency-division multiplexing signal at 38 GHz and a 60 Gb/s 64-QAM single-carrier signal at 26.5 GHz over a 20 km RoF system. The system is promising for facilitating the deployment of ultra-dense small cells in high-frequency bands in 5G and beyond networks.