A linear-cell-based radio-over-fiber (LC-RoF) system is proposed and demonstrated for efficient mobile communication in high-speed trains without hard handover processes. The configuration of the LC-RoF network and possible router architectures are discussed for the field trial test of the proposed system and for advanced systems in the future. Via the LC-RoF network, 90-GHz, millimeter-wave radio access between the ground and a train car is operated in a centralized manner. The resulting throughput of 1.5 Gbit/s is achieved in the field trial test, which is comprised of 250-Mbaud four-subcarrier differential quadrature phase-shift keying with a forward-error correction code implemented in field-programmable gate arrays to the Shinkansen train traveling at 240 km/h without any interruptions in the connections at the change of radio access units.

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High-Speed Railway Communication System Using Linear-Cell-Based Radio-Over-Fiber Network and Its Field Trial in 90-GHz Bands

We demonstrate the first W-band optoelectronic oscillator (OEO), that oscillates at 94.5 GHz with a measured single side band (SSB) phase noise of −101 dBc/Hz at an offset frequency of 10 kHz from the carrier. Side mode suppression of more than 65 dB has been achieved by using injection locking. This OEO has potential application as a signal source in emerging W-band applications (e.g. fiber-wireless links) and opens a path to low phase noise sources beyond 100 GHz.

W-Band Optoelectronic Oscillator

We demonstrate experimentally a bandwidth-reconfigurable mmWave Fiber Wireless (FiWi) fronthaul bus topology for spectrally efficient and flexibly reconfigurable 5G Centralized-Radio Access Networks (C-RAN). The proposed fronthaul architecture includes four 1 Gb/s Intermediate Frequency over Fiber (IFoF) channels that can be flexibly allocated among two in-series Reconfigurable Optical Add/Drop Multiplexer (ROADM) integrated nodes, supporting in total 8 V-band 32-element Phased Array Antenna (PAA) terminals. The ROADM was fabricated as an integrated photonic device exploiting the ultra-low loss Si3N4 TriPleX waveguide integration platform and an architectural layout based on cascaded MZI interleavers. The device has flat top response of 32.5 GHz with a Free Spectral Range (FSR) of 100 GHz and fiber-to-fiber losses of 5 dB, while the V-band PAA supports analog RF beamsteering capabilities within a 90°-sector and 1m wireless distance. Each of the FiWi links carries a 250 MBd QAM16 waveform enabling a total of 1 Gb/s rate per end user beam, complying with the 5G Key Performance Indicator (KPI) user-rate requirement. Bandwidth-reconfigurability is experimentally demonstrated by selectively dropping channels either at the first or at the second ROADM node, allowing in this way the bandwidth allocation to be flexibly defined between two different network segments. Both uplink and downlink performance are experimentally validated for different ratios of bandwidth allocation among the two nodes, revealing Error Vector Magnitude (EVM) values that meet the respective 3GPP signal quality specifications. The two-stage FiWi IFoF/mmWave fronthaul bus topology, based on a miniaturized, integrated, low loss Si3N4 ROADM and supporting high-capacity wireless beamsteering capability can form a promising roadmap towards flexible and reconfigurable 5G C-RAN architectures.

Reconfigurable Fiber Wireless IFoF Fronthaul With 60 GHz Phased Array Antenna and Silicon Photonic ROADM for 5G mmWave C-RANs

We experimentally demonstrate a multi-user Fiber Wireless IFoF/mmWave uplink comprising a 32-element 60 GHz Phased Array Antenna (PAA) and 10 km of fiber for 5G fronthaul networks, supporting beamsteering within a 120° sector and 0.6 Gb/s uplink capacity within a 5 dB bandwidth of 2 GHz. The flexibility of the link is highlighted in two 3-user scenarios with 0.6 Gb/s uplink traffic: A Frequency Division Multiplexing (FDM) scheme with the PAA receiving isotropically at different frequencies and a Spatial Division Multiplexing (SDM) scheme where the same V-band frequency is re-used by all three users but are selectively received by the PAA using beamsteering. Error-free transmission with 100 Mbaud QPSK per user is demonstrated for both cases, forming the first comparison of FDM and SDM towards multi-user 5G mmWave/IFoF networks.

Multi-User V-Band Uplink Using a Massive MIMO Antenna and a Fiber-Wireless IFoF Fronthaul for 5G mmWave Small-Cells

Towards relieving the bandwidth limitations in 5G mobile fronthaul networks, a Fiber Wireless (FiWi) small cell architecture is presented, relying on spectrally efficient analog transport on intermediate frequency over fiber (IFoF) and a millimeter wave (mmWave) phased array antenna (PAA) interfaced with a low-loss optical add/drop multiplexer (OADM) on Si3N4/SiO2 TriPleX platform with 5 dB fiber-to-fiber losses. Specifically, four 1 Gb/s FiWi links, each carrying a 250 MBd 16-QAM signal on 5.8 GHz IFoF, are wavelength division multiplexed (WDM) and transported across a 10 km Single Mode Fiber (SMF), before being demultiplexed into the constituent channels in the OADM device and subsequently wirelessly transmitted by the PAA over a 1 m-long V-band link with 90° degree beamsteering capability. Featuring 4x 1Gb/s user rate with beamsteering to meet the respective 5G key performance indicator (KPI) for the peak user rate and an EVM within the acceptable 3GPP limit of 12.5%, the current work forms the first centralized FiWi point-to-multipoint small cell architecture with efficient transport scheme on IFoF and ubiquitous 360°-degree coverage for emerging 5G mmWave networks.

A 5G Fiber Wireless 4Gb/s WDM Fronthaul for Flexible 360° Coverage in V-Band massive MIMO Small Cells

We demonstrate 97-GHz millimeter-wave radio access system connected to bidirectional radio over fiber network for high-speed train systems. Obtained throughput from a central office to a 240-km/h train car is achieved 1.5 Gbps.

Field Trial of 1.5-Gbps 97-GHz Train Communication System Based on Linear Cell Radio Over Fiber Network for 240-km/h High-Speed Train

In recent years, research and development on the condition monitoring systems using the wireless sensor network in the railway have been proceeded. However, there are few cases of the wireless sensor network design based on the features of the railway environment. In this paper, we propose the procedure to design the wireless sensor network in the railway. And we introduce the demonstration test and the result in the railway slope based on this procedure.

Design of Wireless Sensor Network in the Railway.

In recent years, research and development on the condition monitoring systems using the wireless sensor network in the railway have been proceeded. The railway has a characteristic such as extending linearly, many metal objects becoming obstacles to radio wave propagation. However, there are few cases of the wireless sensor network design based on the features of the railway environment. In this study, we propose the procedure to design the wireless sensor network in the railway. And we introduce the demonstration test and the result in the railway slope based on this procedure.

Nariya Iwaki

Papers

High-Speed Railway Communication System Using Linear-Cell-Based Radio-Over-Fiber Network and Its Field Trial in 90-GHz Bands

Field Trial of 1.5-Gbps 97-GHz Train Communication System Based on Linear Cell Radio Over Fiber Network for 240-km/h High-Speed Train

Design of Wireless Sensor Network in the Railway.

Design of Wireless Sensor Network in the Railway Facilities

Detection of Position of Trackside Workers Using 90 GHz Band Millimeter-wave Radar