Abstract
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.
Highlights
U BIQUITOUS connectivity to the Internet from anywhere and anytime is indispensable for using smart devices based on mobile communication services, such as the fourthgeneration (4G) mobile-communication system. 4G mobile communication services have been started in more than 80 countries, and the fifth-generation (5G) mobile service has been launched [1]–[3]
The number of resources required in the field-programmable gate array (FPGA) for performing carrier-frequency-offset compensation in the BB Proc. could be effectively reduced. In this field trial test, we used an optical LO signal transmitted from the central control unit (CCU) for the operation of the millimeter-wave mixer in the TS-radio access unit (RAU)
We reviewed the RoFsignal-generation technique by using the intermediate frequency (IF)-over-fiber system, and the multiplication-based systems for the simple implementation and possible cost reduction technique for future systems
Summary
U BIQUITOUS connectivity to the Internet from anywhere and anytime is indispensable for using smart devices based on mobile communication services, such as the fourthgeneration (4G) mobile-communication system. 4G mobile communication services have been started in more than 80 countries, and the fifth-generation (5G) mobile service has been launched [1]–[3]. In 4Gand 5G-based mobile communication, a centralized radio access network (C-RAN) is discussed and being implemented in the microwave frequency bands [13]. Under such a bandwidth-limited condition, a digitized optical-fiber-communication system is feasible for the transceivers optimal functioning. Many components in opticalfiber-communication systems can be adapted with moderate costs, which makes the RoF-based C-RAN system a feasible solution for realizing high-capacity RCS in the millimeter-wave bands [20]–[23]. III, the systems setup and obtained results from the field trial on the Hokuriku Shinkansen railway route are shown and discussed for demonstrating the systems feasibility
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