FRMCS Simplified Site Solution: Advancing Smart and Green Railway Development

The approval of China’s 5G railway test frequency has attracted global attention. 5G will be deeply integrated into the railway industry across various applications. Its high bandwidth, low latency and Internet of everything features can fully meet  diverse requirements of railway scenarios and support digital and intelligent high-quality development of the railway industry. However, the high-frequency band and dense networking features of 5G pose great challenges to network coverage capability and engineering construction, often resulting in difficulties related to power supply, engineering, and land acquisition. Therefore, ZTE is actively exploring and launching the future railway mobile communication system (FRMCS) simplified site solution, designed to simplify infrastructure, engineering and site form for the rapid, reliable, and low-carbon deployment of FRMCS.

Simplified Infrastructure: Highly Integrated Design for Flexible Applications

For remote GSM-R sites, the power supply of site equipment typically involves an uninterruptible power supply (UPS) and an AC/DC conversion module. The power goes through AC-DC rectification, DC-AC inversion and AC-DC rectification processes, resulting in a power supply efficiency of no more than 80% for RRUs. In addition, the mainstream UPS has strict environmental requirements, with an operating temperature range of only 0°C to +40°C. Therefore, it cannot be directly used in unprotected outdoor environments and must be used with a protective cabinet and environmental control devices. Standby batteries are effective only when the mains power is interrupted, so in most cases, the entire site may experience a power outage or disconnection if the UPS fails.

For FRMCS, ZTE has launched a new integrated power supply solution that combines UPS functions with power rectification. It provides 220V AC and-48V DC outputs: the-48V DC output powers the FRMCS RRUs with up to 97% power supply efficiency, while the AC output powers low-power AC devices such as cameras. It has the following highlights:

• Wide applications: With an IP65 protection class and an operating temperature range of -40°C to +55°C, it supports a wide range of environments, including equipment rooms, tunnels and other indoor settings, as well as outdoor environments.  
• High reliability: In the event of a mains supply failure or power supply issue, it automatically switches to standby batteries to ensure continued operation of RRUs and other devices.  
• Flexible installation: It can be installed in a cabinet, on a wall, or on a pole.

Simplified Engineering: Reducing Construction Challenges for Improved Efficiency

In the GSM-R system, 2T2R RRUs are usually used and installed on the floor with only four feeder cables per tower, which makes the engineering simple. For the FRMCS system, 8T8R RRUs will be used, and if the RRUs are still installed on the floor, there will be at least 18 feeder cables per tower at each site. A large number of feeder cables and many connectors will lead to high loss, complicated engineering, and a high fault rate.

To avoid these problems, installing FRMCS RRUs on the tower is a good solution. When the FRMCS RRUs are installed on the tower, the number of cables is reduced from 18 to 4, feeder loss is decreased, and the edge rate is increased. Combined with technical measures such as power line carriers, built-in lightning protectors, and armored cables, the approach reduces the complexity of network architecture, lowers engineering construction difficulties, and mitigates installation risks, making the deployment simple. According to test data, when FRMCS RRUs are installed on a tower, feeder loss can be reduced by over 3 dB, the downlink rate at the cell edge increases by about 27%, the uplink rate at the cell edge for a 200 mW signal increases by about 100%, and the uplink rate at the cell edge for a 2W signal increases by about 80%.

ZTE FRMCS RRUs incorporates power line carrier (PLC) technology to combine the RS485 signal and DC power lines into a single cable solution. With this single power cable, the RS485 signal is also transmitted, eliminating the need for a separate RS485 signal cable. Additionally, ZTE FRMCS RRUs use a multi-core optical fiber cable, which allows 18 feeder cables to be replaced by just two optical fiber cables. Compared with the floor-mounted installation solution, the tower-mounted installation solution reduces the number of cables by 80% and the weight of the cables by 90%.

Drawing on long-term operational experience with public-network RRUs, the ports of FRMCS RRUs—including the power supply and RF ports—come with built-in lightning arresters, eliminating the need for on-site lightning arresters. This design reduces installation time and ensures better lightning protection for the equipment. To better protect cables from damage by animals and further simplify engineering installation, armored cables are used, which exempts the need for flexible metal conduit protection and associated engineering. Two-ring fixing clamps are used to secure cables on the tower, simplifying the installation process. Waterproof RF jumpers are used, eliminating the need for on-site waterproof measures for the jumpers. These features can save approximately 120 minutes in engineering operations.

Simplified Site Form: Saving Space for Improved Energy Efficiency

The power supply, distribution, UPS, air conditioner, and other devices are placed separately in the railway equipment room, occupying more space and increasing deployment difficulty. Therefore, to save site space, reduce energy consumption and cut construction costs, ZTE has been committed to building simplified sites. For outdoor scenarios, ZTE has launched the all-on-pole site solution. This solution features a fan-free design, with the outdoor power supply and battery installed on the tower together with the RRUs, eliminating the need for cabinets and environmental control devices. This approach results in a ’zero-footprint’ design, zero cooling energy consumption, and offers a simple, easy-to-install solution that is energy-efficient and reduces carbon emissions.

For indoor scenarios, ZTE has launched an integrated indoor cabinet solution. The power supply, distribution, UPS, battery, and other devices can all be placed in a cabinet with dimensions of 600 mm (width) × 600 mm (depth) × 2200 mm (height). The solution makes full use of cabinet space, reducing the space requirement for the equipment room and increasing the effective space by more than 50%.

As the new benchmark for next-generation railway systems, FRMCS will lead the global railway industry towards high-quality digital and intelligent development. ZTE will continue to explore and seek breakthroughs in FRMCS site construction by introducing intensive, modular, intelligent, and low-carbon technologies to ensure that the railway operates reliably, safely, efficiently, and sustainably. ZTE is committed to continuously contributing to the creation of a modern, smart, and green railway infrastructure.