Background
China State Railway Group issued the “National Railway Planning Outline for Transportation Powerhouse in New Era” in 2020, outlining the direction for advancing railway communication technologies. The outline emphasizes tasks such as developing independent and advanced technological equipment systems, improving the technological level of infrastructure equipment, and empowering smart development through new infrastructure.
To implement China’s decisions on deploying 5G networks and other new infrastructure, the Group has set the goal of building a dedicated 5G mobile communication system for railway (5G-R). This large-scale 5G private network will support railway production and operations. As IP-based railway services grow, objectives for intelligent network operation, resource management, system maintenance, and service applications become clearer. New requirements have been raised for the next-generation railway transport network technology, including secure and reliable 5G-R communication for transportation-related production services, 5G-R slice isolation, transport of multiple existing services, and manageable railway private networks.
To enhance 5G-R construction, the primary focus of the current transport network is selecting a suitable transport solution based on 5G-R’s key requirements and the development evaluation of railway multi-service transport. In the 2022 5G-R transport solution research project led by China Railway Signal & Communication Corp Ltd (CRSC), the IMT-2020 5G transport promotion group thoroughly analyzed SPN, IPRAN, and M-OTN solutions. The current SPN, based on new international standardized technical solutions with deep integration of TDM and packet technologies, holds relative advantages and is expected to become the primary choice for 5G-R access backhaul and integrated railway transport.
SPN 1.0 has been widely adopted by operators and is evolving to 2.0 for multi-service transport. Featuring fine-granularity 10M FGU hard-isolation slicing with 10GE interfaces, E1/STM-1 CBR multi-service transports, mature coarse-granularity MTN hard-isolation slicing, high-precision inband OAM performance measurement, and manageable transport, it can transport 5G-R and traditional railway communications services from L1 to L3, while ensuring high-isolation, high-reliability, and manageable transport of existing SDH services.
Major Challenges
Operators have put 5G into large-scale commercial use. 5G-R, as the private network technology for railways, faces differentiated demands for railway production and operation. The primary challenges include:
Technology Analysis
During the 5G network design phase, the white paper “5G Transport Network Architecture and Technology Solution” released by the IMT-2020 5G transport promotion group in 2018, evaluates three 5G transport technologies (SPN, IPRAN 2.0, and M-OTN) and analyzes three transport solutions. These solutions reflect the ongoing convergence and advancement of transport and packet technologies, differing in the layer and depth of transport and packet convergence. Figure 1 outlines the development of the transport technology route.
These three transport technologies vary in their support for 5G-R transport.
Operators have also carried out performance comparison tests for three transport technologies in addition to technology analysis. The test data analysis shows that SPN leads in key performance indexes that support 5G and integrated service transport (Fig. 2).
The IMT-2020 5G Transport Promotion Group’s research report on 5G-R transport solutions shows that among the three options, SPN has superior technical satisfaction. In the recent 5G-R technical selection test, ZTE’s SPN successfully completed all test requirements.
The ITU-T has released international standards for SPN 1.0 and completed the establishment of formulation of G.fgMTN standards for SPN 2.0 FGU. Over 400,000 SPN devices are deployed in existing networks and are increasingly used in production private networks like power, subway, high-speed rail, and mining. Mature 5G-R transport industry chains are now available.
Considering the primary challenges outlined for 5G-R transport network and the current development roadmap of transport network technologies, adopting an SPN-based 5G-R solution offers the following advantages:
From the perspective of overall 5G-R construction objectives, SPN 2.0 technical standards and products align well with its transport construction requirements, offering advantages in technical capabilities. Currently, China State Railway Group is conducting a range of 5G-R verification tests, with ZTE SPN actively cooperating. ZTE has prioritized meeting the 5G-R transport requirements with SPN 2.0 in product planning and R&D, contributing to the development of smart railways.