Application Methods of Industrial Ethernet Switches in the Metro Industry

1. Key Requirements for Industrial Network Communication in Metro Systems

Metro communication networks are characterized by the following demands:

• Multi-service Integration: The ISCS integrates a wide range of subsystems, including train control, CCTV, public address (PA), passenger information systems (PIS), security, and building automation (BAS).
• High Reliability: Any interruption in the communication network could affect passenger safety and scheduling efficiency, requiring a system availability rate above 99.999%.
• Harsh Operating Environments: Devices must withstand high temperatures, dust, electromagnetic interference (EMI), and constant vibration.
• Strong Real-time Performance: Alarm signals and control commands must be transmitted within milliseconds to ensure quick response to incidents.

These requirements impose strict criteria on network devices in terms of reliability, redundancy design, rapid failover capabilities, and centralized management.

2. Typical Network Architecture in Metro ISCS Systems

A metro ISCS communication network typically adopts a three-layered architecture:

• Core Layer: This layer connects the central control center with stations, depots, and maintenance facilities. It deploys high-reliability Layer 3 Ethernet switches that support dynamic routing protocols like OSPF and redundancy protocols like VRRP, ensuring seamless route switching and stable network performance.
• Aggregation (Local) Layer: Located at the station level, this layer links various subsystems such as power, ventilation, access control, and broadcasting. It uses Layer 2 or Layer 3 managed industrial switches to isolate data between subsystems while maintaining efficient communication.
• Access (Field) Layer: This layer connects front-end devices such as platform screen doors, surveillance cameras, fans, and signaling equipment. It often uses unmanaged or light-managed industrial switches to ensure flexible and real-time access at the field level.

3. Robust Network Solutions for Metro Systems

Metro operations rely on industrial Ethernet switches that maintain top performance under demanding conditions. To ensure reliability, it’s essential to select switches specifically designed for the needs of the Integrated Supervision and Control System (ISCS). This typically involves a system topology that guarantees:

3.1 Product Configuration

To ensure optimal performance and reliability, the metro industry often implements a strategic combination of industrial Ethernet switches, including:

• Layer 3 Managed Industrial Ethernet Switches: These provide the advanced routing and network management necessary for complex metro networks, ensuring high reliability and performance in critical applications.
• Layer 2 Managed Industrial Ethernet Switches: These offer essential features like VLAN and ring network protocols, designed for the rugged environments commonly found in industrial settings, including the metro industry.
• Unmanaged Industrial Ethernet Switches: These offer a cost-effective and reliable solution for simpler network needs, such as connecting edge devices within a larger metro network infrastructure.

This approach ensures superior redundancy, high bandwidth, and low latency, which are crucial for maintaining seamless communication and real-time data transmission within metro systems.

3.2 Technology Behind the Solution

The advanced technology behind switches includes:

• OSPF-Based Dynamic Routing: Dynamic routing protocols automatically adjust routes to optimize network performance.
• Redundancy: The network design includes redundant pathways that provide automatic failover in case of link failure.
• Easy Maintenance: The switches are designed with user-friendly interfaces for straightforward configuration and ongoing maintenance.

4. Overcoming Industry Challenges

Metro networks often face a range of challenges, particularly in high-traffic environments. Some of the key challenges faced by Metro Industry included in the following sheet:

And here comes the further clarifications about the paint points, the technical Solutions:

• Electromagnetic Interference Causing Packet Loss

1) Pain Point:

In industrial environments, particularly in metro systems, high levels of electromagnetic interference (EMI) from power supplies, signaling equipment, and electrical systems can lead to packet loss, degrading network communication reliability.

2) Technical Solution:

• Three-layer industrial-grade switches equipped with strong electromagnetic shielding and grounding protection to minimize EMI effects.
• Advanced error detection and correction mechanisms to ensure data integrity in high-interference environments.
• Use of fiber optic communication where necessary to eliminate interference risks from electromagnetic sources.

• Bandwidth Contention Across Multiple Systems

1) Pain Point:

Multiple subsystems, including signaling, surveillance, passenger information systems (PIS), and SCADA, share the same network infrastructure. Bandwidth contention can cause delays in transmitting critical control and monitoring data.

2) Technical Solution:

• Multi-VLANs across three-layer routing, segmenting network traffic based on priority to prevent bandwidth congestion.
• Quality of Service (QoS) implementation, ensuring that mission-critical applications receive higher bandwidth allocation.
• Traffic shaping and rate limiting to prevent any single subsystem from monopolizing network resources.

•  Device Vibration Causing Connection Dropouts

1) Pain Point:

Metro environments involve constant mechanical vibrations from moving trains, station infrastructure, and maintenance activities. These vibrations can loosen network connections and cause intermittent failures.

2) Technical Solution:

• Anti-vibration hardware design, including reinforced connectors and industrial-grade mounting brackets, to secure networking equipment.
• Fast network ring switching (ERPS - Ethernet Ring Protection Switching) for rapid recovery from link failures, ensuring continuous network operation.
• Redundant power supply and failover mechanisms to minimize downtime due to unexpected connection drops.

By implementing these advanced networking solutions, the metro system could achieve unparalleled reliability, improved operational efficiency, and enhanced passenger safety.

5. Technical Principles: Integrating Redundancy and Smart Design

• Layer 2 Ring Network for Physical Resilience

1) The Layer 2 network adopts an ERPS (Ethernet Ring Protection Switching) dual-ring architecture, achieving 50ms-level link fault recovery, which is 1,000 times more efficient than the traditional STP (Spanning Tree Protocol) with a convergence time of 6-50 seconds.

2) Dual-ring hot backup architecture: The primary ring transmits real-time monitoring data, while the secondary ring carries device management signals.

• Layer 3 Forwarding for Enhanced Network Reliability

1. Layer 3 hot backup architecture: Utilizes OSPF (Open Shortest Path First) + VRRP (Virtual Router Redundancy Protocol) for dual-layer protection, ensuring real-time monitoring data transmission and device management signal support. Metro project tests have recorded zero service interruptions throughout the year.
2. Network reliability: Implements BFD (Bidirectional Forwarding Detection) linked with OSPF, reducing Layer 3 failover time from seconds to milliseconds.

6. Operation and Maintenance Considerations

After deployment, regular maintenance of network devices is essential. The following features are beneficial for metro systems:

• Remote Configuration and Monitoring: Support for SNMP, Web GUI, and CLI interfaces enables remote configuration and monitoring.
• Real-time Monitoring: Real-time monitoring of port status, bandwidth usage, and fault alerts supports early detection and troubleshooting.
• Efficient Maintenance: Batch firmware upgrades and configuration backups reduce maintenance time.

Industrial Ethernet switches have a typical life cycle exceeding 10 years. Their protection features—against dust, moisture, static electricity, and lightning—significantly reduce replacement frequency and improve return on investment.

7. Emerging Trends and Future Outlook

With the rapid development and smart evolution of urban rail transit, metro systems are demanding increasingly reliable, real-time, and flexible network infrastructures. Industrial Ethernet switches, with their outstanding anti-interference capability, high reliability, and intelligent management features, have become vital components in maintaining the efficient operation of ISCS systems.

7.1 Integration of AI and Edge Computing

The integration of Artificial Intelligence (AI) and edge computing into industrial Ethernet switches is becoming increasingly prevalent. AI algorithms can analyze network traffic patterns to predict and prevent potential failures, while edge computing enables data processing closer to the source, reducing latency and bandwidth usage.

7.2 Enhanced Cybersecurity Measures

As metro systems become more connected, the risk of cyber threats increases. Industrial Ethernet switches are now incorporating advanced cybersecurity features such as intrusion detection systems (IDS), firewalls, and secure boot mechanisms to protect critical infrastructure from malicious attacks.

7.3 Adoption of Time-Sensitive Networking (TSN)

Time-Sensitive Networking (TSN) is an emerging technology that provides deterministic Ethernet communication, ensuring timely and reliable data delivery. The adoption of TSN in metro networks can enhance the performance of time-critical applications such as train control and signaling systems

7.4 Support for High-Bandwidth Applications

The increasing use of high-definition video surveillance and real-time data analytics requires industrial Ethernet switches to support higher bandwidths. The deployment of switches with 10G or even 40G capabilities ensures that metro networks can handle the growing data demands efficiently.

8. Conclusion

Industrial Ethernet switches play a pivotal role in the reliable and efficient operation of metro systems. Their ability to withstand harsh environments, provide real-time communication, and support advanced features such as AI, cybersecurity, and TSN makes them indispensable in modern urban rail transit. As metro networks continue to evolve, the adoption of advanced industrial Ethernet switches will be crucial in achieving digital transformation and ensuring passenger safety and satisfaction.