The technological level of daily operations such as rail transit operation, security, and maintenance has been greatly improved compared with the past, but the degree of automation and intelligence still needs to be enhanced, and many tasks are still mainly manual. Traditional manual methods have problems such as tardiness and low efficiency, making it difficult to meet the actual needs of rail transit for ensuring driving safety and improving work efficiency. Taking safety patrol inspection as an example, relying solely on manual patrols makes it hard to detect problems in a timely manner, especially sudden issues such as road accidents and man-made damage. Only the comprehensive construction of real-time monitoring can play a role in preventing disasters, reducing losses and conducting rescue operations before incidents occur. The services provided to passengers during their rail transit trips also need further exploration. Systems and value-added services such as monitoring, broadcasting, and WiFi need to be gradually added and deployed to optimize the operational experience and improve the economic benefits of rail transit.

II. Wireless Private Network Solution for Rail Transit (Subway)

• Wireless Wide Area Network (WWAN): 4G LTE (and 5G in the future) is mainly a “public network” and WAN technology, suitable for enabling internet access for 4G smart terminals such as mobile phones and temporary emergency access to the Internet.
• Wireless Local Area Network (WLAN): WiFi is a short-range WLAN solution, suitable for LAN access of smart terminals (mobile phones, PADs, laptops, etc.) and handheld terminals.
• Wireless MAN Private Network: iMAX wireless MAN private network is suitable for the construction of high-reliability dedicated MAN networks in a specific area, solving network interconnection problems for information points with inconvenient wiring and mobile information points. It is particularly suitable for dedicated network access of mobile nodes such as vehicles, shipborne terminals and unmanned aerial vehicles (UAVs).

1. Wireless Networking for Video Surveillance and Condition Monitoring System Along Subway Lines

2. Train-Ground Wireless Broadband Communication System

The train-ground wireless broadband communication system is a proprietary IP broadband wireless communication system that enables subway trains to achieve high-speed network interconnection with the remote command and monitoring center in real time during operation. It not only meets the needs of data communication, but also supports the access of large-bandwidth service systems such as high-definition video, real-time voice, on-board WiFi, and vehicle status detection.

Given the requirements for high-speed wireless roaming and network switching while maintaining link stability, only a specially designed wireless system can ensure reliable operation. The Guoxin Longxin iMAX-8000H mobile high-capacity multi-mode MESH wireless access system or the iMAX-8000W waveguide wireless communication system is ideally suited for this scenario. Of course, for higher reliability requirements, the two systems can be integrated to form a dual-system hot backup network, meeting stringent reliability demands.

Typical Application Diagram of iMAX Train-Ground Networking for Subway Trains：

A series of iMAX private network base station (BS) systems are deployed at varying distances along subway lines according to different terrain, coverage requirements and other conditions. Equipping the train with the Guoxin Longxin iMAX-8000H mobile high-capacity multi-mode MESH wireless access system enables high-speed, smooth and seamless roaming. Of course, seamless roaming can also be achieved through VRRP virtual hot backup routing technology—a capability that many wireless communication manufacturers cannot deliver.

Deploying a pure air-interface wireless system along subway lines, especially in subway sections, may be subject to interference from co-frequency radio systems under certain circumstances. In scenarios involving high-reliability train control and remote unmanned driving, prolonged communication interruptions are unacceptable, yet the mobility of trains dictates the exclusive use of wireless technology.

The industry has two primary solutions for reliable wireless communication under interference conditions: first, the leaky feeder cable solution; second, the waveguide communication solution. Leaky feeder cables are cost-effective, but their technical limitations only allow low-bandwidth narrowband communication. Waveguides, by contrast, support high-bandwidth real-time communication. The Guoxin Longxin iMAX-8000W series waveguide dedicated mobile communication system is a customized product for this specific application scenario. It can be used in conjunction with leaky feeder cables or slotted waveguides to meet the demand for real-time, high-speed broadband communication between trains (especially subways, light rails and intercity trains) and the ground command center.

The topology diagram of the iMAX-8000W waveguide communication system for train-ground communication of moving trains is as follows:

The distribution of waveguide communication base stations, waveguide length, frequency planning and networking mode all represent technical challenges, while high bandwidth and seamless roaming for trains traveling at high speed are the standout advantages of Guoxin Longxin’s solution.

Pure air-interface wireless and waveguide wireless systems are not mutually exclusive. For high-reliability networking, the two systems can be integrated into a dual-network architecture via the VRRP virtual routing protocol supported by Guoxin Longxin’s iMAX series products, delivering two mutually hot-backup and redundant high-reliability systems for train-ground communication.

Notably, Guoxin Longxin’s iMAX wireless metropolitan area network products feature a “multi-link data mirroring” technology, which enables “zero packet loss roaming” between base stations (BS). This advanced technology is ideal for scenarios with stringent reliability requirements but moderate bandwidth demands, a capability that low-end wireless products such as wireless bridges cannot match.

In addition, Guoxin Longxin offers standardized designs for portable monitoring points, detachable monitoring points and individual patrol systems for emergency repair and line inspection. These solutions can also be modularly customized to meet the actual operational requirements of subway users.

The rail transit industry encompasses a wide range of transit modes, including but not limited to ten categories: metro systems, urban rapid rail systems, light rail systems, medium-to-low speed maglev transit systems, straddle-type monorail systems, suspended monorail systems, autonomous rail transit systems, tram systems, rail-guided rubber-tyred systems and electronically guided rubber-tyred systems. China has operational or trial lines for nearly all of these modes. Guoxin Longxin’s wireless private network technology boasts broader application prospects in light rail, suspended monorail, tram and other transit modes than in metro systems. Benefiting from numerous advantages—low wireless deployment cost, high cost-effectiveness, high reliability, easy deployment, mobility and simple maintenance—it will ultimately become an indispensable component of rail transit communication networking.

Wireless communication networking solutions for the rail transit industry typically impose stringent requirements for reliability, security and stability, all of which demand customized design tailored to local conditions. This requires vendors to possess the capability to develop bespoke solutions based on users’ actual needs and objective conditions. Specific application scenarios are not elaborated separately in this solution; interested users and integrator partners may consult the Guoxin Longxin Technical Center for further details.