A Multi Service Fusion Communication System Scheme for Rail Transit Vehicle Ground Based on TD-LTE

Requirement Background

Urban rail transit, as a stable and efficient public transportation mode, has been steadily advancing in major cities across the country in recent years. The monitoring and control methods and business applications for subways are constantly evolving, such as the train control system CBTC (Communication based Automatic Train Control System), CCTV (Video Surveillance System), PIS (Passenger Information System), and train wireless dispatch systems, which are gradually adopting LTE wireless communication systems to achieve data transmission and interaction. However, due to the limited space of subway tunnels and the fast speed of trains, wireless communication systems face extremely unfavorable conditions such as multipath interference and fast signal fading. Therefore, customized development is needed for the harsh environment of subways to make wireless communication systems meet the actual application requirements of subways.

The TAU locomotive equipment specially customized for the rail transit industry by Bote Shutong can independently carry the three major train services of CBTC (subway train control), CCTV (video surveillance), and PIS (passenger information system). Support LTE QoS mechanism, VRRP dual machine hot backup technology, dual SIM card backup and A/B network switching to ensure secure and reliable data transmission. At the same time, the unique train control "black box" function realizes the storage of CBTC data, providing more favorable guarantees for the alarm and analysis of train control data.

Solution

The scheme is designed to install a core network in the central computer room, base stations on the station platform and in the tunnel, and antennas on the platform. Leakage cables are laid in the tunnel for LTE signal coverage. Ensure that LTE signals cover the entire section of train operation in all directions and without blind spots. Maximizing the normal and smooth operation of the train.

The onboard TAU terminal is arranged at the front and rear of the train, with one each. The two TAUs achieve hot backup through the VRRP protocol. Under normal circumstances, both devices are running, with one as the primary device and the other as a secondary device. Under normal circumstances, data is forwarded through the main TAU to achieve vehicle ground communication. When the primary TAU experiences a malfunction, downtime, or link disconnection, the data is immediately forwarded by the secondary TAU, ensuring that the data is not interrupted. Meanwhile, each TAU also supports dual SIM card switching and A/B network switching. When the LTE network fails, communication between the control center and the train can be achieved by switching the access SIM card or switching the access network, ensuring that there will be no interruption in train ground communication.

The onboard TAU is connected to the train's LCD controller and onboard camera through the onboard switch. It uploads real-time data collected by the camera through the LTE network and receives multicast data from the control center to each onboard screen. Implement PIS and CCTV services.

The onboard TAU also supports the train control "black box" function, which can store CBTC data in real-time. The normal transmission of CBTC data is crucial for the safe operation of trains. So TAU adopts QoS mechanism to ensure the bandwidth guarantee of CBTC data transmission in the process of vehicle ground communication. At the same time, during the transmission of CBTC data, TAU will store each raw data packet related to CBTC, which is equivalent to the "black box" function of train control. When there is an abnormality in train control, it can be analyzed through the data in the "black box".

System network topology diagram

Features of the Solution

1.A single device carries the three major businesses of CBTC, CCTV, and PIS;

2.First use of LTE network to carry CBTC services;

3.Using LTE 1.8G frequency band for data transmission, dedicated frequency band, low interference, in compliance with LTE-M standard;

4.Support PIS multicast services;

5.Support VRRP dual machine hot standby;

6.Support dual SIM card backup and A/B network switching;

7.Support CBTC data storage function.

Introduction to the core equipment TAU in the plan

The core equipment in the plan is the TAU locomotive equipment independently developed by BETTERLTE, which is professionally customized for the rail transit industry. The equipment can independently carry the three major train services of CBTC (subway train control), CCTV (video surveillance), and PIS (passenger information system). Realize vehicle ground communication through the most advanced TD-LTE technology, meet the latest LTE-M standard, and support high bandwidth requirements of 50Mbps upstream and 100Mbps downstream; Unicast, multicast, LTE based QoS mechanism, extended VRRP technology, dual SIM card backup, and A/B network switching for subway application development ensure the efficiency, real-time, security, and reliability of the application. At the same time, the unique train control "black box" function realizes the storage of CBTC data, providing more favorable guarantees for the alarm and analysis of train control data.

TAU appearance diagram

Product Features

Professional hardware design:The DC110V power input and communication interface for the subway are designed with aviation plugs and professional seismic and impact resistant structures to meet the harsh working environment of rail transit.

Professional functional design:Support uplink unicast and downlink multicast functions; Support routing forwarding to achieve real address access from the application center to the business terminal; Support multi-level QoS based on LTE to ensure the highest priority of train control services.

High speed wireless transmission:The product is based on the 4G TD-LTE international standard, supporting maximum transmission rates of DL: 100Mbps and UL: 50Mbps. It supports dual antenna MIMO technology, with downlink MIMO transmission supporting TM1/2/3/4/7/8 mode and uplink transmission supporting single antenna port transmission mode.

High reliability:Adopting dual protection of software watchdog and hardware watchdog, providing multi-level link detection mechanism and automatic fault recovery mechanism, providing VRRP based primary/backup switching and dual SIM card switching, supporting A/B network switching. Support CBTC data storage.

高安全性：Supports VPN features such as GRE, L2TP, and IPsec.

Easy to maintain:Support OMC centralized management and one click reset; Equipment configuration free; It can support remote automatic software upgrades without the need to replace hardware or manually operate the terminal to add new features.

Customized development:Customized development functions can be developed according to industry requirements.