Railway Relies on Huawei eLTE Wireless Network

Background

As a port city, Chongqing is an economic, financial, and innovative center on the upper reaches of the Yangtze River. The city is also a critical railway hub in Western China. In 2005, Chongqing Rail Transit (CRT) established the first urban rail transit system, with four main lines and several other extension lines to be open to the public by 2018. Two major extension lines — CRT Line 5 and the Circle Line — will eventually cover a total length of nearly 100 kilometers. Line 5 will transport north-south passengers while the Circle Line will run around the city. Inter-line operations along with express and slow train operations have been implemented to achieve flexible network operations, which require reliable, open, and interconnected train-to-ground wireless communications that support secure and stable Communication-Based Train Control (CBTC) systems.

Challenges

Traditional CBTC systems generally used Wireless Local Area Networks (WLANs) that operated on public frequency bands. As interference to public frequency bands increases and a growing number of trains travel at higher speeds, traditional CBTC systems are becoming increasingly obsolete in providing satisfactory train-to-ground wireless communications. The challenges are as follows:

• Interference to public frequency bands: With the popularity of Wi-Fi-capable devices, especially on metro trains, Wi-Fi has been installed in an increasing number of cities. This adds more interference to the Wi-Fi network that also uses the CBTC system. 
• Link interruptions due to frequent handovers: With the acceleration of urbanization, metro trains typically run at higher speeds reaching up to 120 km/h. This creates issues such as connection, transmission, and more frequent handovers for Wi-Fi networks.
• Complicated geographic terrain: Chongqing is surrounded by mountainous and jagged topography, complicated by a large number of bridges, which greatly affects the range of train positions. This increases demands even higher network coverage. 
• Vast number of devices and difficult maintenance: Wi-Fi generally covers a short distance of 200 meters, which requires deployment of a large number of access devices in tunnels. This causes difficulty for inspection and maintenance. 

Solution

Huawei provides the eLTE Train-to-Ground Wireless Communication solution to handle CRT’s CBTC requirements for accurate train-to-ground communications. This solution provides multiple services, such as CBTC and train status monitoring. It is reliable and secure, ensuring the safe operations of rail transit.

• Security and reliability: The solution is deployed on the licensed 1.8 GHz band. This boasts reliability to 99.999% with a low latency of milliseconds. The secure and reliable design fulfills CBTC requirements.
• QoS guarantee: This solution provides a hierarchical QoS design for different services based on their attributes, maximizing a guaranteed functionality for CBTC services in the event of insufficient wireless resources.
• Interconnectivity: Huawei eLTE Train-to-Ground Wireless Communication solution is a 3GPP-based solution enhanced for the rail transit industry, effectively connecting different LTE networks.

Benefits

Huawei eLTE supports agile inter-line operations of CRT’s Line 5 and Circle Line. The two major rail lines have paved the way for an expected average daily ridership of over one million passengers in the future, and serve as examples for the construction of safer and more environmentally friendly urban rail transit systems.