The rapid development of communication technologies from Wi-Fi to 4G LTE and 5G has continuously promoted the innovation and development of rail transit communication systems. Recently, CASCO and Zhengzhou Metro’s Communications and Signaling Center made an important progress on the application of the 5G-based CBTC rail transit signaling system and completed laboratory and field tests for the 5G-based on-board log data transmission of the rail transit signaling system. This technology will be used on Zhengzhou Metro Line 5 for the first time, marking the first successful application of 5G technology to the rail transit signaling system.

Zhengzhou Metro Line 5

Zhengzhou Metro Line 5 equipped with CASCO’s CBTC signaling system was officially put into operation on May 20, 2019. During the construction of this line, 4G LTE technology was used for the train-to-ground transmission of signaling system data. The frequency band of the WiFi channel for train-to-ground data transmission was 1.8 GHz.

However, the massive on-board data generated during the train operation (including the on-board signaling system log data, the on-board communication system videos and the train status information) needed to be downloaded and transmitted via the train-to-ground LTE WiFi channel. This severely limited the available wireless bandwidth (only 10MHz), which hindered timely upload of the operation log of the day to the center after the train returns to the depot.

To lift bandwidth restrictions on 4G LTE technology, CASCO sought to integrate the on-board log data transmission of the signaling system into the 5G channel based on its ongoing research on the application of 5G technology. In addition, CASCO has partnered with Zhengzhou Metro’s Communications and Signaling Center to study and test the implementation plan.

The research team selected Huawei’s AirFlash technology for the transmission and download of the on-board signaling system log data, forming an automatic data dump and download scheme. Based on the technical characteristics of 5G technology (such as ultra-wide bandwidth, ultra-low latency and ultra-wide connection), the new transmission solution is featured by an ultra-high speed, no interference risk and end-to-end automatic dumping, thus eliminating the existing bottlenecks.

Thanks to the coordination and support of Zhengzhou Metro’s Communications and Signaling Center as well as CASCO’s Zhengzhou subsidiary team, the laboratory and field tests of this innovative scheme have been completed recently. According to the test data, the wireless link rate averaged 1.5Gbps. The daily on-board signaling system log data can be downloaded in just seconds. It used to take 13 hours to transmit and download daily on-board video data of each train. 5G-based data download and transmission can be completed in half an hour. The on-board CCTV system was limited by the insufficient bandwidth of train-to-ground wireless network. Video recordings could only be stored in the on-board NVR, resulting in delayed data transmission. The 5G-based transmission can enable real-time remote data download, which greatly enhances the time efficiency of data transmission.

It is reported that this technology will be first used on Zhengzhou Metro Line 5 to help improve its daily operation, maintenance, management efficiency, and safety. This technology will be used on other metro lines in Zhengzhou so as to lead Zhengzhou Metro into the 5G era quickly.

Undoubtedly, 5G technology has a broad application prospect in the field of rail transit. 5G technology will play a key role in new projects and the transformation of existing rail lines. It is a key driving force to realize smart transportation and build smart cities. For example, once 5G equipment is deployed in existing depots or switchback stations, on-board signaling logs can then be quickly uploaded within a short period of time when the train returns to the depot or switches back. CASCO will also be committed to integrating 5G solutions with intelligent operation and maintenance systems to conduct intelligent analysis and early warning of signaling system logs as well as to provide strong support for intelligent train operation and maintenance.