5G MBS Facilitating Efficient Deployment of Railway MCS Applications

With the rapid development of railways, especially high-speed railways, the number of mobile terminals in communication networks has multiplied. Railway train-to-ground wireless communication services now extend beyond traditional train control and scheduling to include intelligent operations such as the Internet of things (IoT) and video surveillance. Consequently, railway mobile communication systems are confronted with challenges in handling mass data transmission and digital transformation.

Since the specifications for GSM-R were finalized in 2000, its application ecosystem has faced inevitable decline and is gradually exiting the market. The current GSM-R railway communication system, with a narrowband data bandwidth of only 100 Kbps+, cannot meet the demands for digitalization, networking, and intelligent transformation in railway transportation. The high-speed and low-latency features of the 5G communication system can address the emerging requirements for new functions, services, and scenarios in railways. The future railway mobile communication system (FRMCS), based on 5G, will succeed GSM-R and serve as a key enabler for rail transport digitalization.

In railway mission critical services (MCS), there are numerous point-to-multipoint data transmission requirements in train signaling communication applications, train operation applications, and trackside maintenance applications. Examples include broadcasting warning notifications, group call communications between dispatch consoles and train group members, and transmitting surveillance videos. With numerous group users and a large amount of application data, and the system’s transmission bandwidth becomes a bottleneck restricting service development. Thus, it is imperative for railway communication networks to efficiently and reliably support such point-to-multipoint transmission services. The 5G multicast and broadcast services (MBS) technology addresses this issue by sharing transmission resources with multiple application data streams.

Without changing the existing SA network architecture, the 5G MBS technology enhances and optimizes network functions to transmit data from a single source to multiple UEs, thus achieving network resource sharing. In addition to sharing mobile core network and access network resources, a key advantage of this technology is its capability to share increasingly scarce spectrum resources. Fig. 1 shows the MBS network architecture.

The 5G MBS specifications inherit the large bandwidth techniques, slicing capabilities, and QOS framework of the 5G system. By introducing point-to-multipoint transmission, group scheduling, and the conversion of transmission modes on the air interface, the 5G MBS technology has achieved substantial improvements in system efficiency and user experience.

• High bandwidth and high rates: Building a highway for MCS

If the UE capability is sufficient, the available bandwidth for MBS data transmission can theoretically reach 100 MHz. The flexible subframe design and scheduling bandwidth of the MBS ensure adequate capacity for MCS data transmission across various scenarios. ZTE’s 5G MBS product solution supports flexible MBS data scheduling on the air interface to meet transmission bandwidth requirements in different scenarios.

• Point-to-multipoint transmission: Saving transmission bandwidth

To meet the point-to-multipoint transmission requirements of mission critical push-to-talk (MCPTT), mission critical video (MCVideo), and mission critical data (MCData) services in railway applications, 3GPP has enhanced the 5G MBS technology in MCS.

The 5G MBS optimizes frequency usage by providing a logical channel shared by all users on the radio interface, eliminating the need to allocate spectrum resources to each UE and greatly saving radio transmission bandwidth.

In terms of data transmission for bearer and core networks, ZTE’s devices support both point-to-point and point-to-multipoint data transmission modes, which greatly reduces the transmission bandwidth required for the backhaul network.

• Flexible point-to-point and point-to-multipoint conversion: Ensuring efficient and reliable wireless transmission

In terms of multicast data transmission at the air interface, the MBS mechanism provides a feedback function at the link layer. When the network receives feedback from the UE about data reception failures, it will selectively repeat the transmission to ensure that each UE in the group can reliably receive downlink data, and the mechanism is suitable for those UEs at the cell edge or in areas with weak wireless coverage. The point-to-point and point-to-multipoint conversion mechanism at the link layer enhances both downlink data transmission and the reliability of individual UE data reception, achieving efficient transmission while ensuring a high user experience.

• Two transmission modes: Facilitating MCS deployment and expansion

The 5G MBS technology defines two modes for point-to-multipoint data transmission: 5GC individual delivery method and 5GC shared delivery method. For MCS application data, the individual delivery method uses 5G unicast technology to implement point-to-multipoint data transmission. This method is suitable in the early stages of industry chain development when one or more parties (UE, gNodeB, or 5GC) do not have the MBS capability, or when there are few MCS point-to-multipoint service scenarios and data volumes are small. The shared delivery method, on the other hand, utilizes real multicast technology to enable end-to-end resource sharing across the network, greatly saving resources and reducing future investment.

• End-to-end network slicing: Providing differentiated SLA services in multiple scenarios

Train signals, and operation and maintenance applications in the railway system are supported by the railway 5G private network. While traffic applications generally involve small data volumes, they are sensitive to transmission delay and reliability. In contrast, operation and maintenance data volumes are large, with lower sensitivity to delay and reliability. Leveraging the 5G MBS technology, ZTE provides an end-to-end network slicing solution in the radio access network, bearer transmission network, and core network. This solution meets varying QoS requirements, isolates different user groups, and ensures differentiated SLA services.

The MBS technology is widely used in public security, emergency push notifications, V2X applications, IPTV, wireless software push, group call conferencing, IoT applications, and various vertical industries and consumer sectors. In 2014, ZTE helped China Telecom complete the IPRAN multicast TV service based on 4G MBS technology. In 2020, ZTE launched the first 5G MBS demonstration at the Ultra-High-Definition Video Production Technology Collaboration Center in Beijing, implementing end-to-end multi-channel high-definition video broadcast services on the 700 MHz frequency band. In 2023, ZTE, China Broadcast Network Co., Ltd., Migu Culture Technology Co., Ltd, and leading terminal manufacturers collaborated on 5G MBS broadcast TV and multicast services to accelerate technological development and industrial maturity.

As the pioneer in MBS technology, ZTE offers customized MCS services for users in the railway industry, aiming to improve communication quality and reduce operational costs in a secure, reliable, and effective manner. This not only helps industry users improve operation efficiency and service quality but also positively impacts the development of the entire railway industry.