Recently, the news that the Ministry of Industry and Information Technology approved the 5G-R test frequency for China State Railway Group Co., Ltd. (hereinafter referred to as "China Railway Group") has attracted widespread attention in the industry. What exactly is 5G-R? Why did the Ministry of Industry and Information Technology approve the 5G-R test frequency at this time?
Today, Xiao Zaojun will give you a detailed explanation in the form of questions and answers.
What is 5G-R?
The full English name of 5G-R is 5G-Railway. Railway means "railway" in English.
In the approval, 5G-R is called "a new generation of railway mobile Communication system based on 5G technology." In fact, to put it simply, 5G-R is a 5G technology used in the railway transportation industry.
Some readers may ask: Is 5G-R used for railway passengers to access the Internet?
The answer is: No.
5G-R is a private Network communication system. It is the China Railway Group's dedicated 5G network, specially designed to meet railway communication operation and management needs, and is used internally by the railway.
When passengers access the Internet, they mainly connect to the Public Network communication systems of operators such as China Mobile, China Telecom, and China Unicom.
The two systems are completely independent and isolated, and terminals cannot be mixed.
Because of this, 5G-R needs to apply for spectrum separately for network construction.
The domestic 5G-R working frequency band is 2100MHz. Specifically, the uplink is 1965~1975MHz, and the downlink is 2155~2165MHz, 10MHz each, using the FDD format.
What are the application scenarios for railway private network communication?
Railway transportation is a typical mobile communication scenario, and the demand for wireless communication technology is very strong.
Whether it is a high-speed train or a regular-speed train (green train), whether it is a passenger train or a freight train, it is necessary to maintain close contact with the station at all times. This is the basic prerequisite for safe railway operation.
To sum up, railway private network wireless communication includes the following application scenarios:
1. Mainline train-to-ground communication
All places where the main railway line passes must have signal coverage. This is a typical wide-area coverage scenario.
During train operation, the main communication systems and services used include train operation control system (CTCS/ETCS), locomotive synchronization control and dispatch communication for heavy-duty combined trains, train route forecast, dispatch command information, etc.
These are related to the normal operation of trains, which require extremely high safety and reliability, and are biased towards uRLLC (high reliability and low latency communication) scenarios.
Because trains travel at high speeds (especially high-speed trains), the communication system must also have high-speed adaptability and a certain communication capability can be guaranteed even at a speed of 350km per hour.
You may subconsciously think that the railway private network will have extremely high latency requirements, but in fact, like the train operation control system, the railway specification only requires 150ms, which is not difficult to achieve.
In addition to vehicle-to-ground communications, there is also a demand for vehicle-to-vehicle (T2T) communications, which are mainly used in anti-collision systems.
2. Railway stations and hubs
Railway passenger stations, freight marshaling yards, locomotive depots, depots, train depots, and other areas are also places with intensive communication needs and are hot coverage areas.
The main business includes plane shunting, shunting monitoring, marshaling station automation, passenger station services, on-board data download, station Internet of Things, station maintenance operations, etc.
There are many people, vehicles, and equipment here, and there are certain requirements for communication bandwidth and capacity (the spatial movement speed of the terminal is low, and there is no high-speed adaptability requirement), which is biased towards the eMBB (enhanced mobile broadband) scenario.
3. Infrastructure along the railway
In addition to trains, the infrastructure along the railway also has communication needs.
For example, professional infrastructure equipment such as electricity and public works along the railway (bridges, tunnels, catenaries, towers, etc. At present, important line signals and other equipment are still mainly wired communications).
In recent years, natural disasters such as floods and landslides have occurred frequently along the railway lines. To monitor disasters, the railway department has set up many monitoring IoT nodes, which also have communication needs.
These monitoring nodes have a large number of connections, small bandwidth requirements, and are biased towards the mMTC (mass machine communication) scenario.
4. Vehicle internal communication scenario
Mainly refers to high-speed passenger vehicles such as EMUs, and its business includes train positioning, automatic driving, mobile equipment status detection, intelligent diagnosis, etc.
There are many monitoring systems inside and outside the train, such as 6A (locomotive on-board safety protection system, including locomotive braking system, fire protection, high-voltage insulation, train power supply, running section, video) and 6C (power supply safety detection and monitoring system). They are an important means to grasp the running status of trains.
Other scenarios where railway communications will be used include accident rescue (voice and multimedia clustering), mobile operation and maintenance (data, voice, and multimedia clustering), LBS (location-based services, such as personnel positioning and train positioning, etc.), and high-speed rail Wi-Fi.
High-speed rail Wi-Fi is quite popular now.
In the digital age, passengers have a greater demand for high-speed rail Internet access. The signal coverage of public network operators is good or bad. China Railway Group is also researching and deploying high-speed rail Wi-Fi and looking for business opportunities. China Railway Group has also joined forces with Geely and Tencent to set up China Railway Jixun to promote the construction of high-speed rail Wi-Fi platforms.
What is GSM-R?
Speaking of 5G-R, its predecessor- GSM-R will definitely be mentioned.
As the name suggests, GSM-R is a wireless communication system based on GSM technology and specially designed for the railway industry.
In the early 1990s, when the GSM standard was just established, Siemens began to brew and draft the GSM-R technical standard.
Later, the International Union of Railways (UIC) and the European Telecommunications Standards Institute (ETSI) cooperated to jointly launch the final version of the GSM-R standard for the European railway system.
Compared with the traditional GSM standard, GSM-R mainly adds functions related to railway-specific dispatch communications.
At present, the main railway private network communication technology used in our country includes GSM-R.
After the founding of New China, the railway system began to use train wireless dispatching phones and station wireless phones, using electronic tube equipment with operating frequencies of 2MHz and 40MHz.
In the 1970s, we gradually began to move to transistor devices in the 150MHz and 450MHz frequency bands.
Later, the railway-specific radio frequency was set in the 450MHz band, which was used for intercom communication services such as train wireless dispatching communication, station-level shunting, passenger and freight transportation, and maintenance and repair.
After GSM-R appeared in Europe in the 1990s, our country also learned and introduced it in time.
In 2004, to meet the needs of developing CTCS-3 train operation control systems for high-speed railways, the Ministry of Railways officially adopted the GSM-R standard as my country's national standard for new-generation railway wireless communications.
It is worth mentioning that my country is the first country in Asia to develop GSM-R. The first railway in China to apply GSM-R is the famous Qinghai-Tibet Railway.
Domestic GSM-R uses the 900MHz "golden frequency band" ("obtained" from China Mobile), uplink 885-889MHz, downlink 930-934MHz, 2×4MHz bandwidth, and the maximum coverage distance can reach 6~9km.
Since 2008, almost all new (renovated) railways have adopted GSM-R as a dedicated wireless communication system.
Starting in 2012, the Ministry of Industry and Information Technology stopped approving analog wireless train dispatching systems based on the 450MHz frequency band. Because the system has poor anti-interference ability, low voice quality, and limited services.
After that, Xiamen-Shenzhen High-speed Railway, Guangzhou-Shenzhen-Hong Kong High-speed Railway, Qinghai-Tibet Line, Daqin Line, Jiaoji Line, Wuhan-Guangzhou Line, Zhengxi Line, Shitai Line, Hening Line, Hewu Line, Beijing-Tianjin Intercity Line, Beijing-Tianjin Intercity Line, Important domestic railway lines such as the Shanghai High-speed Railway have adopted GSM-R technology to achieve digital and network upgrades.
As of the end of 2021, the domestic GSM-R coverage line mileage (including under construction) reached 89,000 kilometers, and the number of users exceeded 350,000.
With GSM-R, why do we need to develop 5G-R?
Of course, it’s because 5G-R is more advanced.
Today, the GSM-R standard based on 2G technology has long been unable to meet the development needs of modern railways.
GSM-R mainly focuses on voice services and has low-frequency efficiency. The narrowband data bandwidth is only more than 100 KB at most, making it difficult to carry the large communication bandwidth requirements after the digital transformation of railways.
A few years ago, China proposed building a private railway wireless network based on LTE-R (4G), but after testing for some time, it was not commercialized on a large scale.
Now it seems that the country is planning to get it right in one step, skipping LTE-R and going directly to 5G-R.
5G-R is based on 5G technology and features ultra-large bandwidth, ultra-low latency, and massive connections. Its network performance almost surpasses GSM-R.
In terms of network capabilities, 5G-R supports network slicing, edge computing, and other services, which can provide service quality assurance for key railway businesses.
In terms of security and reliability, 5G-R also has huge improvements. This is very important for railway transportation safety.
What is the difference between 5G-R and public network 5G?
The working principles of 5G-R and public network 5G are basically the same. Especially the wireless air interface part, there is basically no difference.
The main differences between 5G-R are concentrated in service types, networking methods, and performance requirements.
Business types have been introduced before. Railways have many special businesses of their own.
In terms of networking methods, 5G-R is deployed along railway lines, and wireless access networks mostly adopt chain networking.
On the core network side, it needs to match the production mode and organizational mode of the railway department and carry out appropriate network transformation.
The picture below is a diagram of a 5G-R networking architecture:
In addition to the control plane network elements (AMF, SMF, UDM, etc.) and media plane network elements (UPF) included in traditional public network 5G, we can see some 5G-R dedicated equipment, such as railway broadband trunking communications (MCX, Mission Critical X-Service (critical business) equipment, 5G Intelligent Network (5G-IN), 5G Equipment Identification Register (5G-EIR), etc.
Through this MCX device, 5G-R can be interconnected with other communication systems to provide wired and wireless integrated dispatch communication services. It can also be interconnected with the railway fixed telephone network to meet official communication needs.
Who is responsible for developing the 5G-R standards?
5G-R is based on 5G (IMT-2020), and the standard formulation of 5G is of course the responsibility of the famous standardization organization (3rd Generation Partnership Project).
Currently, 5G has gone through the 3GPP R15-R17 stage. R18 is also about to be frozen, which will usher in the 5G-Advanced (5.5G) era.
Another international organization specifically responsible for railway communication standard research is the UIC (International Union of Railways) mentioned earlier, which participated in the formulation of the GSM-R standard.
In 2012, UIC, together with ETSI and 3GPP, launched the FRMCS (Future Railway Mobile Communication System) project. In 2016, UIC included 5G in the research scope of FRMCS.
UIC's goal is to launch the first version of FRMCS based on the R17 version in 2025 for pilot application in railways.
China has also done a lot of work on the 5G-R standard system.
China Railway Group established the NGCR (Next Generation Radio Communications Working Group) in 2015, with five sub-working groups including spectrum, standards, services, industry, and testing.
In August 2020, the China Railway Group released the "Outline of the Advanced Railway Planning for a Strong Transportation Power in the New Era", which clearly stated:
"Strengthen the construction and application of new infrastructure such as 5G communication networks, big data, blockchain, and the Internet of Things, enrich application scenarios, extend the industrial chain, coordinate the construction of a new generation of railway mobile communication private networks, and build a ubiquitous advanced, safe and efficient "Modern Railway Information Infrastructure System".
Later, the China Railway Group issued the "Implementation Opinions of the China Railway Group on Accelerating the Development of Railway Applications of 5G Technology" and the "Three-Year Action Plan for Railway 5G Technology Application and Technology Research", actively deploying 5G-R applications and technology research.
According to preliminary industry forecasts, the parallel development of 5G-R and GSM-R will be achieved in 2025. In 2030, 5G-R will replace GSM-R. Research on 5G-R based on the 900MHz frequency band is also already underway.
What is the significance of this approved testing frequency?
Determining the radio operating frequency is an important prerequisite for the development of wireless communication technology.
Once the spectrum is determined, the industry will have a target for technical research and will have more confidence in this technology. This is conducive to the rapid maturity of the industrial chain and is also conducive to stimulating independent technological innovation.
With the test frequency, China Railway Group can further promote relevant scientific research projects and field tests to verify the feasibility of the 5G-R frequency solution and the compatibility and coexistence with related systems in adjacent frequency bands.
In terms of the core network, bearer network, and access network equipment, as well as terminals and modules, relevant work can also be advanced in great strides.
Conclusion
High-speed rail is our national business card, and so is 5G.
The Ministry of Industry and Information Technology’s timely approval of the trial spectrum shows our country’s determination to vigorously promote railway digital construction.
Combined with the news last year that the Ministry of Industry and Information Technology issued the first enterprise 5G private network frequency to COMAC, we can also see that the state’s support for private network communications is increasing.
Private networks are an important base to support the digital transformation of enterprises. Granting exclusive spectrum is extremely beneficial to the development of private networks.
In the future, let us wait and see whether the country will allocate more frequent resources for private network communications to promote the comprehensive advancement of digital transformation!
Okay, that’s all for today’s article. Thank you all for watching patiently!
——The End——
References:
1. Discussion on key issues in railway 5G-R research and development, Jiang Yongfu, China Railway;
2. Research on railway 5G-R technical standard system, Wang Fang, Shi Bo, Lin Wei, China Railway;
3. Research on railway 5G private network system architecture and networking technology, Zhou Yuhui, China Railway;
4. Railway 5G private network: what is it? How to build? , Hu Yuan, Communications Industry News;
5. Brief analysis of the next-generation railway mobile communication system, Tabby Cat, Zhihu;
6. The Ministry of Industry and Information Technology approved the test frequency of the new generation mobile communication system for railways, Industry and Information Technology WeChat report;
7. Baidu Encyclopedia and Wikipedia.
This article comes from the WeChat public account: Xian Zao Classroom (ID: xzclasscom), author: Xiao Zaojun
