Shulou(Shulou.com)11/24 Report--

Recently, the Ministry of Industry and Information Technology replied to the China National Railway Group Co., Ltd. (hereinafter referred to as "China Railway Group") the news of 5G-R test frequency, which aroused widespread concern in the industry.

What on earth is 5G-R? Why did the Ministry of Industry and Information Technology approve the test frequency of 5G-R at this time?

Today, Mr. Xiaozao will give you a detailed interpretation in the form of questions and answers.

█, what is 5G-R? The full name of 5G-R in English is 5G-Railway. Railway means "railway" in English.

In the approval, 5G-R is called "the new generation 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 for railway passengers to surf the Internet?

The answer is No.

5G-R belongs to the private network (Private Network) communication system. It is the dedicated 5G network of the National Railway Group, specially used to meet the needs of railway communication operation and management, and is used within the railway.

While passengers surf the Internet, they are mainly connected to the public network (Public Network) communication systems of mobile, telecom, Unicom and other operators.

The two systems are completely independent and isolated, and the terminals cannot be mixed.

Because of this, 5G-R needs to apply for spectrum separately to build the network.

The working frequency band of domestic 5G-R is 2100MHz. Specifically, the uplink 1965~1975MHz, downlink 2155~2165MHz, each 10MHz, using the FDD standard.

What are the application scenarios of █ railway private network communication? Railway transportation is a typical mobile communication scene, and the demand for wireless communication technology is very strong.

Whether it is a high-speed railway or a general-speed train (green car), whether it is a passenger train or a freight train, it is necessary to maintain close contact with the station at any time, which is the basic prerequisite for the safe operation of the railway.

To sum up, railway private network wireless communication includes the following application scenarios:

1. Communication from the main line to the ground where all the main lines of the railway pass through, signal coverage is required. This is a typical wide area coverage scenario.

In the process of train operation, the main communication systems and services include: train operation control system (CTCS / ETCS), locomotive synchronization control and dispatching communication of heavy-haul combined trains, train route notice, dispatching command information and so on.

All these are related to the normal operation of the train, which requires extremely high security and reliability, and is partial to uRLLC (high reliability and low delay communication) scenario.

Because the train runs at high speed (especially high-speed rail), the communication system must also have high-speed adaptability, and the speed 350km can also ensure a certain communication capacity.

People may subconsciously think that the special railway network will have a very high delay demand, but in fact, like the train operation control system, the railway specification only gives the requirements of 150ms, which is not difficult to achieve.

In addition to the vehicle location, there is also a demand for vehicle (T2T) communication, which is mainly used in the anti-collision system.

2. Railway station yard, hub railway passenger station, freight marshalling yard, locomotive depot, vehicle depot, bullet train station and other areas are also places with dense communication demand, which belong to hot spots.

The main business includes: plane shunting, shunting monitoring, marshalling yard automation, passenger station service, on-board data download, station Internet of things, station maintenance operation and so on.

There are many people, vehicles and equipment here, and there are certain requirements for communication bandwidth and capacity (the spatial mobility rate of the terminal is low, and there is no requirement for high-speed adaptability), which is partial to eMBB (enhanced Mobile Broadband) scenario.

3. The infrastructure along the railway line, in addition to trains, the infrastructure along the railway line also has communication needs.

For example, along the railway lines, telecommunications, public works and other professional infrastructure equipment (bridges, tunnels, catenary, towers, etc., etc., at present, important line signals and other equipment is still wired communication).

In recent years, natural disasters such as floods and landslides have occurred frequently along the railway. In order to monitor disasters, the railway department has set up many monitoring nodes of the Internet of things, and there are also communication requirements.

These monitoring nodes have a large number of connections and small bandwidth requirements, and are partial to mMTC (Mass Machine Communication) scenarios.

4. The vehicle internal communication scene mainly refers to high-speed passenger vehicles such as EMU, including train positioning, automatic driving, mobile equipment state detection, intelligent diagnosis and so on.

There are many monitoring systems inside and outside the train, such as 6A (locomotive on-board safety protection system, including: locomotive braking system, fire prevention, high-voltage insulation, train power supply, running part, video) and 6C (power supply safety detection and monitoring system). They are an important means to grasp the running state of the train.

Other scenarios that will be used in railway communications include accident rescue (voice and multimedia clustering), mobile operation and maintenance (data, voice and multimedia clustering), LBS (location-based services such as personnel location and train location, etc.) and high-speed rail Wi-Fi.

High-speed rail Wi-Fi is more popular now.

In the digital age, passengers have a great demand for high-speed rail access to the Internet. The signal coverage of public network operators is mixed, and the National Railway Group is also studying and deploying high-speed rail Wi-Fi to look for business opportunities. China Railway Group has also jointly established Geely and Tencent to promote the construction of high-speed rail Wi-Fi platform.

█, what is GSM-R? When it comes to 5G-R, it is certain to mention its predecessor, GSM-R.

As the name implies, GSM-R is a wireless communication system specially designed for the railway industry based on GSM technology.

In the early 1990s, when the GSM standard was established, Siemens began to brew and draft the GSM-R technical standard.

Later, the International Union of Railways (UIC,International Union of Railways) and the European Telecommunication Standards Institute (ETSI) jointly launched the final version of the GSM-R standard for the European railway system.

Compared with the traditional GSM standard, GSM-R mainly adds the related functions of railway special dispatching communication.

At present, the railway private network communication technology mainly used in our country includes GSM-R.

After the founding of the people's Republic of China, the railway system began to use train wireless dispatching phones and station wireless phones, using electronic tube equipment with working frequencies of 2MHz and 40MHz.

In the 1970s, we gradually began to switch to transistor devices in the 150MHz and 450MHz bands.

Later, the special radio frequency for the railway was set in the 450MHz band for intercom communication services such as train wireless dispatching communications, station and yard plane shunting, passenger and freight transport, and maintenance.

After the emergence of GSM-R in Europe in the 1990s, our country also studied and introduced it in time.

In 2004, in order to meet the needs of the development of CTCS-3-class train operation control system in high-speed railway, the Ministry of Railways formally adopted GSM-R standard as the new generation railway wireless communication national standard.

It is worth mentioning that China 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, using the 900MHz "prime band" ("wanted" from China Mobile), uplink 885-889MHz, downlink 930-934MHz 2 × 4MHz bandwidth, the maximum coverage distance can reach 6~9km.

Since 2008, almost all of the new (rebuilt) railways have adopted GSM-R as a dedicated wireless communication system.

Since 2012, the Ministry of Industry and Information Technology has stopped approving the analog wireless train dispatching system based on the 450MHz band. Because the anti-interference ability of the system is poor, the voice quality is low and the service is limited.

After that, important domestic railway lines, such as Xiamen-Shenzhen high-speed railway, Guangzhou-Shenzhen-Hong Kong high-speed railway, Qinghai-Tibet line, Daqin line, Jiaoji line, Wuhan-Guangzhou line, Zhengxi line, Shijiazhuang-Taiyuan line, Heining line, Hewu line, Beijing-Tianjin intercity line and Beijing-Shanghai high-speed railway line, all adopted GSM-R technology and realized digital and network upgrades.

By the end of 2021, the mileage of domestic GSM-R lines (including construction under construction) has reached 89000 km, with more than 350000 users.

Why do you want to do 5G-R when █ has GSM-R? Of course, it's because 5G-R is more advanced.

Today, the GSM-R standard based on 2G technology has been unable to meet the needs of the development of modern railway.

GSM-R is mainly voice service, and the frequency efficiency is low. The narrowband data bandwidth is only more than 100KB at most, so it is difficult to bear the large bandwidth demand of railway digital transformation.

A few years ago, China proposed to build a special railway wireless network based on LTE-R (4G), but after a period of testing, there was no large-scale commercial use.

Now it seems that the country is going to be in place in one step, skip LTE-R and go directly to 5G-R.

Based on 5G technology, 5G-R has the characteristics of ultra-large bandwidth, ultra-low delay and massive connection, and the network performance almost crushes GSM-R.

In terms of network capacity, 5G-R supports network slicing, edge computing and other services, which can provide quality of service guarantee for key railway services.

5G-R has also made great improvements in terms of security and reliability. This is very important for the safety of railway transport.

What's the difference between █ 5G-R and public network 5G? The working principle of 5G-R and public network 5G is basically the same. In particular, there is basically no difference in the wireless empty part.

The main differences of 5G-R are mainly reflected in business types, networking methods and performance requirements.

The type of business has been introduced before, and the railway has many special services of its own.

In terms of networking mode, 5G-R is deployed along the railway line, and the wireless access network is more chained.

On the side of the core network, it is necessary to match the mode of production and organization of the railway department and carry out appropriate network transformation.

The following figure is an illustration of a networking architecture of 5G-R:

Reference source: research on the system architecture and networking technology of railway 5G private network. In addition to the control plane network elements (AMF, SMF, UDM, etc.) and media plane network elements (UPF) contained in the traditional public network 5G, we can see some 5G-R special equipment, such as railway broadband trunking communication (MCX,Mission Critical X-Service). Key business) equipment, 5G intelligent network (5G-IN), 5G equipment identification register (5G-EIR), etc.

This MCX device, through which 5G-R can be interconnected with other communication systems, provides wired and wireless integrated scheduling communication services. It can also realize interconnection with the railway fixed telephone network to meet the needs of official communications.

Who is responsible for setting the █ 5G-R standard? 5G-R is based on 5G (IMT-2020), and 5G's standard setting is of course the responsibility of the famous standardization organization, 3GPP (third Generation partner Project).

At present, 5G has gone through the 3GPP R15-R17 stage. R18 is also about to freeze, and it will usher in the era of 5G-Advanced (5.5G).

Another international organization specializing in the study of railway communication standards is the UIC (International Union of Railways), which is involved in the formulation of GSM-R standards.

In 2012, UIC joined ETSI and 3GPP to launch the FRMCS (Future Railway Mobile Communication System, Future Railway Mobile Communication system) project. In 2016, UIC brought 5G into the scope of FRMCS research.

The goal of UIC is to launch the first version of FRMCS based on R17 in 2025, which will be used in railway pilot projects.

A lot of work has been done in the 5G-R standard system in China.

National Railway Group established NGCR (next Generation Radio Communications working Group) in 2015, with five sub-working groups on spectrum, standards, services, industry and testing.

In August 2020, the National Railway Group issued the outline of the Railway Planning for the Traffic Power in the New era, which clearly put forward:

"strengthen the construction and application of new infrastructure facilities such as 5G communication network, big data, block chain and Internet of things, enrich application scenes, extend the industrial chain, and comprehensively promote the construction of a new generation of railway mobile communication network. Build a ubiquitous, safe and efficient modern railway information infrastructure system.

Later, the National Railway Group successively issued the implementation opinions of the National Railway Group on accelerating the Development of Railway Application of 5G Technology, the three-year Action Plan for tackling key problems in the Application of Railway 5G Technology, and actively deployed 5G-R applications, as well as technical research.

According to the preliminary forecast of the industry, the parallel development of 5G-R and GSM-R will be realized in 2025. GSM-R will be replaced by 5G-R in 2030. The research of 5G-R based on 900MHz band is also under way.

█, what is the significance of the frequency of this approval test? Determining the radio operating frequency is an important prerequisite for the development of a wireless communication technology.

Once the spectrum is determined, the industry will have a goal for technical research, and they will have more confidence in this technology. This is conducive to the rapid maturity of the industrial chain, but also conducive to stimulating independent innovation in science and technology.

With the test frequency, the National Railway Group can further promote relevant scientific research projects and field tests to verify the feasibility of the 5G-R frequency scheme and the compatible coexistence with the related systems in the adjacent frequency band.

In terms of core network, carrier network and access network equipment, and in terms of terminals and modules, related work can also make great strides forward.

█ concludes that high-speed rail is our national business card, and so is 5G.

The timely approval of the test spectrum by the Ministry of Industry and Information Technology shows our country's determination to vigorously promote the construction of railway digitization.

Combined with the news that the Ministry of Industry and Information Technology issued the first enterprise 5G special network frequency to Comac last year, we can also see that the state's support for private network communications is increasing.

Private network is an important base to support the digital transformation of enterprises. The granting of exclusive spectrum is extremely beneficial to the development of the private network.

In the future, whether the country will allocate more frequency resources to private network communications, so as to promote the overall promotion of digital transformation, let us wait and see!

All right, that's all for today's article. Thank you for your patience!

-- The End--

Reference:

1. Discussion on key issues of 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 special network system architecture and networking technology, Zhou Yuhui, China Railway

4. Railway 5G special network: what is it? How to build it? Hu Yuan, Communications Industry Daily

5. a brief analysis of the next generation railway mobile communication system, big cat, Zhihu

6. The Ministry of Industry and Information Technology approved the test frequency of the new generation railway mobile communication system, and WeChat WeChat

7. Baidu encyclopedia, Wikipedia

This article comes from the official account of Wechat: fresh Jujube classroom (ID:xzclasscom), author: Xiaozaojun

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