A few days ago, Shanghai Telecom and ZTE launched the world’s first 5G maglev high-speed line commercial network test. In the fast-moving maglev train, the 5G performance was stable, indicating that the 5G network can provide ideal broadband communication services for maglev trains.
“98kmh, 198kmh…390kmh, 431kmh”, on the Display screen in the maglev car, the numbers are constantly beating, passengers feel the speed and passion it brings, and take pictures one after another.
“102Mbps, 230Mbps…371Mbps, 405Mbps”, in the high-speed maglev train, the technicians stared at the test terminal screen, watching the 5G speed soaring.
For the first time, the world’s fastest land-based vehicles and the fastest mobile communication technologies have converged.
With the further improvement of the maglev 5G network coverage, it will provide passengers with stable high-speed data access services during the fast journey in the near future, and also set a model for the provision of 5G services for various high-speed railways and maglev lines in the future. foundation.
The intersection of the fastest car speed and the fastest mobile internet speed
It connects Longyang Road Station of Line 2 and Shanghai Pudong International Airport in series. It only takes 8 minutes to reach the 30-kilometer distance. Since its opening in 2002, maglev has become a symbol of Shanghai’s speed and has been certified by Guinness as “the world’s most fast land transport”.
What will be the experience of the intersection of 5G and maglev?
On the morning of December 9, the reporter and ZTE technicians came to Longyang Road together to experience the 5G speed on the maglev train.
The starting speed of the maglev train and the acceleration on the way are extremely fast. On the display screen in the carriage, the beating frequency of the second digits obviously cannot keep up with the increase in speed. When the speed reaches 300 kilometers, the centrifugal force can still be felt when turning, and the carriage will also have obvious inclination.
In the high-speed train, technicians held mobile phones and computers to test the speed and stability of 5G. On the computer screen, the test software monitors various data of the mobile phone’s 5G Internet access in real time: network speed, location, signaling, signal strength…
“The results are ok, and the performance is stable.” At this time, the magnetic levitation speed is getting faster and faster, and the interior of the car is shaking slightly, the technician said while maintaining the stability of the body. The reporter saw on the computer screen that the 5G rate reached 405Mbps.
What’s even more “amazing” is that the technicians’ on-site fixed-point test results showed that the maximum 5G peak rate reached 959Mbps, and the average rate reached an astonishing 857Mbps.
“With the continuous improvement and continuous optimization of network construction, the peak rate can reach 1Gbps. It is worth noting that we use the 3.5GHz high frequency band, which is more challenging than the low frequency band. Under the same networking conditions, the low frequency band It has more advantages. 3.5G is the mainstream frequency band of 5G in the world, and we have a wide range of demonstration effects on the performance verification of high-speed linear coverage in this frequency band.” The technician added.
Pass three levels!
Solve the problem of “fast vehicle speed, thick vehicle body, and frequent switching”
Providing high-quality network coverage for high-speed trains is a common problem faced by operators and equipment manufacturers around the world, not to mention providing the most advanced 5G network services for “the fastest land vehicle in the world” – maglev trains , the situation is more complicated.
After many discussions and continuous experiments, ZTE and Shanghai Telecom technicians passed the three barriers of “fast vehicle speed, thick vehicle body, and switching frequency” to solve the Doppler frequency shift caused by the high-speed movement of maglev trains, and the metal vehicle body of the train. In addition, the larger thickness brings about problems such as substantial signal attenuation and frequent handover between the user terminal and the base station.
Compensate for “Doppler” shift “speaking on the same channel”
In daily life, we often hear the phrase “I’m not on the same channel as you”, which describes the difficulty of communication between the two sides. This is especially true for mobile communications. Signal transmission and reception between terminals and base stations need to be on the same frequency for normal communication.
However, due to the existence of the Doppler effect, the faster the moving speed, the greater the deviation of the sending and receiving frequency between the terminal and the base station. Therefore, in the high-speed magnetic levitation, it is not necessary to keep the terminal and the base station talking on the “same channel”. easy.
Through the patented frequency offset compensation algorithm, ZTE can detect and compensate the Doppler frequency offset in the high-speed motion of the terminal, so that the terminal and the base station can send and receive signals on the same frequency, thereby greatly improving the wireless link performance.
“Amplifier” solves the problem of signal attenuation
When 5G coverage of maglev, the second problem encountered is that the train has a thick metal body, which will produce great signal attenuation.
In response to this problem, technicians use a high-gain antenna to solve it, which is like a loudspeaker, amplifying the sound outside, so that people in the room can also hear it. “There are still many challenges, such as which antenna should we choose, how much gain we need, what the angle of the antenna should be, etc. It requires accurate calculation and comprehensive judgment, and requires accurate link budget.”
Base station “merging” greatly reduces the frequency of signal switching
A base station has a certain coverage area, and there will be overlapping coverage areas between two base stations.
When the user is moving at a low speed, there is enough time to complete the handover in the overlapping coverage area of the two base stations, and the mobile phone can switch from one base station cell to another base station cell calmly, so as to keep the communication uninterrupted.
However, in the state of high-speed movement, the time for the mobile phone to pass through the overlapping coverage area between the two base stations will be very short. When the time required for handover cannot be met, the handover will fail and the mobile phone will be dropped.
In order to solve this problem, technicians adopted the method of “merging base stations” to “turn” multiple base stations into one base station.
“Physically, these base station cells are independent, but through background parameter settings, these base stations are logically turned into a cell with a larger coverage.” The technician introduced.
In this way, the number of cell handovers can be greatly reduced, and the overlapping coverage between the two cells can be increased, leaving sufficient time for the mobile phone to smoothly switch to the next cell, thereby solving the problem of frequent signal switching and ensuring user experience.
To the future!
Pushing 5G towards high-speed rail
At present, high-speed rail transit has entered a period of rapid development, and the mileage of high-speed rail in the world has exceeded 40,000 kilometers. In China, high-speed rail passenger traffic reached 2.03 billion in 2018, more than three times that of civil aviation.
When people travel on high-speed rail, there is a general demand for high-speed Internet access. A high-quality broadband network can not only bring a better experience to passengers, but also enhance the brand competitiveness of operators.
The Shanghai Maglev train is currently the first and only commercial operation line of maglev trains in the world. The maximum speed is the highest among the high-speed trains in commercial operation in the world.
Moreover, the 5G network solution for the maglev line can provide a complete set of network equipment for high-speed train broadband communication, and the base station series products can support the global mainstream 5G frequency band, which means that the solution can be extended to various high-speed railways and maglev line, with huge market potential.