"Starlight Doesn't Ask Passers-by: The Story of Huawei's Global Technical Service People"
Tian Tao, editor-in-chief
Published by Life, Reading, and New Knowledge Triptych Bookstore
Until now, Zhang Yong, an engineer in charge of wireless network maintenance and optimization in the Lhasa office, often remembers that day a year ago.
On April 15, 2020, standing at the base camp of Mount Everest (hereinafter referred to as "Everest") at an altitude of 5300 meters, the signal of the 5G base station was turned on, and he could not wait to take out the test equipment to measure the speed.
Downlink 1.66Gbps (gigabits per second), uplink 215Mbps (megabits per second)!
Far exceeded expectations.
The wind was very big and it hurt a little to blow on the face, but looking at the beating numbers on the device, Zhang Yong, who had already opened through an unknown number of base stations, was so excited that he picked up his mobile phone for the first time to take a picture of The Everest at that time.
It was all like a dream, he said. In October 2008, Zhang Yong joined Huawei, entered Tibet three times, and in 2013 remotely supported colleagues in Lhasa to open 4G on Mount Everest. At that time, he never imagined that one day he would be able to climb Mount Everest Base Camp and witness the moment when the 5G base station was opened.
All this has to start in March.
A sudden mission
"Want to open a 5G base station on Everest?"
"What? The signal should cover the summit of Mount Everest! ”
"To do live video backhaul, you need a lot of bandwidth, right?"
"Time is so tight, is it too difficult?"
……
On March 3, 2020, lhasa, an ordinary working day, Zhang Yong and his colleagues came to China Mobile Tibet Company to conduct daily business exchanges with customers. Suddenly, Lao Li, the person in charge of the customer network optimization center, said: "In May, the China Everest Elevation Measurement Mountaineering Team will retest Mount Everest and carry out 5G live broadcasting, and our company will assist in supporting communication support..."
The mission came suddenly, the conference room exploded, and everyone began to discuss.
In 2007, China Mobile and Huawei opened a 2G site at 6500 meters of Everest, and a year later, the pictures of the Olympic flame on Mount Everest were transmitted to the world through the network; in 2013, China Mobile and Huawei once again opened a 4G network at the 5300-meter base camp of Everest.
But in 2020, seven years later, not only to open 5G on Mount Everest, but also to go up to the peak of the 5G signal to meet the measurement needs and live broadcast requirements, which is too difficult!
Although it is very difficult, Zhang Yong thought about it, Huawei's 5G technology is leading in the industry, and customers choose Huawei as the overall solution and main equipment provider of the project, "If we can't do it, then will the team do it?" ”
With such confidence, at 3 p.m. on March 12, Chen Ruiqun and Yuan Zhiyong, experts of the China Regional Department who were far away in Beijing, Wang Wenzheng, director of the delivery department of the mobile system department, and Li Zuozhou, product manager, Wang Bo, director of the delivery business department of the Lhasa office, Daniel Zhang and Zhang Yong of the network security and technology department, several people aligned the basic information of the project with the customer, and began to try to sort out the network construction plan around the business experience needs.
Where can I build a station to ensure that the signal reaches the peak? How is the equipment transported? How to ensure the supply of electricity? How do I lay a fiber optic cable? How do I expand the transmission bandwidth? How to ensure operations? These questions are placed before them one by one.
Changed nearly ten versions of the site scheme
On Mount Everest on 5G, the first thing to do is the site planning scheme.
From the Everest Base Camp at 5300 meters above sea level to the camps along the way, there are mainly transition camps at 5800 meters above sea level, forward camps at 6500 meters, North Pass camps at 7028 meters, camps at 7790 meters, assault camps at 8300 meters, and then climb the last three steps to reach the summit.
Team analysis, from the altitude of 5300 meters above sea level Everest base camp to the peak of the straight line distance is 20 kilometers, theoretically the base station can transmit 5G signals to the peak, but it is very difficult to return the signal at the peak; and the transition camp at 5800 meters above sea level has a mountain barrier, can not see the peak, from this position to the summit transmission signal is difficult to receive; the forward camp at an altitude of 6500 meters is 5.6 kilometers away from the summit, and can see the peak, theoretically, can achieve mutual communication between 5G base stations and terminals.
After discussion, considering the stability of the signal and the bandwidth required for live video broadcasting, we believe that the best way is to adopt a ladder altitude network construction scheme: from the base camp of Mount Everest to the summit of the road, there are mainly three camps at an altitude of 5300 meters, 5800 meters and 6500 meters above sea level, and 5 5G base stations are deployed in the form of independent networking + non-independent networking to achieve 5G signal coverage along Mount Everest, and finally through the 5G base station at an altitude of 6500 meters, so that the signal is covered to the top of Mount Everest; Gigabit broadband and leased line access are available.
With the initial site planning, the Tibet office delivery team also immediately invited our site planning experts and network performance experts to remotely participate in the coverage simulation and link budget review of the Everest site. In the past month, the team has taken the test equipment in a mountainous area in the north of Lhasa, conducted technical verification, and sent a signal from 5.6 kilometers away to the oblique upper to ensure that the equipment can run smoothly in extreme environments such as high cold, low pressure and low temperature, and high winds. After more than ten trials, it was finally tested to meet the signal coverage and business needs along the way and at the summit of Mount Everest, which also gave the team a temporary bottom in mind.
Next up is the question of how to build. The team calculated that the construction of base stations at these altitude points requires main equipment, transmission equipment, supporting materials and optical cables, as well as mountaineering equipment, etc., adding up to about 8 tons of materials.
The team constantly polished the site planning, improved the details of the construction plan, and also focused on solving a series of problems such as equipment transportation, power supply, optical cable laying, and transmission bandwidth expansion. In this way, after nearly ten versions were revised, the plan was finally formed.
At the same time, through communication with the National Elevation Survey team, Xinhua News Agency, China Central Radio and Television Corporation and other units, customers' needs for 5G service use are becoming clearer and clearer, and the team has also made a guidance plan for business use to ensure that voice and data traffic will not exceed the carrying capacity of the network during the use of the business.
Everest Expeditionary Force
Strive for foolproof preparation
It's late March, and the next step is the preparation for the construction of the base station. All matters, including avoiding unpredictable risks, should be considered and foolproof.
How to transport 8 tons of materials up the mountain? After entering the Everest base camp, there is no way to go up, the transport vehicle cannot drive, coupled with the ultra-high altitude, the helicopter can not airdrop materials, and if you want to transport the equipment to the two stations at an altitude of 5800 meters and 6500 meters, in addition to the shoulders of people, the common "car substitute" on the plateau - the yak team will also come in handy.
The team hired a team of local guides who specialized in helping climbers, who were not only experienced in mountaineering, but also yak teams, who were responsible for providing safety and security and material handling services for climbers.
But opening a site requires a professional engineer, who will build a site? At high altitudes, oxygen levels are only half or even lower than those of the plains, and with extreme cold, it is extremely difficult to walk even 100 meters. The customers and Huawei's technical engineers, mostly from the mainland, only a few are Tibetans, even if the physical fitness is good, but they have not climbed Mount Everest, how to ensure everyone's safety? Together with our customers and partners, we have set up a construction team and supervision team of nearly 200 people, and conducted systematic training at a top international mountaineering school in Shigatse, aiming to efficiently complete the construction task of the base station under the premise of ensuring the safety of personnel. The mountaineering school selected more than a dozen young people with good physical fitness for physical, emergency and psychological training, and it was proved that they played an extremely important role in the opening of the station at an altitude of 5800 meters and 6500 meters.
In early April, China Mobile Tibet and Huawei jointly issued a detailed implementation plan. The scheme stipulates the time nodes for the 5G opening of three sites. The progress is moving forward little by little, Zhang Yong is both excited and nervous, excited that he can participate in such a major project is very honorable, nervous is whether the peak can successfully carry out business, this is the real test of Huawei's delivery team, because there is no professional and technical personnel can test and verify the 5G network at such a high altitude.
Yak teams transporting supplies and equipment
At 5300 meters above sea level, here we come!
On April 13, Mount Everest ushered in the most lively day of 2020.
8 tons of materials, a construction team of hundreds of people, and dozens of yaks arrived at the Everest base camp, and Zhang Yong was also in the accompanying team. The morning base camp is particularly sacred and solemn in the chanting of the Lama Sacrifice Mountain, and with the end of the chanting, the Everest 5G project has begun.
Zhang Yong has been working in Tibet intermittently for several years, and this is the first time he has had such close contact with Everest. In the eyes of ordinary people, Mount Everest is quite mysterious, along the way hares, snow chickens, rock sheep can be seen everywhere, rolling snow mountains, seems to be within reach of the sky, he feels that only by being here, can he truly appreciate the majesty of Mount Everest. He couldn't wait to take out his mobile phone and take a wild shot, and when he came back, his hands were frozen, the cold wind blew his ears and face began to lose consciousness, the lack of oxygen made him short of breath, and his eyes narrowed into a slit because of overexposure. This is the other side of the beautiful Everest, with cold winds whistling, extreme cold and lack of oxygen, and strong altitude sickness.
But even if the body is not feeling well, the progress of the project cannot be delayed. Carrying the equipment, pulling the cable, and soon, everyone began to get busy at an altitude of 5300 meters. Installation, commissioning, and methodical progress as planned.
Due to the limited accommodation space in the base camp, it can only accommodate a few front-line construction personnel, and after each day's work, most of the personnel have to be withdrawn to the hotel in Tashi Zongxiang, a 50-minute drive away, at the foot of Mount Everest. During the day, eat instant noodles, biscuits and fast food at the base camp, and return to the hotel in the evening, it is basically eight or nine o'clock in the evening, and everyone will go to the Sichuan restaurant on the side of the road with the customer's engineer to eat a beautiful meal, which is the most relaxing time of the day.
It is said that it is a hotel, in fact, it is a stone house in a triple room with a large bunk, eating and drinking, but no one dares to take off his clothes when sleeping. Zhang Yong often sat up suddenly when he slept at night, because of the lack of oxygen, the severe feeling of suffocation seemed to tighten his neck, and the pressure was breathless, and he had to force himself to stay awake.
A few days after working like this, on April 15, Huawei successfully completed the opening of the 5G site in the base camp.
Downside 1.66Gbps, uplink 215Mbps!
This line of data is like a beating note, telling the world: the first 5G base station was opened at an altitude of 5300 meters above Sea Level, and the first difficulty was overcome! Zhang Yong looked at the busy climbers in the base camp and the silent summit of Mount Everest in the distance, and the corners of his eyes couldn't help but be a little moist, and for a while he didn't know who to share his joy with.
Later, he took out his mobile phone and dialed the WeChat video to his wife and children in Chengdu. Before that, he didn't tell them he came to Everest, and he didn't tell them that he hadn't showered, washed his hair and changed clothes for almost a week, and he had a headache and couldn't sleep for days and nights...
The 5G signal covers Everest Base Camp at an altitude of 5300 meters
Set sail and advance 5800 meters above sea level!
On April 16, nine young men who had undergone two weeks of special training at the Shigatse Mountaineering School — engineering supervisors Li Kui, Luo Sang, and the customer's engineer La Pingren, as well as the team's guide and the Everest "Expeditionary Force" of more than 40 yaks, predetermined towards the site at an altitude of 5,800 and 6,500 meters. Zhang Yong and others stayed at the base camp to support the follow-up opening work.
The team set off in two groups, with the engineering supervisor and engineer carrying lighter equipment up the hill first, while the yak team set off two hours late with 8 tons of supplies.
At about 11 p.m., the vanguard of the Expeditionary Force finally broke through the snow and wind to reach the transitional camp at an altitude of 5,800 meters. The stars were exceptionally bright, and everyone was exhausted, resting on the gravel slopes, and in the empty valley there was only the gasp of everyone. Everyone was waiting for the yak team to arrive, but the left and right did not wait for the yak team's bells. Without supplies, everyone had to squeeze in the kitchen of the only tent, the camp. More than 30 degrees below zero, cold, sleepy, tired, in order to keep warm, everyone sat next to each other. Li Kui later recalled: "It was still very cold to squeeze together, basically everyone didn't sleep all night, just look at me, I look at you to survive." ”
It wasn't until noon the next day that the yaks were "late" to the scene. The rush march of the night made the yaks extremely hard. A yak can generally only carry 40 kilograms of supplies, while the communication fiber laid is generally 2,000 meters long and weighs 500 kilograms. The optical fiber cannot be truncated, but can only be divided into rolls and transported to it. Transporting fiber optics isn't the most difficult, it's transporting generators – a yak accidentally dropped the generator on the snow.
Everyone hurried to load the goods and worked together to separate the goods from the transition camp and the forward battalion, and completed the first operation. The wind on the mountain was bone-chilling, and the snow was falling heavily, and it wasn't until the early morning of April 18 that the wind subsided a little, and the snowflakes stopped falling, and the construction team began to work: connecting the fiber optic cables, erecting the poles, debugging the engine, climbing the poles, installing the equipment, and debugging the base station. A squad of four men, consisting of Li Kui, Luo Sang, Danzin Sanjie and Danzeng Quzhu, marched towards the advancing camp at an altitude of 6500 meters.
Due to the extreme cold, the installation of the base station, which normally took only an hour or two, became very difficult. As far as screws are concerned, it is not convenient to wear thick thermal gloves, and sometimes it can only be installed with bare hands. Some devices are attached to the ice formed by snowflakes and water vapor, and as soon as the hand touches the device, it sticks to it, and the skin on the hand will be torn if it is not careful... At a few tens of degrees below zero, the hands of the installation engineers were shaking in the cold wind. After four or five hours of work, the base station installation was finally completed.
After the installation of the base station, it is also necessary to debug. Zhang Yong, who is guarding the base camp of Mount Everest, can only use the "cloud" testing method and entrust the customer's engineer Laping to help test on the spot.
Test the downstream peak rate is 1.55Gbps, and the upstream peak rate is 170Mbps!
At 15:30 on April 19, when Zhang Yong heard Laping excitedly say "opened" from the walkie-talkie, he put down a big stone again: complete another one!
On the same day, Wang Bo, Daniel Zhang and The customer Lao Li and others also arrived at the Base Camp of Mount Everest, and began to coordinate with Zhang Yong and others the material handling and opening of the base station construction at an altitude of 6500 meters, and they also brought Zhang Yong cold clothing and support materials.
However, the construction of two 5G base stations at an altitude of 6500 meters is the most difficult and heart-wrenching.
Materials and equipment arrived at the Everest Base Camp at an altitude of 5,300 meters
Three twists and turns: 5G at an altitude of 6500 meters opens
The transition camp at an altitude of 5800 meters to the 6500 meters forward camp, the distance is nearly 9 kilometers, all the way is ice Tallinn, there is a section of the trip is almost covered by glaciers, there are fissures between glaciers, walk with extra care, a little careless will fall down. High-intensity walking caused everyone's physical strength to drop sharply, "all the internal organs seemed to be about to collapse", everyone joked afterwards, but at that time, they had to hold hands and move forward cautiously.
After arriving at the camp at an altitude of 6500 meters, after a short rest, everyone began to get busy. Li Kui, who grew up in Guizhou, has only been in Tibet for a year, and although he has passed the training of mountaineering schools, he also has severe altitude sickness, and his headache is so bad that he can't even turn back to Li Suo, so he can only ask the guide and several Tibetan colleagues to help install it. In the cold wind, they worked together to erect the pole, twisted every screw with difficulty, and pulled every antenna with all their might. The most difficult thing is the fixation of the base station, the mountain wind is fierce, and the base station signal transmission source angle is slightly off, which will cause the peak to be unable to cover the 5G signal. Everyone adjusted over and over again, and finally completed the infrastructure construction from site selection to base station on April 20.
The team's initial plan was to complete the opening of the base station at an altitude of 6,500 meters on April 25. Just as everyone was getting ready to start debugging with hope, a bad news discouraged everyone.
Because of the high altitude, the generator was unstable in extreme cold conditions, the equipment could not operate normally, and it soon went on strike, and everyone tried their best to restart it. After returning to the camp tent, the mountaineering team staff asked Li Kui with concern when 5G would be turned on and when the Internet would be available. As a post-90s, Li Kui originally felt that the Internet was a particularly common thing, but he did not expect that it would become so difficult on Everest, but it was precisely because of the difficulty that he realized the value of existence as a communicator.
Li Kui fed the news back to the base camp, and after repeated discussions, Wang Bo, Daniel Zhang, Zhang Yong and customers finally decided to urgently purchase four generators from Xigaze to send to the site at an altitude of 6500 meters, and each two generators supported a base station.
The generator came up, everyone was ready to test, but they didn't expect new problems to come. Heavy snow fell on Mount Everest, and engineers were forced to withdraw from 6500 meters above sea level and bide their time.
For several days, the weather was still bad, often in the morning it was still windy and sunny, and in the afternoon it was a biting cold wind, accompanied by heavy snow. The only thing anyone can do is wait.
It wasn't until April 26, when the weather finally came, that the construction team once again charged at an altitude of 6,500 meters! However, just when all the installations were completed and the commissioning was ready to be opened, an accident occurred: the optical cable that had already passed the test verification had a problem, and the data could not be successfully returned. The 5G base station, which was scheduled to open on the 28th, had to be delayed, and the staff at 5800 meters above sea level and 6500 meters had to start troubleshooting in stages.
At this time, it snowed heavily on Mount Everest again, which brought great difficulties to the investigation work. The low temperature caused the diesel generator to be unable to work, unable to melt fiber, and the staff had to move the equipment to the tent near the stove; wearing gloves was not convenient to operate, so they took off their gloves and insisted on operating in an environment of minus ten degrees. Load-bearing inspection and maintenance, strong winds raged, and the maintenance team was repeatedly forced to stop and hide behind large rocks to rest.
After these difficult times, success is not far away. At 15:00 on April 30, as the last fiber optic cable joint was completed, all the construction personnel turned their expectant eyes to the flattening responsible for parameter adjustment, and everyone clenched their fists and looked forward to the moment when the base station was opened.
"Pass, pass! Downlink 1.31Gbps, uplink 120Mbps! ”
At 15:55, Lapin announced this exciting news to the team members and made a live video call with the base camp.
Receiving the footage transmitted from the video, the base camp site command immediately erupted in enthusiastic cheers. Everyone clapped their hands in celebration and rushed to the front of the video to greet Lapin. Although Laping looked tired, but his smile was bright, even the video working group of the Central Radio and Television Corporation and xinhua news agency joined the celebrating crowd, taking photos and blessing videos with Huawei and China Mobile customers to record this historic moment. This means that the mountaineering route from the base camp to the summit has been fully covered by 4G/5G mobile networks.
For many young people now, the Internet seems to be a natural and easy thing, but I am afraid that only the communicator can understand that every byte must pass through countless base stations, through long optical cables, across mountains, rivers and seas, and carefully walk through the underground of the city's cobweb-like streets and alleys, in order to reach the eyes, into real visible text and images, and the transmission of signals is invisible.
For every participant in the project, after nearly two months of running day and night, it is a great honor to witness 5G "shining" on the world's highest peak for the first time! Pride overflows in the heart, China Mobile, Huawei people, did it!
Customer engineer Lapin successfully made the first video call at an altitude of 6500 meters
Attack on the summit
The opening of the 5G base station only means that the 5G network covers Mount Everest, and the greater test for the Huawei team is how to ensure the smooth live broadcast of the 5G network video of the news organization, as well as the 5G telephone demonstration of the Chinese mountaineering team at the summit, and the backhaul of the Elevation measurement data of Mount Everest through the network.
In late April, China Mobile dispatched three additional network performance experts, Including Li Zuozhou of Huawei's Mobile Systems Department and Zhao Pengfei, a colleague of the Machine Vision Project Team, who also came to the base camp, and began to communicate closely with the on-site technicians of the mountaineering team, the Central Radio and Television Corporation, xinhua news agency and other units, sorted out their business needs, helped to test mobile phone terminals, 5G backpacks and other equipment, and did a good job in advance of business testing and service quality strategy guarantee of card numbers.
On May 6, the mountaineering team set off from the base camp, planning to reach the summit for the first time on the afternoon of May 10. On May 9, as the temperature approached minus 25 degrees, the computer used for debugging could not be turned on and charged. After a night of holding the computer in the sleeping bag, the partner finally turned on the computer at 9 a.m. on May 10, and completed the opening of the camera on the world's highest peak before the first summit of the mountaineering team.
However, due to bad weather, the climbing team has not been able to reach the summit as planned. Until May 26, the day before the third planned summit, the everest base camp suddenly fell heavy snow, all the team members could not help but pinch a handful of sweat, if this time missed the window period, the summit will become more difficult.
By 8 p.m., the snow had reached the ankles. The team and the customer checked over and over again to confirm the live broadcast and network strategy, repeatedly simulating the scene of the summit guarantee, Chen Cheng, a girl in charge of 5G slow live broadcasting at China Mobile Tibet Company, proposed: "Everyone has worked so hard for so long, or let's have the highest K song competition." Relax and wish you success tomorrow! "Good!" Everyone spoke in unison.
"All these years, a person, the wind has passed, the rain has gone, there have been tears, there have been faults, and I remember what I insisted on... Friends walk together for a lifetime..." As Zhou Huajian's "Friends" song sounded, colleagues at the scene temporarily put down the work at hand, stood up, picked up water cups and oxygen cylinders as microphones, and sang loudly, and colleagues who were guaranteed at an altitude of 5800 meters and 6500 meters also joined the singing through 5G video calls, cheering for themselves, and the atmosphere in the dull tent gradually warmed up.
In the more than a month on Mount Everest, we climbed the snowy mountains together, inspected the base stations together, inhaled oxygen together, nibbled on instant noodles together, and quarreled together to solve problems, and everyone has long become comrades-in-arms who share weal and woe and fight side by side.
At 4 a.m. on May 27, the climbers began climbing to the summit from the camp at an altitude of 8,300 meters. Everyone also accompanied Wang Yongfeng, the leader of the mountaineering team, to sit around the fire, waiting for news from the team members.
Time passed by minute by minute, and there was silence in the walkie-talkie, only the occasional "stinging" sound when the signal was interfered with. By 8:05 a.m., the climbers reported for the first time that they had reached the second level. At this time, the Central Radio and Television Corporation is broadcasting live through the video stream of Huawei cameras, and the audience can see the live broadcast image through the zoomed-in lens.
The on-site personnel surrounded the tents of the headquarters of the base camp. At 10:30, by zooming in on the camera's focal length, it was already possible to faintly see two climbers trying to reach the summit, and everyone's heart was raised to the throat eye.
At 11:03, a familiar voice sounded on the intercom: "Eight team members have all reached the top safely!" Hearing the news, everyone cheered enthusiastically, followed by splashes of champagne.
However, after reaching the top, the work is not over, because the picture of the 5G live broadcast has not yet come out.
Later, I learned that because the number of people who could stand at the summit was limited, the good position was left to the survey team members, and the camera teacher of the sacred mountain in Tibet, Ngawang Zhandui, had to stand at the lower position, but this would face the serious obstruction of the signal by the mountain. After Li Zuozhou communicated with Teacher Awang, Teacher Awang moved to a slightly better position, and the other members continuously monitored the log information in the background and made network optimization adjustments according to the information feedback when connecting.
Every second was as long as a century, and the temperature inside the tent was zero degrees that day, but Li Zuozhou could clearly feel the beads of sweat on his forehead. Finally, the voice of Teacher Awang came from the device: "Now that there is a 5G signal, I have started to broadcast live, please be ready to receive it." After about 10 seconds of verification, a clear and stable peak return screen appeared on the news app of the Central Radio and Television Corporation, and Li Zuozhou was so excited that he could not speak for a while, and the teachers of the Central Radio and Television Station hugged and cried.
This is the first time that human beings have reached the summit of Mount Everest live through the 5G network, allowing countless netizens to "see" the world's highest peak clearly and smoothly in an unprecedented angle and way. Everyone was shocked by the beauty of Mount Everest, and even more shocked by such a "display of beauty"!
2020 marks the 60th anniversary of the first successful ascent of Everest from the north slope and the 45th anniversary of China's first accurate determination and publication of everest elevation. Huawei helped China Mobile, a customer, to open 5G, which helps to open the measurement signal in real time, provides communication support for the elevation measurement of Mount Everest, and also verifies the possibility of 5G signal coverage in ultra-high altitude areas, the stability of 5G signals under sustained high wind speeds, and the possibility of transmitting video signals through simple equipment in areas with harsh conditions. As Mr. Ren said in an interview: "The ideal of Huawei's value system is to serve mankind. ”
Some people have asked, what is the significance of opening 5G at the top of Mount Everest?
Much later, the team members returned to Lhasa and sat together and reminisced about what they had experienced on Everest. Wang Bo's words speak to everyone's voice: "I think it is a summit of Science and Technology, and it tells the world where the strength of Huawei's 5G and China's 5G comes from!" ”
(This article is excerpted from "5G Road on top of the world" in "Starlight Doesn't Ask Passers-by")
Author: Xiao Xiaofeng
Editor: Zhou Yiqian