It is reported that at 10:30 on May 24, Beijing time, the Falcon 9 rocket of Musk's SpaceX (American Space Exploration Technology Company) launched 60 Starlink satellites, which was ambitious.
The 2015 plan is huge, with a total of nearly 12000 satellites to be launched by 2025. Some media believe that the plan says the United States will build a next-generation broadband network in space, bypassing 5G and upgrading directly to 6G, according to which it is believed that the United States will build a next-generation broadband network in space, bypassing 5G and upgrading directly to 6G.
Well, this is a huge one.
Uncle Ku will come and have a chat today.
Article: Zhang Chi, popular author of Science, Ph.D. in Communications, pseudonym
Editor: Li Haoran looked at the think tank
Source: Watch Think Tank (Wechat Public Number)
Is it reliable to wrap up the world with tens of thousands of satellites?
At present, there are no more than 1700 satellites in orbit around the world to provide services.
Previously, Musk planned to launch 4,425 satellites, a frightening number that has now risen to 12,000.
We can't help but ask: wrap the world with tens of thousands of satellites, this.
At present, it seems unreliable.
Not to mention the enormous cost pressure required to launch the satellite and the heavy policy resistance it faces, not to mention the technical aspects alone.
First, the rate is not enough.
（依据； 按照） on the basis of
Even considering that the satellite uses phased array technology, the real service area is smaller than the coverage area, but its scope is astonishing.
Now, Beijing alone has built about 20,000 towers, each of which has more than one base station. Can such a satellite serve hundreds of areas as large as Beijing? Of course not enough.
Second, it's hard to connect.
A few days ago, there was a message on the Internet that someone said his mobile phone was connected to the Wi-Fi of Tintin A satellite in Musk.
It is said that its mobile phone is connected to the Wi-Fi of the TintinA satellite of Musk.
In a conversation with others, Musk said
Musk spoke to people on social media.
As a result, many people think that their smartphones will be able to access the satellite Wi-Fi in the future.
The idea is naive, because TintinA and meThe average smartphone they use is not as good as the frequency, and it is impossible for them to communicate directly.
Radio wave has a characteristic, the higher the frequency, the stronger the directivity of the wave, which is more conducive to concentrating energy to transmit signals to distant places.
Musk's Internet satellites use Ka and Ku bands, around 20 GHz.
Musk Internet satellites use Ka and Ku bands, and mobile phones cannot receive them.
The Wi-Fi bands used by our smartphones are 2.4 GHz and 5 GHz respectively, which are relatively omnidirectional and have more uniform signals in any direction around the router for our convenience. But Wi-Fi omnidirectional signal attenuation is very serious. It will attenuate quadratically with the change of distance. If air interference is added, it may be cubic attenuation.
Therefore, signals of 2.4 GHz and 5 GHz can't travel far by themselves, let alone be expected to be transmitted to satellites in space.
So, can our mobile phones receive signals from satellites?
As I said before,The signal frequency of the satellite is about 20 GHz. Our mobile phone has no receiver in this band at all, so it is impossible to receive it.
That is to say, it is impossible for the mobile phone to receive the signal of TintinA satellite, and the Wi-Fi signal of the mobile phone can not be transmitted to the satellite.
Therefore, the image of a successful satellite Wi-Fi connection on a regular mobile phone is deceptive unless you use a satellite phone.
The signal of current mobile phone can not be transmitted to satellite, and the equipment directly communicating with satellite can not have a shielding roof. Therefore, it is necessary to install transponder in outdoor open area, to communicate with satellite at about 20 GHz frequency, and to communicate with mobile phone at 2.4 GHz or 5 GHz.
However, the transponder has a problem with the satellite frequency, which completely coincides with the planned 28 GHz frequency of 5G in China. That is to say, in the future, the streets of our country will be densely covered with 28GHz 5G micro-base stations. If there are satellite transponders with the same frequency beside them, the signals of 5G micro-base stations will be seriously disturbed.
So many experts, don't they understand?
Many netizens will have doubts, Ku Shu said quite reasonable, but Google, Facebook, SpaceX have so many technical experts, do not they understand?
As a matter of fact, conventional scientific research projects need to undergo technical demonstration and repeated demonstration if there are any doubts, so as to ensure that the scientific principles of all technical links are established and there are enough reliable engineering methods.
However, in recent years, IT venture capital thinking has sprung up in the United States. Unlike conventional rigorous scientific research, its basic routine is storytelling, selling feelings, pulling investment, and publicizing a little achievements in order to attract more investment.
This kind of Internet routine hides a large number of technical barriers, so the chances of failure of these projects are very high, and investors'money will follow suit.
Since 2014, American technologists seem to have been working on the Internet for people all over the world.
Ku Shu cites a few examples:
: during the Spring Festival in 2014, a similar news detonated the Internet: an American family called
A lot of people are very excited.
In 2014, a company in the United States announced the launch of
In fact, however, the core technology of the plan is
This is the same as satellite radio and television. You can choose the right information, but you can't upload it.
If you can't upload information, you just can't interact with each other. QQ and Wechat can't be used, and Weibo can't, so you can only passively see and push information.
This is a broadcast service, not the Internet.
Interestingly, the company's promotional pictures convey the impression that they can communicate in both directions, such as the picture below, through which people pass through the wilderness.
In 2015, it was also reported that Google and SpaceX cooperated to launch 700 communication satellites to build a global wireless Internet.
700 listen to a lot, the key depends on how many people are served.
According to the world population of 1/10 of the 700 million users, the average service per satellite is 1 million users. According to the total rate of 1 Gbps per satellite, the average user can only get 1 kbps, which is far below the era of dial-up Internet, and can not be used at all.
Google has also launched plans to use hot air balloons to provide Wi-Fi.
It's not a new trick, it's just a plagiarism of military tethered balloons (balloons that use cables to tie them to ground winches and control their altitude in the atmosphere) and stratosphere airships.
Google uses hot air balloons to provide the Internet with the name
In July 2016, Zuckerberg followed suit and launched a plan to provide Internet services to people all over the world, using laser-emitting UAVs.
Launched by FaceBook
In fact, this kind of UAV has existed for a long time, just because it is mainly used for military purposes and is not known to the public. To that end, Facebook also acquired a British company that manufactures the drones.
In detail, there are many doubts about this UAV scheme:
One is that it's simply too difficult to provide signals with UAVs.
The signal coverage radius provided by UAV to the ground is about 100 kilometers, and its speed is about 100 kilometers per hour. The signal coverage area with a radius of 100 kilometers is moving at high speed. You have to follow the UAV at a speed of 100 kilometers per hour to keep on surfing the Internet.
Or arrange an unmanned aerial vehicle every 200 kilometers to fly in line. Obviously, this relay mode of work is very unreliable.
The second is to use
as mentioned in the report
It is indeed feasible for satellites to communicate with each other through lasers, which is called
In this way, atmospheric disturbance ten thousand meters above the ground is a serious problem.
Laser also has a strong directivity.
If you look at the wall with a laser pen, you will find that if you look at the wall 10 meters away, even if the wrist shakes slightly, the spot on the wall will jump far; if you look at the wall 20 meters away, the spot will jump farther.
Laser has good directivity (graph source network)
The UAV in flight wobbles a lot, thousands of meters from the ground. So, how big is the scale of the laser pulsating back and forth on the ground?
The ground station must continuously and accurately adjust the angle of the laser emitter to keep up with the UAV in its changing position when transmitting laser to the UAV in the aircraft. This is not generally difficult, and commercial applications may be difficult to succeed.
From the above, we can see that whether satellites, hot balloons or UAVs, their propaganda ideas are high enough location, large coverage, and many users. They often play the emotional card of providing freedom of information for the poor, and then give public funding links.
However, due to the limited total rate resources, the average rate resources of users will be extremely thin, which they never mention.
If we want everyone to go online, we have to learn from China.
In theory, the bandwidth resource of a site is basically fixed, and the more users it serves, the less rate a single user will share.
So, how can everyone get online at high speed?
The correct way to operate is to narrow the scope of the site, allocate site resources to fewer people, and everyone will get more resources.
Site service scope is becoming smaller and smaller, which is also the development trend of 5G in the future.
Now, there are about 6 million 4G base stations in the world, China has occupied more than 4 million, and other base stations are jointly owned by more than 190 countries such as the United States.
Among the big countries, China's telecommunication coverage is the first, far ahead of the United States, Russia, Australia and other countries.
Why can China achieve such a success?
This comes from China.
Since 2003, the Ministry of Industry and Information Technology has given three operators the task of Telecom Construction in remote mountainous areas every year. After more than ten years of construction, the goal has been achieved.
In December 2017, the author visited poverty alleviation in poor mountainous areas of Guizhou and came to Yanbo Village, Mud Township, Liupanshui City, which is located in the mountainous and hilly area with an elevation of 2000 meters.
When I got out of the car, I took out my mobile phone to measure the speed, and found that the speed of the network was as high as 30 trillion.
The village cadre introduced the local network situation: the 4G network had already been built, and the village had asked him to arrange villagers to go to the mountain ditch to find the blind area of the signal.
What the village cadres don't know is that their village's Internet speed has surpassed that of Canberra, the capital of Australia.
There are many families in Caowangba Village, Pingzheng Gelao Township, Zunyi City, located in a depression on both sides of a hilltop. For these dozens of households, relevant units have installed two iron towers here to ensure that all people enjoy the convenience brought by modern communications.
In fact, these villagers pay less than 800 yuan a month for their telephone calls, not even enough for the electricity of two iron towers.
China is at the forefront of the world in ensuring telecommunication coverage in the vast remote and impoverished areas. In China, almost all remote villages, along railways and on both sides of national highways have signals.
The telecommunications coverage in the United States is much lower than that in China because they are on the path of complete commercialization.
Therefore, the famous Yellowstone Park has no signal, which is unimaginable in China.
At the end of the day, the Americans shouted
Nowadays, many people lack understanding of the tremendous achievements of China's telecommunications industry, but worship Musk, which is a controversial God in the United States.
In a TV interview, Musk himself admitted publicly that his space heroes, Armstrong and Eugene Cernan, were against him.
In fact, not only these two, but many American experts are well aware that there are a lot of technical problems in the Musk Plan.
Of course, we can't say that Musk's plan is useless, but we should also calmly analyze and treat it objectively. There is no need to be enthusiastic, let alone self-depreciation.
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