https://mil.news.sina.com.cn/china/2019-05-28/doc-ihvhiqay1867543.shtml
美国准备跳过5G直接升级到6G？到底靠不靠谱
美国准备跳过5G直接升级到6G？到底靠不靠谱
802
原标题：美国准备跳过5G，直接升级到6G？
据报道，北京时间5月24日上午10点30分，马斯克旗下的SpaceX（美国太空探索技术公司）的猎鹰9号火箭将60颗Starlink卫星发射升空，其雄心勃勃的“星链（Starlink）”计划终于拉开组网序幕。
这项2015年提出的计划，规模极其巨大，总计要在2025年前发射近12000颗卫星。有自媒体认为，该计划表示美国将在太空中建立下一代宽带网络，绕过5G，直接升级到6G，并据此认为“6G并不遥远”。
那么这个庞大的“星链”计划，到底靠不靠谱？
今天就来聊一聊。
1
用上万颗卫星包裹全球，靠谱吗？
目前，全世界在轨提供服务的卫星也不过1700多颗。
之前，马斯克计划发射4425颗卫星，这个数量已经很吓人了，现在又涨到了12000颗。
我们不禁要问：用上万颗卫星包裹全球，这个“星链”计划靠谱吗？
目前看来，不太靠谱。
且不说发射卫星所需的巨大成本压力以及在政策上面临的重重阻力，单在技术方面，“星链”计划就很不过关。
一是速率不够。
根据“星链”计划的官方文件，一颗卫星的典型覆盖面积是353万平方公里，相当于9个多德国和220个北京。要知道，全世界比这个面积大的国家也只有6个。
▲马斯克“星链”计划卫星的高度和下倾角数据（图源网络）
即使考虑到卫星采用了相控阵技术，真正服务地区比覆盖面积小些，但其范围也是惊人的。
现在，光北京就建设了2万座左右的铁塔，每座铁塔上还不止一家基站，这么一颗卫星就能为上百个北京这么大的区域提供服务，速率能够吗？当然不够。
二是很难连上。
前几天，网上有个消息传爆了：有人称其手机连上了马斯克的TintinA卫星的Wi-Fi。
▲有人称其手机连上了马斯克的TintinA卫星的Wi-Fi（图源网络）
马斯克在跟他人的对话中称“不要告诉别人，密码是martians”。
▲马斯克在社交媒体上与人对话称“不要告诉别人，密码是martians”（图源网络）
于是，很多人就以为，自己的智能手机以后可以接入卫星Wi-Fi了。
这个想法就有点天真了，因为TintinA卫星与我们用的普通智能手机频率对不上，两者不可能直接通信。
无线电波有一个特性，频率越高，电波的指向性就越强，也就更利于集中能量将信号传递到远方。
马斯克的互联网卫星使用的是Ka和Ku波段，在20GHz左右。
▲马斯克互联网卫星使用的是Ka和Ku波段，手机无法接收（图源网络）
而我们用的智能手机使用的Wi-Fi频段分别是2.4GHz和5GHz，相对来说全向性就比较强，在路由器周围任何方向都有较均匀的信号，以方便我们的使用。但Wi-Fi的全向性信号衰减很严重，会随着距离变化呈平方倍衰减，如果加上空中干扰，可能是立方倍衰减。
因此，2.4GHz和5GHz的信号本身就传不了多远，更不用指望传递给太空中的卫星了。
那么，我们的手机能收到卫星发射的信号吗？
前面说过，卫星的信号频率在20GHz左右，我们手机根本就没有接收这个频段的接收器，所以不可能收到。
也就是说，手机不可能收到TintinA卫星的信号，手机的Wi-Fi信号也不可能发射到卫星。
因此，普通手机连接成功卫星Wi-Fi的图片是骗人的，除非你用的是卫星电话。
“星链”如何为地面上的手机提供上网服务？
现行手机的信号不可能发射到卫星，而且与卫星直接通信的设备不能有遮蔽顶，所以要在室外空旷地域装转发器，以20GHz左右的频率与卫星通信，以2.4GHz或5GHz跟手机通信。
▲“星链”要为地面上的手机提供上网服务，需要有转发器（图源网络）
但是，这个转发器的对星频率有问题，它跟我国5G规划的28GHz频率完全重合。也就是说，将来我国的大街上会密布28GHz的5G微基站，旁边如果还有着相同频率的卫星转发器，将会严重干扰5G微基站的信号。
2
那么多专家，难道都不懂？
很多网友会有疑问，库叔说的都挺有道理，但Google、Facebook、SpaceX有那么多技术专家，难道他们不懂？
照理说，常规的科研项目要经过技术论证，稍有疑点就要进行反复论证，以确保所有技术环节的科学原理都成立，而且有足够可靠的工程方法。
然而近年来，美国兴起了IT创投思维，跟常规的严谨科研不同，它的基本套路就是讲故事、卖情怀、拉投资，稍微搞出点成果就大肆宣传，目的是拉来更多投资。
这种报喜不报忧的互联网套路，掩盖了实际存在的大量技术障碍，因此这些项目失败的几率极大，投资人的钱也会跟着打水漂。
从2014年开始，美国科技人士似乎就为全世界人民的上网问题“操碎了心”，搞的计划形形色色，有用卫星的、有用无人机的、有用热气球的，总之就是往天上搞，核心卖点就是要覆盖足够大、用户足够多。
举几个例子：
*2014年春节期间，一则类似消息同样引爆了网络：美国一家名为“媒体发展投资基金”的公司宣布了一个名为“外联网（Outernet）”的计划，要发射几百颗低轨道卫星，为全球4.3亿上不了互联网的人们提供网络服务。
很多人非常兴奋——终于可以高速、廉价、无障碍地上网了。
▲2014年，美国一家公司宣布推出“外联网”计划，目标是让网络覆盖全球（图源网络）
然而实际上，这项计划的核心技术是“单向组播”，地面工作站将信息分组整理后上传到卫星，然后由卫星转发到所覆盖的地域。
这跟卫星广播电视是一个道理，你可以选择适合的信息，但不能上传信息。
不能上传信息就是没有交互性，QQ和微信不能用，微博也发不了，只能被动地看推送信息。
这是广播服务而不是互联网。
有意思的是，该公司的宣传图片却向人们传达了能够双向通信的印象，比如下边这张图片，人在旷野上通过“外联网”跟卫星进行联络，暗示能叫来救援。实际上，信息并不能上传。
▲“媒体发展投资基金”公司推出的“外联网”宣传图片（图源网络）
*2015年，又有消息称，Google与SpaceX合作发射700颗通信卫星，构建全球无线互联网。
700颗听着不少，关键要看服务多少人。
按全世界人口1/10的7亿用户来算，平均每颗要服务100万用户，按照每颗卫星1Gbps总速率来计算，平均每个用户只能分得1kbps，甚至远远低于拨号上网时代，根本就无法使用。
*Google还推出过利用热气球提供Wi-Fi的计划。
这也并不是什么新把戏，只是抄袭了军用系留气球（使用缆绳将其拴在地面绞车上并可控制其在大气中飘浮高度的气球）和平流层飞艇的创意——在吊篮上放置通信转发器，升空后覆盖作战地域，起到了通信中继的作用。
▲谷歌用热气球提供互联网的项目名称为“潜鸟计划”（Project Loon）（图源网络）
*2016年7月份，扎克伯格也跟风搞了个给全世界人民提供互联网服务的计划，这回用的是能发射激光的无人机。
▲FaceBook公司推出的“天鹰”（Aquila）计划，通过可以发射激光的无人机完成信号传输（图源网络）
其实这种无人机早就有，只是因为主要用于军事而不被公众所了解。为此，FaceBook公司还收购了英国一家生产这种无人机的公司。
细究起来，这个无人机方案也存在很多疑点：
一是用无人机提供信号难度简直太大。
无人机向地面提供的信号覆盖半径约为100公里，其航速约为100公里/小时，这个半径100公里的信号覆盖区是高速移动的，你必须以100公里/小时的速度跟着无人机跑才能持续上网。
或者每隔200公里就安排一架无人机，让它们排着队依次飞行。显然，这种接力工作模式很不靠谱。
二是用“激光”作为通信手段，大气干扰太大。
报道中提到用“激光”作为通信手段，曾让很多人感到兴奋，其实很不靠谱。
卫星之间通过激光进行通信确实可行，这叫作“星际激光链路”，但那是在没有大气扰动的太空。
对这种方式而言，距地面上万米距离的大气干扰是个严重的问题。
三是激光还具有极强的方向性。
如果你手持激光笔对着墙上照就会发现：如果10米远，即便手腕抖动很轻微，墙上光斑的跳动距离也会很远；如果对着20米远的墙上照，光斑就跳动得更远。
▲激光具有方向性好的特点（图源网络）
飞行中的无人机抖动很厉害，距离地面成千上万米，那么，激光在地面上来回跳动的尺度得有多大？
地面站给飞机中的无人机发射激光，必须连续精准地调整激光发射器的角度，以跟上不断变化位置的无人机。这个难度不是一般的大，商业应用恐怕很难成功。
由上可见，无论是卫星、热气球还是无人机，其宣传思路都是位置足够高，覆盖面积大，服务用户多，往往打出为贫穷人群提供信息自由的情怀牌，然后给出众筹链接。
但由于总速率资源有限，用户的平均速率资源会极其微薄，这一点他们绝口不提。
后来，“外联网”卫星计划没有圈到钱，黄了；谷歌热气球和FaceBook公司无人机计划也没了下文。
现在，马斯克的“星链”计划又开始火了。。。。。。
3
要让人人都上网，还得学中国
理论上，一个站点的带宽资源基本固定，所服务的用户数越多，单个用户分得的速率就越少。
那么，如何才能让每个人都能高速上网？
正确的操作方式是缩小站点范围，把站点资源分配给更少的人群，每个人得到的资源就更多。
站点服务范围越来越小，这也是未来5G的发展趋势。
现在，全球共有约600万座4G基站，中国就占据了400多万座，其他的基站被美国等190多个国家共同拥有。
在大国中，中国的电信覆盖率是第一，遥遥领先于美国、俄罗斯、澳大利亚等国。
为什么中国能取得这样的成就？
这源于中国的“村村通”政策——政府要求95%以上的偏远山区必须有电信信号，而且资费不得高于城镇地区。
自2003年开始，工信部每年都会给三大运营商下达偏远山区电信建设任务，经过十多年的建设，已经完成了目标。
2017年12月份，笔者曾去贵州贫困山区考察扶贫，来到六盘水市淤泥乡岩博村，处于海拔2000米的山地丘陵地带。
一下车，笔者掏出手机测速，发现网速竟然高达30兆。
村干部介绍了当地的网络情况：4G网早就建成了，乡里曾经要求他安排村民去山沟里寻找信号盲区。
这个村干部不知道的是，他们村的网速已经超过了澳大利亚首都堪培拉！
遵义市平正仡佬族乡草王坝村，有很多家坐落在一座山头两侧的洼地里。为了这几十户人，相关单位在这里安装了两座铁塔，保证所有人享受到现代通讯带来的便捷。
实际上，这些村民一个月交的话费还不到800块钱，连两座铁塔的电费都不够。
在保证广大偏远贫困地区的电信覆盖率方面，中国走在了全球最前列。在中国，几乎所有偏远山村、铁路沿线、国道两边都有信号。
美国的电信覆盖率远低于中国，就是因为他们走的是完全商业化的道路——运营商更乐意在经济发达的人口密集区建设基站，那里赚钱多，不乐意在人口稀疏的偏远地区建站，因为赚不到钱。
所以，著名的黄石公园居然没有信号，这在中国是无法想象的。
说到底，美国人大喊“给全世界人民提供互联网服务”的口号没有多大实际意义，先搞掂本国的电信覆盖率才是要务。
现在，很多人对我国电信业建设的巨大成就缺乏认识，反而把在美国存在巨大争议的马斯克当神一样崇拜。
在电视访谈节目中，马斯克自己也公开承认，他心目中的航天英雄阿姆斯特朗和尤金赛尔南都公开反对他。
其实，不仅这两位，很多美国专家都很清楚马斯克计划存在着大量技术问题。
当然，我们不能说马斯克的这个计划一无是处，但确实也应该冷静分析、客观看待，没有必要一味热捧，更没必要妄自菲薄。
关键字 : 美国卫星通信5G
Is the US ready to skip 5G and upgrade directly to 6G? It’s not reliable
Is the US ready to skip 5G and upgrade directly to 6G? It’s not reliable
802
Original title: The United States is going to skip 5G and upgrade directly to 6G?
According to reports, at 10:30 am on May 24th, Beijing time, Musk's SpaceX (American Space Exploration Technology Corporation) Falcon 9 rocket launched 60 Starlink satellites, its ambitious "star chain ( The Starlink) program finally kicked off the networking.
The plan proposed in 2015 is extremely large, with a total of nearly 12,000 satellites being launched by 2025. Some media believe that the plan indicates that the United States will establish a next-generation broadband network in space, bypassing 5G and directly upgrading to 6G, and accordingly, "6G is not far away."
Then, this huge "star chain" plan is not reliable?
Come talk today.
1
Wrapped with tens of thousands of satellites, is it reliable?
At present, there are more than 1,700 satellites in service around the world.
Previously, Musk planned to launch 4,425 satellites. This number is already scary, and now it has risen to 12,000.
We can't help but ask: With tens of thousands of satellites wrapped around the world, is this "star chain" plan reliable?
At present, it seems that it is not very reliable.
Not to mention the huge cost pressures required to launch satellites and the heavy resistance to policy. In terms of technology alone, the “star chain” plan is not good.
First, the rate is not enough.
According to the official document of the "Star Chain" program, the typical coverage area of a satellite is 3.53 million square kilometers, equivalent to more than 9 Germany and 220 Beijing. You know, there are only six countries in the world that are larger than this.
▲Maximum and downtilt data of Musk's Star Chain program satellite (Source network) ▲ Height and downtilt data of Musk's Star Chain program satellite (Source Network)
Even considering the use of phased array technology in satellites, the real service area is smaller than the coverage area, but its range is also amazing.
Now, Beijing has built about 20,000 towers, and there are more than one base station on each tower. Such a satellite can provide services for hundreds of such large areas in Beijing. Can the rate be? Of course not enough.
Second, it is difficult to connect.
A few days ago, there was a news on the Internet: Some people said that their mobile phone was connected to the Wi-Fi of Muske's TintinA satellite.
▲ Some people say that their mobile phone is connected to the Wi-Fi of Muske's TintinA satellite. (The source network is ▲ Some people call their mobile phone connected to the Wi-Fi of Muske's TintinA satellite (Source Network)
In a conversation with others, Musk called "Don't tell others, the password is martians."
▲ Musk talked to people on social media, saying, "Don't tell others, the password is martians" (图源网络)
Therefore, many people think that their smart phones can access satellite Wi-Fi in the future.
This idea is a bit naive, because the TintinA satellite is not as good as the average smartphone we use, and it is impossible for the two to communicate directly.
Radio waves have a characteristic. The higher the frequency, the stronger the directivity of the electric wave, which is more conducive to concentrating energy to transmit the signal to a distant place.
Musk's Internet satellites use the Ka and Ku bands, around 20 GHz.
▲Muske Internet satellites use Ka and Ku bands, mobile phones can not receive (map source network) ▲ Musk Internet satellites use Ka and Ku bands, mobile phones can not receive (Figure source network)
The Wi-Fi frequency bands used by our smartphones are 2.4GHz and 5GHz respectively. Relatively speaking, the omnidirectionality is relatively strong, and there is a relatively uniform signal in any direction around the router to facilitate our use. However, the omnidirectional signal attenuation of Wi-Fi is very serious, and it will be squared with the change of distance. If it is added to the air, it may be cubic attenuation.
Therefore, the 2.4 GHz and 5 GHz signals themselves cannot be transmitted far, and it is not expected to be transmitted to satellites in space.
So, can our mobile phone receive signals from satellites?
As mentioned earlier, the satellite's signal frequency is around 20 GHz. Our mobile phone does not receive the receiver of this frequency band at all, so it is impossible to receive it.
In other words, it is impossible for a mobile phone to receive a signal from the TintinA satellite, and it is impossible for the mobile phone's Wi-Fi signal to be transmitted to the satellite.
Therefore, the picture of a successful mobile phone connected to a successful satellite Wi-Fi is deceptive unless you are using a satellite phone.
How does the "Star Chain" provide Internet access for mobile phones on the ground?
The signal of the current mobile phone cannot be transmitted to the satellite, and the device directly communicating with the satellite cannot have a shadow top. Therefore, it is necessary to install a transponder in an outdoor space, communicate with the satellite at a frequency of about 20 GHz, and communicate with the mobile phone at 2.4 GHz or 5 GHz.
▲ "Star Chain" to provide Internet access for mobile phones on the ground, need to have a transponder (map source network) ▲ "Star Chain" to provide Internet access for mobile phones on the ground, need to have a transponder (map source network)
However, this transponder has a problem with the star frequency, which completely coincides with the 28GHz frequency of China's 5G plan. That is to say, in the future, there will be a 28GHz 5G micro base station on the street in China. If there is a satellite transponder of the same frequency, it will seriously interfere with the signal of the 5G micro base station.
2
So many experts do not understand?
Many netizens will have doubts. What Shu Shu said is quite reasonable, but Google, Facebook, and SpaceX have so many technical experts. Do they not understand?
It is reasonable to say that conventional scientific research projects must undergo technical argumentation. A little doubt must be repeatedly demonstrated to ensure that the scientific principles of all technical aspects are established and that there are sufficiently reliable engineering methods.
However, in recent years, the United States has developed an IT venture capital thinking. Unlike the conventional rigorous scientific research, its basic routine is to tell stories, sell feelings, and pull investment. It is a big propaganda to make some achievements, and the purpose is to attract more investment.
This kind of Internet routine, which does not report the worry, obscures a large number of technical obstacles that exist in reality. Therefore, the chances of failure of these projects are enormous, and the investors' money will follow suit.
Beginning in 2014, American scientists and technicians seem to have “broken their hearts” for the Internet problems of people all over the world. The plans are all kinds of useful satellites, useful drones, and useful hot air balloons. In short, they are going to heaven. The core selling point is to cover enough and enough users.
Here are a few examples:
* During the Spring Festival of 2014, a similar news also ignited the Internet: a US company called "Media Development Investment Fund" announced a plan called "Outernet" to launch hundreds of low-orbit satellites. To provide network services to 430 million people who cannot access the Internet.
Many people are very excited - finally able to access the Internet at high speed, cheap and unobstructed.
▲In 2014, a US company announced the launch of the “Extranet” program, with the goal of making the network cover the whole world (Source Network)
In reality, however, the core technology of this program is “one-way multicast”. The ground station organizes the information and uploads it to the satellite, which then forwards it to the covered area.
This is the same as satellite radio and television. You can choose the right information, but you can't upload the information.
Can not upload information is no interactive, QQ and WeChat can not be used, Weibo can not send, can only passively see push information.
This is a broadcast service and not an internet.
Interestingly, the company's promotional image conveyed the impression of two-way communication. For example, the picture below, people in the wilderness through the "extranet" to contact the satellite, suggesting that they can call rescue. In fact, the information cannot be uploaded.
▲ "Internet Development Investment Fund" company launched the "extranet" propaganda picture (map source network) ▲ "media development investment fund" company launched the "extranet" propaganda picture (map source network)
*In 2015, it was reported that Google and SpaceX cooperated to launch 700 communication satellites to build a global wireless Internet.
700 listens a lot, the key depends on how many people serve.
According to the 700 million users of 1/10 of the world's population, the average service per user is 1 million users. According to the total rate of 1 Gbps per satellite, the average user can only get 1 kbps, even far less than dial-up. Times can't be used at all.
* Google also launched a plan to use Wi-Fi to provide hot air balloons.
This is not a new trick, just copying the military tethered balloon (a balloon that uses a cable to smash it on the ground winch and control its height in the atmosphere). The idea of a stratospheric airship - placed on the gondola The communication transponder covers the combat area after being lifted off, and plays a role in communication relay.
▲Google's project name for providing Internet with hot air balloon is "Project Loon" (图源网络)
* In July 2016, Zuckerberg also followed suit with a plan to provide Internet services to people all over the world. This time, a drone that can emit lasers was used.
▲FaceBook's "Aquila" plan to complete signal transmission through a drone that can emit lasers (Source Network)
In fact, this type of drone has long existed, but it is mainly used for military purposes and is not known to the public. To this end, FaceBook also acquired a British company that produces such drones.
After careful study, there are many doubts about this drone program:
First, the difficulty of providing signals with drones is simply too great.
The signal provided by the drone to the ground covers a radius of about 100 kilometers and its speed is about 100 km/h. The signal coverage area with a radius of 100 km is moving at high speed. You must follow the drone at a speed of 100 km/h. Run to continue online.
Or arrange a drone every 200 kilometers, let them line up in sequence to fly. Obviously, this relay work mode is very unreliable.
The second is to use "laser" as a means of communication, and atmospheric interference is too great.
The report mentioned the use of "laser" as a means of communication, which has made many people excited, but it is not very reliable.
It is indeed feasible to communicate between the satellites via lasers. This is called the “interstellar laser link”, but it is in space without atmospheric disturbances.
In this way, atmospheric interference from a distance of 10,000 meters above the ground is a serious problem.
Third, the laser also has a strong directivity.
If you hold the laser pointer against the wall, you will find that if you are 10 meters away, even if the wrist is slightly shaken, the distance of the wall flare will be very far; if you look at the wall 20 meters away, the spot will beat. Go further.
▲ laser has good directional characteristics (map source network)
The drones in flight are very shaken, thousands of meters from the ground, so how big is the scale of the laser jumping back and forth on the ground?
The ground station emits laser light to the drones in the aircraft, and the angle of the laser transmitter must be continuously and accurately adjusted to keep up with the drones in changing positions. This difficulty is not as big as it is, and commercial applications are hard to succeed.
It can be seen from the above that whether it is a satellite, a hot air balloon or a drone, its propaganda idea is that the location is high enough, the coverage area is large, and the number of service users is large. It often plays a sentimental card that provides information freedom for the poor, and then gives a crowdfunding link.
However, due to the limited total rate resources, the average rate resources of users will be extremely thin, which they do not mention.
Later, the "Extranet" satellite program did not have the money to go, and the yellow balloon; and the Google Balloon and FaceBook drone plans did not.
Now, Musk’s “Star Chain” plan is starting to fire again. . . . . .
3
To let everyone go online, you have to learn China.
In theory, the bandwidth resources of a site are basically fixed, and the more users served, the less the rate of individual users.
So, how can everyone get high speed online?
The correct way to do this is to narrow down the site and allocate site resources to fewer people, each with more resources.
The scope of site services is getting smaller and smaller, which is also the development trend of 5G in the future.
Today, there are about 6 million 4G base stations in the world, and China has more than 4 million seats. Other base stations are jointly owned by more than 190 countries such as the United States.
Among the big countries, China's telecommunications coverage is the first, far ahead of the United States, Russia, Australia and other countries.
Why can China achieve such an achievement?
This stems from China's “village-to-village” policy—the government requires more than 95% of the remote mountainous areas to have telecommunications signals, and the tariffs must not be higher than the urban areas.
Since 2003, the Ministry of Industry and Information Technology has given the three major operators the task of telecommunications construction in remote mountainous areas every year. After more than ten years of construction, the target has been completed.
In December 2017, the author went to poverty-stricken mountainous areas in Guizhou to study poverty alleviation and went to Yanbo Village, Mudui Township, Liupanshui City, at a hilly area of 2000 meters above sea level.
When I got off the car, I took out the speed of the mobile phone and found that the speed of the network was as high as 30 trillion.
The village cadres introduced the local network situation: the 4G network was built long ago, and the village once asked him to arrange villagers to go to the ravine to find the signal blind spot.
What the village cadres don't know is that their village's speed has exceeded that of the Australian capital Canberra!
In the village of Caowangba, Pingzheng Yizu Township, Zunyi City, many homes are located in the depression on both sides of a hill. For these dozens of people, the relevant units installed two towers here to ensure that everyone enjoys the convenience brought by modern communication.
In fact, the fees charged by these villagers for one month are less than 800 yuan, and the electricity bills of the two towers are not enough. In fact, the fees charged by these villagers for one month are less than 800 yuan, and the electricity bills of the two towers are not enough.
China is at the forefront of the world in ensuring telecommunications coverage in remote and impoverished areas. In China, almost all remote mountain villages, railways, and national highways have signals.
The telecommunications coverage rate in the United States is much lower than that in China because they are taking a completely commercial road – operators are more willing to build base stations in economically developed densely populated areas, where they make more money and are less willing to build stations in remote areas with sparse populations. Because I can't make money.
Therefore, the famous Yellowstone Park has no signal, which is unimaginable in China.
After all, the slogan of Americans shouting "providing Internet services to people all over the world" has little practical significance. It is a priority to first smash the country's telecommunications coverage.
Now, many people lack understanding of the great achievements in the construction of China's telecommunications industry.
美国准备跳过5G直接升级到6G？到底靠不靠谱
美国准备跳过5G直接升级到6G？到底靠不靠谱
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原标题：美国准备跳过5G，直接升级到6G？
据报道，北京时间5月24日上午10点30分，马斯克旗下的SpaceX（美国太空探索技术公司）的猎鹰9号火箭将60颗Starlink卫星发射升空，其雄心勃勃的“星链（Starlink）”计划终于拉开组网序幕。
这项2015年提出的计划，规模极其巨大，总计要在2025年前发射近12000颗卫星。有自媒体认为，该计划表示美国将在太空中建立下一代宽带网络，绕过5G，直接升级到6G，并据此认为“6G并不遥远”。
那么这个庞大的“星链”计划，到底靠不靠谱？
今天就来聊一聊。
1
用上万颗卫星包裹全球，靠谱吗？
目前，全世界在轨提供服务的卫星也不过1700多颗。
之前，马斯克计划发射4425颗卫星，这个数量已经很吓人了，现在又涨到了12000颗。
我们不禁要问：用上万颗卫星包裹全球，这个“星链”计划靠谱吗？
目前看来，不太靠谱。
且不说发射卫星所需的巨大成本压力以及在政策上面临的重重阻力，单在技术方面，“星链”计划就很不过关。
一是速率不够。
根据“星链”计划的官方文件，一颗卫星的典型覆盖面积是353万平方公里，相当于9个多德国和220个北京。要知道，全世界比这个面积大的国家也只有6个。
即使考虑到卫星采用了相控阵技术，真正服务地区比覆盖面积小些，但其范围也是惊人的。
现在，光北京就建设了2万座左右的铁塔，每座铁塔上还不止一家基站，这么一颗卫星就能为上百个北京这么大的区域提供服务，速率能够吗？当然不够。
二是很难连上。
前几天，网上有个消息传爆了：有人称其手机连上了马斯克的TintinA卫星的Wi-Fi。
马斯克在跟他人的对话中称“不要告诉别人，密码是martians”。
▲马斯克在社交媒体上与人对话称“不要告诉别人，密码是martians”（图源网络）
于是，很多人就以为，自己的智能手机以后可以接入卫星Wi-Fi了。
这个想法就有点天真了，因为TintinA卫星与我们用的普通智能手机频率对不上，两者不可能直接通信。
无线电波有一个特性，频率越高，电波的指向性就越强，也就更利于集中能量将信号传递到远方。
马斯克的互联网卫星使用的是Ka和Ku波段，在20GHz左右。
而我们用的智能手机使用的Wi-Fi频段分别是2.4GHz和5GHz，相对来说全向性就比较强，在路由器周围任何方向都有较均匀的信号，以方便我们的使用。但Wi-Fi的全向性信号衰减很严重，会随着距离变化呈平方倍衰减，如果加上空中干扰，可能是立方倍衰减。
因此，2.4GHz和5GHz的信号本身就传不了多远，更不用指望传递给太空中的卫星了。
那么，我们的手机能收到卫星发射的信号吗？
前面说过，卫星的信号频率在20GHz左右，我们手机根本就没有接收这个频段的接收器，所以不可能收到。
也就是说，手机不可能收到TintinA卫星的信号，手机的Wi-Fi信号也不可能发射到卫星。
因此，普通手机连接成功卫星Wi-Fi的图片是骗人的，除非你用的是卫星电话。
“星链”如何为地面上的手机提供上网服务？
现行手机的信号不可能发射到卫星，而且与卫星直接通信的设备不能有遮蔽顶，所以要在室外空旷地域装转发器，以20GHz左右的频率与卫星通信，以2.4GHz或5GHz跟手机通信。
但是，这个转发器的对星频率有问题，它跟我国5G规划的28GHz频率完全重合。也就是说，将来我国的大街上会密布28GHz的5G微基站，旁边如果还有着相同频率的卫星转发器，将会严重干扰5G微基站的信号。
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那么多专家，难道都不懂？
很多网友会有疑问，库叔说的都挺有道理，但Google、Facebook、SpaceX有那么多技术专家，难道他们不懂？
照理说，常规的科研项目要经过技术论证，稍有疑点就要进行反复论证，以确保所有技术环节的科学原理都成立，而且有足够可靠的工程方法。
然而近年来，美国兴起了IT创投思维，跟常规的严谨科研不同，它的基本套路就是讲故事、卖情怀、拉投资，稍微搞出点成果就大肆宣传，目的是拉来更多投资。
这种报喜不报忧的互联网套路，掩盖了实际存在的大量技术障碍，因此这些项目失败的几率极大，投资人的钱也会跟着打水漂。
从2014年开始，美国科技人士似乎就为全世界人民的上网问题“操碎了心”，搞的计划形形色色，有用卫星的、有用无人机的、有用热气球的，总之就是往天上搞，核心卖点就是要覆盖足够大、用户足够多。
举几个例子：
*2014年春节期间，一则类似消息同样引爆了网络：美国一家名为“媒体发展投资基金”的公司宣布了一个名为“外联网（Outernet）”的计划，要发射几百颗低轨道卫星，为全球4.3亿上不了互联网的人们提供网络服务。
很多人非常兴奋——终于可以高速、廉价、无障碍地上网了。
▲2014年，美国一家公司宣布推出“外联网”计划，目标是让网络覆盖全球（图源网络）
然而实际上，这项计划的核心技术是“单向组播”，地面工作站将信息分组整理后上传到卫星，然后由卫星转发到所覆盖的地域。
这跟卫星广播电视是一个道理，你可以选择适合的信息，但不能上传信息。
不能上传信息就是没有交互性，QQ和微信不能用，微博也发不了，只能被动地看推送信息。
这是广播服务而不是互联网。
有意思的是，该公司的宣传图片却向人们传达了能够双向通信的印象，比如下边这张图片，人在旷野上通过“外联网”跟卫星进行联络，暗示能叫来救援。实际上，信息并不能上传。
*2015年，又有消息称，Google与SpaceX合作发射700颗通信卫星，构建全球无线互联网。
700颗听着不少，关键要看服务多少人。
按全世界人口1/10的7亿用户来算，平均每颗要服务100万用户，按照每颗卫星1Gbps总速率来计算，平均每个用户只能分得1kbps，甚至远远低于拨号上网时代，根本就无法使用。
*Google还推出过利用热气球提供Wi-Fi的计划。
这也并不是什么新把戏，只是抄袭了军用系留气球（使用缆绳将其拴在地面绞车上并可控制其在大气中飘浮高度的气球）和平流层飞艇的创意——在吊篮上放置通信转发器，升空后覆盖作战地域，起到了通信中继的作用。
▲谷歌用热气球提供互联网的项目名称为“潜鸟计划”（Project Loon）（图源网络）
*2016年7月份，扎克伯格也跟风搞了个给全世界人民提供互联网服务的计划，这回用的是能发射激光的无人机。
▲FaceBook公司推出的“天鹰”（Aquila）计划，通过可以发射激光的无人机完成信号传输（图源网络）
其实这种无人机早就有，只是因为主要用于军事而不被公众所了解。为此，FaceBook公司还收购了英国一家生产这种无人机的公司。
细究起来，这个无人机方案也存在很多疑点：
一是用无人机提供信号难度简直太大。
无人机向地面提供的信号覆盖半径约为100公里，其航速约为100公里/小时，这个半径100公里的信号覆盖区是高速移动的，你必须以100公里/小时的速度跟着无人机跑才能持续上网。
或者每隔200公里就安排一架无人机，让它们排着队依次飞行。显然，这种接力工作模式很不靠谱。
二是用“激光”作为通信手段，大气干扰太大。
报道中提到用“激光”作为通信手段，曾让很多人感到兴奋，其实很不靠谱。
卫星之间通过激光进行通信确实可行，这叫作“星际激光链路”，但那是在没有大气扰动的太空。
对这种方式而言，距地面上万米距离的大气干扰是个严重的问题。
三是激光还具有极强的方向性。
如果你手持激光笔对着墙上照就会发现：如果10米远，即便手腕抖动很轻微，墙上光斑的跳动距离也会很远；如果对着20米远的墙上照，光斑就跳动得更远。
▲激光具有方向性好的特点（图源网络）
飞行中的无人机抖动很厉害，距离地面成千上万米，那么，激光在地面上来回跳动的尺度得有多大？
地面站给飞机中的无人机发射激光，必须连续精准地调整激光发射器的角度，以跟上不断变化位置的无人机。这个难度不是一般的大，商业应用恐怕很难成功。
由上可见，无论是卫星、热气球还是无人机，其宣传思路都是位置足够高，覆盖面积大，服务用户多，往往打出为贫穷人群提供信息自由的情怀牌，然后给出众筹链接。
但由于总速率资源有限，用户的平均速率资源会极其微薄，这一点他们绝口不提。
后来，“外联网”卫星计划没有圈到钱，黄了；谷歌热气球和FaceBook公司无人机计划也没了下文。
现在，马斯克的“星链”计划又开始火了。。。。。。
3
要让人人都上网，还得学中国
理论上，一个站点的带宽资源基本固定，所服务的用户数越多，单个用户分得的速率就越少。
那么，如何才能让每个人都能高速上网？
正确的操作方式是缩小站点范围，把站点资源分配给更少的人群，每个人得到的资源就更多。
站点服务范围越来越小，这也是未来5G的发展趋势。
现在，全球共有约600万座4G基站，中国就占据了400多万座，其他的基站被美国等190多个国家共同拥有。
在大国中，中国的电信覆盖率是第一，遥遥领先于美国、俄罗斯、澳大利亚等国。
为什么中国能取得这样的成就？
这源于中国的“村村通”政策——政府要求95%以上的偏远山区必须有电信信号，而且资费不得高于城镇地区。
自2003年开始，工信部每年都会给三大运营商下达偏远山区电信建设任务，经过十多年的建设，已经完成了目标。
2017年12月份，笔者曾去贵州贫困山区考察扶贫，来到六盘水市淤泥乡岩博村，处于海拔2000米的山地丘陵地带。
一下车，笔者掏出手机测速，发现网速竟然高达30兆。
村干部介绍了当地的网络情况：4G网早就建成了，乡里曾经要求他安排村民去山沟里寻找信号盲区。
这个村干部不知道的是，他们村的网速已经超过了澳大利亚首都堪培拉！
遵义市平正仡佬族乡草王坝村，有很多家坐落在一座山头两侧的洼地里。为了这几十户人，相关单位在这里安装了两座铁塔，保证所有人享受到现代通讯带来的便捷。
在保证广大偏远贫困地区的电信覆盖率方面，中国走在了全球最前列。在中国，几乎所有偏远山村、铁路沿线、国道两边都有信号。
美国的电信覆盖率远低于中国，就是因为他们走的是完全商业化的道路——运营商更乐意在经济发达的人口密集区建设基站，那里赚钱多，不乐意在人口稀疏的偏远地区建站，因为赚不到钱。
所以，著名的黄石公园居然没有信号，这在中国是无法想象的。
说到底，美国人大喊“给全世界人民提供互联网服务”的口号没有多大实际意义，先搞掂本国的电信覆盖率才是要务。
现在，很多人对我国电信业建设的巨大成就缺乏认识，反而把在美国存在巨大争议的马斯克当神一样崇拜。
在电视访谈节目中，马斯克自己也公开承认，他心目中的航天英雄阿姆斯特朗和尤金赛尔南都公开反对他。
其实，不仅这两位，很多美国专家都很清楚马斯克计划存在着大量技术问题。
当然，我们不能说马斯克的这个计划一无是处，但确实也应该冷静分析、客观看待，没有必要一味热捧，更没必要妄自菲薄。
关键字 : 美国卫星通信5G
Is the US ready to skip 5G and upgrade directly to 6G? It’s not reliable
Is the US ready to skip 5G and upgrade directly to 6G? It’s not reliable
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Original title: The United States is going to skip 5G and upgrade directly to 6G?
According to reports, at 10:30 am on May 24th, Beijing time, Musk's SpaceX (American Space Exploration Technology Corporation) Falcon 9 rocket launched 60 Starlink satellites, its ambitious "star chain ( The Starlink) program finally kicked off the networking.
The plan proposed in 2015 is extremely large, with a total of nearly 12,000 satellites being launched by 2025. Some media believe that the plan indicates that the United States will establish a next-generation broadband network in space, bypassing 5G and directly upgrading to 6G, and accordingly, "6G is not far away."
Then, this huge "star chain" plan is not reliable?
Come talk today.
1
Wrapped with tens of thousands of satellites, is it reliable?
At present, there are more than 1,700 satellites in service around the world.
Previously, Musk planned to launch 4,425 satellites. This number is already scary, and now it has risen to 12,000.
We can't help but ask: With tens of thousands of satellites wrapped around the world, is this "star chain" plan reliable?
At present, it seems that it is not very reliable.
Not to mention the huge cost pressures required to launch satellites and the heavy resistance to policy. In terms of technology alone, the “star chain” plan is not good.
First, the rate is not enough.
According to the official document of the "Star Chain" program, the typical coverage area of a satellite is 3.53 million square kilometers, equivalent to more than 9 Germany and 220 Beijing. You know, there are only six countries in the world that are larger than this.
▲Maximum and downtilt data of Musk's Star Chain program satellite (Source network) ▲ Height and downtilt data of Musk's Star Chain program satellite (Source Network)
Even considering the use of phased array technology in satellites, the real service area is smaller than the coverage area, but its range is also amazing.
Now, Beijing has built about 20,000 towers, and there are more than one base station on each tower. Such a satellite can provide services for hundreds of such large areas in Beijing. Can the rate be? Of course not enough.
Second, it is difficult to connect.
A few days ago, there was a news on the Internet: Some people said that their mobile phone was connected to the Wi-Fi of Muske's TintinA satellite.
▲ Some people say that their mobile phone is connected to the Wi-Fi of Muske's TintinA satellite. (The source network is ▲ Some people call their mobile phone connected to the Wi-Fi of Muske's TintinA satellite (Source Network)
In a conversation with others, Musk called "Don't tell others, the password is martians."
▲ Musk talked to people on social media, saying, "Don't tell others, the password is martians" (图源网络)
Therefore, many people think that their smart phones can access satellite Wi-Fi in the future.
This idea is a bit naive, because the TintinA satellite is not as good as the average smartphone we use, and it is impossible for the two to communicate directly.
Radio waves have a characteristic. The higher the frequency, the stronger the directivity of the electric wave, which is more conducive to concentrating energy to transmit the signal to a distant place.
Musk's Internet satellites use the Ka and Ku bands, around 20 GHz.
▲Muske Internet satellites use Ka and Ku bands, mobile phones can not receive (map source network) ▲ Musk Internet satellites use Ka and Ku bands, mobile phones can not receive (Figure source network)
The Wi-Fi frequency bands used by our smartphones are 2.4GHz and 5GHz respectively. Relatively speaking, the omnidirectionality is relatively strong, and there is a relatively uniform signal in any direction around the router to facilitate our use. However, the omnidirectional signal attenuation of Wi-Fi is very serious, and it will be squared with the change of distance. If it is added to the air, it may be cubic attenuation.
Therefore, the 2.4 GHz and 5 GHz signals themselves cannot be transmitted far, and it is not expected to be transmitted to satellites in space.
So, can our mobile phone receive signals from satellites?
As mentioned earlier, the satellite's signal frequency is around 20 GHz. Our mobile phone does not receive the receiver of this frequency band at all, so it is impossible to receive it.
In other words, it is impossible for a mobile phone to receive a signal from the TintinA satellite, and it is impossible for the mobile phone's Wi-Fi signal to be transmitted to the satellite.
Therefore, the picture of a successful mobile phone connected to a successful satellite Wi-Fi is deceptive unless you are using a satellite phone.
How does the "Star Chain" provide Internet access for mobile phones on the ground?
The signal of the current mobile phone cannot be transmitted to the satellite, and the device directly communicating with the satellite cannot have a shadow top. Therefore, it is necessary to install a transponder in an outdoor space, communicate with the satellite at a frequency of about 20 GHz, and communicate with the mobile phone at 2.4 GHz or 5 GHz.
▲ "Star Chain" to provide Internet access for mobile phones on the ground, need to have a transponder (map source network) ▲ "Star Chain" to provide Internet access for mobile phones on the ground, need to have a transponder (map source network)
However, this transponder has a problem with the star frequency, which completely coincides with the 28GHz frequency of China's 5G plan. That is to say, in the future, there will be a 28GHz 5G micro base station on the street in China. If there is a satellite transponder of the same frequency, it will seriously interfere with the signal of the 5G micro base station.
2
So many experts do not understand?
Many netizens will have doubts. What Shu Shu said is quite reasonable, but Google, Facebook, and SpaceX have so many technical experts. Do they not understand?
It is reasonable to say that conventional scientific research projects must undergo technical argumentation. A little doubt must be repeatedly demonstrated to ensure that the scientific principles of all technical aspects are established and that there are sufficiently reliable engineering methods.
However, in recent years, the United States has developed an IT venture capital thinking. Unlike the conventional rigorous scientific research, its basic routine is to tell stories, sell feelings, and pull investment. It is a big propaganda to make some achievements, and the purpose is to attract more investment.
This kind of Internet routine, which does not report the worry, obscures a large number of technical obstacles that exist in reality. Therefore, the chances of failure of these projects are enormous, and the investors' money will follow suit.
Beginning in 2014, American scientists and technicians seem to have “broken their hearts” for the Internet problems of people all over the world. The plans are all kinds of useful satellites, useful drones, and useful hot air balloons. In short, they are going to heaven. The core selling point is to cover enough and enough users.
Here are a few examples:
* During the Spring Festival of 2014, a similar news also ignited the Internet: a US company called "Media Development Investment Fund" announced a plan called "Outernet" to launch hundreds of low-orbit satellites. To provide network services to 430 million people who cannot access the Internet.
Many people are very excited - finally able to access the Internet at high speed, cheap and unobstructed.
▲In 2014, a US company announced the launch of the “Extranet” program, with the goal of making the network cover the whole world (Source Network)
In reality, however, the core technology of this program is “one-way multicast”. The ground station organizes the information and uploads it to the satellite, which then forwards it to the covered area.
This is the same as satellite radio and television. You can choose the right information, but you can't upload the information.
Can not upload information is no interactive, QQ and WeChat can not be used, Weibo can not send, can only passively see push information.
This is a broadcast service and not an internet.
Interestingly, the company's promotional image conveyed the impression of two-way communication. For example, the picture below, people in the wilderness through the "extranet" to contact the satellite, suggesting that they can call rescue. In fact, the information cannot be uploaded.
▲ "Internet Development Investment Fund" company launched the "extranet" propaganda picture (map source network) ▲ "media development investment fund" company launched the "extranet" propaganda picture (map source network)
*In 2015, it was reported that Google and SpaceX cooperated to launch 700 communication satellites to build a global wireless Internet.
700 listens a lot, the key depends on how many people serve.
According to the 700 million users of 1/10 of the world's population, the average service per user is 1 million users. According to the total rate of 1 Gbps per satellite, the average user can only get 1 kbps, even far less than dial-up. Times can't be used at all.
* Google also launched a plan to use Wi-Fi to provide hot air balloons.
This is not a new trick, just copying the military tethered balloon (a balloon that uses a cable to smash it on the ground winch and control its height in the atmosphere). The idea of a stratospheric airship - placed on the gondola The communication transponder covers the combat area after being lifted off, and plays a role in communication relay.
▲Google's project name for providing Internet with hot air balloon is "Project Loon" (图源网络)
* In July 2016, Zuckerberg also followed suit with a plan to provide Internet services to people all over the world. This time, a drone that can emit lasers was used.
▲FaceBook's "Aquila" plan to complete signal transmission through a drone that can emit lasers (Source Network)
In fact, this type of drone has long existed, but it is mainly used for military purposes and is not known to the public. To this end, FaceBook also acquired a British company that produces such drones.
After careful study, there are many doubts about this drone program:
First, the difficulty of providing signals with drones is simply too great.
The signal provided by the drone to the ground covers a radius of about 100 kilometers and its speed is about 100 km/h. The signal coverage area with a radius of 100 km is moving at high speed. You must follow the drone at a speed of 100 km/h. Run to continue online.
Or arrange a drone every 200 kilometers, let them line up in sequence to fly. Obviously, this relay work mode is very unreliable.
The second is to use "laser" as a means of communication, and atmospheric interference is too great.
The report mentioned the use of "laser" as a means of communication, which has made many people excited, but it is not very reliable.
It is indeed feasible to communicate between the satellites via lasers. This is called the “interstellar laser link”, but it is in space without atmospheric disturbances.
In this way, atmospheric interference from a distance of 10,000 meters above the ground is a serious problem.
Third, the laser also has a strong directivity.
If you hold the laser pointer against the wall, you will find that if you are 10 meters away, even if the wrist is slightly shaken, the distance of the wall flare will be very far; if you look at the wall 20 meters away, the spot will beat. Go further.
▲ laser has good directional characteristics (map source network)
The drones in flight are very shaken, thousands of meters from the ground, so how big is the scale of the laser jumping back and forth on the ground?
The ground station emits laser light to the drones in the aircraft, and the angle of the laser transmitter must be continuously and accurately adjusted to keep up with the drones in changing positions. This difficulty is not as big as it is, and commercial applications are hard to succeed.
It can be seen from the above that whether it is a satellite, a hot air balloon or a drone, its propaganda idea is that the location is high enough, the coverage area is large, and the number of service users is large. It often plays a sentimental card that provides information freedom for the poor, and then gives a crowdfunding link.
However, due to the limited total rate resources, the average rate resources of users will be extremely thin, which they do not mention.
Later, the "Extranet" satellite program did not have the money to go, and the yellow balloon; and the Google Balloon and FaceBook drone plans did not.
Now, Musk’s “Star Chain” plan is starting to fire again. . . . . .
3
To let everyone go online, you have to learn China.
In theory, the bandwidth resources of a site are basically fixed, and the more users served, the less the rate of individual users.
So, how can everyone get high speed online?
The correct way to do this is to narrow down the site and allocate site resources to fewer people, each with more resources.
The scope of site services is getting smaller and smaller, which is also the development trend of 5G in the future.
Today, there are about 6 million 4G base stations in the world, and China has more than 4 million seats. Other base stations are jointly owned by more than 190 countries such as the United States.
Among the big countries, China's telecommunications coverage is the first, far ahead of the United States, Russia, Australia and other countries.
Why can China achieve such an achievement?
This stems from China's “village-to-village” policy—the government requires more than 95% of the remote mountainous areas to have telecommunications signals, and the tariffs must not be higher than the urban areas.
Since 2003, the Ministry of Industry and Information Technology has given the three major operators the task of telecommunications construction in remote mountainous areas every year. After more than ten years of construction, the target has been completed.
In December 2017, the author went to poverty-stricken mountainous areas in Guizhou to study poverty alleviation and went to Yanbo Village, Mudui Township, Liupanshui City, at a hilly area of 2000 meters above sea level.
When I got off the car, I took out the speed of the mobile phone and found that the speed of the network was as high as 30 trillion.
The village cadres introduced the local network situation: the 4G network was built long ago, and the village once asked him to arrange villagers to go to the ravine to find the signal blind spot.
What the village cadres don't know is that their village's speed has exceeded that of the Australian capital Canberra!
In the village of Caowangba, Pingzheng Yizu Township, Zunyi City, many homes are located in the depression on both sides of a hill. For these dozens of people, the relevant units installed two towers here to ensure that everyone enjoys the convenience brought by modern communication.
In fact, the fees charged by these villagers for one month are less than 800 yuan, and the electricity bills of the two towers are not enough. In fact, the fees charged by these villagers for one month are less than 800 yuan, and the electricity bills of the two towers are not enough.
China is at the forefront of the world in ensuring telecommunications coverage in remote and impoverished areas. In China, almost all remote mountain villages, railways, and national highways have signals.
The telecommunications coverage rate in the United States is much lower than that in China because they are taking a completely commercial road – operators are more willing to build base stations in economically developed densely populated areas, where they make more money and are less willing to build stations in remote areas with sparse populations. Because I can't make money.
Therefore, the famous Yellowstone Park has no signal, which is unimaginable in China.
After all, the slogan of Americans shouting "providing Internet services to people all over the world" has little practical significance. It is a priority to first smash the country's telecommunications coverage.
Now, many people lack understanding of the great achievements in the construction of China's telecommunications industry.
