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

Jujube Jun: today's article is the last (second part) of a series of articles entitled "50 years of vicissitudes: the Development of Satellite Communications in China". Read: (top) (middle).

Over the past decade, the whole society has paid more and more attention to satellite communications, and all kinds of news reports have emerged one after another.

There are two reasons for this. First, there is a strong demand for satellite communications from the market and users; second, the evolution of satellite communication technology has made the previously impossible possible.

In today's article, we will learn more about those things about the satellite Internet.

The technological evolution of █ satellite communication in the 1970s and 1980s, when satellite communication was just born, it was mainly used for television and radio signal transmission, as well as some telephone, Telegraph and fax needs.

At that time, the Internet (Internet) had not yet formed, so there was no concept of satellite Internet access.

In the late 1980s and early 1990s, Motorola in the United States began to engage in the Iridium project, which is based on satellite phones, and the business speed is only 2.4Kbps (Iridium Generation). At this rate, there is no user experience at all, and it would be nice to hear each other clearly.

Compared with our national satellite communication, the rate parameters of Iridium first generation and second generation started later. As mentioned in the previous article, in 1984, we launched the first practical communications satellite (Dongfanghong 2). In 1986, we built the first public satellite transmission network (mainly based on equipment purchased abroad).

In the earliest days, the technologies used in satellite communications, mainly SCPC (single channel single carrier) and FDM / FM (frequency division multiplexing / frequency modulation), are analog communication technologies.

With the outbreak of domestic program-controlled telephone business in the 1980s and the beginning of domestic contact with the Internet in the early 1990s, industry experts found that the analog technology used in satellite communications at that time could not adapt to the upgrading of digital communication technology in terrestrial public communication networks and was out of date.

As a result, satellite communications began to turn to IDR (medium data rate) technology.

IDR service is a new type of data communication service provided by Intelsat in the mid-1980s. Compared with the traditional FDM / FM,IDR, it is a digital upgrade and belongs to TDM / FDMA (time Division Multiplexing / Frequency Division multiple access) system.

IDR has four information rates: 1.544, 2.048, 6.312 and 8.448Mbps. When used in combination with DCME (Digital Circuit multiplier equipment), the transmission capacity of satellite dedicated line can be increased to 5 times. For example, the 8.448Mbps circuit can carry 600 channels of voice.

In May 1993, the former Ministry of Post and Telecommunications introduced IDR equipment from Spar Company of Canada to upgrade and build satellite ground stations all over the country.

Although IDR has achieved digital signal upgrades and increased bandwidth, it is still a drop in the bucket for the growing needs of users.

As a result, a new technology began to rise and spread rapidly, and that is the famous VSAT.

VSAT, full name is Very Small Aperture Terminal, very small aperture terminal. Note that VSAT usually refers to a system, not just a terminal.

A complete VSAT system is composed of transponders on communication satellites, ground large-caliber master stations (central stations) and many small-caliber small stations.

The basic architecture of VSAT, VSAT, solves the problem of "citizenization" of satellite communications.

The first is the miniaturization of the ground station. How small is the so-called "very small aperture"? 0.3-2.4 meters. This is very light, a person can carry around. A slightly larger one can also be carried by car and drive around in a car.

In addition to being portable, VSAT has the characteristics of flexible networking, low cost, many applications, simple installation and operation, which is very conducive to the popularization of satellite communications.

In 1984, Intelsat opened VSAT service for the first time. China soon followed up. In 1988, the former China Communications and Broadcasting Satellite Corporation introduced foreign communication equipment and built China's first VSAT communication network. It includes one main station and 35 end stations, providing communication services to eight industry departments, including the Ministry of Railways, the Ministry of Energy, the Seismological Bureau, the Oceanic Administration, the Civil Aviation Administration, the General Administration of Customs, the Economic Information Center and the Agricultural Bank of China.

Later, our country built wireless paging network, securities information broadcasting, village access / household access project, all of which made extensive use of VSAT. There are also many ocean-going marine communications, aircraft communications, corporate and government networks, which also use VSAT.

After the 2008 Wenchuan earthquake, telecom operators introduced a large number of VSAT equipment to deal with natural disasters, as a backup of the ground optical fiber network, as well as emergency communication tools.

After the █ high-throughput communication satellite entered the 21st century, the Internet Internet continued to flourish. The ubiquitous demand for network connectivity has stimulated the evolution of satellite Internet capabilities. If the satellite communication star wants to develop, it must upgrade the bandwidth capacity like the terrestrial cellular mobile communication network.

Many readers have heard of three kinds of orbits: GEO (geosynchronous orbit), MEO (medium Earth orbit) and LEO (low Earth orbit).

Communication satellites are mainly in the first three orbits, and the cost of launching satellites is extremely high. Therefore, it is hoped that a satellite can cover a large area. If you want to have a wide range of coverage, you have to put the satellite higher, that is, the GEO high earth orbit.

As shown in the following picture, three can cover the entire planet:

High-orbit satellites, although the coverage area is large, but the distance is long, communication is more difficult. At that time, the communication technology was not very mature, so the bandwidth of the wireless channel was relatively low and the communication rate was relatively slow.

Later, the satellite communication technology began to upgrade gradually, and finally began to appear a new generation of communication satellites, that is, high-throughput communication satellites (HTS,High Throughput Satellite).

The so-called "high-throughput" means that the bandwidth capacity of this kind of satellite is several times or even dozens of times more than that of traditional satellites (low-throughput, less than 1-2Gbps).

How does it do that?

First, a higher frequency band is used.

Traditional satellites generally use the C-band of 4-8GHz, which is low in frequency and too crowded. High-throughput communication satellites are widely used in Ku band (12-18GHz) and Ka band (27-40GHz). With rich frequency resources, the bandwidth will follow.

Secondly, the upgrade of satellite platform.

Just like the East 3, East 4, and East 5 introduced in the previous article, the satellite platform is getting bigger and bigger, the load capacity is getting stronger and stronger, and the power supply technology (electric propulsion plus chemical propulsion, hybrid) has been upgraded. so that the power can guarantee the high power consumption required for large bandwidth.

Third, the increase in the number of transponders.

This is also the benefit of upgrading the load capacity of the platform. The number of signal transponders has skyrocketed, which means more lanes and more bandwidth.

Fourth, the upgrade of antenna beam technology.

The improvement of antenna technology, especially the use of spot beam, can also enhance the signal capability. This is equivalent to "focusing" the light, not covering a large area, but concentrating on a small area, which is conducive to the improvement of the speed.

The Thailand Thaicom 4 (also known as IPSTAR) communications satellite launched on August 11, 2005 is claimed to be the first high-throughput satellite in the world.

The satellite, developed by Laura of the United States, weighed about 6.50 tons and had a power of 14 kilowatts. It was the largest commercial communications satellite in the world at that time, and was so large that it had to be put into orbit by a French Ariana V rocket.

The total bandwidth of Thaicom 4 satellite is as high as 45Gbps, which can provide users with data services of uplink speed 4Mbps and downlink speed 2Mbps.

The first high-throughput satellite in our country was Zhongxing 16, which was launched on April 12, 2017 (at first it was called Shi XIII, then it was renamed Zhongxing 16). The satellite uses a Ka-band multi-beam broadband communication system with a total capacity of 20Gbps.

In 162019, we launched Zhongxing 18, but failed. On July 9, 2020, we successfully launched "Asia-Pacific 6D", which is China's first Ku band high-throughput broadband satellite, with a total communication capacity of 50Gbps and a single beam capacity of more than 1Gbps.

It is reported that China's first high-throughput satellite, Zhongxing 26, with a capacity of more than 100 Gbps, will be launched in early 2023.

At present, the most powerful high-throughput satellite in the world should be the Viasat-3 of Viasat of the United States, which is said to have reached the Tbps level, but the launch time seems to have been delayed.

The rise of █ Leo communication satellites in addition to increasing satellite throughput, the industry has found that with the gradual decline in satellite launch costs, we have another way to improve satellite data transmission capacity-that is to develop to medium and low orbit.

The reason is simple: the orbit is low, although the coverage is small, but we can use quantity to make up for the coverage. Just like a cellular community, it is covered densely with a large number of satellites.

For satellite Internet, the industry generally divides its development into three stages.

The first stage was in the 1980s and 1990s, represented by Iridium Star. At that time, there were problems in the self-positioning of satellite communications. They tried to replace base stations with satellites, but they went too far and soon went bankrupt and failed.

After 2000, it is the second stage. This time, their idea is more pragmatic, that is, they intend to "eat leftovers".

They position themselves as a supplement to the ground communication system, providing network services specifically for users at sea, remote areas and other places. Although it looks marginal, the cake is actually very big.

Among them, the most representative enterprise is O3b.

In 2007, Greg Wheeler (Greg Wyler) founded O3b Networks Satellite. They work with telecom operators to provide broadband satellite communications services for islands or ships.

In order to balance cost and service experience, O3b Networks chose medium orbit (MEO) to deploy the satellite. The satellite cluster they operate is above the equator, about 8000 kilometers from Earth. This distance makes the ground station of O3b have higher transmission rate and lower delay.

In 2009, O3b received investment from SES, Google and HSBC. In 2013, after years of hard work, O3b finally had 12 satellites and officially launched the service. Soon, they achieved their profit target. Then, in August 2016, SES acquired O3b as a whole.

Greg Wheeler didn't stop messing around, starting another British company called WorldVU Satellite as early as 2012. Later, the company's name was changed to OneWeb.

In addition to Greg Wheeler, another big shot also saw the potential of the Internet and decided to join, which is known as the contemporary "Iron Man"-Elon Musk (Elon Musk).

Musk and Greg Wheeler jointly planned WorldVu's constellation in early 2014. As a result, a few months later, he quit and decided to go it alone.

In 2015, he formally proposed the Starlink project based on his space exploration technology company (SpaceX).

The Star chain project initially planned to launch 4425 satellites, with an increase of 7518 in November 2018, for a total of 12000. In October 2019, the number of SpaceX increased by 30, 000, bringing the total to 42000.

According to Musk's plan, these satellites will provide high-speed broadband Internet services to customers around the world.

The emergence of star chain indicates that satellite Internet has entered the third stage, that is, the era of low-orbit broadband satellite Internet.

On March 30, 2020, OneWeb filed for bankruptcy protection. On the other hand, Musk's star chain is going well so far. As of September 2022, SpaceX has more than 2300 star chain satellites in orbit and more than 500000 active users.

OneWeb screwed up because it couldn't raise enough money in the capital markets. The success of the star chain is due to the fact that SpaceX has recyclable Falcon rockets and can greatly reduce launch costs with the help of multi-star technology. OneWeb does not have the ability to launch a satellite. Before asking a country to help launch, there was a problem that the other party refused to launch. Musk's personal aura has also helped Star chain get more money, which can be safely burned. )

In addition to Star chain and OneWeb, in fact, there are many foreign companies engaged in low-orbit constellation projects, such as South Korea's Samsung space Internet project, Amazon's Kuiper project, Telesat's Telesat LEO project and so on.

█ domestic satellite Internet project progress foreign Leo satellite Internet project has made a lot of progress, we naturally can not be absent.

As we all know, our national communication infrastructure is very strong, with a wide range of optical fiber and mobile communications, and the world's leading speed and bandwidth, which can meet the needs of most users.

However, we still need to develop satellite communications. Because it's very, very important.

First of all, our country has a vast territory, and there are still blind areas in many remote areas. The network coverage rate that operators say is 99%, which refers to "population coverage". The "land coverage rate" is only about 30%. In other words, a large number of deep mountains, deserts, Gobi no man's land and other areas, there is no mobile phone signal.

For resource exploration, forest fire prevention, rescue and disaster relief, adventure tourism, wildlife protection and other purposes, satellite is an important means of communication, but also a means to save lives.

The Internet of things, which is very popular in recent years, has also begun to have the demand for satellites, which is mainly used for asset management, geological hazard monitoring and so on.

In addition to land, two important application areas of satellite communication are marine communication and airborne communication (aircraft communication). These demands are huge, and they are all high-value customers who are willing to pay.

If we don't have our own satellite Internet, we not only have to hand over our market share to others, but may also be controlled by others under special circumstances.

In the 2008 Wenchuan earthquake, we used foreign satellite phones. As a result, the service was inexplicably interrupted for more than ten hours. Since then, China has made efforts to build its own satellite Internet system.

In addition to the above reasons, we need to develop satellite Internet, especially low-orbit LEO satellites, and there is also a factor of seizing resources.

According to the Sadie consultancy report, the Earth's low-Earth orbit can hold about 60,000 satellites. It is predicted that a total of 57000 Leo satellites will be deployed in low-Earth orbit by 2029. So, if we don't rob it, the space orbit resources will be gone.

In addition to space orbit resources, we also have to compete for frequency band resources.

The international principle of space communication frequency band is "apply first, apply first". The main communication bands (Ku and Ka) of low-orbit satellites are gradually becoming saturated, which should be started quickly.

Next, let's take a look at the domestic progress in the low-orbit satellite Internet.

First of all, let's see the national team.

Shortly after the launch of the star chain plan, our country's China Aerospace Science and Technology and Aerospace Science and Industry Group put forward the "Hongyan Project" and "Hongyun Project" Leo satellite communication constellation plans respectively.

The former plans to launch 300 Leo communication satellites to form the first domestic space communication network with a combination of wide and narrow bands.

The latter plans to launch 156satellites (1000 km from the ground) and to build a spaceborne broadband global mobile Internet network to meet the high-speed access needs of a single satellite 4Gbps.

Since the announcement of the two major plans, test satellites have been launched.

Later, the situation changed a little.

On April 20, 2020, the National Development and Reform Commission included satellite Internet, 5G and industrial Internet in the information infrastructure for the first time, defining the great strategic significance of building satellite Internet.

On April 26, 2021, China Satellite Network Group Co., Ltd. (Xingwang Group) was registered in Xiongan New area. It is generally believed that this newly established large central enterprise will reintegrate resources and devote itself to building a larger Leo satellite mobile communication and space Internet system.

On the side of domestic private enterprises, there is also some action.

11:02 on January 16, 2020, Galaxy Aerospace, a private company, successfully launched its first low-orbit broadband communications satellite. The rocket carrying out this launch mission is the Clipper-1A carrier rocket.

The satellite is the world's first low-orbit broadband satellite in the Q / V band. After launch, the satellite can provide 10Gbps bandwidth communication capacity, covering 300000 square kilometers, which is equivalent to the area of about 50 Shanghai.

In addition to the low rail, we have not given up the high rail and the middle rail.

China Satcom was mentioned in previous articles.

In March 2018, the Ministry of Industry and Information Technology issued a license for the operation of basic telecommunications services to China Satcom, approving China Satcom to operate satellite mobile communications services and satellite fixed communications services nationwide. This means that China Satcom has become the "fifth largest operator".

This change is closely related to the vigorous development trend of satellite Internet at home and abroad.

In addition to the high-throughput satellites Zhongxing 16 and 26 mentioned earlier, China Satcom also has a lot of active layout on the satellite Internet.

In terms of marine Internet, China Satcom's Haisintong has provided services to 6000 Chinese ships and offshore platforms, covering more than 95 per cent of the world's routes.

Starfish navigation air Internet, China Satcom also established Star Interconnection in 2020 to complete the commercial maiden flight of domestic Ka broadband aircraft.

At present, China Satcom is constantly expanding its coverage along major international routes.

Another company in the high rail and medium rail layout, is China Telecom.

After China Telecom gave China Satcom to Aerospace Science and Technology Group in 2008, it did not give up its pursuit of satellite communications. On April 21, 2009, China Telecom Group Co., Ltd. established Satellite Communications Co., Ltd. On December 15, 2017, China Telecom established a satellite communications branch (hereinafter referred to as China Telecom Satellite Branch), which specializes in satellite communications business.

The satellite communications project carried out by China Telecom itself is called Tiantong No.1.

On August 6, 2016, Tiantong-01 was launched, which is the first star of the project. So far, three stars have been launched, namely 01,02 and 03 stars. In May 2018, China Telecom's independent satellite phone was released commercially, with the number section 1740.

According to the plan, the Tiantong-1 terminal covers the whole of China and its territorial waters, China's surrounding areas, the Middle East, Africa and other related areas, as well as most of the Pacific and Indian oceans.

Everyone can buy the Tiantong-1 mobile phone online, and the cheaper one is only 5000 yuan each. Tiantong-1 has performed well in major natural disasters in recent years.

The last one to be introduced is CITIC Satellite.

As I mentioned in previous articles, Citic participated in the formation of AsiaSat in the 1980s and has been a shareholder of AsiaSat since then.

In order to facilitate the legal and compliant development of satellite communications business in China, according to the requirements of relevant departments, CITIC Group transferred the business of AsiaSat in China to CITIC Network Co., Ltd., and specially set up CITIC Satellite (Beijing Satellite Communications Branch of CITIC Network Co., Ltd.).

The number of CITIC satellites is small, only a few, but it also covers Asia, Oceania, the Middle East, Russia and northeastern Africa, with strong satellite communication services.

The conclusion of █ is good. I have said so much that what should be introduced is introduced.

As mentioned at the beginning of this article, the whole society is paying more and more attention to satellite communications, and mobile phone manufacturers are starting to think about satellite communications. Maybe soon, our mobile phones will be able to support direct satellite communications, which is not entirely impossible.

In the future 6G, there are also plans and layouts for satellite communications. However, it is mainly focused on the integration of space and space, and the study of how to make satellites cooperate with ground communication systems is not to let satellites replace ground base stations. It is believed that with the advance of 5G-Advanced, more research progress will be announced in the future.

In a word, the development prospect of satellite communication is broad. Satellite Internet is just a process. The goal of mankind is to build a three-dimensional and full-dimensional network platform with the integration of air and space, so that communication can be realized everywhere.

Let's look forward to this day as soon as possible.

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

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