Why is it so difficult to achieve "Internet freedom" at an altitude of 10,000 meters?

At a time when the Internet is highly popular, many passenger planes are still jokingly called "the last piece of pure land away from the Internet." Why is the speed of in-flight WiFi so impressive? When will the civil aviation industry enter the Internet age?

Interview experts

Zhang Chi (popular science expert "Occam's razor", communications teacher)

Wang Yanan (Editor-in-Chief of Aviation Knowledge Magazine, Member of the Science Popularization Committee of the Chinese Society of Aeronautics and Astronautics)

2018 is known as the "first year of in-flight WiFi in China". In January of that year, the Civil Aviation Administration of my country issued the "Guidelines for the Evaluation of the Use of Portable Electronic Devices (PEDs) on Board". Subsequently, electronic devices on civil aircraft were officially lifted, and passengers could use their mobile phones to connect to the Internet in "flight mode".

Today, inflight WiFi is about to enter its fourth year. However, the "2020 Civil Aviation Industry Development Statistical Bulletin" shows that as of the end of 2020, only 213 aircraft from 11 domestic airlines had the ability to access the Internet in the air, with a coverage rate of less than 6%, and aircraft with Internet connectivity are basically distributed among wide-body large passenger aircraft.

(Source: delta.com)

At a time when the Internet has become highly industrialized, civil aviation passenger planes still cannot achieve free Internet access, and are even jokingly called "the last piece of pure land for workers." This also makes people wonder, when will the domestic civil aviation industry, which has a market size of tens of billions, truly enter the "Internet era"?

The two types of airborne WiFi technologies have their own limitations. The principle of airborne WiFi is not complicated. Zhang Chi (Occam's Razor), a science expert and communications teacher, told reporters that according to the connection method, it can be divided into two categories: air-to-ground networking and satellite signals.

The Air-to-Ground method, also known as the ATG method, is to build a dedicated communication base station for aircraft on the ground along the flight route or in a specific airspace, and then use the ground base station to directly transmit information with the aircraft. Since this method is highly dependent on ground infrastructure, its disadvantages are also obvious: if it encounters special terrain such as mountains, rivers, and oceans, it is basically impossible to build a base station. For this reason, the ATG method has strong limitations.

In contrast, the "air-to-air" transmission scheme can circumvent the restrictions of terrain. Aircraft using satellite signals can directly "communicate" with satellites to access the Internet without going through ground base stations.

According to the Radio Regulations of the International Telecommunication Union, different radio communication services have different frequency bands. For example, the most commonly used frequency bands for satellite communications are the C (4-8GHz) and Ku (12-18GHz) bands, the latter of which is the mainstream choice for airlines to provide WiFi services. However, the speed of communication in the Ku band is not fast, and the actual experience is similar to that of terrestrial 2G or 3G networks. To make matters worse, the different postures of the fuselage will also cause a greater impact on signal reception, making the network speed even slower.

▲ATG and satellite communications are currently the two mainstream flight networking technologies (Source: gogoair.com)

Of course, the relevant technology has been constantly improving. On the one hand, the faster Ka-band satellite communication has begun commercial use in China; on the other hand, the traditional Ku satellite is also being upgraded to the Ku high-throughput satellite network. According to media reports, China Eastern Airlines has now increased its network speed to 27.5M/s, which is comparable to 4G network; Juneyao Airlines' Boeing 787 fleet has also been upgraded to carry the Ku high-throughput satellite communication system, allowing passengers to say goodbye to the "slow" network.

In fact, whether using ATG mode or satellite communication, both are ways to access the Internet from outside the aircraft. Passengers sitting in the aircraft use the in-flight WiFi to access the Internet at high altitude. In this system, the onboard communication components can achieve interconnection with the data centers of telecom operators and service providers, and the onboard server + onboard wireless hotspot constitute the wireless LAN in the aircraft, providing users with a familiar Wi-Fi Internet access environment.

What bottlenecks has the development of in-flight WiFi encountered?
As Internet speeds on the ground get faster and faster, it is inevitable that civil aviation will be fully connected to the Internet. In 2018, when in-flight WiFi was just launched, an organization predicted that by 2021, there will be more than 2,400 Chinese civil aviation aircraft that can connect to the Internet, accounting for 50% of the total number of aircraft.

But this forecast is obviously too optimistic. As of the end of 2020, the proportion of domestic in-flight Internet access is still less than 6%, and most passengers cannot enjoy in-flight Internet access services; even if they are "lucky" enough to connect to WiFi, the experience may not meet people's expectations, and sometimes even text messages cannot be sent and received normally.

▲Signals from satellites are sometimes blocked by the tail of the aircraft and cannot reach the radome on top of the aircraft (Source: SAS)

Why is it so difficult to get in-flight WiFi? Zhang Chi believes that the technical characteristics of ATG and satellite communication modes limit their respective development. For example, even if the speed of ATG communication is increased, it is only limited to some land areas and basically fails at sea, so it is not suitable for cross-border and long-distance flights. However, the passengers on these long-distance flights are the ones who have the greatest demand for in-flight Internet access.

Satellite communication channels are expensive. Nowadays, wide-body aircraft generally carry 300-400 passengers. If satellite communication channels are provided to so many people on the aircraft, the rate allocated to each person will become very low, which is a physical limitation.

In addition to the technical level, Wang Yanan, editor-in-chief of "Aviation Knowledge" magazine and member of the Science Popularization Committee of the Chinese Society of Aeronautics, analyzed that the slow progress of air networking is also closely related to cost, market and policy.

To achieve Internet access in airplanes, it is necessary to renovate old facilities or build new equipment. These hardware can be roughly divided into three parts: leased satellites, onboard equipment and ground base stations. Among them, onboard equipment includes ground-to-air communication components, airborne servers, etc. The price of an imported brand set is 6 million yuan, and the price of domestic equipment is also 2-3 million yuan.

For an aircraft worth hundreds of millions of yuan and several decades old, the cost of several million yuan for renovation may not be high. But the problem is that even if the airline equips all its aircraft with WiFi and pays a high price to communication equipment providers and network operators, it will still not be accepted by passengers due to the limited network speed, which can be said to be "losing money and not making any profit."

▲ATG antenna installed by the equipment supplier at the bottom of the test machine (Source: gogoair.com)

In terms of the commercial operation of in-flight WiFi, several major domestic airlines are not mature yet. The reporter learned that Air China and HNA both provide free Internet access, while China Southern Airlines adopts a points redemption system. Only China Eastern Airlines has specified paid services, but the prices are not high - the price of unlimited Internet access is 50 yuan, or 2,500 points (consumption is about 25,000 yuan) can be used to redeem.

"If domestic civil aviation passenger aircraft want to modify the onboard network equipment, they need to report to the Civil Aviation Administration of China and apply for approval. There are certain procedures and procedures, and they can only be implemented after approval." Wang Yanan said. Due to policy restrictions, the domestic ATG solution is still in the test installation stage. Whether it is a telecom operator or an aviation equipment manufacturer, they must comply with the relevant telecom management regulations and obtain relevant approvals and licenses before they can be used.

Taking various factors into consideration, even though most passenger aircraft are equipped with in-flight WiFi, the progress of in-flight network conversion is still slow.

The "network desert" in civil aviation transportation has been taken seriously. At present, China has developed into the world's largest Internet user country, with more than 1 billion Internet users, and is also the world's second largest air transportation market. Therefore, in theory, my country's flights have a great demand for in-flight wireless networks. In addition, as the global COVID-19 pandemic stabilizes in the future and 5G communications are fully popularized, the "network desert" in civil aviation transportation, where blind spots and opportunities coexist, may become a new business opportunity.

(Source: arstechnica.com)

It is understood that the current aviation low-altitude communication technology (i.e. the communication method between pilots and control towers) is still relatively primitive. After the missing Malaysia Airlines 737 disappeared from the radar, the control tower was helpless except to call the pilot through the radio, and finally relied on satellite communication to "handshake" with the passenger plane to determine the direction of the plane.

Therefore, the aviation industry has reached a consensus on development: future aircraft should be networked with each other. Wang Yanan said that aircraft can receive signals from each other and perceive the situation of all aircraft in the airspace: "It is conceivable that future aircraft will be high-level signal transmission and collection units."

"Even if we don't consider passengers using WiFi, (future) airplanes will become a large WiFi router, ensuring higher speeds and faster traffic in air-to-ground communications. On this basis, meeting passengers' network communication needs will be a natural thing," said Wang Yanan.

In the past two years, various forces in China have been accelerating the implementation of in-flight WiFi. In terms of the ATG model, since December last year, China Telecom, China Eastern Airlines, and Juneyao Airlines have jointly established "Air-Ground Interconnection"; Tencent, HNA Airlines, and Shenzhen Donica Airlines have jointly established "Flying Internet". On the one hand, these collaborations can enable operators to better build ground base stations and serve air users; on the other hand, the participation of more companies will help the industry improve its business model and explore a commercial air networking route that is in the interests of airlines and users.

On the other hand, the satellite communication model has also made new progress. At the end of April this year, China Satellite Network Group Co., Ltd. was officially established, and the commercial use rights of more satellites are expected to be opened in the future. Once the speed of satellite communication networking increases and the cost decreases, the user experience will also be improved.

(Source: ecns.cn)

The two ends of a mature industry must have a balanced and stable supply and demand relationship. One side guarantees service quality for consumers, and the other side brings economic returns to investment. Only in this way can the industry develop in a healthy way and avoid falling into a vicious cycle. In the future, airlines need to think more about their business models, conduct pilot operations during testing, and find business models that are more in line with national conditions.

"To solve this problem, we still need to rely on market promotion. For example, some airlines have achieved a high percentage of in-flight Internet usage. Under the same ticket price, passengers will definitely prefer flights with in-flight Internet access. This is also a promotion to the flight business." Wang Yanan said.

But in the final analysis, in-flight Internet is destined to not copy the ground Internet model. Zhang Chi believes that when passengers enjoy the Internet service on the plane, they should have a clearer understanding of the technology itself. "There is always a speed difference between airborne network communication and ground communication. This is caused by physical characteristics. The ground standard cannot be used to apply to the air. The role of satellite communication is always supplementary."

Written by reporter Zhao Tianyu

Editor/Ding Lin

Produced by: Science Central Kitchen

Produced by: Beijing Science and Technology News | Science Plus Client

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