Traditional Culture Encyclopedia - Traditional festivals - What's wrong with satellite internet access? How did it happen?
What's wrong with satellite internet access? How did it happen?
* * * * There are eleven network service providers providing satellite access services in the world, with a total of more than one million users. Users who use satellite to surf the Internet need to equip their computers with a Zhang Weixing network PCI card, which is connected with a satellite receiving antenna with a diameter of about 75cm. The user clicks a website on the browser software, and the website request signal is sent to the user's Internet service provider by the modem. After receiving the request signal, the satellite network operation center obtains the required information from the corresponding website according to the user's request, then uploads the information to the satellite, sends it to the user's receiving antenna at high speed and high bandwidth, and then transmits it to the user's computer.
In addition to a wide variety of services, the biggest feature of satellite Internet access is its high speed. Compared with traditional modems, satellite Internet access speed is several tens to hundreds times faster, which is 28 times that of 14.4k modems. It supports all standard TCP/IP network protocols and applications, such as HTTP, FTP and SMTP. So you can download the big files you want quickly and effectively. The system equipment required for the satellite live broadcast network service is the network operation center (NOC), the 7- 1 1m diameter satellite transmitting antenna, and the uplink master station with 24M satellite bandwidth. At the same time, the network resources designated by users can be obtained by connecting to the Internet through broadband private lines. Satellite signals are converted into satellite signals by QPSK satellite modulation and coding in Ku band, and then broadcast and transmitted to users. The client only needs a Pentium /90, 16M, 20M HD or above, Windows 95 or NT Workstation4.0 operating system, 14.4kbps or above modem, 0.75-0.9m satellite antenna, Ku-band satellite signal receiver, satellite modem card, driver and application software suite. When in use, dial ISP with a common modem, and use satellite 400K rate for uplink and downlink. At the same time, it provides 3M broadcasting bandwidth for website broadcasting, securities information, data transmission, distance education and other functions. For general enterprises, digital packet express and multimedia transmission services with satellite Internet access can transmit digital information from a single point to multiple points very quickly, such as transmitting transmission software, electronic files or training courses in enterprises to branches, distributors, chain stores and members. In addition, the broadcasting function of satellite internet access can be arranged in advance like TV programs, or according to the requirements of users. Satellite Internet service is relatively reasonable in cost because of its high-speed and ideal transmission mode, so it is gradually developing into a brand-new broadband access mode.
In June 5438+10, the national satellite broadband internet access fee was equivalent to ADSL.
China Satcom Satellite Broadband Beijing Gateway Station was handed over on 24th, and the Northeast, North China and Central China have since realized satellite broadband access to telephone, TV and Internet. It is estimated that by June 65438+ 10 this year, the gateway stations in Shanghai and Guangzhou will also be opened, and satellite broadband access will cover the whole country by then.
According to the person in charge of China Satcom, the use of large-capacity satellite broadband system is not only for high-end users such as individuals and groups who need stable broadband access, but also for urban blind areas and remote mountainous areas where ground networks are difficult to cover. The reporter learned that the capacity of broadband satellites is several times higher than that of traditional satellites, which makes satellite communication realize large-scale economic effects for the first time, thus reducing the use cost. The calculation shows that there is almost no difference between broadband satellite access and broadband access such as ADSL.
The new access technology can improve this situation to some extent, that is, the high-speed broadband multimedia access system using the Diiec PC technology of Hughes Company in the United States. This is a one-way satellite broadcasting system with asymmetric Internet access.
What is an asymmetric approach?
A major feature of Internet application is the asymmetry of information transmission. When users browse the Internet, a short request may lead to the return of downloaded files, which contain thousands of times the requested information. If you download through a modem, it often takes a long time. So, can you reduce the bandwidth of uploading and increase the bandwidth of downloading?
DirecPC technology can solve this problem. Direc PC satellite transmission service is a high-speed broadband multimedia access technology introduced by Hughes Network Systems in the United States in 1996. 1996 won the gold medal for the latest product of Data Communication magazine in the United States. In recent years, Direc PC technology is popular all over the world, not only in the United States, but also in Canada, Mexico, Germany, North Africa, the Middle East, India, Japan, South Korea, Taiwan Province Province and other countries and regions.
principle of operation
The basic equipment of the satellite system is the Network Operation Center (NOC), which includes a satellite antenna with a diameter of 7 meters and a 54-meter uplink master station. Others include private broadband networks, which are used to connect to the Internet or broadcast to users through Ku-band QPSK satellite modulation encoders.
The working process of the system is: users access the Internet through dialing, ISDN or special lines, and transmit service requests such as browsing web pages and downloading files to the NOC of the network operation center for processing. Before requesting to leave the user's PC, the client software will attach a header code to the request information. After receiving the request information, NCO will delete the header code and obtain the required content from the corresponding website according to the information address. NOC then sends these contents to the satellite at an uplink speed of 24Mbps, and then the satellite transmits them to the user's receiving antenna and enters the computer. The minimum configuration of the client is a Pentium90 computer, 16M memory, 20M hard disk space, and a modem above14.4kbps. In addition, a satellite receiving antenna with a diameter of 0.75-0.9 m and a computer need to be installed. Operating system is Win95 or Win NT.
Technical features:
1, using asymmetric high-speed satellite transmission technology to optimize network bandwidth;
2. Support standard TCP/IP protocol, WWW, email, newsgroup and Telnet；;
3. Support one-way streaming video and audio real-time multicast;
4. Support one-to-many 3Mbps extremely fast data file transmission, and the receiver is not limited;
5. All transmitted data are encrypted by DES, which is safe and reliable.
At present, there are 1 1 ISPs providing similar services in the world, with about 65,438+million users, distributed in the United States, Japan, South Korea, Taiwan Province Province and other places.
In China, the satellite access systems of "Star Netcom" and Turbo 163, represented by the Engineering Department of Satellite TV Weekly, have been opened. As far as the cost is concerned, satellite access is reasonable, and its ideal transmission mode is high speed, which can be affordable for both enterprises and individual users. Now, Internet users all over the country can enjoy high-speed Internet access via satellite.
In order to access the Internet at high speed, broadband access technology came into being. This paper briefly compares several popular Internet broadband access methods, and emphatically introduces the satellite broadband access technology of the Internet, its application fields and development prospects.
Keywords: Internet satellite communication access technology broadband technology
I. Introduction
After more than 20 years of great development, the Internet has become the computer information network with the widest coverage, the largest scale and the richest information resources in the world. It is not only a special means to transmit scientific research data between universities and scientific research departments, but also a multimedia means for people's daily work, study, life and entertainment. In China, Internet services have developed more rapidly in recent years. According to the latest statistics of China Internet Network Information Center, by the end of 1999, there were 4.5 million domestic users and the total capacity of international lines reached 241m. However, contrary to the development, people who have used the Internet have a feeling that the internet speed is too slow, especially when downloading materials, which makes people feel quite impatient and even give up their visit, so that many netizens jokingly call WWW the World Wide Web. From the perspective of the whole network, the slow speed of the existing Internet backbone network is one of the reasons for the slow network speed, but it is gradually being solved with the expansion of the backbone network; The main reason is that most Internet users still use the traditional Internet access method, that is, a pair of telephone lines plus an analog modem. Even the latest modem based on V.90 standard is only 56kbit/s, and its access rate is low, which can't meet the growing multimedia communication needs of users. It can be seen that the bottleneck effect of access network leads to low network speed. Although FTTH can solve the "bottleneck" effect of access network and is the future development direction, it will be a huge investment to solve the "last mile" bottleneck, which is difficult to achieve at present. Therefore, finding a high-speed access mode that can meet the needs of users and is easy to realize at this stage has become the focus of attention. In this case, the satellite-based Internet came into being, and increasingly showed its strong advantages and development prospects.
Second, the comparison of several high-speed Internet access methods
Judging from the current research results and applications, people are mainly optimistic about ADSL, Cable Modem and satellites.
ADSL broadband access mode, namely asymmetric digital subscriber line technology, has unequal uplink and downlink transmission rates. It can provide an uplink rate of several hundred kbit/s and a downlink rate of up to 6Mbit/s on the existing telephone access network with copper twisted pair as the medium. Its advantages are high access rate, ready-made network, surfing the internet and making phone calls. The disadvantage is that the rate is limited by distance, not everywhere, and the existing PSTN network needs to be transformed. China Shenzhen Data Communication Bureau has opened ADSL broadband access service, and the rate of accessing local network can reach1.5mbit/s. The ADSL terminal equipment and debugging cost is 3800 yuan, and the monthly rent is in 420 yuan.
Cable Modem broadband access mode is to realize high-speed Internet access by using the existing cable TV network CATV and HFC as the medium. Its uplink rate can reach 10 Mbit/s and downlink rate can reach 30 mbit/s. Its advantages are high access rate, ready-made network, access to the Internet and watching TV, and the speed is basically not limited by distance. The disadvantage is that the channel bandwidth of cable TV network is * * *, which means that with the increase of users, the bandwidth of each user will be less and less; The noise of the client will be superimposed on the front end, forming the so-called noise interference "funnel effect"; In addition, traditional cable TV is a broadcasting service, so we should pay attention to safety and reliability when communicating with each other. At the same time, the existing cable TV network needs to be transformed. China Guangdong Video Broadband Network has opened Cable Modem service. At present, the uplink and downlink rate is 10 Mbit/s, the equipment installation fee is 2,500 yuan, and the monthly rental fee is 120 yuan /40MB.
Satellite broadband access refers to users' direct access to the Internet via satellite. At present, the broadband access rate of satellites is generally 400 kbit/s, and the download rate of multimedia can reach 3 mbit/s, which has the advantage of high access rate; No geographical restrictions, and truly realize seamless access to the Internet; It can also receive satellite TV. The disadvantage is that reception will be affected by weather, especially rain and snow; At the same time, the initial investment cost is high. China Telecom and Hongkong Sunway Communication Network will launch a broadband satellite Internet transmission service named TURBO 163 in China. It is estimated that the customer's equipment installation fee is about 3,500 yuan, and the monthly rental fee is about 300 yuan.
Comparing the three broadband Internet access modes, ADSL and Cable Modem have great advantages in MAN, while in WAN, satellite system is the most promising, which can not only realize high-speed seamless access to the Internet, but also realize satellite live broadcast to households.
The third is the core technology of Internet satellite broadband access.
Asymmetric interaction model, we know that users' access to Internet data is asymmetric, with high downlink rate and low uplink rate. However, traditional communication devices and networks are based on symmetric models. Under the condition of asymmetric information, the utilization efficiency of communication resources is very low, which implicitly leads to the waste of resources. The asymmetric interaction model of communication channel matches the asymmetric model of information flow. This mode does not increase the capacity of the physical channel in essence, but giving full play to the role of the communication system will help improve the efficiency of the system. The concept of asymmetric communication model matching will change the concept of traditional communication field.
Broadband technology can allocate bandwidth according to users' needs and provide services at different rates. Ordinary individual users only provide network access services. For professional users, in addition to providing high-speed network access services, it also provides multimedia information transmission, webpage playing and news playing services; For enterprises that can connect to the intranet, provide high-speed internet access for many people at the same time.
In point-to-multipoint broadcasting technology, the biggest advantage of satellite system is "broadcast mode", that is, "point-to-point" mode. This one-way, broadcast information exchange mode is very effective for the high-speed transmission of a large number of * * * information, and undoubtedly has economic benefits for people who need to transmit data at multiple points, such as distance education, while adopting a general network requires extra bandwidth and expenses.
Cache technology, there is a cache area in the satellite network operation center (NOC), which stores the most popular websites for users to access quickly. The NOC here is the core of Internet satellite broadband access system, and it is a computer system with high-performance server as the core. NOC includes buffer area, Internet access module and satellite data transmission module. It has the function of uploading data to the satellite and can surf the Internet at high speed in real time.
In addition, there are PUSH, real-time transmission/control protocol, resource reservation protocol, public key cryptosystem and other technologies.
Internet satellite broadband access system
At present, the common Internet satellite broadband access systems mainly include DirecPC and InSAT, among which DirecPC has more users.
DirecPC combines the satellite communication system with the terrestrial telephone network, that is, the telephone network is used as the uplink channel of the Internet, and the satellite channel is used as the downlink channel of the Internet to realize high-speed Internet access. The biggest difference from ordinary telephone transmission is that DirecPC is not completely transmitted by satellite in both directions, and the user's receiving antenna can only download files and cannot send instructions for the user. Therefore, satellite internet users need to send instructions through the local ISP, but all the instructions sent are accompanied by the satellite internet IP address for file download (the PC card on the user's computer has a dedicated IP address).
The working process of DirecPC satellite direct dial network service is as follows: When dialing the Internet, the DirecPC software in the user's computer will notify the service provider (ISP) at the same time, and transmit the Internet access request to DirecPC Network Operation Center (NOC). If the site the user wants to visit is in the cache area of the NOC, the center will immediately transmit the contents of the webpage to the user via satellite; If the site that the user wants to visit is not in the cache area of the NOC, the center immediately obtains the information that the user needs from the network host where the target information is located, and then transmits it to the user through the satellite channel. It can be seen that the satellite channel replaces the transmission channel from the network where the target information is located to the local network and the telephone line from the local network to the user, and the transmission rate has been greatly improved. Take a 2MB file as an example, it takes 9 minutes to download with a 33.6kit/s modem and 40 seconds to download with a satellite at a speed of 400 kbit/s. For users, besides personal computers, they need to be equipped with a satellite adapter card, a dish antenna and a set of DirecPC software. Insert the adapter card into the computer, install DirecPC software, connect the antenna, and you can surf the Internet. In Ku band, the diameter of the antenna is about 60 cm.
Undoubtedly, the DirecPC satellite direct dial network service is actually a one-way "effective broadband network", which mainly uses satellites to solve the problem of high-speed data download that telephone lines cannot solve, and users still need to rely on terrestrial telephone networks. For places that can't access the Internet through telephone lines now, we can give full play to the characteristics of satellite access system, such as long communication distance, distance-independent, large coverage area, and no geographical restrictions, and adopt two-way satellite transmission, namely InSAT, to access the Internet to realize ubiquitous Internet services.
Two-way satellite transmission can be realized through VSAT. For example, the current TDM/TDMA data VSAT system can be considered to be basically designed according to the client/server mode, and the two-way traffic is ten times different. Of course, other VSAT systems, such as TDMA or SCPC, can also be used. It should be selected according to the needs of practical application, and it is best to improve the existing VSAT system to meet the needs of Internet communication.
The application status and development prospect of verbs (abbreviation of verb)
Internet satellite broadband access can not only provide users with high-speed Internet access services, but also transmit information to every corner of the earth. It is precisely because of these advantages of satellite access that satellite communication is rapidly becoming an important way to access the Internet. In many countries and regions such as North America, Europe and Asia, satellite access to the Internet has been widely used, and its application fields have expanded to remote courses, medical services, securities services, file transmission, multimedia services and instant news alerts. With the launch of TURBO 163 service in China, the bandwidth bottleneck caused by the rapid growth of Internet users in China will be solved. At the same time, I believe that with the launch of China Internet broadband satellite service, it will promote the development of Internet in China.
First, the development of VSAT.
Driven by the Internet, like other communication technologies, satellite communication is turning to meet the comprehensive needs of data communication.
. Specifically, on the one hand, the mature VSAT system based on C-band and Ku-band technologies has evolved to meet the needs of Int.
Ernet business requirements, and become an important part of the global Internet, on the other hand, the use of higher K.
A-band technology, a broadband satellite communication system that can truly realize personal communication, especially the low-orbit satellite group system is being opened.
In the process of development, testing and construction, more and more telecom network operators, ISP and ICP choose satellite communication to provide Internet access.
An important means of rnet service. VSAT is the mainstream technology of satellite communication at present, and its application is quite successful and popular.
However, the service rate provided by traditional VSAT is not too high, the inbound link rate reaches 64 KB/s, and the outbound link rate is generally acceptable.
Up to 5 12kb/s, with the emergence of various new applications, higher speed is required. Some compete in VSAT market.
Large companies invest a lot of money and manpower to improve the network speed in a competition. Because the faster the VSAT network is,
The more competitive the company that buys and sells it is. The VSAT network currently under construction can support the outbound link speed up to 2MB/s.
Rate, many VSAT companies plan to make the network speed reach 20 MB/s or higher at the beginning of this century.
VSAT is very rapid in improving speed, and VSAT products flooding into the market are usually named turbo, cyber and surfer.
Such words are used as prefixes or suffixes. For example, the latest high-speed VSAT products in the industry are: Comsat Laboratory's Link.
Way2000 system, high-speed turbine satellite VSAT of GE Spacenet, SkySurfer VSAT and New Medi of Gilat.
A's CyberStream VSAT product.
Speed alone is not enough. VSAT system constantly absorbs all kinds of latest information technologies, such as IP multicast and digital broadcasting technology.
PUSH technology supports TCP/IP, UDP/IP and other protocols, and extends the characteristics of satellite high-speed broadband broadcasting to the network.
Application provides effective solutions for many new applications. In fact, VSAT has become a rapidly developing country in the world today.
Data services, especially part of the Internet.
The application of VSAT system in Internet access mainly includes the following ways:
1. Provide long-distance Internet connection for large ISP.
According to statistics, at present, about 80% of Internet information in the United States is stored in computers. Many ISP, content providers
Commercial and communication operators and multinational enterprises hope to access the North American Internet backbone efficiently and directly through satellite systems.
Connect and establish a high-speed link with the American Internet. These links may be rate symmetric or asymmetric, and the chain
There is a relatively stable data flow in both directions. Because of the asymmetry of Internet traffic, it is usually aimed at customers.
Provide the exact requirements of asymmetric satellite links. At present, many companies provide such products and services, and the system generally adopts.
SCPC/DAMA system. For example, Loral Orion Company through China Telecom (Hongkong) International Access Company (CTIA).
Support and provide satellite cross-border private network services to multinational companies in China.
2. Extend the Internet to remote areas and provide links between ISPs.
Provide PPP (point-to-point) interconnection for areas with insufficient communication capacity, and provide it between large ISPs and their subordinate small ISPs.
High-speed connection, which is mainly in one country. The incoming rate, that is, the amount of information sent to the main ISP, is relatively low.
Such as the connection between cstnet network center and more than 50 entry points in China, and the VSAT service network of Jinqiao information network.
The high-speed satellite channels of China Education Network can all belong to this application.
3. Connect directly to the computer (including connecting to the LAN server)
For decades, only government agencies and large companies with strong financial resources can enjoy the rapidity, flexibility and flexibility of satellite communication technology.
Conveniently, a series of new technological developments, such as satellite communication and computers, have formed a new VSAT system.
In fact, this new architecture is called Direct to PC or PCVSAT, and satellites will serve ISP through point-to-multipoint connection.
The server is directly connected to the user's computer, so that all kinds of companies, big or small, and even individual users can use spatial data communication.
Powerful.
1) working principle
In this way, the user accesses the database or network by dialing, and then passes through a satellite with a diameter of about several tens of centimeters.
Receiving antenna and special receiving equipment, receiving and downloading database or
Online information. This method gives full play to the access function of existing telephone lines and the broadcasting function of satellite communication. Taju
It has the advantages of convenient installation, avoiding network congestion, low price, large download channel capacity and similar service to optical fiber.
Grade and IP broadcasting services, thus becoming the focus of recent development.
Typical end products of satellites directly connected to computer services include PCs equipped with modems, satellite receiving adapters and small satellites.
Antenna (aperture 60-90cm) and system software. In enterprise applications, the satellite receiving adapter card is installed on the server.
Every PC sends files through the server.
The working process is as follows: the user clicks a website on the browser software, and the modem sends out a website request signal (URL).
Send it to the user's ISP, and then the system software will attach an IP generation to the URL before requesting to leave the user's PC.
Code that instructs ISP to forward the user's URL request to the network operation center (NOC) of the satellite system, and the network operation center receives it.
After this request, delete the code, and then send a request signal to the corresponding website, and the website will send the required information.
Back to the network operation center, network operation center
The information is transmitted to the satellite, and then the satellite sends it to the user's satellite antenna at a high bandwidth rate and enters his PC or
Web server (for enterprise users). In this way, you can browse the web and download text at a speed of up to 400 KB/s..
Pieces, three times faster than the standard ISDN.
2) Provision and use of services
Internationally, one-way satellite internet access has been successfully applied to small and medium-sized enterprises and families. Direct selling PC companies in the United States
, Japan's Direct Internet, Canada's Telesat, Australia's Telstra, India's NIC India, etc.
China and neighboring countries adopt DirecPC system to provide this service. Germany has also launched a similar service called skyDSL.
Service.
It is worth noting that Compaq, the world's largest PC manufacturer, became a partner of DirecPC last year. Then Compaq released it.
A new scheme of providing users with internet service via satellite was introduced. In mid-April, 1999, PC users began to be customized.
Internet access is provided through DirecPC satellite system, and users can access the Internet on the navigation computer of the store or the computer of Compaq Company.
This website orders DirecPC satellite information service for self-assembled personal computers.
1in the middle of 999, a strategic agreement between Hughes network and AOL attracted the attention of the industry, and AOL turned to
Hughes Networks invested $6,543.8+0.5 billion to develop new products and services for Internet and satellite live broadcast. through
Through this cooperation, Hughes Networks will provide AOL interactive TV service for its 7 million DirecTV users, and AOL will
Providing Hughes DirecTV and DirecPC services to its 654.38+06 million users. Designed and manufactured by Hughes Networks.
Set-top boxes for DirecTV and AOL TV.
With the promotion of these famous companies, satellite network service has gradually become a new choice for surfing the Internet.
At present, China plans to provide users with high-speed Internet access, digital package delivery and other services by using the DirecPC system of Hughes.
There are three companies' broadband satellite communication information networks used for media information broadcasting. They are:
① Guangzhou Post and Telecommunications Administration cooperated with Hughes Network Company and Oriental Satellite Company to provide 400 KB/s direct access to computers.
Satellite internet content download service, digital parcel delivery and multimedia broadcasting up to 3 MB/s ... The plan will be in the near future.
Put into operation and provide services to commercial and individual users nationwide.
② Beijing Tianguang Information Communication Service Co., Ltd., a satellite network operation center built by Beijing Tianke Network Integration Company.
At present, the debugging has been completed. The first phase of the project is mainly aimed at enterprise users, and the user terminal is Hughes' PES terminal station plus DirecPC.
Terminal, that is, dial back through PES satellite circuit, DirecPC downloads at high speed. Further development for individual users.
③ China Shuangwei Communication Network and China Zhuke Technology jointly owned by China Telecom Data Communication Bureau were established last year.
In August, we just signed a $3 million contract with Hughes. Sunway Network Company purchased DirecPC equipment and used their satellite technology.
At the beginning of next year, China will launch a satellite Internet access plan named Turbo 163, and the target customer is China.
1/4 customers. The company expects that the charge will not be more than twice as high as the current 163 network, but the speed is ok.
Increase 20 times-that is, the maximum internet access rate.
From the current 38.8K to 400K. Shuangwei Com will take the lead in providing civil Internet service combining satellite and terrestrial network in China.
Commercial company.
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