"Entering the Information Highway" Entering the Information Age PPT Courseware 3

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"Entering the Information Highway" Entering the Information Age PPT Courseware 3

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What is the "Information Superhighway"

The information highway refers to a large-capacity, high-speed communication network that can exchange various information.

Modern communication networks consist of optical fiber communication (laser communication), satellite communication, microwave communication, mobile communication and the Internet (network communication), which realize large-capacity and high-speed transmission of information, forming an "information highway".

1. Optical fiber communication

Optical fiber is referred to as optical fiber.

Optical fiber is a medium for transmitting optical signals.

Lasers are used in fiber optic communications. Not ordinary light. Because the light emitted by ordinary light sources is mixed with light of many frequencies, it is not only difficult to load information, but also has poor communication quality. The laser has high brightness, good monochromaticity and good directivity. The energy is always concentrated in the propagation direction, making it easy to modulate the signal.

The laser in the optical fiber propagates forward in the form of continuous reflection, so the optical cable does not need to be laid in a straight line.

Telephone, television, radio and other signals as well as data files can be transmitted on the "information highway" composed of optical fibers without interfering with each other.

Characteristics of optical fiber:

⑴Large information capacity. Since the frequency of light waves is much higher than the frequency of radio waves, the information capacity carried by light waves is much greater than that of radio waves. One optical fiber can simultaneously transmit an amount of information equivalent to 10,000 telephone lines. On the information highway composed of optical fiber, 500 TV channels can be transmitted simultaneously.

⑵ Fast transmission speed. Because what is transmitted is an optical signal. Optical fiber is by far the fastest transmission medium and can easily reach 1000Mbps.

⑶Long transmission distance. Optical fibers are very thin (as thin as a hair) and have two layers: an inner layer and an inner layer. Light propagates in the inner layer. Therefore, optical fiber has strong anti-interference ability, can reduce signal attenuation, and is suitable for transmitting large amounts of information over long distances.

⑷The frequency band is extremely wide.

⑸Strong anti-interference ability. Light propagates in the inner layer and is not affected by external electromagnetic interference.

⑹Strong confidentiality. Since it transmits light beams, it does not radiate signals outwards, effectively preventing eavesdropping.

⑺Economic. Save metal, not afraid of moisture, not afraid of corrosion, long service life.

2. Satellite communications

1. What is the role of satellites?

2. If people all over the world can see a certain scene immediately, how many satellites are needed as relay stations?

3. Of the many TV programs you watch at home, which ones are delivered via satellite?

Satellite communications use artificial earth satellites as relay stations. The satellite receives the signal from the ground station, amplifies it, and then forwards it to another ground station.

3.Microwave communication

Read the textbook and answer the questions: (Compare to see who can find it faster)

1. Why use microwave communication?

2. What is the wavelength range and frequency range of microwaves?

3.What are the properties of microwaves?

4.What is the function of microwave relay station?

5. What are the distance requirements for establishing a microwave relay station?

6. Can the moon, the earth’s natural satellite, be used as a relay station?

mobile communications

Mobile communication refers to a communication method in a certain area that allows people and vehicles (or ships) to dial and connect with each other through radio communication equipment and telephone exchange equipment between moving people and vehicles (or ships) and users of the local telephone network.

Mobile phones use microwave signals to communicate with the telephone network.

my country's mobile communications adopt a "cell system", which divides the entire coverage area into many hexagonal cells, one after another, forming a honeycomb structure, hence the name "cellular mobile phone". Handheld mobile phones (cell phones) are one of the members of mobile communications.

Cellular mobile communication uses cellular wireless networking to connect terminals and network devices through wireless channels, allowing users to communicate with each other during activities. Its main feature is the mobility of the terminal, and it has the functions of handover and automatic roaming across local networks.

Cellular mobile communication services refer to voice, data, video, image and other services provided through a cellular mobile communication network composed of base station subsystems, mobile switching subsystems and other equipment.

Cellular mobile communication services include: 900/1800MHz GSM second-generation digital cellular mobile communication services, 800MHz CDMA second-generation digital cellular mobile communication services, and third-generation digital cellular mobile communication services. 3G

Global Positioning System (GPS)

The Global Positioning System (GPS) is a system that can quickly provide precise location and time information. Globally available, 24/7 service.

The GPS global satellite positioning system consists of three parts:

Space segment: GPS satellite. There are 24 satellites with atomic clocks in space forming a distribution network, which are distributed in 6 geosynchronous orbits more than 20,000 kilometers above the ground and with an inclination angle of 55°. There are 4 satellites in each orbit.

GPS satellites orbit the earth every 12 hours, allowing any place on the earth to receive signals from 7 to 9 satellites at the same time.

Ground segment: ground monitoring system. Ensure the accurate timing of the space atomic clock and complete the calculation of navigation data.

User segment: GPS signal receiver.

The GPS system was originally jointly developed by the U.S. Army, Navy and Air Force in the 1970s. Its main purpose is to provide real-time, all-weather and global navigation services for the three major areas of land, sea and air, and is used for intelligence collection and nuclear explosion monitoring. Some military purposes such as military and emergency communications are important deployments of the US strategy of global dominance.

Nowadays, the application of GPS system is not limited to the military field, but has developed into various fields such as car navigation, atmospheric observation, geographical survey, ocean rescue, and manned spacecraft protection and detection.

Pros and Cons of the Information Age

⑴While it brings convenience to people, it also gives criminals many opportunities to take advantage of it. Such as Internet scammers, mobile phone text message scammers, etc.

⑵Electromagnetic radiation. Such as the radiation hazards of mobile phones and computers to the human body.

⑶ While useful information is disseminated, false information, bad information, harmful information, etc. are also spread. Such as pornographic, violent videos, pictures, texts, etc. that poison young people.

Practice in class

1. Information theory shows that the higher the _______ of electromagnetic waves as carriers, the more ______ that can be transmitted in the same time.

2. The operating frequency of television broadcasting is generally 30 MHz ~ 3×105MHz, and the operating frequency of sound broadcasting is generally 102 kHz ~ 30MHz. It can be seen that ______ broadcasting transmits more information than ______ broadcasting in the same time.

3. Microwaves are electromagnetic waves with frequencies between _______MHz and _______MHz. The properties of microwaves are closer to _______. They also generally propagate along _______. Microwaves _______ (optional "can" or "cannot") orbit along the surface of the earth. Therefore, a _______ must be built every _______km or so to process the incoming signals and then transmit them out to achieve long-distance communication.

4. The development of modern science and technology has enabled people to realize their dream of satellite communications. Satellite communication uses _______ as a relay station for microwave communication.

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"Stepping onto the Information Highway" Entering the Information Age PPT Courseware 2:

"Entering the Information Highway" Entering the Information Age PPT Courseware 2 What is the Information Highway? The Information Highway refers to a large-capacity, high-speed communication network that can exchange various information. Modern communication networks consist of optical fiber communications (laser communications), satellite communications, micro...

"Stepping onto the Information Highway" Entering the Information Age PPT courseware:

"Entering the Information Highway" Entering the Information Age PPT courseware 1. The information highway refers to the communication network of ________ and ________ that can exchange various information. Signals and data files such as telephone, television, radio, etc. can be transmitted on ________ The information highway that constitutes...

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Update Time: 2024-09-24

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