CLASS IX NetworK and Types of Networks......

 A group of two or more similar things or people interconnected with each other is called network

 Some of the examples of network in our everyday life includes: • Social network • Mobile network • Network of computers • Airlines, railway, banks, hospitals networks A computer network is an interconnection among two or more computers or computing devices. Such interconnection allows computers to share data and resources among each other.

Types of Networks There are various types of computer networks ranging from network of handheld devices (like mobile phones or tablets) connected through Wi-Fi or Bluetooth within a single room to the millions of computers spread across the globe. Some are connected wireless while others are connected through wires. Based on the geographical area covered and data transfer rate, computer networks are broadly categorised as:

 • PAN ( Personal Area Network)

 • LAN (Local Area Network)

 • MAN (Metropolitan Area Network)

 • WAN (Wide Area Network) 

 Personal Area Network (PAN) It is a network formed by connecting a few personal devices like computers, laptops, mobile phones, smart phones, printers etc.A personal area network may be wired or wireless. For example, a mobile phone connected to the laptop through USB forms a wired PAN while two smartphones communicating with each other through Bluetooth technology form a wireless PAN or WPAN.

Local Area Network (LAN) It is a network that connects computers, mobile phones, tablet, mouse, printer, etc., placed at a limited distance. The geographical area covered by a LAN can range from a single room, a floor, an office having one or more buildings in the same premise, laboratory, a school, college, or university campus. The connectivity is done by means of wires, Ethernet cables, fibre optics, or Wi-Fi.

Metropolitan Area Network (MAN) Metropolitan Area Network (MAN) is an extended form of LAN which covers a larger geographical area like a city or a town. Data transfer rate in MAN also ranges in Mbps. but it is considerably less as compared to LAN. Cable TV network or cable based broadband internet services are examples of MAN. This kind of network can be extended up to 30-40 km. Sometimes, many LANs are connected together to form MAN

Wide Area Network (WAN) Wide Area Network connects computers and other LANs and MANs, which are spread across different geographical locations of a country or in different countries or continents. A WAN could be formed by connecting a LAN to other LANs (Figure 10.7) via wired/wireless media. Large business, educational and government organisations connect their different branches in different locations across the world through WAN. The Internet is the largest WAN that connects billions of computers, smartphones and millions of LANs from different continents.

Question:- When we connect computers in a network using cables then it is called guided media. What are the various types of guided media available? Explain each.
Answer:
Three types of cables are used for connecting computers in a network are as follows:

  1. Twisted Pair Cable It consists of two insulated wires twisted around each other and uses copper as the conducting material.
    This property of twisted pair cable provides protection against crosstalk and noise.
  2. Co-axial Cable It contains two conductors, the inner conductor made of solid copper and the outer conductor that serves as a shield against noise. An insulating plastic is placed between the two conductors and this whole set-up is covered with a plastic jacket. For cable TV network co-axial cable is used.
  3. Optical Fibre It consists of thin strands of glass or glass like material, which are capable of carrying light signals from a source at one end to another end.

The unguided media is likewise called wireless communication. It doesn’t need any physical medium to transmit electromagnetic signals. In unguided media, the electromagnetic signals are broadcasted through the air to everybody. These signals are accessible to one who has the gadget equipped for receiving those signals.

The unguided media is additionally called unbounded media as it doesn’t have any line constraint. The unguided media allows the user to associate constantly, as the correspondence is wireless the user can interface himself from anyplace to the network.

The unguided media is classified into radio waves, microwaves, and infrared waves. The radio waves are created effectively; they are low-recurrence signals and can travel a significant distance. The radio waves can penetrate through the structures.

The microwaves are transmitted in a straight line and consequently require line-of-sight transmission. The distance covered by the microwave signal relies upon the stature of the two radio wire. More the taller are reception apparatuses longer is the distance covered by the sign. The microwave has a recurrence higher than the radio waves. Microwave is used for phone correspondence cell phones, TV distribution, and so on

Infrared waves are used for short-range correspondence. Like, the remote control for TVs, VCRs, and so forth uses infrared waves. It can not infiltrate through obstructions. A government license isn’t needed, to work an infrared framework as it is safer against eavesdropping.

 

Wireless Medias or unguided media

When it is impossible to install wires and cables or cabling is expensive then you can use wireless Media. Wireless media generate higher electromagnetic frequencies, such as radio waves, microwaves, & infrared. They transmit a signal over a long distance. In wireless transmission, various types of electromagnetic waves are used to transmit signals. Radio satellite transmission visible light, infrared light, x- rays, and gamma rays.

Wireless media consist of:

  • Radio waves transmission
  • Microwave transmission
  • Infrared transmission

Radio wave transmission

The radio wave one of the types of wireless media in which electromagnetic (radio) energy travels from a transmitting antenna to a receiving antenna. It is used for the radio and TV programs for the portable phone. The computer data also transmitted in the form of radio waves. It does not require a direct physical connection between computers. Each computer attaches to an antenna that transmits and receives radiofrequency. There are two principal ways in which electromagnetic energy travels from a transmitting antenna to a receiving antenna. One is by ground waves that travel near the surface of the earth and the other is by sky waves that are reflected back to earth from the ionosphere.

Types of radio waves

Short wave

This type of radio wave frequencies generally 1.6–30 MHz, just above the medium wave band and about 10 to 80 m (33 to 262 feet) in length. FM and medium wave (MW) are commonly called am. Is an example of short wave transmission.

Very high frequency (VHF)

The VHF is an abbreviation of very high frequency. VHF wavelength between 1 and 10 meters and a frequency between 300 and 30 megahertz. Vhf signals are widely employed for television and radio transmissions.

Ultra-high frequency (UHF)

The UHF (ultrahigh frequency) range of the radio spectrum is the band extending from 300 MHz to 3 GHz. The wavelengths corresponding to these limit frequencies are 1 meter and 10 centimeters.

Microwave transmission

Microwave transmission transmits the signal via radio using a series of microwave towers. Microwave communication is the most common wireless communication medium and is spread widely across the world. The wireless access points and wireless devices work on microwave communication. This communication medium widely used in computers and also cellular communication as well.

Infrared transmission

Infrared radiation is electromagnetic radiation which has a frequency range between approximately 1 and 430 THz .infrared communication device use infrared light beams to transmit signal. Infrared is one of the most primitive forms of wireless communication.  Infrared networks need to have the two devices in line with each other with an angle of +_15 degrees.

Satellite

Satellite communication is also a type of wireless communication but less used in the local networks. It operates over very long distances and at very high-frequency ranges differ widely as well. A satellite has the ability to receive signals from earth and to retransmit those signals back with the use of a transponder.

Difference between Guided and Unguided Media

Guided Media:

In this type of media, signal energy is enclosed and guided inside a solid medium. The guided media is used either for highlight point interface or an imparted connection to different associations. In guided media, obstruction is produced by emanations in the adjacent cables Proper shielding of guided media is needed to diminish the obstruction issue.

Unguided Media:

In the unguided media, the signal energy spreads through a wireless medium. The wireless media is used for radio broadcasting every which way. Microwave links are picked for significant distance broadcasting transmission unguided media. Interference is likewise an issue in unguided media, covering recurrence bands from contending signals can modify or eliminate a signal.

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