Network & Transmission media

Networks

A network is any system that allows electronic devices (computers, tablets, smartphones, phablets, etc...) to communicate in electronic form. There are three types of networks:

1. Local area network (LAN)
2. Metropolitan area network (MAN)
3. Wide area network (WAN)

Local are network (LAN)

A network that connect electronic devices within the same building, or at most within buildings that are in close range. For example a home would contain a LAN to connect multiple computers, smartphones and other devices(switches, hubs, routers).

Above is a diagram that shows us a LAN in a home settings. Note that there is a computer outside of the home environment but it is in close proximity and could be apart/connected to the home LAN via wireless methods.

Metropolitan area network

A network that connects various LANs (in a city, district, mega business) across a wider area.

Wide area network

A network use to connect electronic devices over large areas (such as the entire world). From the WAN we get the WWW (world wide web).

Transmissions Media

Networks use a variety of ways/methods to communicate. These methods/ways are called the transmission media. There are two main types of transmission media:

1. Wired transmission media
2. Wireless transmission media

Wired transmission media

These connection between electronic devices using physical method such as cables and/or wires. Three types of wired transmission media are:

• Coaxial cable - carry electric current at radio frequencies. It is used for cable television and broadband internet. This method provides better insulation than twisted pair from electrical interference but is more expensive.
• Fibre-optic cable - contains a number of glass fibres that transmit light. This wired transmission media is very fast and reliable but expensive method of transmitting data.
• Twisted pair - type of cable made up of pairs of wires. In each pair the wires are twisted around each other.

               

                        Fibre Optics cable

Twisted pair cable

Coaxial cable

Wireless transmission media

In networks data can be transmitted without the need for physical contact but is transmitted via various wireless methods. These methods are:

1. Radio waves
2. Microwaves
3. Infrared waves

Radio Waves

These are used in wireless LAN settings using frequencies of 2.4GHz &5GHz as well as satellites transmitting to earths stationary station and vice-versa via frequencies of 3GHz to 300GHz.

Microwave

Are used to transmit data up to distances of 50km, but it can not get round or through objects in its way using frequencies of 300MHz to 300GHz.

Infrared waves

Used in remote controls and in devices that need to communicate over very short clear/empty distances using frequencies of 300GHz to 400THz.

Wireless network technologies

There are various wireless technologies some are:

• Bluetooth - a wireless technology for communicating over very short distances using radio waves.
• Wi-Fi - a wireless technology for communication in a wireless LAN to eventually access the WWW. An area where Wi-Fi connectivity is available is called a hotspot.

Bandwidth

Bandwidth refers to the amount of data that can be sent via a connection. Three classification of bandwidth are:

1. Broadband - these can carry signals with lots of data such as video signals.
2. Narrowband - these carry less data than broadband and take longer to transmit moving images and large pictures. Mostly used to transmit text based messages.
3. Voiceband - these are very narrowband and the connection is typically quite slow.

Communication terms

Simplex

Communication sends signal in one direction only. For example a television connection one can only receive programs and never not send messages.

Duplex

Communication sends signals in both direction simultaneously. For example the a computer connected to the internet.

Half-duplex

Communications work in both direction, but only one direction at a time. For example a walkie-talkie

Point-to-point.

Communication connects two fixed points, and other users cannot hear the signal. For example a phone conversation.

Broadcast

Communication is sent out from a central point, and anyone who can pick up the signal can hear it. For example a radio station can be heard by anyone with a radio.

Other term

Modem

A modulator and a demodulator that converts analogue signal from telephone line to digital signal for computers and other electronic devices and vice-versa (such as smartphones, tablet etc...).